U.S. patent application number 15/633107 was filed with the patent office on 2018-06-07 for solar cell and solar cell panel including the same.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Jaewon CHANG, Jinsung KIM, Philwon YOON.
Application Number | 20180158970 15/633107 |
Document ID | / |
Family ID | 59366315 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180158970 |
Kind Code |
A1 |
YOON; Philwon ; et
al. |
June 7, 2018 |
SOLAR CELL AND SOLAR CELL PANEL INCLUDING THE SAME
Abstract
Disclosed is a solar cell panel including: a semiconductor
substrate having a long axis and a short axis that intersect; a
first conductivity type region formed on one surface of the
semiconductor substrate; a second conductivity type region formed
on the other surface of the semiconductor substrate; a first
electrode electrically connected to the first conductivity type
region; and a second electrode electrically connected to the second
conductivity type region. The first electrode includes: a plurality
of finger lines positioned in a first direction parallel to the
long axis and being parallel to each other; and a plurality of bus
bars including a plurality of pad portions positioned in a second
direction parallel to the short axis. The plurality of pad portions
include a first outer pad and a second outer pad located on
opposite ends of the plurality of bus bars in the second direction,
respectively.
Inventors: |
YOON; Philwon; (SEOUL,
KR) ; CHANG; Jaewon; (SEOUL, KR) ; KIM;
Jinsung; (SEOUL, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
SEOUL
KR
|
Family ID: |
59366315 |
Appl. No.: |
15/633107 |
Filed: |
June 26, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 10/50 20130101;
H01L 31/022441 20130101; H01L 31/0508 20130101; H01L 31/0201
20130101; H01L 31/048 20130101; H01L 31/06 20130101; H01L 51/447
20130101; H01L 31/022425 20130101; H01L 31/0352 20130101; H01L
31/022433 20130101; H01L 31/0504 20130101 |
International
Class: |
H01L 31/0224 20060101
H01L031/0224; H01L 31/048 20060101 H01L031/048; H01L 31/06 20060101
H01L031/06; H01L 51/44 20060101 H01L051/44 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 2016 |
KR |
10-2016-0163559 |
Claims
1. A solar cell, comprising: a semiconductor substrate having a
long axis and a short axis that intersect; a first conductivity
type region formed on one surface of the semiconductor substrate; a
second conductivity type region formed on another surface of the
semiconductor substrate; a first electrode electrically connected
to the first conductivity type region; and a second electrode
electrically connected to the second conductivity type region,
wherein the first electrode comprises: a plurality of finger lines
positioned in a first direction parallel to the long axis and being
parallel to each other; and a plurality of bus bars including a
plurality of pad portions and positioned in a second direction
parallel to the short axis, and wherein the plurality of pad
portions comprise a first outer pad and a second outer pad located
on opposite ends of the plurality of bus bars in the second
direction, respectively.
2. The solar cell of claim 1, wherein a ratio of a pitch of the
plurality of bus bars in the first direction to a width of the
semiconductor substrate in the second direction is 0.35 or
less.
3. The solar cell of claim 2, wherein the ratio of the pitch of the
plurality of bus bars in the first direction to the width of the
semiconductor substrate in the second direction is 0.1 to 0.35.
4. The solar cell of claim 1, wherein a ratio of a width of the
semiconductor substrate in the second direction to a length of the
semiconductor substrate in the first direction is 0.2 to 0.5.
5. The solar cell of claim 1, wherein a number of the plurality of
bus bars is six or more.
6. The solar cell of claim 5, wherein the number of the plurality
of bus bars is six to fourteen.
7. The solar cell of claim 1, wherein the first outer pad and the
second outer pad are inwardly located on the solar cell than
outermost finger lines among the plurality of finger lines in the
second direction, respectively.
8. The solar cell of claim 1, wherein the first outer pad and the
second outer pad are symmetrically located in the second direction
of the solar cell.
9. The solar cell of claim 1, wherein the plurality of pad portions
further comprise an inner pad positioned between the first outer
pad and the second outer pad, and wherein at least one of the
plurality of bus bars further comprises a line portion connecting
the plurality of pad portions in the second direction.
10. The solar cell of claim 1, wherein an electrode area of the
solar cell in which the plurality of finger lines are disposed
comprises: a first electrode area located between two adjacent bus
bars of the plurality of bus bars; and a second electrode area
located between one bus bar of the plurality of bus bars and a
short side of the solar cell, and wherein a width of the first
electrode area is smaller than a width of the second electrode
area.
11. The solar cell of claim 1, further comprising a cut surface and
a non-cut surface, and wherein a first gap between one of the first
conductive type region and the second conductivity type region or
one of the first electrode and the second electrode and the cut
surface is smaller than a second gap between one of the first
conductive type region and the second conductivity type region or
one of the first electrode and the second electrode and the non-cut
surface.
12. A solar cell panel, comprising: a plurality of solar cells
including a first solar cell and a second solar cell; and a
plurality of leads connecting the first solar cell and the second
solar cell and having a rounded portion, wherein each of the
plurality of solar cells comprises: a semiconductor substrate
having a long axis and a short axis that intersect; a first
conductivity type region formed on one surface of the semiconductor
substrate; a second conductivity type region formed on another
surface of the semiconductor substrate; a first electrode
electrically connected to the first conductivity type region; and a
second electrode electrically connected to the second conductivity
type region, wherein the first electrode comprises: a plurality of
finger lines positioned in a first direction parallel to the long
axis and being parallel to each other; and a plurality of bus bars
including a plurality of pad portions and positioned in a second
direction parallel to the short axis, and wherein the plurality of
pad portions comprise a first outer pad and a second outer pad
located on opposite ends of the plurality of bus bars in the second
direction, respectively, wherein the plurality of leads extend
along the second direction.
13. The solar cell panel of claim 12, wherein a ratio of a pitch of
the plurality of bus bars in the first direction to a width of the
semiconductor substrate in the second direction is 0.35 or
less.
14. The solar cell panel of claim 13, wherein the ratio of the
pitch of the plurality of bus bars in the first direction to the
width of the semiconductor substrate in the second direction is 0.1
to 0.35.
15. The solar cell panel of claim 12, wherein a ratio of a width of
the semiconductor substrate in the second direction to a length of
the semiconductor substrate in the first direction is 0.2 to
0.5.
16. The solar cell panel of claim 12, wherein a number of the
plurality of bus bars or a number of the plurality of leads is six
or more.
17. The solar cell panel of claim 16, wherein the number of the
plurality of bus bars or the number of the plurality of leads is
six to fourteen.
18. The solar cell panel of claim 12, wherein at least one of the
plurality of leads includes a core layer and a solder layer located
on an outer surface of the core layer, and wherein the at least one
of the plurality of leads is fixed to the plurality of pad portions
by the solder layer.
19. The solar cell panel of claim 18, wherein a width of the solder
layer gradually increases toward the plurality of pad portions at a
portion of the solder layer adjacent to the plurality of pad
portions.
20. The solar cell panel of claim 12, wherein each of the first
solar cell and the second solar cell has first and second long
sides formed along the long axis and being parallel to each other,
first and second short sides formed along the short axis and being
parallel to each other, a first inclined side connecting the first
long side and the first short side, and a second inclined side
connecting the first long side and the second short side, and
wherein the first long side of the first solar cell and the first
long side of the second solar cell face each other, the first and
second inclined sides of the first solar cell and the first and
second inclined sides of the second solar cell face each other, or
the second long side of the first solar cell and the second long
side of the second solar cell face each other.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Korean
Patent Application No. 10-2016-0163559 filed on Dec. 2, 2016, the
disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the invention
[0002] Embodiments of the invention relate to a solar cell and a
solar cell panel including the same, and, more particularly, to a
solar cell improved in structure and a solar cell panel including
the same.
2. Description of the Related Art
[0003] Recently, as existing energy resources such as petroleum and
coal are expected to be depleted, interest in alternative energy to
replace them is increasing. Among them, solar cells are attracting
attention as a next-generation battery that converts solar energy
into electric energy.
[0004] A plurality of solar cells are connected in series or in
parallel by a ribbon, and are then packaged through a packaging
process for protecting the plurality of solar cells, thereby
forming a solar cell panel. Solar cell panels require long-term
reliability because they must generate electricity for a long time
in various environments. Generally, a plurality of solar cells are
connected by a ribbon.
[0005] However, when a solar cell is connected using a ribbon
having a large width of about 1.5 mm, a number of ribbons disposed
in the solar cell should be reduced because light loss may occur
due to a large width of the ribbon. On the other hand, if a number
of the ribbons is increased in order to reduce a movement distance
of carriers, a resistance is lowered, but an output may be largely
lowered due to the shading loss.
SUMMARY OF THE INVENTION
[0006] Therefore, embodiments of the invention have been made in
view of the above problems, and the invention is to provide a solar
cell and a solar cell panel being capable of improving an output of
a solar cell panel.
[0007] A solar cell according to an embodiment includes: a
semiconductor substrate having a long axis and a short axis that
intersect; a first conductivity type region formed on one surface
of the semiconductor substrate; a second conductivity type region
formed on the other surface of the semiconductor substrate; a first
electrode electrically connected to the first conductivity type
region; and a second electrode electrically connected to the second
conductivity type region. The first electrode includes: a plurality
of finger lines positioned in a first direction parallel to the
long axis and being parallel to each other; and a plurality of bus
bars including a plurality of pad portions and positioned in a
second direction parallel to the short axis. The plurality of pad
portions include a first outer pad and a second outer pad located
on opposite ends of the plurality of bus bars in the second
direction, respectively.
[0008] A solar cell panel according to a solar cell panel includes:
a plurality of solar cells including a first solar cell and a
second solar cell; and a plurality of leads connecting the first
solar cell and the second solar cell and having a rounded portion.
Each of the plurality of solar cells includes: a semiconductor
substrate having a long axis and a short axis that intersect; a
first conductivity type region formed on one surface of the
semiconductor substrate; a second conductivity type region formed
on the other surface of the semiconductor substrate; a first
electrode electrically connected to the first conductivity type
region; and a second electrode electrically connected to the second
conductivity type region. The first electrode includes: a plurality
of finger lines positioned in a first direction parallel to the
long axis and being parallel to each other; and a plurality of bus
bars including a plurality of pad portions and positioned in a
second direction parallel to the short axis. The plurality of pad
portions include a first outer pad and a second outer pad located
on opposite ends of the plurality of plurality of bus bars in the
second direction, respectively. The plurality of leads extend along
the second direction.
[0009] According to the embodiments, light loss can be minimized by
using a bus bar having a small width and/or a lead having a wire
shape, and a movement path of carriers can be reduced by increasing
a number of bus bars and/or leads. Thus, efficiency of the solar
cell and an output of the solar cell panel can be improved.
Further, the light loss can be minimized due to diffused reflection
or the like by using the lead having the wire shape, and the
movement path of carriers can be reduced by reducing a pitch of the
leads. Thus, the efficiency of the solar cell and the output of the
solar cell panel can be improved.
[0010] Particularly, the efficiency of the solar cell and the
output of the solar cell panel can be maximized by applying the
lead to the solar cell having a long axis and a short axis. In this
instance, the lead may be arranged in a direction of the short axis
and the outer pads may be positioned at both sides in the short
axis direction. Then, the movement path through the lead can be
minimized and the attachment property of the lead can be
enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above and other objects, features and other advantages
of the invention will be more clearly understood from the following
detailed description taken in conjunction with the accompanying
drawings, in which:
[0012] FIG. 1 is a perspective view of a solar cell panel according
to an embodiment of the invention;
[0013] FIG. 2 is a schematic cross-sectional view taken along line
II-II in FIG. 1;
[0014] FIG. 3 is a partial cross-sectional view of an example of a
solar cell and leads connected thereto, which are included in the
solar cell panel shown in FIG. 1;
[0015] FIG. 4 is a front plan view schematically showing a mother
solar cell including a plurality of solar cells applicable to the
solar cell panel shown in FIG. 1;
[0016] FIG. 5 is a front plan view schematically showing a first
solar cell and a second solar cell manufactured by cutting the
mother solar cell shown in FIG. 4;
[0017] FIG. 6 is a front plan view schematically showing a mother
solar cell including a plurality of solar cells applicable to a
solar cell panel according to a modified embodiment of the
invention;
[0018] FIG. 7 is a perspective view schematically showing the first
solar cell and the second solar cell connected by the leads, which
are included in the solar cell panel shown in FIG. 1;
[0019] FIG. 8 is a partial front plan view of a solar cell and
leads included in a solar cell panel according to another
embodiment of the invention;
[0020] FIG. 9 is a cross-sectional view of a solar cell panel
according to yet another embodiment of the invention; and
[0021] FIG. 10 is a front plan view schematically showing a first
solar cell and a second solar cell, which are applicable to the
solar cell panel shown in FIG. 9 and manufactured by cutting a
mother solar cell.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0022] Reference will now be made in detail to various embodiments
of the invention, examples of which are illustrated in accompanying
drawings. The invention may, however, be embodied in many alternate
forms and should not be construed as limited to the embodiments set
forth herein.
[0023] In the drawings, illustration of parts unrelated to
embodiments of the invention is omitted for clarity and simplicity
of description. The same reference numerals designate the same or
very similar elements throughout the specification. In the
drawings, the thicknesses, widths or the like of elements are
exaggerated or reduced for clarity of description, and should not
be construed as limited to those illustrated in the drawings.
[0024] It will be understood that the terms "comprises" and/or
"comprising," or "includes" and/or "including" used in the
specification specify the presence of stated elements, but do not
preclude the presence or addition of one or more other elements. In
addition, it will be understood that, when an element such as a
layer, film, region, or plate is referred to as being "on" another
element, it may be directly disposed on another element or may be
disposed such that an intervening element is also present
therebetween. Accordingly, when an element such as a layer, film,
region, or plate is disposed "directly on" another element, this
means that there is no intervening element between the
elements.
[0025] Hereinafter, a solar cell and a solar cell panel according
to an embodiment of the invention will be described in detail with
reference to the accompanying drawings.
[0026] FIG. 1 is a perspective view of a solar cell panel according
to an embodiment of the invention, and FIG. 2 is a schematic
cross-sectional view taken along line II-II in FIG. 1.
[0027] Referring to FIGS. 1 and 2, a solar cell panel 100 according
to an embodiment includes a plurality of solar cells 150 and leads
142 electrically connecting the plurality of solar cells 150. The
solar cell panel 100 includes a sealing member 130 that surrounds
and seals the plurality of solar cells 150 and the leads 142
connecting the plurality of solar cells 150, a front substrate 110
positioned at a front surface of the solar cell 150 on the sealing
member 130, and a back substrate 120 positioned at a back surface
of the solar cell 150 on the sealing member 130. This will be
explained in more detail.
[0028] First, the solar cell 150 may include a photoelectric
conversion unit that converts solar energy into electric energy,
and an electrode electrically connected to the photoelectric
conversion unit and collects and delivers current. The plurality of
solar cells 150 maybe electrically connected in series, parallel,
or series-parallel by the lead 142. Specifically, the lead 142
electrically connects two neighboring solar cells 150 among the
plurality of solar cells 150.
[0029] Bus ribbons 145 connect opposite ends of the leads 142 in
solar cell strings, each of which is a column of the plurality of
solar cells 150 connected through the leads 142, in an alternating
manner. The bus ribbons 145 may be arranged at opposite ends of the
solar cell strings, to extend in a direction crossing the solar
cell strings. The bus ribbons 145 may connect adjacent ones of the
solar cell strings, or connect the solar cell strings to a junction
box for preventing reversal of current. The material, shape, and
connecting structure of the bus ribbons 145 may be varied and thus
the embodiments of the invention are not limited thereto.
[0030] The sealing member 130 may include a first sealing member
131 disposed at the front surface of the solar cells 150 connected
to each other by the leads 142, and a second sealing member 132
disposed at the back surface of the solar cells 150. The first
sealing member 131 and the second sealing member 132 block
permeation of moisture or oxygen, and chemically combine elements
constituting the solar cell panel 100. For the first sealing member
131 and the second sealing member 132, an insulating material
having transparent property and adhesive property may be used. As
an example, ethylene vinyl acetate (EVA) copolymer resin, polyvinyl
butyral, silicone resin, ester-based resin, olefin-based resin, or
the like may be used for the first sealing member 131 and the
second sealing member 132. The back substrate 120, the second
sealing member 132, the solar cells 150, the first sealing member
131, the front substrate 110 or so on may have an integrated
structure to form the solar cell panel 100 through a lamination
process using the first sealing member 131 and the second sealing
member 132.
[0031] The front substrate 110 is disposed on the first sealing
member 131 and constitutes a front surface of the solar cell panel
100. The back substrate 120 is disposed on the second sealing
member 132 and constitutes a back surface of the solar cell panel
100. The front substrate 110 and the back substrate 120 may be made
of an insulating material capable of protecting the solar cells 150
from external impact, moisture, ultraviolet, or so on. Also, the
front substrate 110 may be made of an optically-transparent
material that light can be transmitted through. The back substrate
120 may be a sheet or a film made of an optically-transparent
material, a non-optically-transparent material, a reflective
material, or the like. For example, the front substrate 110 may be
a glass substrate and the back substrate 120 may be a sheet or a
film. The back substrate 120 may have a Tedlar/PET/Tedlar (TPT)
type or may have a structure in which a layer of polyvinylidene
fluoride (PVDF) resin or the like is formed on at least one surface
of a base film (e.g., polyethylene terephthalate (PET)).
[0032] However, the embodiments of the invention are not limited
thereto. Thus, the first sealing member 131 and the second sealing
member 132, the front substrate 110, or the back substrate 120 may
be made of any of various materials other than the above materials
and may have any of various structures other than the above
structures. For example, the front substrate 110 or the back
substrate 120 may have various structures (e.g., a substrate, a
film, a sheet, or so on) or various materials.
[0033] Referring to FIG. 3, an example of the solar cell 150 and
the leads 142 included in the solar cell panel 100 according to the
embodiment of the invention will be described in more detail.
[0034] FIG. 3 is a partial cross-sectional view of an example of
the solar cell 150 and the leads 142 connected thereto, which are
included in the solar cell panel 100 shown in FIG. 1.
[0035] Referring to FIG. 3, the solar cell 150 includes a
semiconductor substrate 160, a first conductivity type region 20
formed on or formed at one surface of the semiconductor substrate
160, a second conductivity type region 30 formed on or formed at
the other surface of the substrate 160, a first electrode 42
connected to the first conductivity type region 20, and a second
electrode 44 connected to the second conductivity type region 30.
Also, the solar cell may further include first and second
passivation layers 22 and 32, an anti-reflection layer 24, and the
like.
[0036] The semiconductor substrate 160 may include a base region 10
having a first or second conductivity type. The base region 10
includes a first or second conductivity type dopant with a
relatively low doping concentration. As an example, the base region
10 may have a second conductivity type. The base region 10 may be
comprised of a single crystalline semiconductor (e.g., a
single-crystalline or polycrystalline semiconductor of a single
material, e.g., single-crystalline or polycrystalline silicon,
particularly, single-crystalline silicon) including a first or
second conductivity type dopant. The solar cell 150 based on the
base region 10 or the semiconductor substrate 160 having a high
degree of crystallinity and having few defects is excellent in
electrical characteristics.
[0037] An anti-reflection structure capable of minimizing
reflection may be formed at the front surface and the back surface
of the semiconductor substrate 160. For example, a texturing
structure having a concavo-convex shape in the form of a pyramid or
the like may be provided as the anti-reflection structure. The
texturing structure formed at the semiconductor substrate 160 may
have a certain shape (e.g., a pyramid shape) having an outer
surface formed along a specific crystal plane (e.g., (111) plane)
of the semiconductor. When the surface roughness of the
semiconductor substrate 160 is increased due to the unevenness
formed at the front surface of the semiconductor substrate 160 by
such texturing, the reflectance of the light incident into the
semiconductor substrate 160 can be reduced to minimize the optical
loss. However, the embodiments of the invention are not limited
thereto, and the texturing structure may be formed at only one
surface of the semiconductor substrate 160, or the texturing
structure may not be formed at the front and back sides of the
semiconductor substrate 160.
[0038] The first conductivity type region 20 having the first
conductivity type may be formed at one surface (e.g., the front
surface) of the semiconductor substrate 160. The second
conductivity type region 30 having the second conductivity type may
be formed at the other surface (e.g., the back surface) of the
semiconductor substrate 160. The first and second conductivity type
regions 20 and 30 may have a different conductivity type than the
base region 10 or may have a higher doping concentration than the
base region 10 in the instance that the first or second
conductivity type regions 20 and 30 has the conductivity type the
same as the conductivity type of the base region 10.
[0039] In the drawing, the first and second conductivity type
regions 20 and 30 are constituted by a doped region constituting a
part of the semiconductor substrate 160 as an example. In this
instance, the first conductivity type region 20 may be composed of
a crystalline semiconductor (e.g., a single-crystalline or
polycrystalline semiconductor, for example, a single-crystalline or
polycrystalline silicon, particularly, a single-crystalline
silicon) including the first conductive type dopant. The second
conductivity type region 30 may be composed of a crystalline
semiconductor (e.g., a single-crystalline or polycrystalline
semiconductor, for example, a single-crystalline or polycrystalline
silicon, particularly, a single-crystalline silicon) including the
second conductivity type dopant. As described above, when the first
and second conductivity type regions 20 and 30 constitute a part of
the semiconductor substrate 160, the junction characteristics with
the base region 10 can be improved.
[0040] However, the embodiments of the invention are not limited
thereto, and at least one of the first and second conductivity type
regions 20 and 30 may be formed separately from the semiconductor
substrate 160 on the semiconductor substrate 160. In this instance,
the first or second conductivity type regions 20 or 30 maybe formed
of a semiconductor layer (e.g., an amorphous semiconductor layer, a
micro-crystalline semiconductor layer, or a polycrystalline
semiconductor layer, for example, an amorphous silicon layer, a
micro-crystalline silicon layer, or a polycrystalline silicon
layer) having a crystal structure different from that of the
semiconductor substrate 160 so that the first or second
conductivity type regions 20 or 30 can be easily formed on the
semiconductor substrate 160.
[0041] One of the first and second conductivity type regions 20 and
30, which has a conductivity type different from that of the base
region 10, constitutes at least a part of the emitter region. The
emitter region forms a pn junction with the base region 10 to
produce a carrier by photoelectric conversion. The other of the
first and second conductivity type regions 20 and 30 having the
same conductivity type as the base region 10 constitutes at least a
part of a surface field region. The surface field region forms an
electric field that prevents or reduces carriers from being lost by
recombination on the surface of the semiconductor substrate 160.
For example, in the embodiment, the base region 10 has the second
conductivity type, the first conductivity type region 20
constitutes the emitter region, and the second conductivity type
region 30 constitutes a back surface field region. However, the
embodiments of the invention are not limited thereto.
[0042] In the drawings, each of the first and second conductivity
type regions 20 and 30 is formed at an entire portion in a plan
view and has a homogeneous structure having a uniform doping
concentration. In this instance, the first and second conductivity
type regions 20 and 30 can be formed to have a sufficient area and
can be manufactured by a simple process. However, the embodiments
of the invention are not limited thereto. Thus, the first
conductivity type region 20 may have the homogeneous structure or a
selective structure, and the second conductivity type region 30 may
have the homogeneous structure, a selective structure, or a local
structure. In the selective structure, a portion of the first or
second conductivity type region 20 or 30 adjacent to the first or
second electrode 42 or 44 has a high doping concentration, a large
junction depth, and/or a low resistance, and the other portion of
the first or second conductivity type region 20 or 30 has a low
doping concentration, a small junction depth, and/or high
resistance. In the local structure, the second conductivity type
region 30 may be formed locally only at a portion where the second
electrode 44 is located.
[0043] For example, in the embodiment, the base region 10 and the
second conductivity type region 30 may have an n-type and the first
conductivity type region 20 may have a p-type. Then, the base
region 10 and the first conductivity type region 20 form a pn
junction. When light is incident to the pn junction, electrons
generated by the photoelectric effect move toward the back surface
of the semiconductor substrate 160 and are collected by the second
electrode 44, and the holes move toward the front surface of the
semiconductor substrate 160 and collected by the first electrode
42. Thereby, electric energy is generated. Then, the holes having a
low moving speed than electrons may move to the front surface of
the semiconductor substrate 160 not the back surface thereof,
thereby improving the efficiency. However, the embodiments of the
invention are not limited thereto. Thus, the base region 10 and the
second conductivity type region 30 may have a p-type and the first
conductivity type region 20 may have an n-type.
[0044] An insulating layer such as the first and second passivation
layers 22 and 32 and the anti-reflection layer 24 may be formed on
the surface of the semiconductor substrate 160. More specifically,
a first passivation layer 22 may be formed on (e.g., be in contact
with) the front surface of the semiconductor substrate 160, more
particularly, on the first conductivity type region 20 formed at
the semiconductor substrate 160. The anti-reflection layer 24 may
be formed on (e.g., be in contact with) the first passivation layer
22. The second passivation layer 32 maybe formed on the back
surface of the semiconductor substrate 160, more particularly, on
the second conductivity type region 30 formed at the semiconductor
substrate 160.
[0045] The first passivation layer 22 and the anti-reflection layer
24 may be formed on a substantially entire portion of the front
surface of the semiconductor substrate 160 except for the portion
corresponding to the first electrode 42 (more particularly, the
portion where a first opening portion 102 is formed) . Similarly,
the second passivation layer 32 may be formed on a substantially
entire portion of the back surface of the semiconductor substrate
160 except the portion corresponding to the second electrode 44
(more particularly, the portion where a second opening 104 is
formed).
[0046] The first passivation layer 22 or the second passivation
layer 32 is in contact with the semiconductor substrate 160 to
passivate the defects existing in the surface or a bulk of the
semiconductor substrate 160. Accordingly, the open-circuit voltage
of the solar cell 150 can be increased by removing recombination
sites of the minority carriers. The anti-reflection layer 24
reduces the reflectance of light incident to the front surface of
the semiconductor substrate 160, thereby increasing the amount of
light reaching the pn junction. Accordingly, the short circuit
current Isc of the solar cell 150 can be increased.
[0047] The first passivation layer 22, the anti-reflection layer
24, and the second passivation layer 32 may be formed of any of
various materials. For example, the first passivation layer 22, the
anti-reflection layer 24, or the second passivation layer 32 may be
formed of a single layer including one layer selected from a group
consisting of a silicon nitride layer, a silicon nitride layer
containing hydrogen, a silicon oxide layer, a silicon oxynitride
layer, an aluminum oxide layer, a silicon carbide layer, MgF.sub.2,
ZnS, TiO.sub.2 and CeO.sub.2, or a multilayer in which two or more
layers selected from the above group are combined.
[0048] For example, in the embodiment, the first passivation layer
22 and/or the anti-reflection layer 24, and the second passivation
layer 32 may not have a dopant or the like so as to have good
insulating properties, passivation properties, and the like.
However, the embodiments of the invention are not limited
thereto.
[0049] The first electrode 42 may be formed by filling at least a
portion of the first opening 102 and be electrically connected to
(e.g., be in contact with) the first conductivity type region 20.
The second electrode 44 may be formed by filling at least a portion
of the second opening 104 and be electrically connected to (e.g.,
be in contact with) the second conductivity type region 30. The
first and second electrodes 42 and 44 are made of various
conductive materials (e.g., a metal) and may have various shapes.
The shape of the first and second electrodes 42 and 44 will be
described later.
[0050] As described above, in the embodiment, the first and second
electrodes 42 and 44 of the solar cell 150 have a predetermined
pattern so that the solar cell 150 can receive light from the front
and back surfaces of the semiconductor substrate 160, and thus, the
solar cell 150 has a bi-facial structure. Accordingly, the amount
of light used in the solar cell 150 can be increased and thus it
contributes to improving the efficiency of the solar cell 150.
[0051] However, the embodiments of the invention are not limited
thereto, and the second electrode 44 may be formed entirely on the
back surface of the semiconductor substrate 160. The first and
second conductivity type regions 20 and 30 and the first and second
electrodes 42 and 44 may be located together on one surface (e.g.,
the back surface) of the semiconductor substrate 160. Also, at
least one of the first and second conductivity type regions 20 and
30 may be formed on both sides of the semiconductor substrate 160.
That is, the solar cell 150 described in the above is merely one
example, but the embodiments of the invention are not limited
thereto.
[0052] The solar cells 150 connected by the leads 142 may include a
first solar cell 151 and/or a second solar cell 152, which are unit
solar cells manufactured by cutting a mother solar cell 150a and
having a long axis (or a major axis) in a length direction (or
first direction) and a short axis (or a minor axis) in a width
direction (or second direction) , where the long axis and the short
axis cross each other or intersect. Hereinafter, the mother solar
cell 150a including the plurality of solar cells 150 will be
described with reference to FIG. 4 together with FIGS. 1 to 3, and
the first and second solar cells 151 and 152 manufactured by
cutting the mother solar cell 150a will be described in detail with
reference to FIG. 5.
[0053] FIG. 4 is a front plan view schematically showing the mother
solar cell 150a including the plurality of solar cells 150
applicable to the solar cell panel 100 shown in FIG. 1. FIG. 5 is a
front plan view schematically showing the first solar cell 151 and
the second solar cell 152 manufactured by cutting the mother solar
cell 150a shown in FIG. 4. For simplicity and clarity, the
semiconductor substrate 160 and the first electrode 42 are mainly
shown in FIGS. 4 and 5.
[0054] Referring to FIGS. 4 and 5, in the embodiment, the mother
solar cell 150a is cut along a cutting line CL to form the first
and second solar cells 151 and 152, which are the plurality of unit
solar cells. Each of the first and second solar cells 151 and 152
serving as a unit solar cell functions as one solar cell 150. When
the mother solar cell 150a is separated into two solar cells 150,
the output loss (that is, cell to module loss (CTM loss)), which
may be generated during the plurality of solar cells 150 are
connected to form a solar cell panel 100, can be reduced.
[0055] To explain this in more detail, the output loss has a value
obtained by multiplying the square of the current by the resistance
of each solar cell, and the output loss of the solar cell panel
including the plurality of solar cells has a value obtained by
multiplying the above value, obtained by multiplying the square of
the current by the resistance of each solar cell, by the number of
solar cells. However, there is also the current generated by the
area of the solar cell itself in the current of each solar cell.
The corresponding current is increased when the area of the solar
cell is increased, while the corresponding current is decreased
when the area of the solar cell is decreased.
[0056] When the mother solar cell 150a is cut to form the plurality
of solar cells 150 and the plurality of solar cells 150 are
connected to each other as in the embodiment, the current is
reduced in proportion to the area while the number of the solar
cells 150 is increased inversely. For example, when there is one
cut line CL and two solar cells 150 are manufactured from the one
mother solar cell 150a, the current in each solar cell 150 is a
half of the current of the mother solar cell 150a and the number of
solar cells 150 is twice that of the mother solar cell 150a. As
described above, since the current is reflected as square value in
the output loss and the number is reflected as it is, when the
current is reduced to the half and the number is doubled, the
output loss value is reduced to a half. Accordingly, when the
plurality of solar cells 150 are manufactured by cutting the mother
solar cell 150a and thus the solar cell panel 100 is manufactured
using the plurality of solar cells 150 as in the embodiment, the
output loss of the solar cell panel 100 can be reduced.
[0057] In the embodiment, the mother solar cell 150a is
manufactured by a general or conventional manufacturing method and
then cut to the plurality of solar cells 150 to reduce the area of
the solar cell 150. Accordingly, after the mother solar cell 150a
is manufactured by using the existing equipment and the optimized
design, the mother solar cell 150a is cut. As a result, the
equipment and process cost can be minimized. On the other hand, if
the size of the mother solar cell 150a itself is reduced, there is
a burden to replace the used equipment or to change the setting of
the equipment or the design of the solar cell 150.
[0058] Generally, the semiconductor substrate 160 of the mother
solar cell 150a is manufactured from an ingot, and thus, has a
circular shape, a square shape, or the like where lengths of two
sides according to two axes perpendicular to each other (e.g., an
axis parallel to a finger line 42a and another axis parallel to a
bus bar 42b) are substantially the same as or similar to each
other. For example, in the embodiment, the semiconductor substrate
160 of the mother solar cell 150a may have an octagonal shape
having inclined sides 163a and 163b at four corner portions in an
approximate square shape. With such a shape, the semiconductor
substrate 160 having the widest area can be obtained from the same
ingot. Accordingly, the mother solar cell 150a has a symmetrical
shape, and a maximum horizontal axis and a maximum vertical axis
have the same lengths, and a minimum horizontal axis and a minimum
vertical axis have the same lengths.
[0059] Since the solar cell 150 is formed by cutting the mother
solar cell 150a along the cutting line CL in the embodiment, the
semiconductor substrate 160 of the solar cell 150 has a shape
having a long axis and a short axis. In the embodiment, the cutting
line CL extends in a first direction that is a longitudinal
direction of the first and second conductivity type regions 32 and
34 and the finger line 42a. The plurality of solar cells 150 extend
in the first direction in the mother solar cell 150a.
[0060] The solar cell 150 has first and second long sides 161a and
161b parallel to each other and along the long axis (e.g., the
first direction) and first and second short sides 162a and 162b
parallel to each other and along the short axis (e.g., a second
direction crossing to the first direction and parallel to a
longitudinal direction of the bus bar 42b). Also, the semiconductor
substrate 160 may have a first inclined side 163a and a second
inclined side 163b. The first inclined side 163a connects the first
long side 161a and the first short side 162a, and the second
inclined side 163b connects the first long side 161a and the second
short side 162b. The second long side 161b and the first short side
162a may be connected to each other and the second long side 161b
and the second short side 162b may be connected to each other. The
first long side 161a is shorter than the second long side 161b, the
first short side 162a and the second short side 162b may have the
same lengths, and the first inclined side 163a and the second
inclined side 163b may have the same lengths. However, the
embodiments of the invention are not limited thereto, and the solar
cell 150 or the semiconductor substrate 160 may have a rectangular
shape consisting of the first and second long sides 161a and 161b
and the first and second short sides 162a and 162b without the
first and second inclined sides 163a and 163b. Various other
variations are possible.
[0061] Referring to FIGS. 1 to 5, in the embodiment, the first
electrodes 42 at a surface of the semiconductor substrate 160 may
include the finger lines 42a and the bus bar 42b. The finger lines
42a extend in the first direction (a horizontal direction in the
drawing) parallel to the long axis and parallel to each other. The
bus bar 42b is electrically connected to the finger lines 42a and
extend in the second direction (a vertical direction in the
drawing) crossing (e.g., perpendicular to) the finger lines 42a.
The lead 142 is connected or attached to the bus bar 42b. In the
drawings, the first electrode 42 further includes a peripheral line
42c, an edge electrode portion 42d, and a peripheral portion 42e.
The peripheral lines 42c may connect ends of the plurality of
finger lines 42a in the vicinity of both sides of the plurality of
finger lines 42a as a whole. The peripheral line 42c, the edge
electrode portion 42d, and the peripheral portion 42e may have the
same or similar width as the finger line 42a and may be made of the
same material as the finger line 42a. However, the peripheral line
42c, the edge electrode portion 42d, and the peripheral portion 42e
may be not included.
[0062] The finger lines 42a may have uniform widths and be spaced
apart from each other with a uniform pitch. At this instance, the
width of the lead 142 may be smaller than the pitch of the finger
lines 42a, and may be larger than the width of the finger line 42a.
However, the embodiments of the invention are not limited thereto
and various modifications are possible. Here, the finger lines 42a
may extend in the first direction parallel to the long axis to be
parallel to each other, and may be parallel to main edges of the
solar cell 150 (more particularly, the first and second long sides
161a and 161b).
[0063] The bus bar 42b may be positioned so as to correspond to a
portion where the lead 142 for connection with the neighboring
solar cell 150 is located. The bus bars 42b may be provided so as
to correspond one-to-one to the leads 142 located on the same
surface as the bus bars 142. Accordingly, in the embodiment, a
number of the bus bars 42b and a number of the leads 142 are the
same on one surface of the solar cell 150.
[0064] In the embodiment, the bus bar 42b may include a plurality
of pad portions 422 positioned in the second direction to
correspond to the respective lead 142. The bus bar 42b may further
include a line portion 421 having a width smaller than a width of
the pad portion 422 and longitudinally extending in a direction
that the lead 142 is connected between the pad portions 422.
[0065] The pad portion 422 is a region having a relatively large
width, and thus, the lead 142 is substantially attached and fixed
to the pad portion 422. A width of the pad portion 422 measured in
the first direction is larger than each of a width of the line
portion 421, a width of the finger line 42a, a width of the
peripheral line 42c, a width of the edge electrode portion 42d,
and/or a width of the peripheral portion 42e. Also, the width of
the pad portion 422 measured in the first direction may be the same
as or greater than a width of the lead 142. A length of the pad
portion 422 measured in the second direction may be also greater
than each of the width of the line portion 421, the width of the
finger line 42a, the width of the peripheral line 42c, the width of
the edge electrode portion 42d, and/or the width of the peripheral
portion 42e. By the pad portion 422, the adhesion force between the
lead 142 and the bus bar 42b can be improved and the contact
resistance between the lead 142 and the bus bar 42b can be
reduced.
[0066] In this instance, the plurality of pad portions 422 include
outer pads 424 located on both sides (or opposite sides or opposite
ends) of the bus bar 42b in the second direction. Here, the outer
pads 424 may include a first outer pad 424a and a second outer pad
424b, which are the closest pad portions 422 to the first or second
long sides 161a or 161b of the solar cell 150 (or the semiconductor
substrate 160) in the second direction among the plurality of pad
portions 422. Accordingly, the finger lines 42a extend in the first
direction parallel to the long axis, and thus, the finger lines 42a
can be densely and uniformly arranged in the solar cell 150. Also,
the outer pads 424a are positioned on both sides in the second
direction parallel to the short axis, and thus, the attachment
characteristics of the lead 142 attached to the outer pads 424a can
be improved.
[0067] The outer pads 424 may be inwardly positioned than the
outermost finger lines 42a adjacent to the long sides 161a and 161b
when viewed in the second direction. Thus, the distance between the
first and second outer pads 424a and 424b in the second direction
is smaller than the distance between the outermost finger lines 42a
located on both sides in the second direction (i.e., the uppermost
and lowermost finger lines 42a in the drawings.
[0068] The lead 142 is connected from the front surface of the
solar cell 150 to the back surface of the solar cell 150 in the
vicinity of the long sides 161a and 161b of the solar cell 150.
Accordingly, in the vicinity of the long sides 161a and 161b of the
solar cell 150, a force applied to the lead 142 toward an outside
of the solar cell is large and thus the adhesion between the lead
142 and the electrodes 42 and 44 may be reduced. Such a problem may
be largely generated in the instance of the lead 142 with a wire
shape having a narrow width and a contacted surface with a small
area as in the embodiment. In consideration of this, in the
embodiment, the outer pads 424 having a large area are formed
adjacent to the long sides 161a and 161b. In addition, the outer
pads 424 and the long sides 161a and 161b of the solar cell 150 are
separated from each other by a predetermined distance to minimize
the force applied to the lead 142.
[0069] For example, the first outer pad 424a and the second outer
pad 424b may be symmetrical to each other in the second direction
with respect to an imaginary line (e.g., an imaginary line passing
through a center between outer edges of the first and second outer
pads 424a and 424b) extending along the first direction of the
solar cell 150. Thus, the current flow can be stable, and an
apparatus used for a general or conventional symmetrical structure
can be used as is.
[0070] The plurality of pad portions 422 include inner pads 426
other than the outer pads 424. The inner pad 426 maybe a pad
located between the two outer pads 424. In the embodiment, a
plurality of inner pads 426 are provided at predetermined intervals
in each of the bus bars 42b so that the attachment characteristics
with the lead 142 can be improved.
[0071] The line portion 421 connects the plurality of finger lines
42a and the pad portions 422 to provide a path through which the
carrier can bypass when some finger lines 42a are disconnected. A
width of the line portion 421 measured in the first direction may
be smaller than widths of the pad portion 422 and the lead 142 and
may be smaller than, the same as, or greater than the width of the
finger line 42a measured in the second direction. When the line
portion 421 has a relatively narrow width, the area of the first
electrode 42 can be minimized and thus the shading loss and
material cost can be reduced. The lead 142 may be attached to the
line portion 421 or the lead 142 may be placed on the line portion
421 in the state that the lead 142 is not attached to the line
portion 421.
[0072] In the embodiment, six or more bus bars 42b (or six or more
leads 142 corresponding to the bus bars 424 one-to-one) may be
provided on one side of the semiconductor substrate 160 in the
first direction. Thus, by reducing the pitch of the bus bar 42b,
the movement path of the current flowing along the finger line 42a
arranged along the long axis can be minimized. For example, six to
thirty-three bus bars 42b (or six to thirty-three leads 142
corresponding to the bus bars 424 one-to-one) may be provided in
the first direction on one surface of the semiconductor substrate
160. If the number of the bus bars 42b or the leads 142 exceeds
thirty-three, the material cost and optical loss may increase.
Considering that the solar cell 150 has the short axis and the long
axis and thus has a relatively small area, along with the material
cost and optical loss, the number of the bus bars 42b or the leads
142 may be six to fourteen (e.g., six to twelve). However, the
embodiments of the invention are not limited thereto, and the
number of the leads 142 and thus the number of the bus bars 42b may
have any of different values.
[0073] In the embodiment, the solar cell 150 (or the semiconductor
substrate 160) may include an electrode area EA and an edge area
PA.
[0074] In the embodiment, the electrode area EA is a region in
which the finger lines 42a parallel to each other are arranged at a
uniform pitch, and the electrode area EA may include a plurality of
electrode areas EA defined by the bus bars 42b. The edge area PA
may be a region located adjacent to the edge of the semiconductor
substrate 160 or the solar cell 150 and may include a region
between the adjacent two electrode areas EA. The edge area PA may
be a region where the first electrode 42 is located at a density
lower than that of the finger line 42a of the electrode area EA or
a region where the first electrode 42 is not located.
[0075] The electrode area EA may include a first electrode area EA1
located between two neighboring bus bars 42b and two second
electrode areas EA2 located between the bus bar 42b and the short
sides 162a and 162b of the solar cell 150, respectively. In this
instance, a width W1 of the first electrode area EA1 may be smaller
than a width W2 of the second electrode area EA2. In the
embodiment, a large number of bus bars 42b are provided. Therefore,
when the width W2 of the second electrode area EA2 is relatively
large, the inclined sides 163a and 163b may be positioned in the
second electrode area EA2. Since the bus bar 42b and the lead 142
are not located on the inclined sides 163a and 163b, a problem of
interference or a problem that the current flow is not smooth,
which may occur when they are located on the inclined sides 163a
and 163b or current, can be prevented or reduce. However, the
embodiments of the invention are not limited thereto, and the width
W1 of the first electrode area EA1 and the width W2 of the second
electrode area EA may have any of various values.
[0076] The edge area PA may include a first edge area PA1 and a
second edge area PA2. The first edge area PA1 corresponds to a
portion where the lead 142 is located between the finger lines 42a.
The second edge area PA2 is a portion other than the first end
portion PA1 has a predetermined width between the outermost finger
lines 42a and the edge of the semiconductor substrate 160. The
first edge area PA1 may be located at a portion adjacent to the
edge of the solar cell 150 where the lead 142 is located. The first
edge area PA1 is an area for separating the outer pad 424 from the
edge of the solar cell 150 so that the lead 142 can be attached to
the first electrode 42 with sufficient bonding force.
[0077] The first electrode 42 may further include the edge
electrode portion 42d which overlaps the lead 142 in the first edge
area PA1 and the peripheral portion 42e for partitioning the
electrode area EA and the first edge area PA1.
[0078] The peripheral portion 42e extends from an end (or the outer
pad 424) of the bus bar 42b, extends via ends of the plurality of
finger lines 42a adjacent to the edge area PA1, and reaches ends of
the outermost finger lines 42a. The peripheral portion 42e serves
to provide a path through which the carrier flows when the finger
line 42a adjacent to the edge area PA1 is disconnected or the like.
The edge electrode portion 42d located in the edge area PA1 may be
connected to the finger line 42a via the peripheral portion 42e.
The current collected by the finger line 42a located in the
electrode area EA adjacent to the edge area PA1 may pass the
peripheral portion 42e and the edge electrode portion 42d, and
reach the lead 142. However, the embodiments of the invention are
not limited thereto, and the edge electrode portion 42d in the
first edge area PA1 may be directly connected to the finger line
42a without passing through the peripheral portion 42e. Various
other variations are possible.
[0079] The peripheral portion 42e may be inclined to the finger
lines 42a and the bus bars 42b so that a width of the first edge
area PA1 gradually increases as it goes toward the edge of the
solar cell 150 (i.e., the long side 161a, 161b). In one example,
the first edge area PA1 may have a rough or general triangular
shape, and the two peripheral portions 42e that define the first
edge area PA1 may have a rough or general "V shape". Thereby, an
interval between both ends of the finger lines 42a in the two
electrode areas EA adjacent to the first edge area PA1 may
gradually increase.
[0080] Thus, the lead 142 may be stably positioned in the first
edge area PA1 so that the lead 142 is not attached to the
peripheral portion 42e. In the embodiment, an end of the lead 142
that is not connected to the other solar cell 150 passes the end of
the outer pad 424 and extends to the inside of the first edge area
PA1. Thus, the end of the lead 142 can be stably fixed and the lead
142 can be attached with the sufficient adhesive force by the pad
portions 422. Also, a problem, such as short-circuit, that may
generated when the lead 142 extends to the second edge area PA2 can
be prevented.
[0081] The lead 142 overlaps or is in contact with the edge
electrode portion 42d and thus is electrically connected to the
edge electrode portion 42d. As a result, the edge electrode portion
42d is a path through which the current can flow to the lead 142,
and the current generated in the portion of the electrode area EA
adjacent to the first edge area PA1 can be transferred to the lead
142. Thus, even when the first edge area PA1 is provided to improve
the adhesive force or the bonding force of the lead 142, it is
possible to prevent or reduce the efficiency from being lowered.
Thus, the efficiency of the solar cell 150 can be improved and the
output of the solar cell panel 100 can be improved.
[0082] In this instance, the edge electrode portion 42d may have a
shape that can be connected to the finger line 42a, the bus bar
42b, or the lead 142 in the embodiment. The edge electrode portion
42d is positioned in the first edge area PA1 so as to have a
density less than that of the finger line 42a in the electrode area
EA.
[0083] In one example, the first edge areas PA1 and the edge
electrode portions 42d located therein may be symmetrical with
respect to an imaginary line (e.g., an imaginary line passing
through a center between the outer edges of the first and second
outer pads 424a and 424b) along the first direction of the solar
cell 150. As a result, the current can be effectively collected at
both edge portions of the semiconductor substrate 160 and the
attachment characteristics of the lead 142 can be improved.
[0084] In the embodiment, the edge electrode portion 42d has an
opening in an interior thereof and the end of the edge electrode
portion 42d is located in the same line as the outermost finger
line 42a or outwardly protrudes than the outermost finger line 42a
(i.e., is closer the edge of the semiconductor substrate 160 (that
is, the long sides 161a, 161b) than the outermost finger line 42d.
The edge electrode portion 42d can have the low density while the
edge electrode portion 42d and the finger line 42a can be smoothly
connected. Thus, the collected current can be effectively
transmitted to the lead 142 without being remained.
[0085] More particularly, the edge electrode portion 42d includes a
first electrode portion 4241 inwardly located than the outermost
finger line 42a and a second electrode portion 4242 extending in a
direction crossing the first electrode portion 4241 from the first
electrode portion 4241 to the same line of the outer finger line
42a or the outside of the outermost finger line 42a.
[0086] In this instance, the first electrode portion 4241 may be
parallel to the finger line 42a or cross (e.g., is perpendicular
to) the line portion 421 and may be connected to the finger lines
42a (directly connected to the finger lines 42a or connected to the
finger lines 42a via the peripheral portion 42e) in the electrode
areas EA at both sides of the first edge area PA1. The second
electrode portion 4242 may cross (e.g., be perpendicular to) the
finger line 42a or may be parallel to the line portion 421.
[0087] In the embodiment, for example, the width of the line
portion 421, the finger line 42a, the peripheral line 42c, the edge
electrode portion 42d, or the peripheral portion 42e (in a
direction crossing (e.g., perpendicular to) its longitudinal
direction) maybe in the range of about 35 .mu.m to 350 .mu.m. In
the range of the width, it is possible to prevent or limit an
increase in optical loss, material cost, and the like, while
improving contact characteristics. For example, the width of the
line portion 421, the finger line 42a, the peripheral line 42c, the
edge electrode portion 42d, or the peripheral portion 42e may be
about 35 .mu.m to 200 .mu.m (more specifically, about 35 .mu.m to
120 .mu.m. The width of the pad portion 422 in the first direction
may be about 0.25 mm to 2.5 mm. The width of the pad portion 422 is
determined so as to reduce the shading loss due to optical loss
while ensuring a sufficient contact area with the lead 142. For
example, the width of the pad portion 422 may be about 0.8 mm to
1.5 mm.
[0088] Additionally, a length of the outer pad 424 in the second
direction may be greater than a length of the inner pad 426. For
example, the length of the outer pad 424 may be about 0.4 mm to 30
mm, and the length of the outer pad 424 may be about 0.4 mm to 3.2
mm considering the light loss more. The length of the inner pad 426
may be about 0.035 mm to 1 mm, more particularly, about 0.4 mm to 1
mm. As a result, the adhesion force by the outer pad 424 to which a
large force is applied can be further improved, and the optical
loss, the material cost, and the like can be reduced because the
area of the inner pad 426 is reduced.
[0089] In the embodiment, the first electrode 42, the lead 142, the
electrode area EA, the edge area PA, and the like are symmetrical
with respect to each other in the first direction and with respect
to an imaginary line (e.g., an imaginary line passing through a
center between the outer edges of the first and second outer pads
424a and 424b). Thus, current flow can be stably realized. However,
the embodiments of the invention are not limited thereto.
[0090] The solar cell 150 according to the embodiment may include
an alignment mark 420. When the solar cell panel 100 is
manufactured, the solar cell 150 can be aligned and positioned at a
desired position by using the alignment marks 420. The alignment
mark 420 may be formed by any of various methods using any of
various materials. For example, the alignment mark 420 may be
formed using a material the same as the first electrode 42 in the
process of forming the first electrode 42. However, the embodiments
of the invention are not limited thereto.
[0091] Similarly, in the embodiment, the second electrode 44
located on the other side of the semiconductor substrate 160
includes a bus bar at a position corresponding to the bus bar 42b
in the second direction, and may include a finger line, a
peripheral line, an edge electrode portion, a peripheral portion,
and the like. It is sufficient that the second electrode 44 has the
bus bar, and thus, the second electrode 44 may not include the
finger line, the peripheral line, the edge electrode portion, the
peripheral portion, and the like. The descriptions of the finger
line 42a, the bus bar 42b, the peripheral line 42c, the edge
electrode portion 42d, and the peripheral portion 42e of the first
electrode 42 may be applied to the finger line, the bus bar, the
peripheral line, the edge electrode portion, and the peripheral
portion of the second electrode 44 as they are. Also, the second
electrode 44 may have an alignment mark.
[0092] The first and second electrodes 42 and 44 may include the
same number of bus bars 42b, and the bus bar 42b of the first and
second electrodes 42 and 44 may be positioned at the same positions
at the opposite surfaces of the semiconductor substrate 160. The
width, pitch, and number of the finger lines 42a of the first
electrode 42 may be the same as those of the finger lines of the
second electrode 44, or at least one of the width, pitch, and
number of the finger lines 42a of the first electrode 42 may be
different from that of the finger lines of the second electrode 44.
The width, length, pitch, and number of the pad portions 422 of the
first electrodes 42 may be the same as those of the pad portions of
the second electrodes 44. At least one of the width, length, pitch,
and number of the pad portions 422 of the first electrodes 42 may
be different from that of the pad portions of the second electrodes
44. In addition, the first electrode 42 and the second electrode
may have different planar shapes. Also, various other modifications
are possible.
[0093] In the solar cell 150 having the long axis and the short
axis, a ratio (W1/W3) of the pitch of the bus bar 42b (i.e., the
width W1 of the first electrode area EA1) with respect to the width
W3 of the semiconductor substrate 160 (or the solar cell 150) in
the second direction may be 0.35 or less. By limiting the ratio
(W1/W3) of the pitch of the bus bar 42b to the width W3 of the
semiconductor substrate 160 below a certain value, the current
flowing path can be minimized and thus the efficiency of solar cell
1500 can be further improved.
[0094] Conventionally, the ratio (W1/W3) of the pitch of the bus
bar 42b to the width W3 of the semiconductor substrate 160 exceeds
0.35 even though the long axis and the short axis are provided, and
the path through which the current flows cannot be optimized.
Accordingly, it has been difficult to sufficiently realize the
effect of the solar cell 150 having the short axis and the long
axis in order to reduce the current. On the other hand, in the
embodiment, the efficiency of the solar cell 150 having the short
axis and the long axis can be effectively improved by limiting the
ratio (W1/W3) of the pitch of the bus bar 42b to the width W3 of
the semiconductor substrate 160 below the certain value.
[0095] For example, the ratio (W1/W3) of the pitch of the bus bar
42b to the width W3 of the semiconductor substrate 160 may be about
0.1 to 0.35. A reduction of the pitch of the bus bar 42b may reduce
the current flow path, but the number of the bus bars 42b and the
number of the leads 142 may be excessively increased, which may
increase cost and process time. Accordingly, the ratio (W1/W3) of
the pitch of the bus bars 42b to the width W3 of the semiconductor
substrate 160 may be 0.1 or more. However, the embodiments of the
invention are not limited thereto.
[0096] In the embodiment, the cutting line CL may be arranged in
the first direction parallel to the longitudinal direction of the
finger line 42a or the long axis. The electrodes 42 and 44 may be
symmetrical with respect to the imaginary line parallel to the
first direction. Therefore, even after cutting the solar cell 150,
there is no large difference between the two sides when viewed in
the second direction, and therefore the solar cell 150 can be
freely arranged in the solar cell panel 100 without the distinction
of the both sides.
[0097] In this instance, the second long sides 161b of the first or
second solar cells 151 and 152 corresponds to a cut surface formed
by cutting along the cutting line CL, while the first long side
161a, the first and second short sides 162c and 162b, and the first
and second inclined sides 163a and 163b are non-cut surfaces.
Whether it is the cut surface or the non-cut surface may be seen
from the presence or the absence of the first and second inclined
sides 163a and 163b or the difference in surface roughness on the
microscope, the difference in surface morphology, and the like.
[0098] In this instance, a first gap (or a first interval) W4
between the cut surface and the conductivity type regions 20 and 30
and/or ends of the electrodes 42 and 44 adjacent to the cut surface
may be smaller than a second gap (or a second interval) W5 between
the non-cut surface and the conductivity type regions 20 and 30
and/or the ends of the electrodes 42 and 44 adjacent to the non-cut
surface. A portion including the cut line CL is a non-active region
in which the conductivity type regions 20 and 30 and/or the
electrodes 42 and 44 are not formed to prevent shunts and the like.
This is for maximizing an area contributing to a photoelectric
conversion by minimizing a width of the non-active region. As
described above, the conductivity type regions 20 and 30 and the
electrodes 42 and 44 are not symmetrical with respect to the first
long side 161a which is the non-cut face and the second long side
161b which is the cut surface, while the conductivity type regions
20 and 30 and the electrodes 42 and 44 are symmetrical with respect
to the first and second short sides 161a and 162b which is the
non-cut surface. However, the embodiments of the invention are not
limited thereto, and the first gap W4 may be equal to or larger
than the second gap W5.
[0099] For simple descriptions and illustrations, it is exemplified
that two solar cells 150 are manufactured in one mother solar cell
150a. In this instance, the cutting line CL may pass a center of
the mother solar cell 150a. Then, each solar cell 150 has
substantially the same area and can have similar electrical
characteristics. Particularly, when the mother solar cell 150a
having an approximate octagonal shape is cut to manufacture two
solar cells 150, each solar cell 150 is divided to include first
and second long sides 161a and 161b, the first and second short
sides 162a and 162b, and the first and second included sides 163a
and 163b.
[0100] However, the embodiments of the invention are not limited
thereto. Therefore, as shown in FIG. 6, there may be two or more
cutting lines CL parallel to each other. According to this, the
number of solar cells 150 manufactured from one mother solar cell
150a may be one more than the number of the cutting lines CL. The
areas where the conductivity type regions 20 and 30 and the
electrodes 42 and 44 are formed may be formed with substantially
the same width and may be spaced apart by a uniform distance when
the number of the cutting lines CL is two or more.
[0101] However, in the embodiment, since the outer pads 424 located
inwardly than the outermost finger lines 42a in the second
direction parallel to the short axis are located on both sides, if
the cutting lines CL are too many, it is difficult to arrange them
smoothly. In consideration of this, the number of the cutting line
CL may be three or less and the number of the solar cells 150
manufactured from one mother solar cell 150a may be four or less.
Accordingly, for example, a ratio (W3/L) of the width W3 (see FIG.
4) of the semiconductor substrate 160 in the second direction to
the length L (see FIG. 4) of the semiconductor substrate 160 in the
first direction may be about 0.2 to 0.5. Even though the ratio
(W3/L) is 0.25 when four solar cells 150 are manufactured from one
mother solar cell 150a the portion including the cut line CL, the
ratio (W3/L) is limited to 0.2 or more in the embodiment in
consideration of the process error, design freedom, and the
like.
[0102] As shown in FIG. 6, when mother solar cell 150a having the
approximate octagonal shape is cut along two or more cut surfaces,
the upper and lower solar cells 150 in the drawing are the first
and second solar cells 151 and 152, respectively, having the first
and second long sides 161a and 161b (see FIG. 5), the first and
second short sides 162a and 162b (see FIG. 5), and the first and
second inclined sides 163a and 163b (see FIG. 5). At this instance,
the second long side 161b is the cut surface cut by the cutting
line CL and the remaining edges are the non-cut surfaces. The
descriptions of FIGS. 4 and 5 maybe applied to the first and second
solar cells 151 and 152 as they are.
[0103] The solar cell 150 positioned in a center portion is a third
solar cell 153 having the first and second long sides 161a and 161b
and the first and second short sides 162a and 162b without the
first and second inclined sides 163a and 163b. In the third solar
cell 153, the first and second long sides 161a and 161b are cut
surfaces cut by the cutting line CL and the first and second short
sides 162a and 162b are non-cut surfaces. Accordingly, the third
solar cell 153 may have a rectangular shape different from the
first and second solar cells 151 and 152. In this instance, since
the first and second long sides 161a and 161b are both formed by
the cut surfaces, the conductivity type regions 20 and 30 and/or
the electrodes 42 and 44 are symmetrical in the second
direction.
[0104] The solar cell 150 described above is electrically connected
to the neighboring solar cell 150 by the leads 142 positioned on
(e.g., in contact with) the first electrode 42 or the second
electrode 44. This will be described in more detail with reference
to FIG. 7 together with FIGS. 1 to 5.
[0105] FIG. 7 is a perspective view schematically showing the first
solar cell 151 and the second solar cell 152 connected by the leads
142, which are included in the solar cell panel 100 shown in FIG.
1. Here, the first and second solar cells 151 and 152 are unit
solar cells manufactured by cutting the mother solar cell 150a and
have the long and short axes. The first and second solar cells 151
and 152 are schematically shown only based on the semiconductor
substrate 160 and the electrodes 42 and 44 in FIG. 7 for simplicity
and clarity.
[0106] As shown in FIG. 7, two solar cells 150 (e.g., the first
solar cell 151 and the second solar cell 152) adjacent to each
other among the plurality of solar cells 150 are connected by the
lead 142. In this instance, the lead 142 electrically connects the
first electrode 42 on the front surface of the first solar cell 151
and the second electrode 44 on the back side of the second solar
cell 152 positioned on one side (the left and lower side) of the
first solar cell 151. Another lead 1420a electrically connects the
second electrode 44 on the back surface of the first solar cell 151
and the first electrode 42 on the front side of another solar cell,
which will be positioned on the other side (the right and upper
side) of the first solar cell 151. Still another lead 1420b
electrically connects the first electrode 42 on the front surface
of the second solar cell 152 and the second electrode 44 on the
back side of still another second solar cell, which will be
positioned on one side (the left and lower side) of the second
solar cell 152. Accordingly, the plurality of solar cells 150 can
be connected to each other by the leads 142, 1420a, and 1420b.
Hereinafter, the descriptions of the lead 142 can be applied to the
leads 142, 1420a, and 1420b that connect the two adjacent solar
cells 150 to each other.
[0107] In this embodiment, each lead 142 may include a first
section connected to the first electrode 42 of the first solar cell
151 (in more detail, the bus bar 42b of the first electrode 42) at
the front surface of the first solar cell 151 while extending from
the first long side 161a of the first solar cell 151 toward the
second long side 161b of the first solar cell 151 opposite the
first long side 161a, a second section connected to the second
electrode 44 of the second solar cell 152 (in more detail, the bus
bar of the second electrode 44) at the back surface of the second
solar cell 152 while extending from the second long side 161b of
the second solar cell 152 toward the first long side 161a of the
second solar cell 152 opposite the second long side 161b of the
second solar cell 152, and a third section extending from the front
surface of the first solar cell 151 to the back surface of the
second solar cell 152, to connect the first section and second
section. Accordingly, the lead 142 maybe arranged to extend across
the first solar cell 151 along a portion of the first solar cell
151 while extending across the second solar cell 152 along a
portion of the second solar cell 152. Since the lead 142 is formed
only in regions corresponding to portions of the first and second
solar cells 151 and 152 (e.g., the bus bar 42b) while having the
smaller width than the first and second solar cells 151 and 152,
the lead 142 may effectively connect the first and second solar
cells 151 and 152 in spite of the small area thereof.
[0108] For example, the lead 142 may be arranged at the
corresponding first and second electrodes 42 and 44 of the first
and second solar cells 151 and 152, to extend lengthily along the
bus bar 42b of the first and second electrodes 42 and 44 while
contacting the bus bar 42b. Accordingly, the lead 142 continuously
contacts the first and second electrodes 42 and 44 and, as such,
electrical connection characteristics may be enhanced. In the
embodiment, the lead 142 may extend in the second direction
parallel to the short axis. However, the embodiments of the
invention are not limited thereto.
[0109] With reference to one surface of each solar cell 150, the
plurality of leads 142 are provided and, as such, electrical
connection characteristics of the solar cell 150 to another,
neighboring solar cell 150 may be enhanced. In particular, in the
embodiment, each lead 142 is constituted by a wire having a smaller
width than a ribbon having a relatively great width (e.g., 1 to 2
mm), which has been used in conventional instances. To this end, a
number of leads 142 (e.g., two to five) greater than a number of
ribbons as described above is used with reference to one surface of
each solar cell 150.
[0110] In one example, each lead 142 includes a core layer 142a,
and a solder layer 142b coated on an outer surface of the core
layer 142a with a small thickness. The solder layer 142b may
include a solder material for soldering the lead 142 and the
electrodes 42 and 44. For example, the core layer 142a may include
a material exhibiting excellent electrical conductivity (e.g., a
metal, in more detail, Ni, Cu, Ag, or Al) as a major material
thereof (e.g., a material having a content of 50 wt % or more, in
more detail, a material having a content of 90 wt % or more). The
solder layer 142b may include a material such as Pb, Sn, SnIn,
SnBi, SnPb, SnPbAg, SnCuAg or SnCu as a major material thereof. Of
course, the invention is not limited to the above-described
materials and, the core layer 142a and the solder layer 142b may
include any of various materials.
[0111] When the wire, which has a smaller width than the existing
ribbon, is used as the lead 142, material costs may be greatly
reduced. Since the lead 142 has a smaller width than the ribbon, it
may be possible to use a sufficient number of leads 142 and, as
such, the movement distance of carriers can be minimized.
Accordingly, the output power of the solar cell panel 100 can be
enhanced.
[0112] Also, the wire constituting the lead 142 in accordance with
the embodiment may have a rounded portion. That is, the wire
constituting the lead 142 may have a circular or oval
cross-section, a curved cross-section, or a rounded cross-section,
to induce reflection or diffuse reflection. Accordingly, light
reflected from a rounded surface of the wire constituting the lead
142 may be reflected or totally reflected upon the front substrate
110 or back substrate 120 disposed at the front surface or back
surface of the solar cell 150 and, as such, may be again incident
upon the solar cell 150. Thus, the output power of the solar cell
panel 100 can be effectively enhanced. Of course, embodiments of
the invention are not limited thereto, and the wire constituting
the lead 142 may have a quadrangular shape or a polygonal shape.
The wire may also have any of various other shapes.
[0113] In this embodiment, the lead 142 may have a width (or a
diameter) less than 1 mm (i.e. 250 to 500 .mu.m). For reference, in
the embodiment, a thickness of the solder layer 142b is very small
and is varied depending on a position of the lead 142, and thus,
the width of the lead 142 may be a width of the core layer 142a. On
the other hand, the width of the lead 142 may be a width of a
portion of the lead 142 on the line portion 421 (see FIG. 5)
measured in a position passing though a center of the lead 142. By
the lead 142, which has the wire shape while having the width, the
current generated in the solar cell 150 can be effectively
transferred to an outer circuit (e.g., a bus ribbon or a bypass
diode of a junction box) or to another solar cell 150. In this
embodiment, the lead 142 may be fixed to the electrodes 42 and 44
of the solar cell 150 in the state that each lead 142 is
independently disposed on and fixed to the electrodes 42 and 44,
and thus, leads 142 are not inserted into a separate layer, film,
or the like to be fixed to electrode 42 and 44. If the width of the
lead 142 is less than 250 .mu.m, the strength of the lead 142 may
be insufficient, and the lead 142 may exhibit inferior electrical
connection characteristics and low attachment force because the
connection area between the lead 142 and the electrodes 42 and 44
is too small. On the other hand, if the width W1 of the lead 142 is
greater than 1 mm (e.g., 500 um), the material costs of the lead
142 increase, and the lead 142 may obstruct incidence of light upon
the front surface of the solar cell 150, and thus, shading loss may
increase. In addition, force applied to the lead 142 in a direction
away from the electrodes 42 and 44 may increase and, as such,
attachment force between the lead 142 and the electrodes 42 and 44
may be reduced. In severe instances, cracks or the like may be
generated at the electrodes 42 and 44 or the semiconductor
substrate 160. For example, the width W1 of the lead 142 may be 350
to 450 um (in particular, 350 to 400 um). In this range, output
power of the solar cell panel 100 can be enhanced while the
attachment force to the electrodes 42 and 44 can be increased.
[0114] In this instance, the solder layer 142b of each lead 142 is
positioned separately from the other lead 142 or the other solder
layer 142b. Here, the lead 142 has a cross-section of a circular
shape before the attachment, while a shape of the lead 142 on the
pad portion 422 is deformed when or after the lead 142 is bonded to
(e.g., is in contact with) the electrodes 42 and 44 by using the
solder layer 142b. That is, in the tabbing process, each of the
solder layers 142b flow down to the first or second electrodes 42
and 44 (more specifically, the pad portion 422). Accordingly, as
shown in FIG. 3, the width of the solder layer 142b may gradually
increase toward the pad portion 422 at a portion adjacent to the
pad portion 422. As an example, the portion of the solder layer
142b adjacent to the pad portion 422 may have a width equal to or
greater than the diameter or the width of the core layer 142a. More
particularly, an upper portion of the solder layer 142b on the core
layer 142a has a shape protruding toward an outside of the solar
cell 150 according to the shape of the core layer 142a, while the
portion of the solder layer 142b adjacent to the pad portion 422 or
a lower portion of the solder layer 142b includes a portion having
a concave shape with respect to the outside of the solar cell 150.
As a result, an inflection point where a curvature changes is
located on the side of the solder layer 142b. It can be seen from
the shape of the solder layer 142b that the leads 142 are
individually attached and fixed by the solder layer 142b without
being inserted or covered in a separate layer, film, or the like.
The solar cell 150 and the lead 142 can be connected by a simple
structure and a simple process through fixing the lead 142 by the
solder layer 142b without using the separate layer or a film. In
particular, the lead 142 having the narrow width and the rounded
shape as in the embodiment can be attached without using the
separate layer, film (e.g., a conductive adhesive film including a
resin and a conductive material). Accordingly, the process cost and
time of the process for attaching the lead 142 can be
minimized.
[0115] On the other hand, even after the tabbing process, the
portion of the lead 142 positioned between the two solar cells 150
has a shape the same as or similar to a shape before the tabbing
process (e.g., a cross-section shape of the circular shape).
[0116] For example, in the embodiment, the second long side 161b
(see FIG. 5) of the first solar cell 151 and the second long side
161b of the second solar cell 152 having the same lengths may face
each other. Also, the first long side 161a (see FIG. 5) of the
first solar cell 151 and the first long side 161a of another solar
cell, which is adjacent to the first solar cell 151 and is opposite
to the second solar cell 152, may face each other. Also, the first
long side 161a of the second solar cell 152 and the first long side
161a of yet another solar cell, which is adjacent to the second
solar cell 152, may face each other. Accordingly, the first long
sides 161a, the second long sides 161b, or the inclined sides 163a
and 163b (see FIG. 5) having the same length are arranged so as to
face each other to improve appearance and a structural
stability.
[0117] This is because the cutting line CL is parallel to the
finger line 42a, and thus, the bus bar 42b is symmetrical with
respect to the imaginary line along the first direction. According
to this, the first and second solar cells 151 and 152 manufactured
from the mother solar cell 150a can be electrically connected as
they are without rotating, thereby reducing the processing time and
cost required for the rotation. However, the embodiments of the
invention are not limited thereto, and the first long side 161a and
the second long side 161b of the adjacent solar cells 150 may be
arranged to face each other.
[0118] According to the solar cell 150 and the solar cell panel 100
including the same, stated in the above, light loss can be
minimized by using the bus bar 42b having the small width and/or
the lead 142 having the wire shape, and a movement path of the
carrier can be reduced by increasing the number of bus bars 42b
and/or the leads 142. Thus, efficiency of the solar cell 150 and an
output of the solar cell panel 100 can be improved. Further, the
light loss can be minimized due to diffused reflection or the like
by using the lead 142 having the wire shape, and the movement path
of the carrier can be reduced by reducing the pitch of the leads
142. Thus, the efficiency of the solar cell 150 and the output of
the solar cell panel 100 can be improved.
[0119] Particularly, the efficiency of the solar cell 150 and the
output of the solar cell panel 100 can be maximized by applying the
lead 142 to the solar cell 150 having the long axis and the short
axis. In this instance, the lead 142 may be arranged in the
direction parallel to the short axis and the outer pads 424 may be
positioned at both sides in the direction parallel to the short
axis. Then, the movement path through the lead 142 can be minimized
and the attachment property of the lead 142 can be enhanced.
[0120] Hereinafter, a solar cell panel according to other
embodiments of the invention will be described in detail. Detailed
descriptions will be omitted for the same or extremely similar
parts as those described above, and only different parts will be
described in detail. It is also within the scope of the invention
to combine the above-described embodiments or variations thereof
with the following embodiments or modifications thereof.
[0121] FIG. 8 is a partial front plan view of a solar cell and
leads included in a solar cell panel according to another
embodiment of the invention. In FIG. 8, a semiconductor substrate
160, a first electrode 42, and a lead 142 are mainly shown for
simplicity and clarity.
[0122] Referring to FIG. 8, at least a part of finger lines 42a
arranged between two neighboring bus bars 42b may include
disconnected portions S where a part of the finger line 42a is
removed and thus the finger line 42a does not continuously
extend.
[0123] In this instance, the disconnected portions S maybe formed
at the finger lines 42a arranged in the first electrode areas EA1,
respectively, and may not be formed at the finger lines 42a
arranged in the second electrode areas EA2. Although the finger
lines 42a in each first electrode area EA1 have respective
disconnected portions S, current may smoothly flow through the
finger lines 42a because the finger lines 42a are connected to two
neighboring bus bars 42b or leads 142 at opposite sides thereof. In
this instance, accordingly, it may be possible to reduce the area
of the first electrode 42 without obstructing flow of current in
the first electrode area EA1 and, as such, manufacturing costs and
shading loss may be reduced. On the other hand, the finger lines
42a in each second electrode area EA2 are connected to one bus bar
42b or lead 142 only at one side thereof, and have no disconnected
portion S and, as such, current may smoothly flow to the bus bar
42b or lead 142 disposed at one side of the finger lines 42a.
[0124] The disconnected portions S of the finger lines 42a in each
first electrode area EA1 may be centrally arranged between two
neighboring bus bars 42b corresponding to the first electrode area
EA1 . Accordingly, it may be possible to minimize a current
movement path.
[0125] The width of each disconnected portion S may be 0.5 times or
more the pitch of each finger line 42a, and may be 0.5 times or
less the pitch of each bus bar 42b. When the width of each
disconnected portion S is less than 0.5 times the pitch of each
finger line 42a, effects of the disconnected portion S may be
insufficient because the disconnected portion S is too narrow. On
the other hand, when the width of each disconnected portion S is
greater than 0.5 times the pitch of each bus bar 42b, electrical
characteristics may be degraded because the disconnected portion S
is too wide. Meanwhile, for example, the width of each disconnected
portion S may be greater than the width W6 of each pad section 422
in each bus bar 42b. Within this range, effects of the disconnected
portion S may be maximized. Of course, the embodiments of the
invention are not limited to the above-described conditions, and
the width of each disconnected portion S may have any of various
values.
[0126] The ratio of the number of finger lines 42a having
disconnected portions S in each first electrode area EA1 may be
0.33 to 1 times the total number of finger lines 42a in the first
electrode area EA1 when the numbers of the finger lines 42a are
measured in a direction parallel to the bus bars 42b. Within this
range, effects of the disconnected portion S may be maximized. In
this instance, accordingly, it may be possible to minimize the
average movement distance of carriers while providing a sufficient
number of disconnected portions S. Of course, the embodiments of
the invention are not limited to the above-described conditions,
and the above-described number ratio may be varied.
[0127] Although the disconnected portions S are illustrated in FIG.
8 as being provided at each first electrode area EA1, the invention
is not limited thereto. The disconnected portions S may be provided
at a part of the plurality of first electrode areas EA1, and may
not be provided at the remaining part of the plurality of first
electrode areas EA1. It is exemplified that, in the first electrode
areas EA1, the finger lines 42a connecting two neighboring lines
42b and the finger lines 42a having the disconnected portions S are
alternately arranged one by one in the second direction. Then, the
process cost and the light loss can be reduced, also, the current
flow path can be optimized. However, the embodiments of the
invention are not limited thereto, and thus, the arrangement of the
finger lines 42a connecting two neighboring lines 42b and the
finger lines 42a having the disconnected portions S may be
variously varied. Further, in the drawings and above description,
although illustration and description has been given in conjunction
with the first electrode 42, the description may be applied to the
second electrode 44 in the same manner.
[0128] FIG. 9 is a cross-sectional view of a solar cell panel
according to yet another embodiment of the invention. FIG. 10 is a
front plan view schematically showing a first solar cell and a
second solar cell, which are applicable to the solar cell panel
shown in FIG. 9 and manufactured by cutting a mother solar
cell.
[0129] Referring to FIG. 9, in the embodiment, a plurality of solar
cells 150 are connected to each other by a connecting member 144
rather than the lead 142 (see FIG. 1). In this instance, the
plurality of solar cells 150 may be electrically connected (e.g.,
connected in series) to each other by the connecting member 144 to
form one row (or string).
[0130] More particularly, the connecting member 144 is located
between a first electrode 42 of a first solar cell 151 and a second
electrode 44 of a second solar cell 152 to electrically and
physically connect them. That is, peripheral portions of the first
solar cell 151 and the second solar cell 152 are positioned so as
to overlap with each other. The connecting member 144 is disposed
between a pad electrode 42f of the first electrode 42 of the first
solar cell 151, which is positioned at one side (a lower side of
FIG. 9), and a pad electrode 44f of the second electrode 44 of the
second solar cell 152, which is positioned at the other side (an
upper side of FIG. 9) to electrically and physically connect them.
For example, the connecting member 144 may be in contact with the
pad electrodes 42f and 44f. The connection member 144 maybe formed
of any of various materials capable of electrically and physically
connecting the solar cell 150, for example, a conductive adhesive
layer, a solder, or the like. This connection is repeated so that a
plurality of solar cells 150 form one row (or string). The solar
cell panel 100 may include one or more rows of solar cells 150.
When a plurality of columns are provided, various configurations
can be applied to the electrical connection for them.
[0131] Referring to FIG. 10, in the embodiment, one mother solar
cell is cut along a cutting line to manufacture the first and
second solar cells 151 and 152, which are a plurality of solar
cells 150. The structure of the solar cell 150 described with
reference to FIGS. 1 to 8 may be applied as it is to the structure
of the solar cell 150 in this embodiment, except for shapes of the
first and second electrodes 42 and 44. Hereinafter, the first and
second electrodes 42 and 44 included in each solar cell 150 will be
described in more detail.
[0132] The first electrode 42 located on one surface of the
semiconductor substrate 160 may include a plurality of finger lines
42a extending in a first direction (a horizontal direction in FIG.
10) parallel to the long axis and parallel to each other, a bus bar
42b formed in a second direction (a vertical direction in FIG. 10)
that crosses (e.g., is perpendicular to) the finger line 42a and
electrically connected to the finger lines 42a. In FIG. 10, the
first electrode 42 may further include a peripheral line 42c. A
width, a pitch, a shape, and the like of the plurality of finger
lines 42a, the bus bar 42b, and the peripheral lines 42c described
with reference to FIGS. 1 to 8 may be applied to this
embodiment.
[0133] In the embodiment, the bus bar 42b provides a path for
transferring the carriers collected by the finger lines 42a to the
pad electrode 42f connected to the connecting member 144. In the
embodiment, a number of the bus bars 42b may be sufficiently
secured to six or more (e.g., six to thirty-three, more
specifically, six to fourteen, for example, six to twelve) to
minimize the movement path of the carrier. However, since the
connecting member 144 is not directly connected to the bus bar 42b,
only the line portion 421 is provided without a pad portion 422
(see FIG. 1), thereby minimizing the shading loss. However, the
embodiments of the invention are not limited thereto, and the bus
bar 42b may include the pad portion 422.
[0134] In the embodiment, the first electrode 42 may include the
pad electrode 42f to which the connecting member 144 is connected
or attached. The pad electrode 42f is a portion overlapping another
solar cell 150 so that the connecting member 144 connecting the
neighboring solar cell 150 is directly positioned (e.g., is in
direct contact with) on the pad electrode 42f. In this instance, a
width of the pad electrode 42f may be larger than a width of the
line portion 421 of the finger line 42a and/or a width of the bus
bar 42b. Then, the pad electrode 42f and the connecting member 144
are adhered with a sufficient area, and thus, the electrical
characteristics and adhesion characteristics can be improved.
However, the embodiments of the invention are not limited thereto.
Therefore, a width of the pad electrode 42f may be the same as or
less than the width of the line portion 421 of the finger line 42a
and/or the width of the bus bar 42b. Alternatively, the pad
electrode 42f may not be provided, and the connecting member 44 may
be in contact with a part of the finger line 42a and/or the bus bar
42b.
[0135] The pad electrode 42f is positioned adjacent to the first or
second long side 161a and 162a of the solar cell 150 to minimize
the area of the solar cell 150 that overlaps the neighboring solar
cell 150 while interposing the connecting member 144. The pad
electrode 42f has a shape extending in a direction parallel to the
first or second long side 161a or 161b (i.e., the first direction
parallel to the finger line 42a and crossing the bus bar electrode
42b). Thus, the connection area between the connection member 144
and the pad electrode 42f can be maximized and thus the connection
member 144 and the pad electrode 42f can be stably connected to
each other.
[0136] The pad electrode 42f may be directly connected to a first
conductivity type region 20(see FIG. 1) by penetrating through the
insulating layer (e.g., the first passivation layer 22 (see FIG. 1)
and the anti-reflection layer 24 (see FIG. 1)) on the first
conductivity type region 20, or may be positioned on the insulating
layer to be apart from the first conductivity type region 20.
[0137] The second electrode 44 located on the other surface of the
semiconductor substrate 160 may include a finger line, a bus bar,
and a pad electrode 44f corresponding to the finger line 42a, the
bus bar 42b, and the pad electrode 42f of the first electrode 42,
respectively. Also, the second electrode 44 may further include a
peripheral line corresponding to the peripheral line 42c of the
first electrode 42. The descriptions of the first electrode 42 may
be applied to the second electrode 44, the descriptions of the
first passivation layer 22 and the anti-reflection layer 24 related
to the first electrode 42 may be applied to the second passivation
layer 32 related to the second electrode 44, and the descriptions
of the first conductivity type region 20 related to the first
electrode 42 may be applied to a second conductivity region 30
related to the second electrode 44. The width, pitch, and the like
of the finger lines 42a, the bus bar 42, and the pad electrode 42f
of the first electrode 42 maybe the same as or different from those
of the finger lines, the bus bar, and the pad electrode 44f of the
second electrode 44.
[0138] In the embodiment, it is exemplified that one pad electrode
42f of the first electrode 42 is provided in each solar cell 150 to
be adjacent to one side in the second direction, and one pad
electrode 44f of the second electrode 44 is provided in each solar
cell 150 to be adjacent to the other side in the second direction.
According to this structure, when the unit solar cells 150 are
connected, the pad electrode 42f of the first electrode 42 located
on the one side of the first solar cell 151 and the pad electrode
44f of the second electrode 44 of the second solar cell 152 located
on the other side of the solar cell 152 are adjacent to each other.
Thus, the neighboring solar cells 150 can be stably connected only
by adjoining the pad electrodes 42f and 44f of the neighboring
solar cells 150 using the connecting member 144. In addition, since
the pad electrodes 42f and 44f are disposed only on one side, the
material cost of the first and second electrodes 42 and 44 can be
reduced and the manufacturing process of the first and second
electrodes 42 and 44 can be simplified.
[0139] Also, in each unit solar cell 150 manufactured from one
mother solar cell, the pad electrode 42f of the first electrode 42
is adjacent to one edge (a lower edge in FIG. 10) of the solar cell
150 in the second direction, and the pad electrode 44f of the
second electrode 44 is adjacent to the other edge (e.g., an upper
edge in FIG. 10) of the solar cell 150 in the second direction.
Accordingly, when the plurality of solar cells 150 are connected in
series to form the solar cell panel 100, a plurality of solar cells
150 can be connected without changing the arrangement of the solar
cells 150. Thus, the manufacturing process of the solar cell panel
100 can be simplified. However, the embodiments of the invention
are not limited thereto.
[0140] For example, when the first and second solar cells 151 and
152 are formed from one mother solar cell, the pad electrodes 42f
of the first electrode 42 included in the first and second solar
cells 151 and 152 are adjacent to different long sides and the pad
electrodes 44f of the second electrodes 44 included in the first
and second solar cells 151 and 152 are adjacent to different long
sides. For example, the pad electrode 42f of the first electrode 42
is adjacent to the second long side 161b in the first solar cell
151, and the pad electrode 42f of the first electrode 42 is
adjacent to the first long side 161a in the second solar cell 152.
Also, the pad electrode 44f of the second electrode 44 is adjacent
to the first long side 161a in the first solar cell 151, and the
pad electrode 44f of the second electrode 44 is adjacent to the
second long side 161b in the second solar cell 152. When the first
and second solar cells 151 and 152 having the above structure are
connected by using the connection member 144, the pad electrode 42f
of the first electrode 42 adjacent to the first long side 161a of
the first solar cell 151 is connected to the pad electrode 44f of
the second electrode 44 adjacent to the first long side 161a of the
second solar cell 152. Accordingly, the long sides having the same
length can be connected to each other, and thus, the first and
second solar cells 151 and 152 can be stably connected.
[0141] The above described features, configurations, effects, and
the like are included in at least one of the embodiments of the
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 including in
the scope and spirit of the invention as disclosed in the
accompanying claims.
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