U.S. patent application number 16/146958 was filed with the patent office on 2019-01-31 for post-processing apparatus of solar cell.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Minho CHOI, Gyeayoung KWAG, Jinhyung LEE, Kyoungsoo LEE, Sangwook PARK.
Application Number | 20190035655 16/146958 |
Document ID | / |
Family ID | 53432932 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190035655 |
Kind Code |
A1 |
LEE; Kyoungsoo ; et
al. |
January 31, 2019 |
POST-PROCESSING APPARATUS OF SOLAR CELL
Abstract
A post-processing apparatus of a solar cell that carries out a
post-processing operation including a main period for heat-treating
a solar cell having a semiconductor substrate while providing light
to the solar cell, the post-processing apparatus including a main
section to carry out the main period, wherein the main section
comprises a first heat source unit to provide heat to the
semiconductor substrate and a light source unit to provide light to
the semiconductor substrate, the first heat source unit and the
light source unit being positioned in the main section, and the
light source unit comprises a light source constituted by a plasma
lighting system (PLS).
Inventors: |
LEE; Kyoungsoo; (Seoul,
KR) ; CHOI; Minho; (Seoul, KR) ; LEE;
Jinhyung; (Seoul, KR) ; KWAG; Gyeayoung;
(Seoul, KR) ; PARK; Sangwook; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
53432932 |
Appl. No.: |
16/146958 |
Filed: |
September 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14741286 |
Jun 16, 2015 |
10109511 |
|
|
16146958 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/67115 20130101;
H05B 3/0047 20130101; H01L 21/6776 20130101; Y02E 10/50 20130101;
Y02P 70/50 20151101; H01L 31/1864 20130101; Y02E 10/547
20130101 |
International
Class: |
H01L 21/67 20060101
H01L021/67; H01L 31/18 20060101 H01L031/18; H01L 21/677 20060101
H01L021/677; H05B 3/00 20060101 H05B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2014 |
KR |
10-2014-0073575 |
Claims
1. A post-processing apparatus of a solar cell that carries out a
post-processing operation including a main period for heat-treating
a solar cell having a semiconductor substrate while providing light
to the solar cell, the post-processing apparatus comprising: a main
section to carry out the main period, wherein the main section
comprises a first heat source unit to provide heat to the
semiconductor substrate and a light source unit to provide light to
the semiconductor substrate, the first heat source unit and the
light source unit being positioned in the main section, and the
light source unit comprises a light source constituted by a plasma
lighting system (PLS).
2. The post-processing apparatus according to claim 1, wherein
light provided to the semiconductor substrate by the light source
has a wavelength of 600 nm to 1000 nm.
3. The post-processing apparatus according to claim 1, wherein the
light source is provided at a light emitting surface thereof with a
cover substrate comprising a base substrate and a plurality of
layers positioned on the base substrate, the plurality of layers
comprising oxides having different refractive indices.
4. The post-processing apparatus according to claim 1, wherein the
light source unit and the first heat source unit respectively
provide light and heat to the semiconductor substrate in a state in
which the light source unit and the first heat source unit are
spaced apart from each other.
5. The post-processing apparatus according to claim 1, further
comprising: a temperature rising section to carry out a temperature
rising period for preliminarily heating the semiconductor
substrate, the temperature rising period being carried out before
the main period, wherein the temperature rising section comprises a
second heat source unit to preliminarily heat the semiconductor
substrate, the second heat source unit being positioned in the
temperature rising section.
6. The post-processing apparatus according to claim 5, further
comprising an additional heat source unit positioned at an entrance
of the temperature rising section such that the additional heat
source unit is opposite to the second heat source unit.
7. The post-processing apparatus according to claim 1, further
comprising a cooling section to carry out a cooling period for
cooling the semiconductor substrate, the cooling period being
carried out after the main period.
8. The post-processing apparatus according to claim 1, further
comprising: a temperature rising section to carry out a temperature
rising period for preliminarily heating the semiconductor
substrate, the temperature rising period being carried out before
the main period; a cooling section to carry out a cooling period
for cooling the semiconductor substrate, the cooling period being
carried out after the main period; and a conveyor belt passing
though the temperature rising section, the main section, and the
cooling section, and the solar cell being placed on the conveyor
belt, wherein the temperature rising period, the main period, and
the cooling period are carried out based on an in-line process.
9. The post-processing apparatus according to claim 8, further
comprising a partition wall unit positioned at at least one of a
space defined between the temperature rising section and the main
section for partitioning the temperature rising section and the
main section, and a space defined between the main section and the
cooling section for partitioning the main section and the cooling
section.
10. The post-processing apparatus according to claim 8, wherein at
least one of the temperature rising section and the cooling section
further comprise an additional light source positioned adjacent to
the main section.
11. The post-processing apparatus according to claim 8, further
comprising: an air curtain member positioned at at least one of an
entrance of the temperature rising section, a space defined between
the temperature rising section and the main section, a space
defined between the main section and the cooling section, and an
exit of the cooling section.
12. The post-processing apparatus according to claim 1, further
comprising: a temperature rising section to carry out a temperature
rising period for preliminarily heating the semiconductor
substrate, the temperature rising period being carried out before
the main period; and a cooling section to carry out a cooling
period for cooling the semiconductor substrate, the cooling period
being carried out after the main period, wherein the temperature
rising section, the main section, and the cooling section have a
batch structure in which a process is carried out in a state in
which the solar cell is stationary.
13. The post-processing apparatus according to claim 1, wherein the
solar cell is placed on a conveyor belt or a work table, and the
conveyor belt or the work table has a mesh structure.
14. The post-processing apparatus according to claim 1, wherein the
main section has a temperature of 100 to 800.degree. C., and the
main section has temperature and light intensity satisfying
Equation 1 and light intensity and process time satisfying
Equations 2 to 5. 1750-31.8T+(0.16)T.sup.2.ltoreq.I.ltoreq.10.sup.5
<Equation 1> 1.7.times.10.sup.2.ltoreq.I<10.sup.3, and
P.sub.min=13000-(31.7)1+(0.02)(I).sup.2.ltoreq.P.ltoreq.10000
<Equation 2> 10.sup.3.ltoreq.I<10.sup.4, and
1030-(0.25)I+(1.5.times.10.sup.-5)(I).sup.2.ltoreq.P.ltoreq.10000
<Equation 3> 10.sup.4.ltoreq.I.ltoreq.5.times.10.sup.4, and
35.5-(0.0012)I+(10.sup.-8)(I).sup.2.ltoreq.P.ltoreq.10000
<Equation 4> 5.times.10.sup.4.ltoreq.I.ltoreq.10.sup.5, and
0.5.ltoreq.P.ltoreq.10000 <Equation 5> where T is temperate
(.degree. C.) of the main section, I is light intensity
(mW/cm.sup.2) of the main section, and P is process time (sec) of
the main section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. patent application
Ser. No. 14/741,286, filed on Jun. 16, 2018, which claims the
priority benefit of Korean Patent Application No. 10-2014-0073575,
filed on Jun. 17, 2014 in the Korean Intellectual Property Office,
all of which are hereby expressly incorporated by reference into
the present application.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] Embodiments of the present invention relate to a
post-processing apparatus of a solar cell, and more particularly to
a post-processing apparatus of a solar cell based on a crystalline
semiconductor substrate.
Description of the Related Art
[0003] In recent years, exhaustion of existing energy resources,
such as petroleum and coal, has been forecast with the result that
interest in alternative energy resources substituting for the
existing energy resources has risen. Among such alternative energy
resources is a solar cell that converts photovoltaic energy into
electrical energy using a semiconductor device, which is in the
spotlight as a next-generation cell.
[0004] The solar cell may be fabricated through formation of
various layers and electrodes based on design. The design of
various layers and electrodes may determine the efficiency of the
solar cell. Low efficiency of the solar cell must be overcome in
order to commercialize the solar cell. For this reason, various
layers and electrodes of the solar cell are designed such that the
efficiency of the solar cell can be maximized, and various
processing procedures are carried out to maximize the efficiency of
the solar cell. Consequently, it is necessary to provide a
post-processing apparatus of a solar cell that is capable of
maximizing the efficiency of the solar cell.
SUMMARY OF THE INVENTION
[0005] Therefore, the embodiments of the present invention have
been made in view of the above problems, and it is an object of the
embodiments of the present invention to provide a post-processing
apparatus of a solar cell that is capable of reducing an output
loss of the solar cell.
[0006] In accordance with an aspect of the present invention, the
above and other objects can be accomplished by the provision of a
post-processing apparatus that carries out a post-processing
operation including a main period for heat-treating a solar cell
including a semiconductor substrate while providing light to the
solar cell, the post-processing apparatus including a main section
to carry out the main period, wherein the main section includes a
first heat source unit to provide heat to the semiconductor
substrate and a light source unit to provide light to the
semiconductor substrate, the first heat source unit and the light
source unit being positioned in the main section, and the light
source unit includes a light source constituted by a plasma
lighting system (PLS).
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The above and other objects, features and other advantages
of the embodiments of the present invention will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings, in which:
[0008] FIG. 1 is a sectional view showing an example of a solar
cell manufactured using a manufacturing method of a solar cell
according to an embodiment of the present invention;
[0009] FIG. 2 is a plan view showing the front of the solar cell
shown in FIG. 1 according to an embodiment of the present
invention;
[0010] FIG. 3 is a flowchart showing a manufacturing method of a
solar cell according to an embodiment of the present invention;
[0011] FIGS. 4A to 4G are sectional views showing the manufacturing
method of the solar cell shown in FIG. 3 according to an embodiment
of the present invention;
[0012] FIG. 5 is a graph showing a relationship between time and
temperature of a main processing process of a post-processing
operation of the manufacturing method of the solar cell according
to the embodiment of the present invention;
[0013] FIG. 6 is a graph showing a state of hydrogen based on a
relationship between temperature and light intensity at the
post-processing operation of the manufacturing method of the solar
cell according to the embodiment of the present invention;
[0014] FIG. 7 is a graph showing a state of hydrogen based on a
relationship between light intensity and process time at the
post-processing operation of the manufacturing method of the solar
cell according to the embodiment of the present invention;
[0015] FIG. 8 is a sectional view showing another example of the
solar cell manufactured using the manufacturing method of the solar
cell according to the embodiment of the present invention;
[0016] FIG. 9 is a sectional view showing a further example of the
solar cell manufactured using the manufacturing method of the solar
cell according to the embodiment of the present invention;
[0017] FIG. 10 is a graph showing temperature and light intensity
lines exhibiting the same output losses in an experimental example
of the present invention;
[0018] FIG. 11 is a graph showing light intensity and process time
lines exhibiting the same output losses in an experimental example
of the present invention;
[0019] FIG. 12 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to an
embodiment of the present invention;
[0020] FIG. 13 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to a
modification of an embodiment of the present invention;
[0021] FIG. 14 is a view showing an example of a worktable applied
to the post-processing apparatus of the solar cell shown in FIG. 13
according to an embodiment of the present invention;
[0022] FIG. 15 is a partial plan view showing another example of
the worktable applied to the post-processing apparatus of the solar
cell shown in FIG. 13 according to an embodiment of the present
invention;
[0023] FIG. 16 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to another
modification of an embodiment of the present invention;
[0024] FIG. 17 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to another
modification of an embodiment of the present invention; and
[0025] FIG. 18 is a view schematically showing the structure of a
light source unit applicable to a post-processing apparatus of a
solar cell according to a further modification of an embodiment of
the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] Reference will now be made in detail to the embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings. However, it will be understood that the
present invention should not be limited to the embodiments and may
be modified in various ways.
[0027] In the drawings, to clearly and briefly explain the
embodiments of the present invention, illustration of elements
having no connection with the description is omitted, and the same
or similar elements are designated by the same reference numerals
throughout the specification. In addition, in the drawings, for
more clear explanation, the dimensions of elements, such as
thickness, width, and the like, are exaggerated or reduced, and
thus the thickness, width, and the like of the embodiments of the
present invention are not limited to the illustration of the
drawings.
[0028] In the entire specification, when an element is referred to
as "including" another element, the element should not be
understood as excluding other elements so long as there is no
special conflicting description, and the element may include at
least one other element. In addition, it will be understood that,
when an element such as a layer, film, region or substrate is
referred to as being "on" another element, it can be directly on
the other element or intervening elements may also be present. On
the other hand, when an element such as a layer, film, region or
substrate is referred to as being "directly on" another element,
this means that there are no intervening elements therebetween.
[0029] Hereinafter, a post-processing apparatus of a solar cell
according to an embodiment of the present invention will be
described in detail with reference to the accompanying drawings. An
example of a solar cell manufactured using a manufacturing method
of a solar cell including a post-processing operation carried out
by the post-processing apparatus of the solar cell according to the
embodiment of the present invention will be described first, the
manufacturing method of the solar cell including the
post-processing operation will be described, and then the
post-processing apparatus of the solar cell will be described.
[0030] FIG. 1 is a sectional view showing an example of a solar
cell manufactured using a manufacturing method of a solar cell
according to an embodiment of the present invention, and FIG. 2 is
a plan view showing the front of the solar cell shown in FIG. 1. A
semiconductor substrate and an electrode are mainly shown in FIG.
2.
[0031] Referring to FIG. 1, a solar cell 100 according to this
embodiment includes a semiconductor substrate 110 including a base
region 10, a first conductive region 20 of a first conductive type,
a second conductive region 30 of a second conductive type, a first
electrode 42 connected to the first conductive region 20, and a
second electrode 44 connected to the second conductive region 30.
The solar cell 100 may further include dielectric films, such as a
first passivation film 22 and an anti-reflection film 24.
Hereinafter, the solar cell 100 will be described in more
detail.
[0032] The semiconductor substrate 110 may be formed of a
crystalline semiconductor. For example, the semiconductor substrate
110 may be formed of a single crystalline semiconductor (e.g.
single crystalline silicon) or a polycrystalline semiconductor
(e.g. polycrystalline silicon). In particular, the semiconductor
substrate 110 may be formed of a single crystalline semiconductor
(e.g. a single crystalline semiconductor wafer, more specifically a
single crystalline silicon wafer). In an instance in which the
semiconductor substrate 110 is formed of a single crystalline
semiconductor (e.g. single crystalline silicon) as described above,
the solar cell 100 may be a single crystalline semiconductor solar
cell (e.g. a single crystalline silicon solar cell). Since the
solar cell 100 is based on the semiconductor substrate 110 formed
of a crystalline semiconductor exhibiting high crystallinity and
thus low defectiveness as described above, the solar cell 100 may
exhibit excellent electrical characteristics.
[0033] The front surface and/or the back surface of the
semiconductor substrate 110 may be textured such that the front
surface and/or the back surface of the semiconductor substrate 110
have a rugged shape. For example, the rugged shape may be a
pyramidal shape, formed at a (111) surface of the semiconductor
substrate 110, having an irregular size. In an instance in which
the rugged shape is formed at the front surface of the
semiconductor substrate 110 by texturing as described above, the
surface roughness of the semiconductor substrate 110 may be
increased with the result that the reflectance of light incident
upon the front surface of the semiconductor substrate 110 may be
decreased. Consequently, the quantity of light reaching a pn
junction formed by the base region 10 and the first conductive
region 20 may be increased with the result that light loss of the
solar cell 100 may be minimized. In this embodiment of the present
invention, the rugged shape is formed at the front surface of the
semiconductor substrate 110 to decrease the reflectance of incident
light, whereas the rugged shape is not formed at the back surface
of the semiconductor substrate 110 to increase the reflectance of
incident light. However, the embodiments of the present invention
are not limited thereto. For example, the rugged shape may be
formed at both the front surface and the back surface of the
semiconductor substrate 110, or the rugged shape may not be formed
at either the front surface or the back surface of the
semiconductor substrate 110.
[0034] The base region 10 of the semiconductor substrate 110 may be
a second conductive base region 10 having a relatively low doping
concentration of a second conductive dopant. For example, the base
region 10 may be more distant from the front surface of the
semiconductor substrate 110 and more adjacent to the back surface
of the semiconductor substrate 110 than the first conductive region
20. In addition, the base region 10 may be more adjacent to the
front surface of the semiconductor substrate 110 and more distant
from the back surface of the semiconductor substrate 110 than the
second conductive region 30. However, the embodiments of the
present invention are not limited thereto. The base region 10 may
be differently positioned.
[0035] The base region 10 may be formed of a crystalline
semiconductor having a second conductive dopant. For example, the
base region 10 may be formed of a single crystalline semiconductor
(e.g. single crystalline silicon) or a polycrystalline
semiconductor (e.g. polycrystalline silicon) having a second
conductive dopant. In particular, the base region 10 may be formed
of a single crystalline semiconductor (e.g. a single crystalline
semiconductor wafer, more specifically a single crystalline silicon
wafer) having a second conductive dopant.
[0036] The second conductive type may be an n-type or a p-type. In
an instance in which the base region 10 is of an n-type, the base
region 10 may be formed of a single crystalline semiconductor or a
polycrystalline semiconductor doped with a group-V element, such as
phosphorus (P), arsenic (As), bismuth (Bi), or antimony (Sb). On
the other hand, in an instance in which the base region 10 is of a
p-type, the base region 10 may be formed of a single crystalline
semiconductor or a polycrystalline semiconductor doped with a
group-III element, such as boron (B), aluminum (Al), gallium (Ga),
or Indium (In). However, the embodiments of the present invention
are not limited thereto. The base region 10 and the second
conductive dopant may be formed of various materials.
[0037] For example, the base region 10 may be of a p-type. In this
case, materials included in the second electrode 44 may be diffused
in to the semiconductor substrate 110 to form the second conductive
region 30 at an operation of firing the second electrode 44. As a
result, an additional doping process for forming the second
conductive region 30 may be omitted, thereby simplifying a
manufacturing process of the solar cell 100. However, the
embodiments of the present invention are not limited thereto. For
example, the base region 10 and the second conductive region 30 may
be of a p-type, and the first conductive region 20 may be of an
n-type.
[0038] The first conductive region 20 of the first conductive type,
which is opposite to the second conductive type of the base region
10, may be formed at the front surface of the semiconductor
substrate 110. The first conductive region 20 may form a pn
junction together with the base region 10 to constitute an emitter
region for generating carriers through photoelectric
conversion.
[0039] In this embodiment of the present invention, the first
conductive region 20 may be a doped region constituting a portion
of the semiconductor substrate 110. In this case, the first
conductive region 20 may be formed of a crystalline semiconductor
having a first conductive dopant. For example, the first conductive
region 20 may be formed of a single crystalline semiconductor (e.g.
single crystalline silicon) or a polycrystalline semiconductor
(e.g. polycrystalline silicon) having a first conductive dopant. In
particular, the first conductive region 20 may be formed of a
single crystalline semiconductor (e.g. a single crystalline
semiconductor wafer, more specifically a single crystalline silicon
wafer) having a first conductive dopant. In an instance in which
the first conductive region 20 constitutes a portion of the
semiconductor substrate 110 as described above, junction
characteristics between the first conductive region 20 and the base
region 10 may be improved.
[0040] However, the embodiments of the present invention are not
limited thereto. For example, the first conductive region 20 may be
formed on the semiconductor substrate 110 separately from the
semiconductor substrate 110, which will hereinafter be described in
more detail with reference to FIG. 9.
[0041] The first conductive type may be a p-type or an n-type. In
an instance in which the first conductive region 20 is of a p-type,
the first conductive region 20 may be formed of a single
crystalline semiconductor or a polycrystalline semiconductor doped
with a group-III element, such as boron (B), aluminum (Al), gallium
(Ga), or Indium (In). On the other hand, in an instance in which
the first conductive region 20 is of an n-type, the first
conductive region 20 may be formed of a single crystalline
semiconductor or a polycrystalline semiconductor doped with a
group-V element, such as phosphorus (P), arsenic (As), bismuth
(Bi), or antimony (Sb). However, the embodiments of the present
invention are not limited thereto. Various materials may be used as
the first conductive dopant.
[0042] In the figure, the first conductive region 20 is shown as
having a homogeneous structure of a generally uniform doping
concentration. However, the embodiments of the present invention
are not limited thereto. In another embodiment of the present
invention, the first conductive region 20 may have a selective
structure, which will hereinafter be described in detail with
reference to FIG. 8.
[0043] The second conductive region 30 of the second conductive
type, which is the same as the second conductive type of the base
region 10, having a higher doping concentration of a second
conductive dopant than the base region 10, may be formed at the
back surface of the semiconductor substrate 110. The second
conductive region 30 may form a back surface field to constitute a
back surface field region for preventing or reducing loss of the
carriers due to recombination at the surface of the semiconductor
substrate 110 (more exactly, the back surface of the semiconductor
substrate 110).
[0044] In this embodiment of the present invention, the second
conductive region 30 may be a doped region constituting a portion
of the semiconductor substrate 110. In this case, the second
conductive region 30 may be formed of a crystalline semiconductor
having a second conductive dopant. For example, the second
conductive region 30 may be formed of a single crystalline
semiconductor (e.g. single crystalline silicon) or a
polycrystalline semiconductor (e.g. polycrystalline silicon) having
a second conductive dopant. In particular, the second conductive
region 30 may be formed of a single crystalline semiconductor (e.g.
a single crystalline semiconductor wafer, more specifically a
single crystalline silicon wafer) having a second conductive
dopant. In an instance in which the second conductive region 30
constitutes a portion of the semiconductor substrate 110 as
described above, junction characteristics between the second
conductive region 30 and the base region 10 may be improved.
[0045] However, the embodiments of the present invention are not
limited thereto. For example, the second conductive region 30 may
be formed on the semiconductor substrate 110 separately from the
semiconductor substrate 110, which will hereinafter be described in
more detail with reference to FIG. 9.
[0046] The second conductive type may be an n-type or a p-type. In
an instance in which the second conductive region 30 is of an
n-type, the second conductive region 30 may be formed of a single
crystalline semiconductor or a polycrystalline semiconductor doped
with a group-V element, such as phosphorus (P), arsenic (As),
bismuth (Bi), or antimony (Sb). On the other hand, in an instance
in which the second conductive region 30 is of a p-type, the second
conductive region 30 may be formed of a single crystalline
semiconductor or a polycrystalline semiconductor doped with a
group-III element, such as boron (B), aluminum (Al), gallium (Ga),
or Indium (In). However, the embodiments of the present invention
are not limited thereto. Various materials may be used as the
second conductive dopant. The second conductive dopant of the
second conductive region 30 may be formed of a material identical
to that of the second conductive dopant of the base region 10 or a
material different from that of the second conductive dopant of the
base region 10.
[0047] In this embodiment of the present invention, the second
conductive region 30 is shown as having a homogeneous structure of
a generally uniform doping concentration. However, the embodiments
of the present invention are not limited thereto. In another
embodiment of the present invention, the second conductive region
30 may have a selective structure or a local structure, which will
hereinafter be described in detail with reference to FIG. 8.
[0048] In this embodiment of the present invention, the first and
second conductive regions 20 and 30 formed at the semiconductor
substrate 110 are doped with the first and second conductive
dopants, and the base region 10 is doped with the second conductive
dopant. As a result, the dopants are distributed throughout the
semiconductor substrate 110. At this time, any specific dopant may
be combined with a different material or element in the
semiconductor substrate 110 to lower the characteristics of the
solar cell 100. For example, in an instance in which the
semiconductor substrate 110 has boron (B) as a dopant, boron (B)
may react with oxygen (O) to form a B-O combination. Such a B-O
combination may greatly reduce lifetime of the carriers, thereby
lowering the characteristics of the solar cell 100. Particularly,
in an instance in which boron (B) is used as the second conductive
agent included in the base region 10, and therefore the base region
10 is of a p-type, a large amount of the B-O combination may be
distributed over the large area of the semiconductor substrate 110,
thereby greatly lowering the characteristics of the solar cell
100.
[0049] In this embodiment of the present invention, therefore, a
post-processing operation (ST50) (see FIG. 3) may be carried out
such that any combination (e.g. the above-mentioned B-O
combination) which may lower the characteristics of the solar cell
100 is not generated to prevent or reduce lowering or deterioration
of the characteristics of the solar cell 100, which will
hereinafter be described in more detail when describing a method of
manufacturing the solar cell 100.
[0050] The semiconductor substrate 110 may have a thickness T1 of
200 .mu.m or less. If the thickness T1 of the semiconductor
substrate 110 is greater than 200 .mu.m, it may be difficult for
effects obtained by carrying out the post-processing operation
(ST50) to be exhibited throughout the semiconductor substrate 110.
For example, the semiconductor substrate 110 may have a thickness
T1 of 100 .mu.m to 200 .mu.m. If the thickness T1 of the
semiconductor substrate 110 is less than 100 .mu.m, the efficiency
of the solar cell 100 may be decreased and the mechanical
characteristics of the solar cell 100 may not be sufficient since
the thickness T1 of the semiconductor substrate 110 is insufficient
to perform photoelectric conversion. However, the embodiments of
the present invention are not limited thereto. The thickness T1 of
the semiconductor substrate 110 may be variously changed.
[0051] The first passivation film 22 and the anti-reflection film
24 are sequentially formed on the front surface of the
semiconductor substrate 110, more exactly on the first conductive
region 20 formed on the semiconductor substrate 110, and the first
electrode 42 is formed at the first conductive region 20 in contact
through the first passivation film 22 and the anti-reflection film
24 (i.e. via an opening 102 formed through the first passivation
film 22 and the anti-reflection film 24).
[0052] The first passivation film 22 and the anti-reflection film
24 may be substantially formed throughout the front surface of the
semiconductor substrate 110 excluding the opening 102 corresponding
to the first electrode 42.
[0053] The first passivation film 22 is formed at the first
conductive region 20 in contact to passivate defects existing on
the surface of the first conductive region 20 or in a bulk of the
first conductive region 20. The passivation of defects may remove a
recombination site of minority carriers, which may increase an
open-circuit voltage Voc of the solar cell 100. The anti-reflection
film 24 reduces the reflectance of light incident upon the front
surface of the semiconductor substrate 110. Through reduction in
the reflectance of light incident upon the front surface of the
semiconductor substrate 110, the quantity of light reaching the pn
junction formed by the base region 10 and the first conductive
region 20 may be increased with the result that a short-circuit
current Isc of the solar cell 100 may be increased. As described
above, the first passivation film 22 and the anti-reflection film
24 may increase the open-circuit voltage and the short-circuit
current of the solar cell 100, thereby improving the efficiency of
the solar cell 100.
[0054] The first passivation film 22 may be formed of various
materials. For example, the first passivation film 22 may be formed
of a dielectric material including hydrogen. In an instance in
which the first passivation film 22 includes hydrogen as described
above, the first passivation film 22 may function to passivate the
surface of the semiconductor substrate 110 and, in addition,
function as a hydrogen source for supplying hydrogen to the surface
of the semiconductor substrate 110 or into a bulk of the
semiconductor substrate 110 at the post-processing operation
(ST50).
[0055] For example, the first passivation film 22 may include
10.sup.20 to 10.sup.22 ea/cm.sup.3 of hydrogen. The hydrogen
content of the first passivation film 22 is limited to a range in
which the first passivation film 22 can effectively function as the
hydrogen source when the first passivation film 22 passivates the
surface of the semiconductor substrate 110 and at the
post-processing operation (ST50). However, the embodiments of the
present invention are not limited thereto. The hydrogen content of
the first passivation film 22 may be variously changed.
[0056] For example, the first passivation film 22 may include a
silicon nitride (SiNx:H) including hydrogen, a silicon oxide
nitride (SiOxNy:H) including hydrogen, a silicon carbide (SiCx:H)
including hydrogen, or a silicon oxide (SiOx:H) including hydrogen.
However, the embodiments of the present invention are not limited
thereto. The first passivation film 22 may include various other
materials.
[0057] The first passivation film 22 may have a thickness of 50 nm
to 200 nm. If the thickness of the first passivation film 22 is
less than 50 nm, the passivation effect may not be sufficient, and
the hydrogen diffusion effect at the post-processing operation
(ST50) may not be sufficient. On the other hand, if the thickness
of the first passivation film 22 is greater than 200 nm, the
process time may be increased while the effects are not greatly
improved, and the thickness of the solar cell 100 may be increased.
However, the embodiments of the present invention are not limited
thereto. The thickness of the first passivation film 22 may be
variously changed.
[0058] The anti-reflection film 24 may be formed of various
materials. For example, the anti-reflection film 24 may have a
single film structure or a multi-layer film structure formed of at
least one selected from a group consisting of a silicon nitride, a
silicon nitride including hydrogen, a silicon oxide, a silicon
oxide nitride, an aluminum oxide, MgF.sub.2, ZnS, TiO.sub.2, and
CeO.sub.2. For example, the anti-reflection film 24 may include a
silicon nitride.
[0059] In this embodiment of the present invention, the
anti-reflection film 24 formed at the semiconductor substrate 110
in contact includes hydrogen such that the anti-reflection film 24
can effectively function to passivate the surface of the
semiconductor substrate 110 and function as the hydrogen source.
However, the embodiments of the present invention are not limited
thereto. For example, only the anti-reflection film 24 may include
hydrogen, or both the anti-reflection film 24 and the first
passivation film 22 may include hydrogen. In an instance in which
the anti-reflection film 24 includes hydrogen, the material,
hydrogen content, thickness, etc. of the anti-reflection film 24
may be equal to or similar to those of the first passivation film
22.
[0060] Furthermore, in this embodiment of the present invention,
the first passivation film 22, which is a dielectric film disposed
at the front surface of the semiconductor substrate 110, includes
hydrogen such that the first passivation film 22 can supply the
hydrogen at the post-processing operation (ST50). This is because a
short-wavelength light is easily incident upon the front surface of
the semiconductor substrate 110 with the result that undesired
combination (e.g. the above-mentioned B-O combination) may be
highly generated, whereas generation of undesired combination is
advantageously prevented or reduced when hydrogen is supplied to
the front surface of the semiconductor substrate 110. However, the
embodiments of the present invention are not limited thereto. For
example, a dielectric film formed on the front surface and/or the
back surface of the semiconductor substrate 110 may include
hydrogen such that the dielectric film can supply the hydrogen at
the post-processing operation (ST50).
[0061] In addition, in the above-described embodiment of the
present invention, both the first passivation film 22 and the
anti-reflection film 24 are included. However, the embodiments of
the present invention are not limited thereto. For example, any one
selected from between the first passivation film 22 and the
anti-reflection film 24 may perform both a reflection preventing
function and a passivation function in a state in which the other
selected from between the first passivation film 22 and the
anti-reflection film 24 is not provided. In another example,
various films may be formed on the front surface of the
semiconductor substrate 110 in addition to the first passivation
film 22 and the anti-reflection film 24. Various other
modifications are also possible.
[0062] The first electrode 42 is electrically connected to the
first conductive region 20 through the first passivation film 22
and the anti-reflection film 24 (i.e. via the opening 102 formed
through the first passivation film 22 and the anti-reflection film
24). The first electrode 42 may be formed of various materials such
that the first electrode 42 can have various shapes. The shape of
the first electrode 42 will hereinafter be described with reference
to FIG. 2.
[0063] The second electrode 44 is formed on the back surface of the
semiconductor substrate 110, more exactly on the second conductive
region 30 formed on the semiconductor substrate 110. In this
embodiment of the present invention, the second electrode 44 is
formed throughout the back surface of the semiconductor substrate
110 such that light can be reflected by the back surface of the
semiconductor substrate 110. In this case, light reaching the back
surface of the semiconductor substrate 110 is reflected to the
interior of the semiconductor substrate 110, thereby improving the
efficiency in use of the light. At this time, the second electrode
44 may be formed at the back surface of the semiconductor substrate
110 or the second conductive region 30 in contact.
[0064] In this embodiment of the present invention, materials
included in the second electrode 44 may be diffused into the
semiconductor substrate 110 to form the second conductive region 30
at the operation of firing the second electrode 44. As a result, an
additional doping process for forming the second conductive region
30 may be omitted, thereby simplifying the manufacturing process of
the solar cell 100. In addition, damage to the semiconductor
substrate 110 or defects of the semiconductor substrate 110, which
may occur at a process of forming the second conductive region 30
through doping, may be prevented or reduced.
[0065] Hereinafter, the planar shape of the first electrode 42 will
be described in detail with reference to FIG. 2.
[0066] Referring to FIG. 2, the first electrode 42 may include a
plurality of finger electrodes 42a arranged at a uniform pitch such
that the finger electrodes 42a are spaced apart from each other. In
the figure, the finger electrodes 42a are illustrated as being
parallel to each other and, in addition, parallel to the edge of
the semiconductor substrate 110. However, the embodiments of the
present invention are not limited thereto. The first electrode 42
may further include at least one bus bar electrode 42b formed in a
direction intersecting the finger electrodes 42a for
interconnecting the finger electrodes 42a. Only one bus bar
electrode 42b may be provided, or a plurality of bus bar electrodes
42b arranged at a larger pitch than the finger electrodes 42a may
be provided as shown in FIG. 2. In this case, the width of each of
the bus bar electrodes 42b may be greater than that of each of the
finger electrodes 42a. However, the embodiments of the present
invention are not limited thereto. For example, the width of each
of the bus bar electrodes 42b may be equal to or less than that of
each of the finger electrodes 42a.
[0067] When viewed in section, the finger electrodes 42a and the
bus bar electrodes 42b of the first electrode 42 may be formed
through the first passivation film 22 and the anti-reflection film
24. That is, the opening 102 may be formed through the first
passivation film 22 and the anti-reflection film 24 such that the
opening 102 corresponds to the finger electrodes 42a and the bus
bar electrodes 42b. In another example, the finger electrodes 42a
of the first electrode 42 may be formed through the first
passivation film 22 and the anti-reflection film 24, and the bus
bar electrodes 42b of the first electrode 42 may be formed on the
first passivation film 22 and the anti-reflection film 24. In this
case, the opening 102 may be formed through the first passivation
film 22 and the anti-reflection film 24 such that the opening 102
corresponds to the finger electrodes 42a but not the bus bar
electrodes 42b.
[0068] The solar cell 100 may be processed so as to prevent or
reduce generation of any combination which may lower the
characteristics of the solar cell 100 at the post-processing
operation (ST50) as previously described, which will hereinafter be
described in more detail when describing a manufacturing method of
the solar cell 100.
[0069] FIG. 3 is a flowchart showing a manufacturing method of a
solar cell according to an embodiment of the present invention, and
FIGS. 4A to 4G are sectional views showing the manufacturing method
of the solar cell shown in FIG. 3. A detailed description will not
be given of parts of the solar cell shown in FIGS. 3 and 4A to 4G
identical to or similar to those of the solar cell 100 described
with reference to FIGS. 1 and 2. Hereinafter, only parts of the
solar cell shown in FIGS. 3 and 4A to 4G different from those of
the solar cell 100 described with reference to FIGS. 1 and 2 will
be described in more detail.
[0070] Referring to FIG. 3, the manufacturing method of the solar
cell 100 according to the embodiment of the present invention
includes a semiconductor substrate preparing operation (ST10), a
conductive region forming operation (ST20), a dielectric film
forming operation (ST30), an electrode forming operation (ST40),
and a post-processing operation (ST50). The electrode forming
operation (ST40) may include an operation of forming first and
second electrode layers (ST42) and a firing operation (ST44). The
post-processing operation (ST50) may include a hydrogen diffusion
process (ST52), a preliminary heat treatment process (ST54), and a
main processing process (ST56). The firing operation (ST44) and the
hydrogen diffusion process (ST52) may be simultaneously carried
out. The manufacturing method of the solar cell 100 according to
the embodiment of the present invention will be described in detail
with reference to FIGS. 4A to 4G.
[0071] First, as shown in FIG. 4A, a semiconductor substrate 110
including a base region 10 having a second conductive dopant is
prepared at the semiconductor substrate preparing operation (ST10).
For example, in this embodiment of the present invention, the
semiconductor substrate 110 may be formed of a silicon substrate
(e.g. a silicon wafer) having a p-type dopant (specifically boron
(B)). However, the embodiments of the present invention are not
limited thereto. For example, the base region 10 may have a p-type
dopant other than boron or an n-type dopant.
[0072] At this time, the front surface and/or the back surface of
the semiconductor substrate 110 may be textured such that front
surface and/or the back surface of the semiconductor substrate 110
has a rugged shape (irregular or textured shape). The surface of
the semiconductor substrate 110 may be textured using wet texturing
or dry texturing. In the wet texturing, the semiconductor substrate
110 is soaked in a texturing solution. The wet texturing has an
advantage in that the process time is short. In the dry texturing,
on the other hand, the surface of the semiconductor substrate 110
is cut using a diamond grill or a laser. In the dry texturing, a
rugged shape is uniformly formed. However, the process time is
long, and the semiconductor substrate 110 may be damaged.
Alternatively, the semiconductor substrate 110 may be textured
using reactive ion etching (RIE), etc. As described above, the
semiconductor substrate 110 may be textured using various
methods.
[0073] For example, the front surface of the semiconductor
substrate 110 may be textured such that the front surface of the
semiconductor substrate 110 has a rugged shape, and the back
surface of the semiconductor substrate 110 may be mirror-ground to
have a lower surface roughness than the front surface of the
semiconductor substrate 110. However, the embodiments of the
present invention are not limited thereto. The semiconductor
substrate 110 may have various other structures.
[0074] Subsequently, as shown in FIG. 4B, a conductive region is
formed at the semiconductor substrate 110 at the conductive region
forming operation (ST20). More specifically, in this embodiment of
the present invention, a first conductive region 20 is formed at
the front surface of the semiconductor substrate 110 at the
conductive region forming operation, and a second conductive region
30 (see FIG. 4E), which will be positioned at the back surface of
the semiconductor substrate 110, is formed at a subsequent
operation of firing a second electrode 44. However, the embodiments
of the present invention are not limited thereto. For example, the
first conductive region 20 and/or the second conductive region 30
may be formed at the conductive region forming operation. In this
case, the second conductive region 30 may be formed using a method
identical to or similar to a method of forming the first conductive
region 20, which will hereinafter be described.
[0075] The first conductive region 20 may be formed by doping a
dopant using various methods, such as ion injection, thermal
diffusion, and laser doping. In another example, an additional
layer having a first conductive dopant may be formed on the
semiconductor substrate 110 to form the first conductive region
20.
[0076] Subsequently, as shown in FIG. 4C, a dielectric film is
formed on the front surface of the semiconductor substrate 110 or
on the first conductive region 20 at the dielectric film forming
operation (ST30).
[0077] More specifically, a first passivation film 22 and an
anti-reflection film 24 are formed on the first conductive region
20. In this embodiment of the present invention, no dielectric film
is positioned at the back surface of the semiconductor substrate
110. Alternatively, another dielectric film (e.g. a second
passivation film) may be positioned at the back surface of the
semiconductor substrate 110. The dielectric film may also be formed
at the back surface of the semiconductor substrate 110 at this
operation. In this case, the dielectric film may also be formed on
the back surface of the semiconductor substrate 110 using a method
identical to or similar to a method of forming the first
passivation film 22 and the anti-reflection film 24, which will
hereinafter be described.
[0078] The first passivation film 22 and/or the anti-reflection
film 24 may be formed using various methods, such as vacuum
deposition, chemical vapor deposition, spin coating, screen
printing, and spray coating.
[0079] In this embodiment of the present invention, the first
passivation film 22 may be formed of a dielectric material
including hydrogen. As a result, the first passivation film 22 may
function to passivate the surface of the semiconductor substrate
110 using hydrogen and, in addition, function as a hydrogen source
for supplying hydrogen to the semiconductor substrate 110 at the
post-processing operation (ST50).
[0080] Subsequently, as shown in FIGS. 4D and 4E, first and second
electrodes 42 and 44 are formed at the electrode forming step
(ST40), which will hereinafter be described in more detail.
[0081] First, as shown in FIG. 4D, a paste for forming first and
second electrodes is applied onto the dielectric films, such as the
first passivation film 22 and the anti-reflection film 24, or the
semiconductor substrate 110 by printing (e.g. screen printing) to
form first and second electrode layers 420 and 440 at the operation
of forming the first and second electrode layers (ST42). The first
and second electrode layers 420 and 440 may be formed using various
other methods or processes.
[0082] Subsequently, as shown in FIG. 4E, the first and second
electrode layers 420 and 440 are fired to form first and second
electrodes 42 and 44 at the firing operation (ST44).
[0083] During firing, an opening 102 is formed through the
dielectric films, such as the first passivation film 22 and the
anti-reflection film 24, by firing through or laser firing contact
with the result that the first electrode layer 420 is connected to
(e.g. contacts) the first conductive region 20. In an instance in
which the firing through or the laser firing contact is used as
described above, the opening 102 is formed during firing. As a
result, it is not necessary to carry out an additional process of
forming the opening 102.
[0084] In addition, a material (e.g. aluminum) constituting the
second electrode 44 may be diffused to the back surface of the
semiconductor substrate 110 to form the second conductive region 30
at the semiconductor substrate 110. However, the embodiments of the
present invention are not limited thereto. For example, the second
conductive region 30 may be formed at the conductive region forming
operation (ST20) as previously described.
[0085] For example, at the firing operation (ST44), temperature
(specifically, peak temperature) may be 700 to 800.degree. C., and
process time may be 5 to 20 seconds. These conditions are limited
to a range in which process time can be minimized while firing is
sufficiently achieved. However, the embodiments of the present
invention are not limited thereto. In addition, the firing
operation (ST44) may be carried out using heat generated from an
ultraviolet lamp. However, the embodiments of the present invention
are not limited thereto. Various other methods may also be
used.
[0086] As described above, in this embodiment of the present
invention, the electrode forming operation (ST40) includes the
firing operation (ST44). The firing operation (ST44) may be a part
of the post-processing operation (S50), which will be subsequently
carried out. That is, the firing operation (ST44) and a part of the
post-processing operation (S50) may be simultaneously carried out,
which will hereinafter be described in more detail when describing
the post-processing operation (S50).
[0087] However, the embodiments of the present invention are not
limited thereto. The electrode forming operation (ST40) may not
include the firing operation (ST44). For example, the opening 102
may be formed through the first passivation film 22 and the
anti-reflection film 24, the opening 102 may be filled with a
conductive material using various methods, such as plating and
deposition, to form the first electrode 42, and the second
electrode 44 may be formed using various methods, such as plating,
deposition, and printing. In addition, the first electrode 42 and
the second electrode 44 may be formed using various other
methods.
[0088] Subsequently, the post-processing operation (S50) is carried
out to post-process the solar cell 100 including the semiconductor
substrate 110 by passivating the semiconductor substrate 110. More
specifically, the post-processing operation (S50) is carried out to
prevent lowering in characteristics of the solar cell 100 which may
be caused due to a specific combination generated at the surface of
the semiconductor substrate 110 or in the bulk of the semiconductor
substrate 110. For example, in an instance in which the
semiconductor substrate 110 includes boron, the B-O combination may
be easily generated in the semiconductor substrate 110 when light
is supplied to the semiconductor substrate 110. Such a B-O
combination may greatly reduce the lifetime of the carriers,
thereby lowering the characteristics of the solar cell 100. In this
embodiment of the present invention, therefore, the post-processing
operation (S50) is carried out such that specific combination (e.g.
the B-O combination) which may lower the characteristics of the
solar cell 100 is not generated in the semiconductor substrate 110
as described above, thereby improving the characteristics of the
solar cell 100.
[0089] In an instance in which the semiconductor substrate 110 is
heat-treated at a high temperature after the post-processing
operation (S50), the effects obtained by the post-processing
operation (S50) may be lowered or disappear. For this reason, the
post-processing operation (S50) may be carried out in the second
half of the manufacturing method of the solar cell 100.
Specifically, the post-processing operation (S50) may be carried
out simultaneously with the firing operation (ST44) or after the
firing operation (ST44), which is carried out at a relatively high
temperature. For example, a part of the post-processing operation
(S50) may be carried out simultaneously with the firing step
(ST44), and the rest of the post-processing operation (S50) may be
carried out after the firing operation (ST44). Alternatively, the
entirety of the post-processing operation (S50) may be carried out
after the firing operation (ST44). As a result, the effects
obtained by the post-processing operation (S50) may not be lowered
or disappear. The post-processing operation (S50) will hereinafter
be described in more detail.
[0090] The post-processing operation (S50) includes the main
processing process (ST56), which is capable of restraining
generation of combination lowering the characteristics of the solar
cell 100 and generating combination (e.g. a B-H combination) which
may not badly or adversely affect the characteristics of the solar
cell 100 through heat treatment of the semiconductor substrate
together with the supply of light to the semiconductor substrate.
In addition, the post-processing operation (S50) may further
include the hydrogen diffusion process (ST52) and/or the
preliminary heat treatment process (ST54), which are carried out
before the main processing process (ST56), for improving the
effects of the main processing process (ST56). In this embodiment
of the present invention, the hydrogen diffusion process (ST52),
the preliminary heat treatment process (ST54), and the main
processing process (ST56) are sequentially carried out to maximize
the effects of the post-processing operation (S50). Hereinafter,
the hydrogen diffusion process (ST52), the preliminary heat
treatment process (ST54), and the main processing process (ST56)
will be described in detail.
[0091] First, hydrogen is diffused in the semiconductor substrate
110 at the hydrogen diffusion process (ST52). At the hydrogen
diffusion process (ST52), the semiconductor substrate 110 is
heat-treated at a high temperature at which hydrogen is diffused
deeply in the semiconductor substrate 110.
[0092] At this time, hydrogen may be supplied from various hydrogen
sources to the semiconductor substrate 110. For example, the
semiconductor substrate 110 may be placed in a furnace under a
hydrogen atmosphere such that hydrogen in the hydrogen atmosphere
can be supplied into the semiconductor substrate 110. In this case,
the hydrogen in the hydrogen atmosphere is a hydrogen source.
Alternatively, in an instance in which the dielectric films (i.e.
the first passivation film 22 and the anti-reflection film 24)
formed on the semiconductor substrate 110 include hydrogen, the
hydrogen from the dielectric films may be supplied into the
semiconductor substrate 110 by heat treatment. In this case, the
hydrogen in the dielectric films is a hydrogen source.
[0093] In this embodiment of the present invention, the dielectric
films, specifically the first passivation film 22 contacting the
semiconductor substrate 110, include hydrogen, and the hydrogen is
supplied into the semiconductor substrate 110. In an instance in
which the first passivation film 22 is used as a hydrogen source as
described above, it is not necessary to provide a process or an
apparatus for forming the hydrogen atmosphere. In addition, the
first passivation film 22 may function as a kind of capping film
for further accelerating the diffusion of hydrogen in the
semiconductor substrate 110.
[0094] The hydrogen diffusion process (ST52) may be carried out at
a temperature (more exactly, a peak temperature) of 400 to
800.degree. C. (more specifically, 400 to 700.degree. C.) for 5
seconds to 20 minutes (more specifically, 1 to 20 minutes). If the
temperature of the hydrogen diffusion process (ST52) is less than
400.degree. C. or the process time is less than 5 seconds, hydrogen
diffusion may not be sufficiently achieved. On the other hand, if
the temperature of the hydrogen diffusion process (ST52) is greater
than 800.degree. C. or the process time is greater than 20 minutes,
a process cost and time are increased, thereby lowering
productivity. In other words, hydrogen may be effectively diffused
in the semiconductor substrate 110 within the above-defined
temperature and time ranges, thereby achieving high productivity.
In consideration of the process cost and the productivity, the
temperature of the hydrogen diffusion process (ST52) may be 400 to
700.degree. C. In consideration of the hydrogen diffusion, on the
other hand, the process time may be 1 to 20 minutes. However, the
embodiments of the present invention are not limited thereto. The
temperature and the process time of the hydrogen diffusion process
(ST52) may be variously changed.
[0095] At this time, various heat source units which are capable of
uniformly maintaining the temperature of the hydrogen diffusion
process (ST52) may be used. For example, an ultraviolet lamp or a
resistance heating type heater may be used as a heat source unit.
However, the embodiments of the present invention are not limited
thereto. Various other heat source units may be used.
[0096] The temperature and the process time of the hydrogen
diffusion process (ST52) may be equal to, similar to, or overlap
with those of the firing operation (ST44) of the electrode forming
operation (ST40). In addition, heat source units used at the
hydrogen diffusion process (ST52) and the firing operation (ST44)
may be identical to or similar to each other. Consequently, the
hydrogen diffusion process (ST52) may be carried out simultaneously
with the firing operation (ST44). That is, as shown in FIG. 4E,
hydrogen diffusion may be achieved at the firing operation (ST44)
without additionally carrying out the hydrogen diffusion process
(ST52). Since the hydrogen diffusion process (ST52) is not
additionally carried out, the process may be simplified, and
process cost may be reduced. However, the embodiments of the
present invention are not limited thereto. For example, the
hydrogen diffusion process (ST52) may be carried out as a separate
operation after the firing operation (ST44).
[0097] Subsequently, as shown in FIG. 4F, the preliminary heat
treatment process (ST54) may be carried out to heat-treat the
semiconductor substrate 110 such that hydrogen diffused in the
semiconductor substrate 110 can react with a different material and
element in the semiconductor substrate 110 to generate a
combination including the hydrogen. In particular, the hydrogen may
be combined with the dopant of the semiconductor substrate 110. For
example, in an instance in which the semiconductor substrate 110
includes boron as a dopant, the B-H combination, in which hydrogen
and boron are combined with each other, may be generated.
[0098] At the preliminary heat treatment process (ST54), only heat
treatment is carried out without additional supply of light to the
semiconductor substrate with the result that the B-O combination is
not generated but the B-H combination is generated. As described
above, no light is supplied at the preliminary heat treatment
process (ST54). Even in an instance in which natural light is
supplied, the light has a light intensity of about 100 mW/cm.sup.2,
which is lower than that of the main processing process (ST56).
However, the embodiments of the present invention are not limited
thereto. The light intensity of the preliminary heat treatment
process (ST54) may be changed.
[0099] The temperature of the preliminary heat treatment process
(ST54) may be 100 to 300.degree. C., which is lower than that of
the hydrogen diffusion process (ST52). As previously described, the
preliminary heat treatment process (ST54) is carried out to
generate the B-H combination. If the temperature of the preliminary
heat treatment process (ST54) is less than 100.degree. C., no
energy for the B-H combination is provided with the result that the
B-H combination may not be satisfactorily generated. On the other
hand, if the temperature of the preliminary heat treatment process
(ST54) is greater than 300.degree. C., hydrogen combination is
superior to the B-H combination. As a result, hydrogen combination
may be generated, and the B-H combination may be decomposed. In an
instance in which the temperature of the preliminary heat treatment
process (ST54) is 100 to 300.degree. C., therefore, it is possible
to generate a large amount of the B-H combination through the
preliminary heat treatment process (ST54).
[0100] The process time of the preliminary heat treatment process
(ST54) may be 1 to 30 minutes. If the process time of the
preliminary heat treatment process (ST54) is less than 1 minute, it
may be difficult to sufficiently generate the desired B-H
combination. On the other hand, if the process time of the
preliminary heat treatment process (ST54) is greater than 30
minutes, the process time may be increased while the effects
obtained through preliminary heat treatment are not greatly
improved, thereby lowering productivity. However, the embodiments
of the present invention are not limited thereto. The process time
of the preliminary heat treatment process (ST54) may be
changed.
[0101] In an instance in which the B-H combination is generated
through the preliminary heat treatment process (ST54) as described
above, hydrogen exists near the surface of the semiconductor
substrate 110 or in the semiconductor substrate 110 in a state in
which the hydrogen is combined with boron (B), which is the dopant
of the semiconductor substrate 110. In particular, a large amount
of the B-H combination exists near the surface of the semiconductor
substrate 110. As a result, the diffusion distance and time of
hydrogen into the semiconductor substrate 110 may be reduced at the
main processing process (ST56), which will be subsequently carried
out.
[0102] Subsequently, as shown in FIG. 4G, the semiconductor
substrate 110 is heat-treated at a temperature higher than a room
temperature in a state in which light is supplied to the
semiconductor substrate 110 at the main processing process (ST56).
In an instance in which light is supplied to the semiconductor
substrate 110 at the main processing process (ST56), hydrogen may
not be in an H.sup.+ state, in which the hydrogen is stable, but
may be in an H.sup.0 or H-state, in which the hydrogen is unstable,
even during a short time by carrier injection from the light. Since
the hydrogen in the H.sup.0 or H.sup.- state is not stable, the
state of the hydrogen may be converted into the H.sup.+ state, in
which the hydrogen is stable, after a predetermined time.
[0103] Since the diffusion speed of the hydrogen in the H.sup.0 or
H.sup.- state generated by the light is much greater than that of
the hydrogen in the H.sup.+ state, the hydrogen may be rapidly
diffused in the semiconductor substrate 110. Consequently, the
hydrogen is uniformly distributed in the semiconductor substrate
110 with the result that the hydrogen functions to remove defects
in the semiconductor substrate 110 or to prevent or reduce
generation of undesired combination in the semiconductor substrate
110. For example, in an instance in which the hydrogen in the
H.sup.0 or H.sup.- state is diffused in the semiconductor substrate
110 and is then converted into the H.sup.+ state, in which the
hydrogen is stable, the B-H combination is generated, thereby
preventing or reducing generation of the B-O combination. That is,
the B-O combination, which may generated at the beginning of the
main processing process (ST56) due to light emitted to the
semiconductor substrate 110, may be decomposed to generate B-H
combination. After that, the B-H combination is generally
predominant in the semiconductor substrate 110 with the result that
the B-O combination is not generated. As described above, the B-H
combination, which is distributed at the surface of the
semiconductor substrate 110, may be uniformly distributed in the
semiconductor substrate 110, thereby preventing or reducing
generation of the undesired B-O combination in the semiconductor
substrate 110.
[0104] In this embodiment of the present invention, it is necessary
to provide the temperature, the light intensity, and the time based
on a predetermined relationship thereamong so as to convert the
hydrogen in the H.sup.+ state into the hydrogen in the H.sup.0 or
H.sup.- state, and to concretely define the relationship so as to
maximize the effects of the main processing process (ST56). That
is, if a predetermined light intensity and/or process time is not
provided although light is supplied to the semiconductor substrate
at a uniform temperature, hydrogen exists in the H.sup.+ state, in
which the hydrogen is stable. Only when the predetermined light
intensity and/or process time is provided, the state of the
hydrogen may be converted into the H.sup.0 or H.sup.- state.
[0105] At this time, the main processing process (ST56) may be
carried out to have a time-temperature graph as shown in FIG. 5.
FIG. 5 is a graph showing a relationship between time and
temperature of the main processing process of the post-processing
operation of the manufacturing method of the solar cell according
to the embodiment of the present invention.
[0106] That is, as shown in FIG. 5, the main processing process
(ST56) may include a main period (ST562) having a temperature (more
specifically, a peak temperature) for hydrogen conversion. The main
processing process (ST56) may further include a temperature rising
period (ST561) for increasing the temperature from the room
temperature to the temperature of the main period, the temperature
rising period (ST561) being carried out before the main period
(ST562), and a cooling period (ST563) for decreasing the
temperature to the room temperature, the cooling period (ST563)
being carried out after the main period (ST562). During the main
processing process (ST56), therefore, the occurrence of problems
caused due to abrupt change of temperature may be prevented, and a
desired reaction may be stably achieved. In this embodiment of the
present invention, the temperature of the main processing process
(ST56) means that of the main period (ST562), in which hydrogen
conversion is actually achieved. The light intensity of the main
processing process (ST56) may mean that of the main period (ST562),
and the process time of the main processing process (ST56) may mean
that of the main period (ST562), in which hydrogen conversion is
actually achieved.
[0107] It is necessary that the temperature of the main processing
process (ST56) be sufficient to convert hydrogen in an H.sup.+
state into hydrogen in an H.sup.0 or H.sup.- state and to decompose
the B-O combination which may be generated due to the supply of
light. For example, the temperature of the main processing process
(ST56) may be 100 to 800.degree. C. If the temperature of the main
processing process (ST56) is less than 100.degree. C., thermal
energy is less than energy necessary to decompose the B-O
combination with the result that the B-O combination generated due
to the supply of light may survive. On the other hand, if the
temperature of the main processing process (ST56) is greater than
800.degree. C., a process cost may be increased due to the high
temperature. However, the embodiments of the present invention are
not limited thereto.
[0108] First, a relationship between temperature and light
intensity of the main processing process (ST56) for converting
hydrogen in an H.sup.+ state into hydrogen in an H.sup.0 or H.sup.-
state will be described before a relationship between light
intensity and time of the main processing process (ST56) will be
described.
[0109] FIG. 6 is a graph showing a state of hydrogen based on a
relationship between temperature and light intensity at the
post-processing operation of the manufacturing method of the solar
cell according to the embodiment of the present invention.
[0110] A relationship between temperature and light intensity was
analyzed based on the fact that the minimum value I.sub.min of the
light intensity necessary for hydrogen conversion varies according
to temperature T of the main processing process (ST56). The results
were obtained as shown in FIG. 6. It can be seen from FIG. 6 that
the minimum value I.sub.min of the light intensity increases as the
temperature T of the main processing process (ST56) increases. In
this embodiment of the present invention, therefore, the minimum
value I.sub.min of the light intensity per temperature T is
represented by Equation 1.
I.sub.min=1750-31.8T+(0.16)T.sup.2 <Equation 1> [0111] where
the unit of T is .degree. C., and the unit of I.sub.min is
mW/cm.sup.2.
[0112] Only in an instance in which light intensity I of light
supplied simultaneously with heat treatment is equal to or greater
than the minimum value I.sub.min of the light intensity on the
assumption that the temperature T of the main processing process
(ST56) has a uniform value, therefore, the state of the hydrogen
may be converted into the H.sup.0 or H.sup.- state. For reference,
in an instance in which the temperature T is 100 to 800.degree. C.,
the minimum value I.sub.min of the light intensity may be
1.7.times.10.sup.2 mW/cm.sup.2 to 7.871.times.10.sup.4
mW/cm.sup.2.
[0113] Consequently, the light intensity I of the light to be
supplied based on the temperature T of the main processing process
(ST56) may satisfy the conditions of Equation 2.
1750-31.8T+(0.16)T.sup.2.ltoreq.I <Equation 2> [0114] where
the unit of T is .degree. C., and the unit of I is mW/cm.sup.2.
[0115] In an instance in which the light intensity I of the light
satisfying Equation 2 is provided at a specific temperature T of
the main processing process (ST56), therefore, hydrogen in the H+
state may be converted into hydrogen in the H.sup.0 or H.sup.-
state. At this time, it may be difficult to acquire a desired value
of the light intensity I of the light if the light intensity I is
excessively high. The light intensity I may have a value of
10.sup.5 mW/cm.sup.2 within a range of the temperature T of the
main processing process (ST56). Consequently, the light intensity I
to be provided based on the temperature T of the main processing
process (ST56) may satisfy the conditions of Equation 3.
1750-31.8T+(0.16)T.sup.2.ltoreq.I.ltoreq.10.sup.5 <Equation
3> [0116] where the unit of T is .degree. C., and the unit of I
is mW/cm.sup.2.
[0117] The above-described range of the temperature T and the
ranges of the temperature T and the light intensity I satisfying
Equation 3 approximately correspond to a region denoted by A in
FIG. 6.
[0118] A relationship between light intensity and process time was
analyzed based on the fact that the minimum value P.sub.min of the
process time necessary for hydrogen conversion (the minimum process
time necessary to convert hydrogen in the H+ state into hydrogen in
the H.sup.0 state) varies according to the light intensity I of the
main processing process (ST56). The results were obtained as shown
in FIG. 7. FIG. 7 is a graph showing a state of hydrogen based on a
relationship between light intensity and process time at the
post-processing operation of the manufacturing method of the solar
cell according to the embodiment of the present invention.
[0119] As shown in FIG. 7, the minimum value P.sub.min of the
process time decreases as the light intensity I increases. That is,
in an instance in which the light intensity I is high, a relatively
short process time is needed. On the other hand, in an instance in
which the light intensity I is low, a relatively long process time
is needed. In this embodiment of the present invention, the minimum
value P.sub.min of the process time based on the light intensity I
approximately corresponds to Equations 4 to 7. In an instance in
which the light intensity I is 5.times.10.sub.4 mW/cm.sup.2 or more
as represented by Equation 7, the minimum process time is greatly
decreased with the result that it is difficult to perform
arithmetic calculation. In addition, it is difficult to carry out
the process within the decreased process time. For this reason, it
is assumed that the minimum value P.sub.min of the process time is
uniform for the above-mentioned light intensity I.
1.7.times.10.sup.2.ltoreq.I<10.sup.3, and
P.sub.min=13000-(31.7)1+(0.02)(I).sup.2 <Equation 4>
10.sup.3.ltoreq.I<10.sup.4, and
P.sub.min=1030-(0.25)I+(1.5.times.10.sup.-5)(I).sup.2 <Equation
5>
10.sup.4.ltoreq.I.ltoreq.5.times.10.sup.4, and
P.sub.min=35.5-(0.0012)I+(10.sup.-8)(I).sup.2 <Equation
6>
5.times.10.sup.4.ltoreq.I.ltoreq.10.sup.5, and P.sub.min=0.5
<Equation 7> [0120] where the unit of I is mW/cm.sup.2, and
the unit of P.sub.min is sec.
[0121] In an instance in which the process time P of the main
processing process (ST56) is equal to or greater than the minimum
value P.sub.min of the process time when the light intensity I of
the main processing process (ST56) has a uniform value, therefore,
the state of the hydrogen may be effectively converted into the
H.sup.0 or H.sup.- state. Consequently, the process time P of the
main processing process (ST56) based on the light intensity I may
satisfy any one of Equations 8 to 11.
1.7.times.10.sup.2.ltoreq.I<10.sup.3, and
13000-(31.7)I+(0.02)(I).sup.2.ltoreq.P <Equation 8>
10.sup.3.ltoreq.I<10.sup.4, and
1030-(0.25)I+(1.5.times.10.sup.5)(I).sup.2.ltoreq.P <Equation
9>
10.sup.4.ltoreq.I.ltoreq.5.times.10.sup.4, and
35.5-(0.0012)I+(10.sup.-8)(I).sup.2.ltoreq.P <Equation
10>
5.times.10.sup.4.ltoreq.I.ltoreq.10.sup.5, and 0.5.ltoreq.P
<Equation 11> [0122] where the unit of I.sub.min is
mW/cm.sup.2, and the unit of P is sec.
[0123] In an instance in which the process is carried out with the
light intensity I of the main processing process (ST56) during the
process time P satisfying Equations 8 to 11, therefore, it is
possible to convert the hydrogen in the H.sup.+ state into the
hydrogen in the H.sup.0 or H.sup.- state. At this time,
productivity may be lowered if the process time P is excessively
long. For this reason, the process time P of the main processing
process (ST56) may have a value of 10,000 sec or less.
Consequently, the process time P of the main processing process
(ST56) based on the light intensity I may satisfy any one of
Equations 12 to 15.
1.7.times.10.sup.2.ltoreq.I<10.sup.3, and
13000-(31.7)I+(0.02)(I).sup.2.ltoreq.P.ltoreq.10000 <Equation
12>
10.sup.3.ltoreq.I<10.sup.4, and
1030-(0.25)I+(1.5.times.10.sup.5)(I).sup.2.ltoreq.P.ltoreq.10000
<Equation 13>
10.sup.4.ltoreq.I<5.times.10.sup.4, and
35.5-(0.0012)I+(10.sup.-8)(I).sup.2.ltoreq.P.ltoreq.10000
<Equation 14>
5.times.10.sup.4.ltoreq.I.ltoreq.10.sup.5, and
0.5.ltoreq.P.ltoreq.10000 <Equation 15>
[0124] The ranges of the light intensity I and the process time P
satisfying Equations 12 to 15 approximately correspond to a region
denoted by B in FIG. 7.
[0125] As described above, in this embodiment of the present
invention, the ranges of the temperature T and the light intensity
I of the main processing process (ST56) are defined to achieve
hydrogen conversion. In addition, the range of the process time P
is also defined to effectively achieve hydrogen conversion.
Consequently, it is possible to effectively prevent lowering in
characteristics of the semiconductor substrate 110 which may be
caused in the semiconductor substrate 110 when light is emitted to
the semiconductor substrate 110.
[0126] As described above, in this embodiment of the present
invention, the post-processing operation (ST50) includes the main
processing process (ST56) which is carried out at predetermined
ranges of the temperature T and the light intensity I, thereby
preventing undesired combination (e.g. the B-O combination), which
may lower the characteristics of the solar cell 100, from being
generated in the semiconductor substrate 110 and, instead,
generating combination including hydrogen (e.g. the B-H
combination) in the semiconductor substrate 110. Consequently, it
is possible to prevent lowering in characteristics of the solar
cell 100 due to undesired combination. At this time, the process
time P of the main processing process (ST56) may be defined to be
within a predetermined range to more effectively prevent generation
of undesired combination.
[0127] In addition, the hydrogen diffusion process (ST52) for
diffusing hydrogen and/or the preliminary heat treatment process
(ST54) for generating combination including hydrogen (e.g. the B-H
combination) may be further carried out before the main processing
process (ST56) to further improve the effects of the
post-processing operation (ST50).
[0128] In the above description, the base region 10 of the
semiconductor substrate 110 includes boron (B). Alternatively, the
first conductive region 20 may include boron (B). Even in an
instance in which the semiconductor substrate 110 does not include
boron (B), combination including hydrogen (e.g. the B-H
combination) may be generated in the semiconductor substrate 110,
thereby improving the characteristics of the solar cell 100.
[0129] In addition, the manufacturing method of the solar cell 100
according to the embodiment of the present invention may be applied
to manufacture of a solar cell 100 including a semiconductor
substrate 110 having a crystalline structure. Such a solar cell 100
will hereinafter be described in detail with reference to FIGS. 8
and 9. Parts identical to or similar to those of the solar cell
according to the previous embodiment of the present invention may
be equally applied to the following embodiments of the present
invention, and therefore a detailed description thereof will be
omitted.
[0130] FIG. 8 is a sectional view showing another example of the
solar cell manufactured using the manufacturing method of the solar
cell according to the embodiment of the present invention.
[0131] Referring to FIG. 8, the solar cell according to this
embodiment is configured such that a second passivation film 32 is
formed on a back surface of a semiconductor substrate 110, and a
second electrode 44 is connected to a second conductive region 30
through the second passivation film 32 (i.e. via an opening
104).
[0132] The second passivation film 32 may be substantially formed
throughout the back surface of the semiconductor substrate 110
excluding the opening 104 corresponding to the second electrode 44.
The second passivation film 32 is formed at the second conductive
region 30 in contact to passivate defects existing on the surface
of the second conductive region 30 or in a bulk of the second
conductive region 30. The passivation of defects may remove a
recombination site of minority carriers, which may increase an
open-circuit voltage Voc of the solar cell 100.
[0133] The second passivation film 32 may be formed of various
materials. For example, the second passivation film 32 may be
formed of a dielectric material including hydrogen. In an instance
in which the second passivation film 32 includes hydrogen as
described above, the second passivation film 32 may function to
passivate the surface of the semiconductor substrate 110 and, in
addition, function as a hydrogen source for supplying hydrogen to
the surface of the semiconductor substrate 110 or into a bulk of
the semiconductor substrate 110 at a post-processing operation
(ST50) (see FIG. 3).
[0134] For example, the second passivation film 32 may include
10.sup.20 to 10.sup.22 ea/cm.sup.3 of hydrogen. The hydrogen
content of the second passivation film 32 is limited to a range in
which the second passivation film 32 can effectively function as
the hydrogen source when the second passivation film 32 passivates
the surface of the semiconductor substrate 110 and at the
post-processing operation (ST50). However, the embodiments of the
present invention are not limited thereto. The hydrogen content of
the second passivation film 32 may be variously changed.
[0135] For example, the second passivation film 32 may include a
silicon nitride (SiNx:H) including hydrogen, a silicon oxide
nitride (SiOxNy:H) including hydrogen, a silicon carbide (SiCx:H)
including hydrogen, or a silicon oxide (SiOx:H) including hydrogen.
However, the embodiments of the present invention are not limited
thereto. The second passivation film 32 may include various other
materials.
[0136] As described above, in this embodiment of the present
invention, both the first passivation film 22 formed at the front
surface of the semiconductor substrate 110 and the second
passivation film 32 formed at the back surface of the semiconductor
substrate 110 function as a hydrogen source at the post-processing
operation (ST50), thereby doubling the effects of the
post-processing operation (ST50).
[0137] However, the embodiments of the present invention are not
limited thereto. The second passivation film 32 may include various
materials. Alternatively, only the second passivation film 32 may
include hydrogen, and the first passivation film 22 may not include
hydrogen. In addition, various films may be formed on the back
surface of the semiconductor substrate 110 in addition to the
second passivation film 32. Various other modifications are also
possible.
[0138] The second electrode 44 is electrically connected to the
second conductive region 30 via the opening 104 formed through the
second passivation film 32. The second electrode 44 may be formed
of various materials such that the second electrode 44 can have
various shapes.
[0139] For example, the second electrode 44 may have a planar shape
identical to or similar to that of the first electrode 42
previously described with reference to FIGS. 1 and 2. Consequently,
the semiconductor substrate 110 has a bi-facial structure in which
light is incident upon both the front surface and the back surface
of the semiconductor substrate 110. As a result, the quantity of
light used for photoelectric conversion is increased, thereby
improving the efficiency of the solar cell 100. The width and pitch
of finger electrodes and bus bar electrodes of the second electrode
44 may be equal to or different from those of the finger electrodes
42a and bus bar electrodes 42b of the first electrode 42.
[0140] In another example, the second electrode 44 may be formed
throughout the second passivation film 32 and may be connected to
the back surface of the semiconductor substrate 110 or the second
conductive region 30 in point contact via the opening 104. In this
case, the back surface of the semiconductor substrate 10 is not
textured. That is, no rugged shape is formed at the back surface of
the semiconductor substrate 10. Consequently, light may be
effectively reflected by the second electrode 44 formed throughout
the second passivation film 32. Various other modifications are
also possible.
[0141] In this embodiment of the present invention, not only the
first conductive region 20 has a selective structure but also the
second conductive region 30 has a selective structure.
[0142] That is, the first conductive region 20 may include a first
part 20a formed adjacent to (e.g. in contact with) the first
electrode 42 and a second part 20b formed at a region where the
first electrode 42 is not positioned. The first part 20a has a
relatively high dopant concentration and a relatively large
junction depth. Consequently, the first part 20a exhibits
relatively low resistance. On the other hand, the second part 20b
has a lower dopant concentration and a smaller junction depth than
the first part 20a. Consequently, the second part 20b exhibits
higher resistance than the first part 20a.
[0143] As described above, in this embodiment of the present
invention, the first part 20a having relatively low resistance may
be formed at a part adjacent to the first electrode 42 to reduce
contact resistance with the first electrode 42. In addition, the
second part 20b having relatively high resistance may be formed at
a part corresponding to a light receiving region, upon which light
is incident, between the first electrodes 42 to constitute a
shallow emitter. Consequently, it is possible to improve current
density of the solar cell 100. That is, in this embodiment of the
present invention, the first conductive region 20 may have a
selective structure, thereby maximizing the efficiency of the solar
cell 100.
[0144] In addition, the second conductive region 30 may include a
first part 30a formed adjacent to (e.g. in contact with) the second
electrode 44 and a second part 30b formed at a region where the
second electrode 44 is not positioned. The first part 30a has a
relatively high dopant concentration and a relatively large
junction depth. Consequently, the first part 30a exhibits
relatively low resistance. On the other hand, the second part 30b
has a lower dopant concentration and a smaller junction depth than
the first part 30a. Consequently, the second part 30b exhibits
higher resistance than the first part 30a.
[0145] As described above, in this embodiment of the present
invention, the second part 30a having relatively low resistance may
be formed at a part adjacent to the second electrode 44 to reduce
contact resistance with the second electrode 44. In addition, the
second part 30b having relatively high resistance may be formed at
a part corresponding to a region, upon which light is incident,
between the second electrodes 44 to prevent recombination between
holes and electrons. Consequently, it is possible to improve
current density of the solar cell 100. That is, in this embodiment
of the present invention, the second conductive region 30 may have
a selective structure, thereby maximizing the efficiency of the
solar cell 100.
[0146] However, the embodiments of the present invention are not
limited thereto. The first conductive region 20 and/or the second
conductive region 30 may have a homogeneous structure as shown in
FIG. 1. Alternatively, the second conductive region 30 may have a
local structure which does not include the second part 30b but
includes only the second part 30a.
[0147] FIG. 9 is a sectional view showing a further example of the
solar cell manufactured using the manufacturing method of the solar
cell according to the embodiment of the present invention.
[0148] Referring to FIG. 9, the solar cell according to this
embodiment is configured such that conductive regions 20 and 30 are
formed on a semiconductor substrate 110 separately from the
semiconductor substrate 110 and have a crystalline structure
different from that of the semiconductor substrate 110.
Consequently, the semiconductor substrate 110 may not include the
conductive regions 20 and 30 but include only a base region 10.
[0149] More specifically, a first tunneling layer 52 may be formed
on the front surface of the semiconductor substrate 110, and the
first conductive region 20 may be positioned on the first tunneling
layer 52.
[0150] The first tunneling layer 52 may improve the passivation
characteristics of the front surface of the semiconductor substrate
110, and generated carriers may be smoothly transmitted due to a
tunneling effect. The first tunneling layer 52 may include various
materials, such as a nitride, a semiconductor, and a conductive
polymer, which are capable of tunneling the carriers. For example,
the first tunneling layer 52 may include a silicon oxide, a silicon
nitride, a silicon oxide nitride, an intrinsic amorphous
semiconductor (e.g. intrinsic amorphous silicon), and an intrinsic
polycrystalline semiconductor (e.g. intrinsic polycrystalline
silicon). In an instance in which the first tunneling layer 52
includes an intrinsic amorphous semiconductor, the semiconductor
substrate 110 may be easily manufactured using a simple
manufacturing process since the first tunneling layer 52 exhibits
characteristics similar to those of the semiconductor substrate
110, thereby more effectively improving the surface characteristics
of the semiconductor substrate 110. Consequently, it is possible to
prevent surface recombination which may be generated at the surface
of the semiconductor substrate 110, thereby improving the
passivation characteristics of the semiconductor substrate 110.
[0151] The first tunneling layer 52 may be formed throughout the
front surface of the semiconductor substrate 110. Consequently, the
entirety of the front surface of the semiconductor substrate 110
may be passivated, and the first tunneling layer 52 may be easily
formed without additional patterning.
[0152] In order to sufficiently achieve the tunneling effect, the
first tunneling layer 52 may have a thickness of 5 nm or less.
Specifically, the first tunneling layer 52 may have a thickness of
0.5 to 5 nm (e.g. 1 to 4 nm). If the thickness of the first
tunneling layer 52 is greater than 5 nm, tunneling may not be
satisfactorily achieved with the result that the solar cell 100 may
not be operated. On the other hand, if the thickness of the first
tunneling layer 52 is less than 0.5 nm, it may be difficult to form
the first tunneling layer 52 such that the first tunneling layer 52
has desired quality. In order to further improve the tunneling
effect, the first tunneling layer 52 may have a thickness of 1 to 4
nm. However, the embodiments of the present invention are not
limited thereto. The thickness of the first tunneling layer 52 may
be variously changed.
[0153] The first conductive region 20 of a first conductive type,
which is opposite to that of the semiconductor substrate 110 or the
base region 10, may be formed on the first tunneling layer 52. The
first conductive region 20 may form a pn junction (e.g. a pn tunnel
junction) together with the semiconductor substrate 110 or the base
region 10 to constitute an emitter region for generating carriers
through photoelectric conversion.
[0154] The first conductive region 20, which is formed on the first
tunneling layer 52 separately from the semiconductor substrate 110,
may have a crystalline structure different from that of the
semiconductor substrate 110. That is, the first conductive region
20 may include an amorphous semiconductor (e.g. amorphous silicon),
a micro-crystalline semiconductor (e.g. micro-crystalline silicon),
or a polycrystalline semiconductor (e.g. polycrystalline silicon),
which may be easily formed on the first conductive region 20 using
various methods, such as deposition. Consequently, the first
conductive region 20 may be formed of an amorphous semiconductor
(e.g. amorphous silicon), a micro-crystalline semiconductor (e.g.
micro-crystalline silicon), or a polycrystalline semiconductor
(e.g. polycrystalline silicon) having a first conductive dopant.
The first conductive dopant may be included in a semiconductor
layer when the semiconductor layer is formed for forming the first
conductive region 20 or may be included in the semiconductor layer
using various doping methods, such as thermal diffusion, ion
injection, and laser doping, after the semiconductor layer is
formed.
[0155] Similarly, a second tunneling layer 54 may be formed on the
back surface of the semiconductor substrate 110, and the second
conductive region 30 may be positioned on the second tunneling
layer 54. The material and thickness of the second tunneling layer
54 are similar to those of the first tunneling layer 52, and
therefore a detailed description thereof will be omitted. The
material and crystalline structure of the second conductive region
30 are identical to or similar to those of the first conductive
region 20 except that the second conductive region 30 has a first
conductive dopant, and therefore a detailed description thereof
will be omitted.
[0156] In this embodiment of the present invention, a first
transparent conduction layer 421 may be formed between a first
electrode 42 and the first conductive region 20, and a second
transparent conduction layer 441 may be formed between a second
electrode 44 and the second conductive region 30.
[0157] In an instance in which the tunneling layers 52 and 54 are
formed on the front surface of the semiconductor substrate 110, and
then the conductive regions 20 and 30 are formed on the tunneling
layers 52 and 54 as described above, it is possible to greatly
improve the passivation characteristics of the semiconductor
substrate 110. In addition, it is possible to reduce the thickness
of the semiconductor substrate 110, which is expensive, thereby
reducing manufacturing cost. Furthermore, it is possible to
manufacture the solar cell 100 at a low process temperature. Since
the crystallinity of the conductive regions 20 and 30 is relatively
low, however, carrier mobility may be relatively low. In this
embodiment of the present invention, therefore, the first
transparent conduction layer 421 is formed between the first
electrode 42 and the first conductive region 20, and the second
transparent conduction layer 441 is formed between the second
electrode 44 and the second conductive region 30, thereby reducing
resistance when the carriers move in a horizontal direction.
[0158] The first transparent conduction layer 421 may be formed
throughout the first conductive region 20, which may mean that not
only the first transparent conduction layer 421 may cover the
entirety of the first conductive region 20 without an empty space
or an empty region but also the first transparent conduction layer
421 may not be formed at a portion of the first conductive region
20. In an instance in which the first transparent conduction layer
421 is formed throughout the first conductive region 20, the
carriers may easily reach the first electrode 42 via the first
transparent conduction layer 421, thereby reducing resistance in
the horizontal direction.
[0159] Since the first transparent conduction layer 421 is formed
throughout the first conductive region 20, the first transparent
conduction layer 421 may be formed of a light transmissive
material. That is, the first transparent conduction layer 421 may
be formed of a transparent conductive material for easily moving
the carriers while transmitting light. Consequently, transmission
of light is not blocked even in an instance in which the first
transparent conduction layer 421 is formed throughout the first
conductive region 20. For example, the first transparent conduction
layer 421 may include an indium tin oxide (ITO) or a carbon nano
tube (CNT). However, the embodiments of the present invention are
not limited thereto. The first transparent conduction layer 421 may
include various other materials.
[0160] The material and shape of the second transparent conduction
layer 441 may be similar to those of the first transparent
conduction layer 421, and therefore a detailed description thereof
will be omitted.
[0161] On the first transparent conduction layer 421 may be
positioned an anti-reflection film 24 having an opening 102, via
which the first electrode 42 is connected to the first transparent
conduction layer 421. The anti-reflection film 24 may include a
dielectric material having a lower refractive index than the first
transparent conduction layer 421. In an instance in which the
anti-reflection film 24 having a lower refractive index than the
first transparent conduction layer 421 is formed on the first
transparent conduction layer 421 as described above, the first
transparent conduction layer 421 and the anti-reflection film 24
may function as a double anti-reflection film. In addition, in an
instance in which the anti-reflection film 24 includes a dielectric
material, the anti-reflection film 24 may be used as a mask layer
when the first electrode 42 is formed so as to have a pattern. In
addition, the anti-reflection film 24 may also function as a
protective layer for protecting the first transparent conduction
layer 421.
[0162] In this embodiment of the present invention, the
anti-reflection film 24 includes hydrogen. In this case, the
anti-reflection film 24 may function as a hydrogen source at the
post-processing operation (ST50). The material of the
anti-reflection film 24 may be identical to or similar to that of
the first passivation film 22 or the anti-reflection film 24
previously described with reference to FIG. 1, and the hydrogen
content of the anti-reflection film 24 may be equal to or similar
to that of the first passivation film 22 previously described with
reference to FIG. 1.
[0163] In the above description and the figures, the
anti-reflection film 24 positioned on the front surface of the
semiconductor substrate 110 is illustrated as including hydrogen.
However, the embodiments of the present invention are not limited
thereto. For example, a dielectric film (e.g. the second
passivation film 32 shown in FIG. 1 or an additional
anti-reflection film) may be further positioned on the back surface
of the semiconductor substrate 110, and the dielectric film
positioned on the back surface of the semiconductor substrate 110
may include hydrogen.
[0164] The semiconductor substrate 110 including the base region 10
may be of a p-type having boron. In this case, it is possible to
greatly improve the characteristics of the solar cell 100 due to
the effects obtained by the post-processing operation (ST50).
However, the embodiments of the present invention are not limited
thereto. For example, the semiconductor substrate 110 may have a
different dopant, or may be of an n-type. Even in this case, it is
possible to achieve the effects obtained by the post-processing
operation (ST50).
[0165] Hereinafter, the embodiments of the present invention will
be described in more detail with reference to an experimental
example. The experimental example is provided merely to describe
the embodiments of the present invention in more detail and thus
does not restrict the embodiments of the present invention.
Experimental Example
[0166] A solar cell having a structure as shown in FIG. 1 was
manufactured using a semiconductor substrate including a p-type
base region having boron. At this time, a passivation film included
about 10.sup.20 ea/cm.sup.3 of hydrogen, and a peak temperature was
700.degree. C. and process time was 10 sec at an electrode firing
operation. At the electrode firing operation, a hydrogen diffusion
process was simultaneously carried out.
[0167] Subsequently, a preliminary heat treatment process was
carried out at a temperature of about 200.degree. C. for 5 minutes.
A main processing process was carried out for a plurality of solar
cells while changing the temperature, the light intensity, and the
time, within a temperature range of 200 to 700.degree. C. and a
light intensity range of 10.sup.4 mW/cm.sup.2 to 8.times.10.sup.4
mW/cm.sup.2 to measure an output loss of each solar cell. Based on
the measured output loss values of the solar cells, temperature and
light intensity exhibiting the same output losses were mapped as
shown in FIG. 10, and light intensity and time exhibiting the same
output losses were mapped as shown in FIG. 11.
[0168] In FIG. 10, dotted lines L1, L2, L3, L4, and L5
interconnecting points indicating the same output losses are shown.
The output loss is reduced in order of L5, L4, L3, L2, and L1. In
addition, the minimum values I.sub.min of the light intensity
calculated according to Equation 1 at temperatures of 300.degree.
C., 400.degree. C., 500.degree. C., 600.degree. C., and 700.degree.
C. are shown as quadrangular points, and a line interconnecting the
quadrangular points is shown as a solid line. In FIG. 11, dotted
lines L11, L12, L13 interconnecting points indicating the same
output losses are shown. The output loss is reduced in order of
L13, L12, and L11.
[0169] Referring to FIG. 10, it can be seen that it is possible to
reduce the output loss of the solar cell only when light having a
predetermined light intensity or more is supplied at a uniform
temperature and that it is necessary to also increase the light
intensity as the temperature increases in order to reduce the
output loss of the solar cell. It can also be seen that in an
instance in which the light intensity is greater than that shown as
the quadrangular point at each temperature, the output loss is
reduced. Consequently, it can be seen that in an instance in which
the main processing process is carried out at the temperature and
the light intensity according to equations defined by the
embodiments of the present invention, it is possible to actually
reduce the output loss of the solar cell.
[0170] Referring to FIG. 11, it can be seen that in an instance in
which the light intensity is high, it is possible to greatly reduce
the output loss even when the main processing process is carried
out during a short process time. This coincides with the time-light
intensity equations defined in the embodiments of the present
invention.
[0171] At least the main processing process (ST56) (see FIG. 3) of
the post-processing operation (ST50) (see FIG. 3) of the
manufacturing method of the solar cell 100 may be carried out by a
post-processing apparatus 200 of a solar cell according to an
embodiment of the present invention (hereinafter, simply referred
to as a "post-processing apparatus"). Hereinafter, a
post-processing apparatus 200 according to an embodiment of the
present invention will be described in detail.
[0172] FIG. 12 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to an
embodiment of the present invention.
[0173] Referring to FIG. 12, the post-processing apparatus 200 of
the solar cell according to this embodiment basically includes a
main section 220, having a light source unit 222 and a first heat
source unit 224, for carrying out the main period (ST562) (see FIG.
5) for the semiconductor substrate 110 (see FIG. 1) or the solar
cell 100 including the semiconductor substrate 110. A temperature
rising section 210 for carrying out the temperature rising period
(ST561) (see FIG. 5) may be positioned before the main section 220,
and a cooling section 230 for carrying out the cooling period
(ST563) (see FIG. 5) may be positioned after the main section
220.
[0174] In this embodiment of the present invention, the temperature
rising section 210, the main section 220, and the cooling section
230 are sequentially arranged. In a state in which the solar cell
100 is placed on a conveying unit, such as a conveyer belt 202, the
conveyer belt 202 may move such that the solar cell 100 placed on
the conveyer belt 202 sequentially passes through the temperature
rising section 210, the main section 220, and the cooling section
230. Consequently, the process of the temperature rising period
(ST561) is carried out for the solar cell 100 in the temperature
rising section 210. Subsequently, the process of the main period
(ST562) is carried out for the solar cell 100 in the main section
220. Subsequently, the process of the cooling period (ST563) is
carried out for the solar cell 100 in the cooling section 230.
[0175] The conveyer belt 202 may have various structures and
mechanisms in which the solar cell 100 can be stably placed on the
conveyer belt 202. For example, the conveyer belt 202 may have a
mesh structure in which light and heat can be more effectively
provided to the solar cell 100, and the solar cell 100 can be
maintained at a uniform temperature. In an example, a worktable 204
shown in FIG. 14 may extend to constitute the conveyer belt 202.
The shape of the worktable 204 will hereinafter be described in
more detail with reference to FIG. 14. However, the embodiments of
the present invention are not limited thereto. The conveyer belt
202 may have various structures.
[0176] For example, the conveyer belt 202 may have a moving speed
of 50 mm/min to 1000 mm/min. At this moving speed, the solar cell
100 can be moved without impact or damage to the solar cell 100,
and the process of the temperature rising period, the process of
the main period (ST562), and the process of the cooling period
(ST563) can be carried out for the solar cell 100 during desired
time.
[0177] However, the embodiments of the present invention are not
limited thereto. The moving speed of the conveyer belt 202 may be
variously changed. For example, in an instance in which an
additional heat source unit 216 is positioned in the temperature
rising section 210 to accelerate the increase of temperature, the
moving speed of the conveyer belt 202 may be increased.
Alternatively, in an instance in which the size of the temperature
rising section 210, the main section 220, or the cooling section
230 is large and thus the process can be carried out during a
sufficient time even when the moving speed of the conveyer belt 202
is high, the moving speed of the conveyer belt 202 may be
increased. On the other hand, in an instance in which the size of
the temperature rising section 210, the main section 220, or the
cooling section 230 is small, the moving speed of the conveyer belt
202 may be decreased such that the process can be carried out
during a sufficient time. In addition, the moving speeds of the
conveyer belt 202 in the temperature rising section 210, the main
section 220, and the cooling section 230 may be different from each
other. Various other modifications are also possible.
[0178] In an instance in which the process is carried out in the
temperature rising section 210, the main section 220, and the
cooling section 230 based on an in-line process using the conveyer
belt 202 as described above, it is possible to increase output due
to the continuous process. In this embodiment of the present
invention, the conveyer belt 202 is used as an example of the
conveying means for the in-line process. However, the embodiments
of the present invention are not limited thereto. Various
structures and mechanisms that are capable of carrying out the
in-line process may be used.
[0179] As described above, in this embodiment of the present
invention, the in-line process using the conveyer belt is carried
out. However, the embodiments of the present invention are not
limited thereto. For example, the post-processing apparatus 200 may
have a batch structure in which the process can be carried out in a
state in which the solar cell 100 is not moved, i.e. the solar cell
100 is fixed at a specific position, which will be described in
detail with reference to FIGS. 13 to 16.
[0180] Hereinafter, the main section 220 in which the basic
process, i.e. the main period (ST562), of the main processing
process (ST56) is carried out will be described in detail, and then
the temperature rising section 210 and the cooling section 230 will
be described in detail.
[0181] As previously described, in the main period (ST562), the
solar cell 100 (or the semiconductor substrate 110) is heat-treated
at a uniform temperature in a state in which light having a uniform
light intensity is supplied to the solar cell 100. To this end, the
main section 220 includes a light source unit 222 for supplying a
light having a uniform light intensity to the solar cell 100 and a
heat source unit (or a first heat source unit) 224 for heating the
solar cell 100 at a uniform temperature.
[0182] The light source unit 222 functions to supply light having a
uniform light intensity to the solar cell 100. As previously
described, light having a light intensity of 1.7.times.10.sup.2
mW/cm.sup.2 to 10.sup.5 mW/cm.sup.2 is needed in the main period
(ST562). Consequently, the light source unit 222 may supply light
having a light intensity of 1.7.times.10.sup.2 mW/cm.sup.2 to
10.sup.5 mW/cm.sup.2.
[0183] At this time, various methods of adjusting the light
intensity of the light source unit 222 may be used to supply light
having light intensity necessary for the main period (ST562). That
is, it is possible to adjust the number, kind, and output of light
sources 222a and 222b constituting the light source unit 222 or to
change the distance between the light sources 222a and 222b and the
solar cell 100.
[0184] In this embodiment of the present invention, the light
source unit 222, including the light sources 222a and 222b, may
supply a sufficient amount of light to the solar cell 100. However,
the embodiments of the present invention are not limited thereto.
In an instance in which light having a high light intensity is not
needed, only one of the light sources 222a and 222b may be
provided.
[0185] Furthermore, in this embodiment of the present invention,
each of the light sources 222a and 222b may be constituted by a
plasma lighting system (PLS) for supplying light based on plasma
emission. In the plasma lighting system, a bulb is filled with a
specific gas, an electromagnetic wave, such as a microwave
generated by a magnetron, or an incident beam is applied to the
bulb to ionize the gas in the bulb (i.e. to generate plasma), and
light is emitted from the plasma.
[0186] The plasma lighting system does not use an electrode, a
filament, and mercury, which are components of a conventional
lighting system. Consequently, the plasma lighting system is
environmentally friendly and exhibits a semi-permanent lifetime. In
addition, the plasma lighting system has a very excellent luminous
flux maintenance factor. For this reason, the change in quantity of
light is small even when the plasma lighting system is used based
on super luminous flux for a long time. Furthermore, the plasma
lighting system exhibits high thermal resistance and thus high
thermal stability. Consequently, the plasma lighting system may be
used in a space in which the heat source unit 224 is positioned. In
addition, the plasma lighting system may emit light having a
sufficient light intensity. For reference, another light source,
such as a light emitting diode, exhibits low thermal resistance
with the result that it is difficult to use the light emitting
diode together with the heat source unit 224, and the light
emitting diode emits only light having low light intensity. In
addition, the plasma lighting system may emit almost uniform
continuous light over all wavelengths of visible light.
Consequently, the plasma lighting system may supply light similar
to solar light. In this embodiment of the present invention, a
compound of indium (In) and bromine (Br) may be used as the gas
filling the bulb of the plasma lighting system. In this case, the
plasma lighting system may have a spectrum more similar to that of
solar light than in an instance in which sulfur is used as the gas
filling the bulb of the plasma lighting system. In an instance in
which light having a spectrum similar to that of the solar light is
supplied, it is possible to carry out the main processing process
(ST56) under conditions similar to those of the solar light,
thereby effectively preventing output loss, which may be caused due
to the solar light, through the main processing process (ST56).
[0187] In this embodiment of the present invention, a cover
substrate 223 positioned on the front surface (i.e. light emitting
surface) of each of the light sources 222a and 222b may include a
base substrate 223a and a plurality of layers 223b, positioned on
the base substrate 223a, including materials having different
refractive indices.
[0188] The base substrate 223a may be formed of a light
transmissive material having a sufficient strength to protect the
light sources 222a and 222b. For example, the base substrate 223a
may be formed of glass.
[0189] The layers 223b, which are configured by stacking layers
having different refractive indices, may block undesired light. For
example, the layers 223b may be formed of oxide materials having
different refractive indices. In this case, the layers 223b may
block light having a wavelength of less than 600 nm (specifically,
400 nm to 600 nm) and greater than 1000 nm. Various materials and
stack structures of the layers 223b may be applied so long as the
layers 223b can block light having a wavelength of less than 600 nm
(specifically, 400 nm to 600 nm) and greater than 1000 nm.
[0190] In the figure, the layers 223b are illustrated as being
positioned at the outer surface of the base substrate 223a.
However, the embodiments of the present invention are not limited
thereto. For example, the layers 223b may be positioned at the
inner surface of the base substrate 223a. Alternatively, the layers
223b may be positioned at both the inner surface and the outer
surface of the base substrate 223a.
[0191] In this embodiment of the present invention, the outer
surface of the cover substrate 223 (i.e. the surface of the cover
substrate 223 opposite to the solar cell 100) may be flat. As a
result, light may be uniformly supplied to the solar cell 100
through the cover substrate 223 such that the light can be
uniformly distributed over the solar cell 100. On the other hand, a
light source of a general plasma lighting system is used outside.
For this reason, a concave cover substrate is generally used to
improve straightness of light.
[0192] Consequently, the light emitted from the light sources 222a
and 222b to the solar cell 100 may have a wavelength of 600 nm to
1000 nm. In an instance in which an ultraviolet light portion of
the light emitted from the light sources 222a and 222b is blocked
as described above, it is possible to minimize lowering in
passivation characteristics of the passivation film 22 (see FIG. 1)
and/or 32 (see FIG. 8) which may be caused when ultraviolet light
is emitted to the solar cell 100. In addition, in an instance in
which an infrared light portion of the light emitted from the light
sources 222a and 222b is blocked, it is possible to minimize an
amount of heat supplied from the light sources 222a and 222b to the
solar cell 100. On the other hand, in an instance in which the
light sources 222a and 222b emit infrared light to the solar cell
100, the light source unit 222 as well as the heat source unit 224
may supply heat to the solar cell 100 with the result that it may
be difficult to maintain the solar cell 100 at a desired
temperature. In this embodiment of the present invention,
therefore, it is possible to maximally prevent the light source
unit 222 from affecting the temperature of the solar cell 100 such
that the temperature of the solar cell 100 can be independently
controlled by the heat source unit 224.
[0193] In this embodiment of the present invention, the cover
substrate 223 constituting each of the light sources 222a and 222b
may block a portion of the light such that only an efficient
portion of the light for the main period (ST562) can be supplied to
the solar cell 100. Consequently, it is possible to maximize the
effects of the main period (ST562) through such a simple structure.
However, the embodiments of the present invention are not limited
thereto. For example, a filter may be disposed between the light
sources 222a and 222b and the solar cell 100 for blocking a portion
of the light.
[0194] In this embodiment of the present invention, the light
sources 222a and 222b, each of which includes the plasma lighting
system, are used. Consequently, it is possible to stably supply
light having a desired light intensity to the solar cell 100.
However, the embodiments of the present invention are not limited
thereto. For example, one of the light sources 222a and 222b in the
main section 220 may be constituted by the plasma lighting system,
and the other of the light sources 222a and 222b may be constituted
by another type of light source. Various other modifications are
also possible.
[0195] In the main section 220, the heat source unit 224 may supply
an appropriate amount of heat to the solar cell 100 such that the
solar cell 100 has a desired temperature. Various mechanisms,
structures, and shapes of the heat source unit 224 may be
applied.
[0196] In this embodiment of the present invention, the heat source
unit 224, including a plurality of heat sources 224a and 224b, may
supply a sufficient amount of heat to the solar cell 100. However,
the embodiments of the present invention are not limited thereto.
Only one of the heat sources 224a and 224b may be provided in
consideration of the structure, mechanism, and shape of the heat
sources 224a and 224b and heat treatment temperature of the solar
cell 100.
[0197] For example, each of the heat sources 224a and 224b
constituting the heat source unit 224 may be an ultraviolet lamp.
In an example, each of the heat sources 224a and 224b may be a
halogen lamp. In another example, a coil heater may be used as each
of the heat sources 224a and 224b. In an instance in which an
ultraviolet lamp, such as a halogen lamp, is used as each of the
heat sources 224a and 224b, it is possible to more rapidly increase
the temperature of the solar cell 100 than in an instance in which
the coil heater is used. On the other hand, in an instance in which
a coil heater is used as each of the heat sources 224a and 224b, it
is possible to reduce facility costs.
[0198] In this embodiment of the present invention, the heat source
unit 224 may be spaced apart from the solar cell 100 or the
conveyor belt 202, on which the solar cell 100 is placed, such that
the heat source unit 224 can heat the solar cell 100 in an
atmospheric heating fashion in which the heat source unit 224 heats
air in the main section 220 by radiation. As a result, it is
possible to minimize damage to the solar cell 100 caused by the
heat source unit 224 and generation of heat from a local part of
the solar cell 100. For example, in an instance in which each of
the heat sources 224a and 224b of the heat source unit 224 is an
ultraviolet lamp, the passivation characteristics of the
passivation films 22 and 32 may be lowered by ultraviolet light
emitted from the heat sources 224a and 224b. In addition, in a case
in which the heat sources 224a and 224b of the heat source unit 224
directly contact each other, the heat sources 224a and 224b may
locally heat the solar cell 100 due to a process error with the
result that a portion of the solar cell 100 may be heated to an
undesired temperature.
[0199] However, the embodiments of the present invention are not
limited thereto. For example, the solar cell 100 may be heated by
conduction instead of atmospheric heating, which will hereinafter
be described in detail with reference to FIG. 13.
[0200] As described above, in the main period (ST562), the solar
cell 100 is heat-treated in a state in which light is supplied from
the light source unit 222 and heat is supplied from the heat source
unit 224 such that the solar cell 100 is maintained at a uniform
temperature. In this embodiment of the present invention, the light
source unit 222 and the heat source unit 224 may supply light and
heat to the solar cell 100 in a state in which the light source
unit 222 and the heat source unit 224 are separated from each
other. That is, the light sources 222a and 222b constituting the
light source unit 222 are adjacent to each other, and the heat
sources 224a and 224b constituting the heat source unit 224 are
adjacent to each other such that the light sources 222a and 222b
constituting the light source unit 222 and the heat sources 224a
and 224b constituting the heat source unit 224 are spaced apart
from each other. In this state, the light source unit 222 and the
heat source unit 224 may supply light and heat to the solar cell
100, thereby minimizing the light source unit 222 and the heat
source unit 224 from affecting each other.
[0201] For example, in the main section 220, the light source unit
222 may be positioned at one side of the solar cell 100, and the
heat source unit 224 may be positioned at the other side of the
solar cell 100 (for example, at the other side of the solar cell
100 opposite to the one side of the solar cell 100). As a result,
light and heat from the light source unit 222 and the heat source
unit 224 may be effectively supplied to the solar cell 100 in a
state in which interference between the light source unit 222 and
the heat source unit 224 is minimized.
[0202] In an example, the light source unit 222 may be positioned
at the upper side of the solar cell 100 (i.e. the upper side of the
conveyor belt 202), and the heat source unit 224 may be positioned
at the lower side of the solar cell 100 (i.e. the lower side of the
conveyor belt 202). In an instance in which the light source unit
222 is positioned at the lower side of the conveyor belt 202, a
portion of light emitted from the light source unit 222 is blocked
by the conveyor belt 202 with the result that the light may not be
effectively supplied to the solar cell 100. On the other hand, in
an instance in which the heat source unit 224 is positioned at the
lower side of the conveyor belt 202, it is possible to supply a
sufficient amount of heat to the solar cell 100 by atmospheric
heating. In this embodiment of the present invention, therefore,
the light source unit 222 is positioned at the upper side of the
solar cell 100 or the conveyor belt 202, and the heat source unit
224 is positioned at the lower side of the solar cell 100 or the
conveyor belt 202). However, the embodiments of the present
invention are not limited thereto. Positions of the light source
unit 222 and the heat source unit 224 may be changed.
[0203] The temperature rising section 210, which is positioned
before the main section 220, is a section for carrying out the
temperature rising period (ST561) of the main processing process
(ST56). That is, the temperature rising section 210 is a section
for preliminarily heating the solar cell 100 at a temperature
necessary for the main period (ST562) of the main processing
process (ST56). To this end, the temperature rising section 210
includes a heat source unit (or a second heat source unit) 214 for
supplying heat to the solar cell 100.
[0204] The heat source unit 214 of the temperature rising section
210 may be positioned at the same side (e.g. the lower side) as the
heat source unit 224 of the main section 220. In an instance in
which the heat source unit 214 of the temperature rising section
210 and the heat source unit 224 of the main section 220 are
positioned at one side as described above, the structure of the
post-processing apparatus 200 may be simplified. However, the
embodiments of the present invention are not limited thereto. The
heat source unit 214 of the temperature rising section 210 and the
heat source unit 224 of the main section 220 may be variously
modified.
[0205] In the temperature rising section 210, the heat source unit
214 may supply an appropriate amount of heat to the solar cell 100
such that the solar cell 100 can be preliminarily heated to a
desired temperature. Various mechanisms, structures, and shapes of
the heat source unit 214 may be applied.
[0206] In this embodiment of the present invention, the heat source
unit 214, including a plurality of heat sources 214a and 214b, may
supply a sufficient amount of heat to the solar cell 100. However,
the embodiments of the present invention are not limited thereto.
Only one of the heat sources 214a and 214b may be provided in
consideration of the structure, mechanism, and shape of the heat
sources 214a and 214b and heat treatment temperature of the solar
cell 100.
[0207] For example, each of the heat sources 214a and 214b
constituting the heat source unit 214 may be an ultraviolet lamp.
In an example, each of the heat sources 214a and 214b may be a
halogen lamp. In another example, a coil heater may be used as each
of the heat sources 214a and 214b. In an instance in which an
ultraviolet lamp, such as a halogen lamp, is used as each of the
heat sources 214a and 214b, it is possible to more rapidly increase
the temperature of the solar cell 100 than in an instance in which
a coil heater is used. On the other hand, in an instance in which a
coil heater is used as each of the heat sources 214a and 214b, it
is possible to reduce facility costs.
[0208] In this embodiment of the present invention, the heat source
unit 214 may be spaced apart from the solar cell 100 or the
conveyor belt 202, on which the solar cell 100 is placed, such that
the heat source unit 214 can heat the solar cell 100 in an
atmospheric heating fashion in which the heat source unit 214 heats
air in the temperature rising section 210 by radiation. As a
result, it is possible to minimize damage to the solar cell 100
caused by the heat source unit 214 and generation of heat from a
local part of the solar cell 100.
[0209] The temperature rising section 210 may further include an
additional heat source unit 216 positioned at the side opposite to
the heat source unit 214 (e.g. the upper side of the solar cell 100
or the conveyor belt 202). In an instance in which the heat source
unit 214 and the additional heat source unit 216 supply heat to the
solar cell 100 at the opposite sides of the solar cell 100 in the
temperature rising section 210 as described above, it is possible
to increase the temperature rising speed of the solar cell 100. The
additional heat source unit 216 may be adjacent to the entrance of
the temperature rising section 210, through which the solar cell
100 is introduced into the temperature rising section 210. As a
result, the temperature rising speed of the solar cell 100 in the
temperature rising section 210 may be increased, thereby improving
productivity.
[0210] Various mechanisms, structures, and shapes of the additional
heat source unit 216 may be applied. In this embodiment of the
present invention, the additional heat source unit 216 includes one
heat source. However, the embodiments of the present invention are
not limited thereto. The additional heat source unit 216 may
include a plurality of heat sources in consideration of the
structure, mechanism, and shape of the additional heat source unit
216 and heat treatment temperature of the solar cell 100.
[0211] In addition, an additional light source (or a first
additional light source) 212 may be also positioned in the
temperature rising section 210. When it is necessary to supply a
larger amount of light in the main period (ST562) carried out in
the main section 220 or when it is necessary to increase the
process time of the main period (ST562), the additional light
source 212 of the temperature rising section 210 may be provided to
carry out the same process as that of the main period (ST562) in
the temperature rising section 210. That is, a portion of the
temperature rising section 210 may be used as the main section 220
as needed, which will hereinafter be described in more detail when
describing a partition wall unit 240.
[0212] The additional light source 212 may be positioned in the
temperature rising section 210 in a state in which the additional
light source 212 is adjacent to the main section 220 such that a
portion of the temperature rising section 210 can be easily used as
the main section 220. Referring to FIG. 5, a portion of the
temperature rising period (ST561) adjacent to the main period
(ST562) has a temperature equal to or similar to that of the main
period (ST562). Consequently, a portion of the temperature rising
section 210 may be used as the main section 220.
[0213] Various mechanisms, structures, and shapes of the additional
light source 212 may be applied. For example, the additional light
source 212 may be constituted by the same plasma lighting system as
each of the light sources 222a and 222b of the light source unit
222 and may have a structure identical to or similar to that of
each of the light sources 222a and 222b of the light source unit
222. In this embodiment of the present invention, one additional
light source 212 is provided. However, the embodiments of the
present invention are not limited thereto. A plurality of
additional light sources 212 may be provided in consideration of
the structure, mechanism, and shape of each of the additional light
sources 212 and required intensity of light.
[0214] However, the additional light source 212 is not a requisite.
Since light is not fundamentally supplied to the solar cell 100 in
the temperature rising period (ST561) carried out in the
temperature rising section 210, therefore, the temperature rising
section 210 may carry out only the temperature rising period
(ST561) without the provision of the additional light source
212.
[0215] Between the temperature rising section 210 and the main
section 220 may be positioned a partition wall unit 240 for
partitioning or defining the temperature rising section 210 and the
main section 220. The partition wall unit 240 functions to prevent
generation of undesired combination in the temperature rising
period (ST561) which may be caused by light supplied from the main
section 220 to the solar cell 100 positioned in the temperature
rising section 210.
[0216] Various structures of the partition wall unit 240 may be
applied. For example, the partition wall unit 240 may be a
structure (e.g. a metal plate or a dielectric plate) for physically
partitioning the temperature rising section 210 and the main
section 220. The partition wall unit 240 may be installed such that
the partition wall unit 240 can be moved upward and downward. When
it is necessary to supply a larger amount of light in the main
period (ST562) carried out in the main section 220 or when it is
necessary to increase the process time of the main period (ST562),
therefore, the partition wall unit 240 may be moved upward such
that the additional light source 212 of the temperature rising
section 210 can carry out the same process as that of the main
period (ST562) in the temperature rising section 210. When it is
not necessary to use the additional light source 212, the partition
wall unit 240 may be moved downward to prevent introduction of
light from the main section 220 to the temperature rising section
210.
[0217] The cooling section 230, which is positioned after the main
section 220, is a section for carrying out the cooling period
(ST563) of the main processing process (ST56). That is, the cooling
section 230 is a section for cooling the solar cell 100 having
passed the main period (ST562) of the main processing process
(ST56). For this reason, the cooling section 230 includes no heat
source unit.
[0218] The solar cell 100 may be slowly cooled by air or more
rapidly cooled using an additional cooling apparatus. However, the
embodiments of the present invention are not limited thereto.
Various structures for cooling may be applied.
[0219] An additional light source 232 may be also positioned in the
cooling section 230. When it is necessary to supply a larger amount
of light in the main period (ST562) carried out in the main section
220 or when it is necessary to increase the process time of the
main period (ST562), the additional light source 232 of the cooling
section 230 may be provided to carry out the same process as that
of the main period (ST562) in the cooling section 230. That is, a
portion of the cooling section 230 may be used as the main section
220 as needed. The additional light source 232 may be positioned in
the cooling section 230 in a state in which the additional light
source 232 is adjacent to the main section 220 such that a portion
of the cooling section 230 can be easily used as the main section
220.
[0220] Various mechanisms, structures, and shapes of the additional
light source 232 may be applied. For example, the additional light
source 232 may be constituted by the same plasma lighting system as
each of the light sources 222a and 222b of the light source unit
222 and may have a structure identical to or similar to that of
each of the light sources 222a and 222b of the light source unit
222. In this embodiment of the present invention, one additional
light source 232 is provided. However, the embodiments of the
present invention are not limited thereto. A plurality of
additional light sources 212 may be provided in consideration of
the structure, mechanism, and shape of each of the additional light
sources 212 and required intensity of light.
[0221] However, the additional light source 232 is not a requisite.
Since it is not necessary to fundamentally supply heat to the solar
cell 100 in the cooling period (ST563) carried out in the cooling
section 230, therefore, the cooling section 230 may carry out only
the cooling period (ST563) without the provision of the additional
light source 232.
[0222] A partition wall unit may also be positioned between the
main section 220 and the cooling section 230. This partition wall
unit may have a structure identical to or similar to that of the
partition wall unit positioned between the temperature rising
section 210 and the main section 220. Since the solar cell 100 is
little affected even when light is introduced into the cooling
section 230, however, no partition wall unit may be positioned
between the main section 220 and the cooling section 230. As a
result, it is possible to simplify the structure of the
post-processing apparatus 200.
[0223] In this embodiment of the present invention, air curtain
members 252, 254, 256, and 258 may be installed at at least one of
the interfaces defined among the temperature rising section 210,
the main section 220, and the cooling section 230. For example,
each of the air curtain members 252, 254, 256, and 258 may have a
bar shape with a plurality of air injection holes, through which
air is supplied. However, the embodiments of the present invention
are not limited thereto. Various structures and mechanisms of the
air curtain members 252, 254, 256, and 258 may be applied.
[0224] In this embodiment of the present invention, the first air
curtain member 252 may be positioned at the entrance of the
temperature rising section 210, the second air curtain member 254
may be positioned between the temperature rising section 210 and
the main section 220, the third air curtain member 256 may be
positioned between the main section 220 and the cooling section
230, and the fourth air curtain member 258 may be positioned at the
exit of the cooling section 230. The second air curtain member 254
may be installed at the partition wall unit 240 positioned between
the temperature rising section 210 and the main section 220.
Alternatively, the second air curtain member 254 may be installed
separately from the partition wall unit 240. In an instance in
which a partition wall unit is provided between the main section
220 and the cooling section 230, the third air curtain member 256
may also be installed at the partition wall unit. Alternatively,
the third air curtain member 256 may be installed separately from
the partition wall unit. Various other modifications are also
possible.
[0225] The first air curtain member 252 may be positioned at the
entrance of the temperature rising section 210 for blocking
external air to prevent heat loss of the post-processing apparatus
200. The second air curtain member 254 may partition the
temperature rising section 210 and the main section 220 for
preventing interference between the temperature rising section 210
and the main section 220 in terms of heat and light. The third air
curtain member 256 may partition the main section 220 and the
cooling section 230 for preventing interference between the main
section 220 and the cooling section 230 in terms of heat and light.
The fourth air curtain member 258 may be positioned at the exit of
the cooling section 230 for blocking external air and assisting
cooling of the solar cell 100.
[0226] As described above, in this embodiment of the present
invention, the first to fourth air curtain members 252, 254, 256,
and 258 are provided. However, the embodiments of the present
invention are not limited thereto. For example, only one of the
first to fourth air curtain members 252, 254, 256, and 258 may be
provided. In addition, one or more additional air curtain members
may be further provided at positions different from those of the
first to fourth air curtain members 252, 254, 256, and 258.
[0227] Hereinafter, the operation of the post-processing apparatus
200 with the above-stated construction will be described in detail.
A solar cell 100, which will pass through the main processing
process (ST56) of the post-processing operation (S50), is placed on
the conveyor belt 202, and then the conveyor belt 202 is
sequentially moved through the temperature rising section 210, the
main section 220, and the cooling section 230. In the temperature
rising section 210, the solar cell 100 is preliminarily heated to a
temperature necessary for the main period (ST562) by the heat
source unit 214. In the main section 220, the light source unit 222
emits light to the solar cell 100, and the heat source unit 224
supplies heat to the solar cell 100 to passivate the surface of the
semiconductor substrate 110 or the bulk of the semiconductor
substrate 110 (e.g. H.sup.+ is converted into H.sup.0 or H.sup.- to
generate the B-H combination). In the cooling section 230, the
solar cell 100 is cooled.
[0228] In the main section 220, the light source unit 222 emits
light having light intensity necessary for the main period (ST562),
and the heat source unit 224 maintains the solar cell 100 at a
temperature necessary for the main period (ST562). In addition, the
moving speed of the conveyor belt 202 may be adjusted such that the
solar cell 100 can stay in the main section 220 for a desired
process time. As a result, the main processing process (ST56) may
be carried out on the solar cell 100 based on heat treatment
temperature, light intensity, and process time satisfying the
conditions of Equations 1 to 15.
[0229] That is, in the post-processing apparatus 200 according to
this embodiment of the present invention, the main processing
process (ST56) of the post-processing operation (S50) for supplying
both heat and light may be stably and efficiently carried out to
post-process the semiconductor substrate 110 or the solar cell
including the semiconductor substrate 110, temperature, light
intensity, and process time necessary for the main processing
process (ST56) of the post-processing operation (S50) may be
maintained to maximize the effects of the main processing process
(ST56).
[0230] The post-processing apparatus 200 may post-process the solar
cell 100 in a stand-alone fashion in which the solar cell 100 is
post-processed after the electrode forming operation (ST40) (see
FIG. 3). Alternatively, the post-processing apparatus 200 may
sequentially carry out a portion or the entirety of the electrode
forming operation (ST40) (specifically, the firing operation (ST44)
and/or the hydrogen diffusion process (ST52)) and the preliminary
heat treatment process (ST54). Alternatively, the post-processing
apparatus 200 may control operations of the light source unit 22
and the heat source units 214 and 224 such that a portion or the
entirety of the electrode forming operation (ST40) (specifically,
the firing operation (ST44) and/or the hydrogen diffusion process
(ST52)) and the preliminary heat treatment process (ST54) are all
carried out in the post-processing apparatus 200. Various other
modifications are also possible.
[0231] In the above-described embodiment of the present invention,
the in-line process using the conveyer belt 202 is carried out, and
the atmospheric heating is used in the temperature rising section
210 and the main section 220. However, the embodiments of the
present invention are not limited thereto. Hereinafter, a
modification of the post-processing apparatus 200 will be described
in detail with reference to FIG. 13.
[0232] FIG. 13 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to a
modification of the embodiments of the present invention. FIG. 14
is a view showing an example of a worktable applied to the
post-processing apparatus of the solar cell shown in FIG. 13. (a)
of FIG. 14 is a plan view schematically showing the worktable, (b)
of FIG. 14 is a partial perspective view showing first and second
parts, and (c) FIG. 14 is a partial perspective view showing a
state in which solar cells are positioned on the first and second
parts. Parts identical to or similar to those of the
post-processing apparatus according to the previous embodiment of
the present invention may be equally applied to the following
embodiments of the present invention, and therefore a detailed
description thereof will be omitted.
[0233] As shown in FIG. 13, in this modification, no conveyor belt
is positioned in the temperature rising section 210, the main
section 220, and the cooling section 230, and the process is
carried out in a state in which the solar cell 100 is stationary.
When the process is completed, the solar cell 100 may be moved by a
worker or a transfer device, such as a working beam. That is, the
solar cell 100 may be preliminarily heated in a state in which the
solar cell 100 is positioned in the temperature rising section 210.
When the preliminary heating process is completed, the solar cell
100 positioned in the temperature rising section 210 may be moved
into the main section 220. When the process is completed in the
main section 220, the solar cell 100 positioned in the main section
220 may be moved into the cooling section 230.
[0234] That is, in this embodiment of the present invention, the
post-processing apparatus 200 has a batch structure in which the
process is carried out in a state in which the solar cell 100 is
stationary. In an instance in which the process is carried out in a
state in which the solar cell 100 is stationary as described above,
it is possible to easily adjust and maintain light intensity and
thermal energy required for the temperature rising section 210, the
main section 220, and the cooling section 230 and to easily adjust
process time. In addition, interference with an external
environment may be minimized during the process, thereby improving
uniformity of the process. Furthermore, the conveyor belt may be
omitted, thereby reducing facility costs.
[0235] In this embodiment of the present invention, the temperature
rising section 210, the main section 220, and the cooling section
230 are all positioned in one chamber 208. In an instance in which
the temperature rising section 210, the main section 220, and the
cooling section 230 are all positioned in one chamber 208 as
described above, an installation space for the temperature rising
section 210, the main section 220, and the cooling section 230 may
be minimized.
[0236] For example, a support table 206 for supporting the solar
cell 100 may be positioned in the temperature rising section 210,
the main section 220, and the cooling section 230. The support
table 206 may have a material or structure which does not interrupt
the supply of thermal energy from the heat source units 214 and 224
to the solar cell 100. However, the embodiments of the present
invention are not limited thereto. Another structure for fixing the
solar cell 100 may be provided instead of the support table
206.
[0237] Solar cells 100 may be individually placed on the support
table 206 and individually moved. Alternatively, as shown in FIG.
14, a plurality of solar cells 100 may be placed on a worktable
(tray) 204, and then the worktable 204 may be placed on the support
table 206. In this case, it is possible to simultaneously move a
large number of solar cells 100, thereby improving process
efficiency.
[0238] In this embodiment of the present invention, the solar cells
100 may be placed on the worktable 204 in a state in which
interference with the light source unit 222 positioned at the upper
side of the worktable 204 and interference with the heat source
units 214 and 224 positioned at the lower side of the worktable 204
are minimized.
[0239] For example, the worktable 204 may include a frame part 204a
forming an outer edge of the worktable 204, a plurality of first
parts 204b extending in one direction at uniform intervals, and a
plurality of second parts 204c extending in a direction
intersecting the first parts 204b at uniform intervals.
[0240] The first parts 204b and the second parts 204c intersect
each other in the frame part 204a. As a result, the worktable 204
has a matrix or mesh structure. More specifically, a space S (e.g.
a quadrangular space) is defined by two neighboring first parts
204b and two neighboring second parts 204c. The side of the space S
is blocked by the first parts 204b and the second parts 204c.
Consequently, the space S may be formed in the shape of a closed
opening when viewed from above. In the figure, the first parts 204b
and the second parts 204c are illustrated as each having a straight
shape and being coupled to each other. However, the embodiments of
the present invention are not limited thereto. For example, the
first parts 204b and the second parts 204c may have a single
structure including one layer. Various other modifications are also
possible.
[0241] In this embodiment of the present invention, the edge of
each solar cell 100 is placed on two neighboring first parts 204b
and two neighboring second parts 204c. That is, the vertical width
of each solar cell 100 may be less than the width of the two
neighboring first parts 204b, and the horizontal width of each
solar cell 100 may be less than the width of the two neighboring
second parts 204c. Consequently, the area of the space S is less
than that of each solar cell 100 with the result that the edge of
each solar cell 100 is placed over the first and second parts 204b
and 204c. That is, each solar cell 100 is placed over the space S
defined by the two neighboring first parts 204b and the two
neighboring second parts 204c while entirely covering the space S.
As a result, thermal energy from the heat source units 214 and 224
positioned at the lower side of the worktable 204 may be
effectively transferred to the solar cell 100 through the space S.
On the other hand, light from the light source unit 222 at the
upper side of the worktable 204 may be blocked by the worktable 204
and the solar cell 100 with the result that the heat source units
214 and 224 are prevented from being affected by the light from the
light source unit 222. Consequently, it is possible to prevent
lowering in temperature uniformity of the solar cell 100 due to
interference between the light source unit 222 and the heat source
units 214 and 224.
[0242] In the embodiment shown in FIG. 14, the edge of each solar
cell 100 is placed over the first and second parts 204b and 204c.
However, the embodiments of the present invention are not limited
thereto. The worktable 204 may have various structures for fixing
the solar cell 100. In another modification, as shown in FIG. 15,
the vertical width of each solar cell 100 may be equal to the width
of two neighboring first parts 204b, and the horizontal width of
each solar cell 100 may be equal to the width of two neighboring
second parts 204c. In addition, protrusions P may protrude inwardly
from the first and second parts 204b and 204c for each space S such
that each solar cell 100 is placed on the protrusions P. As a
result, a major portion of the area of the solar cell 100 excluding
portions corresponding to the protrusions P may be placed over the
space C, thereby effectively achieving heat transfer. As shown in
(a) of FIG. 15, the protrusions P may be provided at the first and
second parts 204b and 204c on four corners of each space S.
Alternatively, as shown in (b) of FIG. 15, the protrusions P may be
provided at the first and second parts 204b and 204c on the middle
parts of four sides of each space S. The position and number of the
protrusions P may be variously changed.
[0243] Referring back to FIG. 14, a plurality of spaces S may be
defined by the first parts 204b and the second parts 204c.
Consequently, a corresponding number of solar cells 100 may be
placed on the worktable 204. For example, 10 to 20 spaces S may be
formed in one direction (e.g. a horizontal direction), and 10 to 20
spaces S may be formed in another direction (e.g. a vertical
direction) intersecting the above-mentioned direction. As a result,
100 to 400 spaces S may be formed on each worktable 204.
Consequently, 100 to 400 solar cells 100 may be simultaneously
processed on one worktable 204, thereby simplifying the process and
achieving mass production.
[0244] The strength of the work table 204 may be increased by the
provision of the frame part 204a, thereby improving structural
stability of the work table 204. For example, the width of the
frame part 204a may be greater than that of the first and second
parts 204b and 204c to further increase the strength of the work
table 204. However, the embodiments of the present invention are
not limited thereto. The width of the frame part 204a may be
variously changed. In addition, the frame part 204a may be omitted
to simplify the structure of the work table 204.
[0245] In this embodiment of the present invention, the material of
the frame part 204a may be different from that of the first and
second parts 204b and 204c. For example, the material of the frame
part 204a may have a higher strength than that of the first and
second parts 204b and 204c. In this case, the strength of the work
table 204 may be increased. In addition, the material of the first
and second parts 204b and 204c may have a higher thermal
conductivity than that of the frame part 204a. In this case,
transfer of heat from the heat source units 214 and 224 to the
solar cell 100 may not be interrupted. For example, the frame part
204a may be made of stainless steel (SUS), and the first and second
parts 204b and 204c may be made of aluminum. However, the
embodiments of the present invention are not limited thereto. The
frame part 204a and the first and second parts 204b and 204c may be
made of various other materials.
[0246] FIG. 16 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to another
modification of the embodiments of the present invention. Parts
identical to or similar to those of the post-processing apparatus
according to the previous embodiment of the embodiments of the
present invention may be equally applied to the following
embodiments of the present invention, and therefore a detailed
description thereof will be omitted.
[0247] Referring to FIG. 16, in this embodiment of the present
invention, the post-processing apparatus 200 has a batch structure
in a state in which a temperature rising section 210, a main
section 220, and a cooling section 230 have separate spaces.
Consequently, it is possible to easily adjust and maintain light
intensity and thermal energy required for the temperature rising
section 210, the main section 220, and the cooling section 230 and
to easily adjust process time. In addition, interference with an
external environment may be minimized during the process, thereby
improving uniformity of the process. Furthermore, no conveyor belt
may be provided, thereby reducing facility costs.
[0248] However, the embodiments of the present invention are not
limited thereto. For example, the temperature rising section 210
and the main section 220 may be continuously positioned such that
the process can be carried out based on an in-line process, and the
cooling section 230 may have a separate structure. In another
example, the temperature rising section 210 may have a separate
structure, and the main section 220 and the cooling section 230 may
be continuously positioned such that the process can be carried out
based on the in-line process. In another example, the temperature
rising section 210 and the main section 220 may have a batch
structure in a state in which the temperature rising section 210
and the main section 220 are positioned in one chamber, and the
cooling section 230 may have a separate structure. In a further
example, the temperature rising section 210 may have a separate
structure, and the main section 220 and the cooling section 230 may
have a batch structure in a state in which the main section 220 and
the cooling section 230 are positioned in one chamber. Various
other modifications are also possible.
[0249] In this embodiment of the present invention, a work table
204, on which a solar cell 100 is placed, may be preliminarily
heated or heat-treated in a state in which the work table 204 is in
contact with a heat source unit 214 of the temperature rising
section 210 or a heat source unit 224 of the main section 220. As a
result, heat from the work table 204 is transferred to the solar
cell 100 by conduction.
[0250] In an instance in which the heat from the work table 204 is
transferred to the solar cell 100 by conduction as described above,
it is possible to heat the solar cell 100 within a short time. In
addition, the process is carried out in a state in which the solar
cell 100 is stationary in the temperature rising section 210 and
the main section 220. Consequently, it is possible to easily adjust
time during which light and heat are supplied to the solar cell 100
by adjusting time during which the solar cell 100 stays in the
temperature rising section 210 or the main section 220. In
addition, it is possible to carry out the process for a desired
process time without increasing the size of the temperature rising
section 210 and the main section 220.
[0251] In the figure, the temperature rising section 210 is
illustrated as including an additional heat source unit 216 for
carrying out atmospheric heating by radiation to improve heating
efficiency. However, the embodiments of the present invention are
not limited thereto. The additional heat source unit 216 may not be
provided. Various other modifications are also possible.
[0252] However, the embodiments of the present invention are not
limited thereto. For example, the work table 204, on which the
solar cell 100 is placed, may be preliminarily heated or
heat-treated in a state in which the work table 204 is spaced apart
from the heat source unit 214 of the temperature rising section 210
or the heat source unit 224 of the main section 220. In this case,
heat is transferred to the solar cell 100 by radiation.
Consequently, it is possible to stably supply heat to the solar
cell 100 while minimizing possible damage to the solar cell
100.
[0253] FIG. 17 is a view schematically showing the structure of a
post-processing apparatus of a solar cell according to another
modification of the embodiments of the present invention.
[0254] Referring to FIG. 17, in this embodiment of the present
invention, the post-processing apparatus 200 may include a
plurality of post-processing units, each of which includes a
temperature rising section 210, a main section 220, and a cooling
section 230. For example, one post-processing unit including a
temperature rising section 210, a main section 220, and a cooling
section 230 may be positioned above another post-processing unit
including a temperature rising section 210, a main section 220, and
a cooling section 230. That is, a plurality of post-processing
units may be positioned in a vertical direction to have a
multi-stage structure, thereby improving productivity while
minimizing an installation space.
[0255] Each post-processing unit of the post-processing apparatus
200 shown in FIG. 17 has the same structure as the post-processing
apparatus 200 shown in FIG. 13. However, the embodiments of the
present invention are not limited thereto. For example, each
post-processing unit of the post-processing apparatus 200 shown in
FIG. 17 has the same structure as the post-processing apparatus 200
shown in FIG. 12 or 16. Various other modifications are also
possible.
[0256] FIG. 18 is a view schematically showing the structure of a
light source unit applicable to a post-processing apparatus of a
solar cell according to a further modification of the embodiments
of the present invention.
[0257] Referring to FIG. 18, in this embodiment of the present
invention, the outer surface of a cover substrate 223 (i.e. the
surface of the cover substrate 223 opposite to a solar cell 100
(see FIG. 12)) may be convex to the solar cell 100. As a result,
light may be more uniformly supplied to the solar cell 100 through
the cover substrate 223 such that the light can be more uniformly
distributed over the solar cell 100. The outer surface of the cover
substrate 223 may be variously convex. For example, the cover
substrate 223 may include a base substrate 223a (see FIG. 12) which
is convex outward and a plurality of layers 223b (see FIG. 12),
positioned on the base substrate 223a, having different refractive
indices. As a result, the cover substrate 223 may be convex
outward. Various other modifications are also possible. On the
other hand, a light source of a general plasma lighting system is
used outside. For this reason, an outwardly concave cover substrate
is generally used to improve straightness of light.
[0258] As is apparent from the above description, it is possible
for the post-processing apparatus according to the embodiments of
the present invention to stably and efficiently carry out the
post-processing operation for supplying both heat and light so as
to post-process the solar cell and to maintain temperature, light
intensity, and process time necessary for the post-processing
operation, thereby maximizing the effects of the main processing
process.
[0259] The above described features, configurations, effects, and
the like are included in at least one of the embodiments of the
present invention, and should not be limited to only one
embodiment. In addition, the features, configurations, effects, and
the like as illustrated in each embodiment may be implemented with
regard to other embodiments as they are combined with one another
or modified by those skilled in the art. Thus, content related to
these combinations and modifications should be construed as
included in the scope and spirit of the invention as disclosed in
the accompanying claims.
* * * * *