U.S. patent application number 16/404102 was filed with the patent office on 2019-08-22 for solar cell.
The applicant listed for this patent is LG Electronics Inc.. Invention is credited to Sungjin KIM, Gyeayoung KWAG, Taeyoung KWON, Seongeun LEE.
Application Number | 20190259904 16/404102 |
Document ID | / |
Family ID | 46161088 |
Filed Date | 2019-08-22 |
United States Patent
Application |
20190259904 |
Kind Code |
A1 |
KIM; Sungjin ; et
al. |
August 22, 2019 |
SOLAR CELL
Abstract
A solar cell includes a photoelectric conversion layer; and a
front electrode on the photoelectric conversion layer, wherein the
front electrode includes a plurality of first finger electrodes; a
plurality of second finger electrodes; a bus electrode directly
connected to at least one of the plurality of first finger
electrodes; a plurality of connecting electrodes connected to the
plurality of second finger electrodes, the plurality of connecting
electrodes forming at least one space therebetween; and an
auxiliary electrode formed at the at least one space, wherein the
auxiliary electrode connects at least two connecting electrodes of
the plurality of connecting electrodes.
Inventors: |
KIM; Sungjin; (Changwon-si,
KR) ; KWON; Taeyoung; (Changwon-si, KR) ; LEE;
Seongeun; (Changwon-si, KR) ; KWAG; Gyeayoung;
(Changwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG Electronics Inc. |
Seoul |
|
KR |
|
|
Family ID: |
46161088 |
Appl. No.: |
16/404102 |
Filed: |
May 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15601370 |
May 22, 2017 |
10340412 |
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16404102 |
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14810169 |
Jul 27, 2015 |
9660129 |
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15601370 |
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13312028 |
Dec 6, 2011 |
9117963 |
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14810169 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/1804 20130101;
Y02E 10/547 20130101; H01L 31/022433 20130101; Y02P 70/50 20151101;
Y02P 70/521 20151101 |
International
Class: |
H01L 31/18 20060101
H01L031/18; H01L 31/0224 20060101 H01L031/0224 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2010 |
KR |
10-2010-0123692 |
Claims
1. (canceled)
2. A solar cell comprising: a photoelectric conversion layer; and a
front electrode that is disposed on the photoelectric conversion
layer, and that comprises: a bus bar electrode that extends along a
first direction; a plurality of connecting electrodes that extend
along the first direction, that are connected to the bus bar
electrode, and that extend away from the bus bar electrode along
the first direction; at least one first finger electrode that is
connected to the bus bar electrode, and that extends away from the
bus bar electrode along a second direction and along a third
direction opposite to the second direction; and at least one second
finger electrode that is connected to at least one of the plurality
of connecting electrodes, and that extends away from the plurality
of connecting electrodes along the second direction and along the
third direction opposite to the second direction.
3. The solar cell according to claim 2, wherein each connecting
electrode among the plurality of connecting electrodes comprises
(i) a first end and (ii) a second end that is opposite the first
end, wherein the first end of the connecting electrode is connected
to an end portion of the bus bar electrode, and wherein the second
end of the connecting electrode is spaced apart from the bus bar
electrode such that the connecting electrode extends along the
first direction, away from the bus bar electrode, to the second end
of the connecting electrode.
4. The solar cell according to claim 2, wherein the plurality of
connecting electrodes are parallel to the bus bar electrode and are
perpendicular to at least one of (i) the at least one first finger
electrode, or (ii) the at least one second finger electrode.
5. The solar cell according to claim 4, wherein the plurality of
connecting electrodes are parallel to each other, and wherein at
least two connecting electrodes among the plurality of connecting
electrodes are symmetrically arranged about a longitudinal axis of
the bus bar electrode.
6. The solar cell according to claim 2, wherein the plurality of
connecting electrodes define at least one space therebetween.
7. The solar cell according to claim 6, wherein the at least one
second finger electrode is arranged outside of the at least one
space between the plurality of connecting electrodes.
8. The solar cell according to claim 6, further comprising at least
one auxiliary electrode that is arranged in the at least one space
between the plurality of connecting electrodes, and that is
connected to at least two connecting electrodes among the plurality
of connecting electrodes.
9. The solar cell according to claim 8, wherein the at least one
auxiliary electrode is arranged parallel to the at least one second
finger electrode.
10. The solar cell according to claim 9, wherein one of the at
least one auxiliary electrode is arranged collinear with one of the
at least one second finger electrode.
11. The solar cell according to claim 8, wherein the at least one
space between the plurality of connecting electrodes comprises an
enclosed space that is defined by (i) two connecting electrodes
among the plurality of connecting electrodes, (ii) one of the at
least one auxiliary electrode, and (iii) an end portion of the bus
bar electrode.
12. The solar cell according to claim 8, wherein the at least one
space between the plurality of connecting electrodes comprises an
enclosed space that is defined by (i) two connecting electrodes
among the plurality of connecting electrodes, and (ii) two
auxiliary electrodes among the at least one auxiliary
electrode.
13. The solar cell according to claim 2, wherein the at least one
second finger electrode and the plurality of connecting electrodes
are arranged closer to an edge of the photoelectric conversion
layer as compared to the bus bar electrode and the at least one
first finger electrode.
14. The solar cell according to claim 2, wherein the at least one
second finger electrode and the plurality of connecting electrodes
are arranged further towards the first direction as compared to the
bus bar electrode and the at least one first finger electrode.
15. The solar cell according to claim 2, wherein for each second
finger electrode of the at least one second finger electrode: the
second finger electrode is connected to an outermost connecting
electrode among the plurality of connecting electrodes, and the
second finger electrode extends away from the plurality of
connecting electrodes along the second direction or along the third
direction opposite to the second direction.
16. The solar cell according to claim 2, wherein for each second
finger electrode of the at least one second finger electrode: a
first portion of the second finger electrode is connected to the at
least one of the plurality of connecting electrodes, and extends
away from the plurality of connecting electrodes along a fourth
direction; and a second portion of the second finger electrode
extends away from the first portion and away from the plurality of
connecting electrodes along the second direction or along the third
direction opposite to the second direction.
17. The solar cell according to claim 2, wherein a width of each of
the plurality of connecting electrodes is smaller than a width of
the bus bar electrode.
18. A solar cell module comprising: a plurality of solar cells,
with each of the plurality of solar cells comprising (i) a
photoelectric conversion layer and (ii) an electrode that is
disposed on the photoelectric conversion layer; a plurality of
interconnectors that are configured to electrically interconnect
electrodes of the plurality of solar cells, wherein each of the
plurality of interconnectors is configured to electrically
interconnect electrodes of adjacent solar cells; at least one
sealing film that is configured to seal the plurality of solar
cells; a front substrate that is disposed on front surfaces of the
plurality of solar cells; and a rear substrate that is disposed on
rear surfaces of the plurality of solar cells, wherein for each of
the plurality of solar cells, the electrode comprises: a bus bar
electrode that extends along a first direction; a plurality of
connecting electrodes that extend along the first direction, that
are connected to the bus bar electrode, and that extend away from
the bus bar electrode along the first direction; at least one first
finger electrode that is connected to the bus bar electrode, and
that extends away from the bus bar electrode along a second
direction and along a third direction opposite to the second
direction; and at least one second finger electrode that is
connected to at least one of the plurality of connecting
electrodes, and that extends away from the plurality of connecting
electrodes along the second direction and along the third direction
opposite to the second direction.
19. The solar cell module according to claim 18, wherein a first
end of the bus bar electrode is connected to the plurality of
connecting electrodes, and wherein a second end of the bus bar
electrode is connected to an interconnector among the plurality of
interconnectors.
20. The solar cell module according to claim 18, wherein the
plurality of connecting electrodes define at least one space
therebetween, and wherein at least one auxiliary electrode is
arranged in the at least one space between the plurality of
connecting electrodes, and is connected to at least two connecting
electrodes among the plurality of connecting electrodes.
21. The solar cell module according to claim 18, wherein a width of
each of the plurality of connecting electrodes is smaller than a
width of the bus bar electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/601,370, filed on May 22, 2017, now allowed, which is a
continuation of U.S. application Ser. No. 14/810,169, filed on Jul.
27, 2015, now U.S. Pat. No. 9,660,129, which is a continuation of
U.S. application Ser. No. 13/312,028, filed on Dec. 6, 2011, now
U.S. Pat. No. 9,117,963, which claims the benefit under 35 U.S.C.
.sctn. 119(a) to Korean Patent Application No. 10-2010-0123692,
filed on Dec. 6, 2010, all of which are hereby expressly
incorporated by reference into the present application.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] Embodiments of the invention relate to a solar cell, and
more particularly, to a solar cell having an improved electrode
structure.
Discussion of the Related Art
[0003] Recently, as conventional energy resource such as petroleum
and coal are expected to be exhausted and the environment is
seriously polluted, significance of development in next-generation
clean energy is increasing. Also, demand for renewable energy is
increasing in the 21st century, and thus, interest in solar cells
is also increasing. Solar cells do not pollute the environment, use
a practically infinite energy resource, and can be used
semi-permanently. Thus, solar cells are expected to be an energy
source for solving future energy problems.
[0004] Solar cells can be largely classified into a crystalline
silicon solar cell, a thin-film solar cell, and a dye-sensitized
solar cell. The cost of the crystalline silicon solar cell has
increased due to a short supply of a silicon raw material and a
shortage of a silicon substrate induced by installing a large
number of solar cell systems in recent years. For this reason, a
thin-film silicon solar cell, a dye-sensitized solar cell, and a
plastic solar cell are in the spotlight because their cost is low,
their consumption of the raw material is less, and their supply of
the raw material is stable. Despite the low cost, however, low
conversion efficiency and short lifetime of the solar cells, such
as the thin-film silicon solar cell, the dye-sensitized solar cell,
and the plastic solar cell, are blocking the industrialization
thereof. Therefore, recent studies about the solar cells are
focused on techniques for improving the efficiency of the solar
cells. To improve the efficiency of the solar cells, a structure or
a pattern of a front electrode formed on a light incident surface
of the solar cell needs to be improved.
SUMMARY OF THE INVENTION
[0005] Embodiments of the present invention are directed to a solar
cell including a front electrode pattern that is able to minimize a
loss of a light incident area.
[0006] A solar cell according to an embodiment of the invention
includes a photoelectric conversion layer and a front electrode on
the photoelectric conversion layer. The front electrode includes a
bus bar electrode; at least one first finger electrode directly
connected to the bus bar electrode; a plurality of connecting
electrodes extending from the bus bar electrode and having a width
smaller than a width of the bus bar electrode, wherein the
plurality of connecting electrodes includes portions that are
spaced apart from each other to form a space therebetween; at least
one second finger electrode connected to at least one of the
plurality of connecting electrodes; and an auxiliary electrode
formed at the space between the portions of the plurality of
connecting electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is an exploded perspective view of a solar cell
according to an embodiment of the invention;
[0008] FIG. 2 is a schematic cross-sectional view of the solar cell
shown in FIG. 1;
[0009] FIG. 3 is a plan view of a front electrode formed on a front
portion of a typical solar cell.
[0010] FIG. 4 is a partial view of a solar cell module formed by
combining the solar cells shown in FIG. 3;
[0011] FIG. 5 is a plan view of a front electrode formed on a front
portion of a solar cell according to an embodiment of the
invention;
[0012] FIG. 6 is a partial view of a solar cell module formed by
combining solar cells according to the embodiment of the invention;
and
[0013] FIGS. 7 to 9 are plan views of finger electrodes and bus bar
electrodes of the solar cell shown in FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
[0014] In the following description, it will be understood that
when a layer or film is referred to as being "on" another layer or
substrate, it can be directly on the other layer or substrate, or
intervening layers may also be present. Further, it will be
understood that when a layer is referred to as being "under"
another layer, it can be directly under the other layer, and one or
more intervening layers may also be present. In the figures, the
dimensions of layers and regions are exaggerated or schematically
illustrated, or some layers are omitted for clarity of
illustration. In addition, the dimension of each part as drawn may
not reflect an actual size.
[0015] Hereinafter, embodiments of the invention will be described
with reference to the accompanying drawings.
[0016] FIG. 1 is an exploded perspective view of a solar cell
according to an embodiment of the invention, and FIG. 2 is a
schematic cross-sectional view of the solar cell shown in FIG.
1.
[0017] Referring to FIGS. 1 and 2, a solar cell module 100
according to an embodiment of the invention includes a plurality of
solar cells 150, a plurality of ribbons 143 for connecting the
plurality of solar cells 150, at least one bus ribbon 145 for
connecting the ribbons 143, a first sealing film 131 and a second
sealing film 132 for sealing the solar cells 150 on both sides, a
front substrate 110 for protecting a light incident surface of the
solar cells 150, and a rear substrate 120 for protecting a rear
surface of the solar cells 150.
[0018] Each solar cell 150 is a semiconductor device for converting
solar energy to electric energy. Referring to FIG. 2, the solar
cell 150 includes a photoelectric conversion layer 151, electrode
layers 152 formed on at least one surface of the photoelectric
conversion layer 151, and the ribbons 143 for connecting the solar
cells 150. At an interface surface of the electrode layer 152 and
the ribbon 143, a eutectic mixture may be formed. In FIG. 2, the
electrode layers 152 include a front electrode layer and a rear
electrode layer as an example. However, embodiments of the
invention are not limited thereto. Thus, the electrode layers 152
may be formed only at the rear surface of the photoelectric
conversion layer 151 in other embodiments of the invention. In this
instance, the ribbon 143 connects the electrode layers 152 formed
on the rear surfaces (or the rear sides) of two solar cells 150
adjacent to each other among the solar cells 150.
[0019] The photoelectric conversion layer 151 may include silicon,
a compound semiconductor, or a tandem structure. In the
photoelectric conversion layer 151, a P-N junction is formed, and
thus, the electric energy is generated by a photoelectric effect
when light, such as sun light, is incident.
[0020] The electrode layer 152 connected to a p-type layer 123 may
be formed, for example, by coating a paste for an electrode
including aluminum, silica, binder, and so on, on one surface on
the photoelectric conversion layer 151 and heat-treating the paste.
During a firing process, organic materials and a solvent included
in the coated paste are removed. Upon the heat-treating, the
aluminum for forming the electrode is diffused through the rear
surface of the photoelectric conversion layer 151 to form a back
surface field at the interface of the electrode layer 152 and the
photoelectric conversion layer 151.
[0021] According to embodiments of the invention, the solar cell
150 includes the ribbon 143, and the ribbon 143 is adjacent to (or
attached to) one surface of the electrode layer 152. At the
interface of the electrode layer 152 and the ribbon 143, the
eutectic matrix may be formed. At least an outer surface of the
ribbon 143 includes at least one of Cu, Nu, Ca, Sn, Zn, In, and Sb
for a eutectic bonding.
[0022] A front surface of the photoelectric conversion layer 151
may include a textured surface. Performing texturing of the front
surface forms a pattern of convex-concave shapes or an uneven
surface. Since the surface of photoelectric conversion layer 151
has a large roughness because of the textured surface, the
reflectance of the incident light decreases and the photoelectric
conversion layer 122 absorbs more light. That is, the light loss
can be reduced.
[0023] Referring again to FIG. 1, the ribbon 143 may include two
lines attached to an upper portion and a lower portion of the solar
cells 150 in order to connect the solar cells 150. The solar cells
150 electrically connected by the ribbon 143 form a string 140. A
plurality of strings 140 adjacent to each other may be arranged to
form a plurality of columns.
[0024] The bus ribbon 145 is positioned where the string 140 is not
formed, and is connected to the ribbon 143. The bus ribbon 145 may
be connected to a lead line that is connected to a junction box for
charging and discharging the electric energy and for preventing
countercurrent.
[0025] Also, the bus ribbon 145 alternately connects both ends of
the ribbons 143 of the strings 140, thereby electrically connecting
the strings 140. The bus ribbon 145 may be arranged in a row
direction at the both ends of the strings 140 arranged to form the
plurality of columns. The strings 140 for forming the plurality of
columns may be formed between the first sealing film 131 and the
second sealing film 132.
[0026] The first sealing film 131 may be positioned on the light
incident surface of the solar cells 150, and the second sealing
film 132 may be positioned on the rear surface of the solar cells
150. The first sealing film 131 and the second sealing film 132 may
be attached by a lamination method. The first sealing film 131 and
the second sealing film 132 block moisture and oxygen that may be
harmful to the solar cells 150.
[0027] In addition, the first sealing film 131 and the second
sealing film 132 chemically combine elements of the solar cells 150
to each other. The first sealing film 131 and the second sealing
film 132 may include an ethylene-vinyl acetate (EVA) copolymer
resin, polyvinyl butyral, an ethylene-vinyl acetate having a
partial oxide, a silicone resin, an ester-based resin, and/or an
olefin-based resin.
[0028] The front substrate 110 is positioned on the first sealing
film 131 so that the sun light can penetrate therethrough. The
front substrate 110 may be formed of a transparent material, such
as a tempered glass, in order to protect the solar cells 150 from
an external impact. Specifically, the front substrate 110 may be a
low-iron tempered glass in order to reduce or prevent the
reflection of the sun light and to improve the transmissivity of
the sun light.
[0029] The rear substrate 120 protects the solar cells 150 at the
rear surface thereof and may be waterproof, may insulate, or may
filter ultraviolet light. The rear substrate 150 may be a TPT
(Tedlar/PET/Tedlar) type. However, embodiments of the invention are
not limited thereto. In addition, the rear substrate 120 may
include a material having a high reflectivity property in order to
reuse the sun light incident through the front substrate 110, or
include a material of a transparent property that allows the sun
light to be incident.
[0030] FIG. 3 is a plan view of a front electrode formed on a front
portion of a typical solar cell, and FIG. 4 is a partial view of a
solar cell module formed by combining the solar cells shown in FIG.
3. A solar cell 200 shown in FIGS. 3 and 4 has a typical structure.
The FIGS. 3 and 4 show a front surface of the solar cell 200 where
finger electrodes 220 and bus bar electrodes 210 are formed.
[0031] FIG. 3 shows a typical pattern of the front electrode. FIG.
3 shows the pattern as including the finger electrodes 220 that are
densely positioned and the bus bar electrodes 210. However, such is
just one example pattern of the front electrode. Thus, the front
electrodes having various patterns are disclosed.
[0032] The front electrode having metal is formed on the front
surface of the solar cell 200 in order to collect charges generated
by the incident sun light. The front electrode includes grids that
are generally referred to as the finger electrodes 220 or finger
metal lines, and the bus bar electrodes 210 having a bar shape and
being electrically connected to the grids as main electrodes. When
the solar cell 200 generates electric energy, the electrons or the
holes are collected by the bus bar electrodes 210 via the finger
electrodes 220, and then, are collected by the ribbon 145.
[0033] However, since the sun light is reflected by the front
electrode, and the sun light cannot penetrate the front electrode,
the front electrode generates a shading loss and reduces the
efficiency of the solar cell. Thus, in order to reduce the shading
loss, an area of the front electrode that covers the light incident
surface of the solar cell needs to be decreased. However, if the
width of the finger electrodes is decreased to reduce the contact
area and the shading loss, resistance of the finger electrodes may
be increased due to the reduction of the cross-sectional area of
the electrodes. Thus, electric loss may be increased.
[0034] That is, the front electrode on the front surface of the
solar cells 200 is needed to have an optimal structure for having a
high opening ratio in order to absorb more light and for minimizing
the resistance and the shading loss. Typically, the width and the
area of the finger electrodes 220 may be adjusted in order to
improve the efficiency of the solar cells 200 by reducing the
shading loss. However, the finger electrodes 220 basically have a
width larger than 100 .mu.m, and thus, the adjustment of the width
and the area of the finger electrodes 220 is limited. In addition,
a lithography method and a laser transfer method have been proposed
in order to reduce the width of the finger electrodes 220. However,
the manufacturing cost of such methods may be high.
[0035] For example, the bus bar electrodes 210 of the solar cell
200 are positioned to have a predetermined distance (about
2.about.3 mm) from edges of the solar cell 200, and thus, the bus
bar electrodes 210 have a length of about 153mm in a solar cell 200
having a wafer size of 156 mm. Further, the ribbon 143 connecting
the solar cells and being attached thereto during manufacturing of
a solar cell module have a predetermined distance (C of FIG. 2;
about 2 mm) from an end of the bus bar electrode 210. Accordingly,
the ribbon 143 is not attached to the solar cell at a portion 230
of the bus bar electrodes 210, and the portion 230 is a loss area
for reducing the light incident area.
[0036] FIG. 5 is a plan view of a front electrode formed on a front
portion of a solar cell according to an embodiment of the
invention, and FIG. 6 is a partial view of a solar cell module
formed by combining solar cells according to the embodiment of the
invention. The solar cell 300 shown in FIG. 5 according to an
embodiment of the invention includes finger electrodes 320 and bus
bar electrodes 310 having a structure different from those of the
solar cells 200 of FIG. 4. In the solar cell according to this
embodiment of the invention, the bus bar electrodes 310 have a
shape for reducing loss of the light incident area.
[0037] As shown in FIG. 5, the bus bar electrode 310 is shorter
than a typical bus bar electrode. That is, while the typical bus
bar electrode is formed across essentially an entire light incident
surface of the solar cell from one end (an upper end) to an
opposite end (a lower end), an upper portion of the bus bar
electrode 310 is formed differently (e.g., not formed or partially
removed) in the embodiment of the invention. Thus, the sun light
can penetrate the upper portion of the bus bar electrode 310 where
the ribbon is not connected. Accordingly, the light incident area
can increase, compared to a typical solar cell. The improved
structure of the shapes of the bus bar electrodes 310 and the
finger electrodes 320 are shown in FIGS. 7 to 9.
[0038] FIGS. 7 to 9 are plan views of finger electrodes and bus bar
electrodes of the solar cell shown in FIG. 5. That is, FIGS. 7 to 9
are enlarged views of portions having shapes of the bus bar
electrodes 310 and the finger electrodes 320 of an improved
structure. Referring to FIG. 7, finger electrodes 620 and 640 are
connected to a bus bar electrode 610 through connecting electrodes
630. The finger electrodes 620 and 640 include first finger
electrodes 620 and second finger electrodes 640. The first finger
electrodes 620 are directly connected to the bus bar electrode 610,
and the second finger electrodes 640 are connected to the bus bar
electrode 610 through the connecting electrodes 630. Therefore, the
second finger electrodes 640 have intersections 660 with the
connecting electrodes 630. The second finger electrodes 640 are
positioned at the upper portion of the solar cell, that is, at the
portion where the part of the bus bar electrode 610 is not formed
or is removed.
[0039] Referring to FIG. 7, the bus bar electrode 610 and the
connecting electrodes 630 are vertically formed (or formed parallel
to each other), and the first finger electrodes 620 and the second
finger electrodes 640 are horizontally formed (or formed parallel
to each other). Thus, the bus bar electrode 610 and the first
finger electrodes 620 intersect, and the connecting electrodes 630
and the second finger electrodes 640 have the intersections 660.
The connecting electrodes 630 have a width smaller than that of the
bus bar electrode 610, and thus, the area of the connecting
electrodes 630 covering the light incident surface of the solar
cell is small. Thus, compared to the bus bar electrode 610, the
connecting electrodes 630 reduce the area generating the shading
loss. The connecting electrodes 630 are formed at one end of the
bus bar electrode 610 (specifically, the portion where the ribbon
143 is not attached to the bus bar electrode 610). Accordingly, the
light incident surface can increase at the portion where the ribbon
143 is not attached.
[0040] Also, a portion of the second finger electrode 640 adjacent
to the intersection 660 with the connecting electrode 630 may be
bent (or inclined) at a predetermined angle. Thus, a path from the
second finger electrode 640 to the connecting electrodes 630 can
decrease. Accordingly, the shading loss can be reduced, and a metal
paste used for forming the connecting electrodes 630 and the second
finger electrodes 640 can also decrease. In this instance, when the
portion of the second finger electrode 640 has the angle of 45
degrees with the connecting electrodes 630, the path from the
second finger electrode 640 to the connecting electrodes 630 can be
minimized, compared with other angles. Considering a tolerance (or
margin of error), the angle between the second finger electrode 640
and the connecting electrode 630 may be in a range of about 40 to
about 50 degrees. Other angles may be used, including an angle of
90 degrees.
[0041] In addition, the width of the connecting electrode 630 may
be changed at some portions. The plurality of the second finger
electrodes 640 (that is, two or more second finger electrodes 640)
are connected to one connecting electrode 630. Thus, when the
connecting electrode 630 is uniform, the internal resistance of the
connecting electrode 630 increases as the number of the second
finger electrodes 640 connected to the connecting electrode 630
increase. The number of the intersections 660 of the connecting
electrode 630 with the second finger electrodes 640 decreases as
the distance from the bus bar electrode 610 increases. That is, in
order to achieve uniform resistance, the connecting electrode 630
may have a cross section gradually decreasing as the distance from
the bus bar electrode 610 increases. In this instance, the
connecting electrode 660 has the cross section varying at each of
the intersections 660 of the connecting electrodes 630 and the
second finger electrodes 640. In embodiments of the invention, a
thickness of the connecting electrodes 630 may increase based on
the number of connections 660 made with the second finger
electrodes 640 in going from the edge of the solar cell to the bus
bar electrode 610.
[0042] However, embodiments of the invention are not limited
thereto. Thus, if some amount of shading loss by the connecting
electrodes 630 is acceptable, the connecting electrodes 630 may
have a uniform cross section though its entire length. In this
instance, the connecting electrodes 630 may have a cross section
(which may be predetermined) in a range that the internal
resistance of the connecting electrodes 630 does not exceed a
predetermined value.
[0043] In the embodiment of the invention, the plurality of the
second finger electrodes 640 are connected to one connecting
electrodes 630. Thus, when a short-circuit is generated at any one
portion of the connecting electrodes 630, the electrons-flowing
path through the second finger electrodes 640 is blocked. Thus, in
order to address the above instance, the plurality of the
connecting electrodes 630 (that is, two or more connecting
electrodes 630) may be formed. The plurality of connecting
electrodes 630 may be formed apart from each other to form a space
therebetween. Thus, a space between the connecting electrodes 630
may have an opening 630a, or may have a portion 630b which is open
toward an outside. At the space between the connecting electrodes
630, a bridge electrode 650 connecting the connecting electrodes
630 may be formed. Accordingly, when the short-circuit is generated
at one connecting electrode 630, the carriers flowing through the
second finger electrodes 640 connected to the one connecting
electrodes 630 can flow toward the bus bar electrode 610 via the
bridge electrode 650 and another connecting electrode 630, so that
ultimately, the second finger electrodes 640 connected to the
connecting electrode 630 with the short-circuit can be electrically
connected to the bus bar electrode 610. That is, the bridge
electrode 650 is formed at the space disposed between the adjacent
connecting electrodes 630 as an auxiliary electrode. Thus, the
problem due to the short- circuit in the connecting electrodes 630
can be addressed.
[0044] In this instance, the bridge electrode 650 may be connected
to portions of the connecting electrodes 630 that are positioned
between two adjacent second finger electrodes 640. Thereby, a
problem due to a plurality of electrodes being concentrated at one
portion can be addressed. That is, the electrically connected
portions can be dispersed, and thus, safety and stability can be
improved. In the embodiment of the invention, the connecting
electrodes 630 having widths smaller than that of the bus bar
electrode 610 are formed at one end of the bus bar electrode 610
where the ribbon 143 is not attached, and thus, an area of a light
incident surface can increase at a portion where the ribbon 143 is
not attached. Specifically, light can be incident through the
opening 630a defined by the bus bar electrode 610, the connecting
electrodes 630, and the bridge electrode 650, or the portion 630b
open towards the outside between the connecting electrodes 630, and
thus, the area of the light incident surface can increase.
[0045] In embodiments of the invention, the bridge electrode 650
and the connecting electrodes 630 may have a lattice arrangement.
Also, when a plurality of bridge electrodes 650 are used, lengths
of the plurality of bridge electrodes 650 may be the same.
Additionally, increase in the cross section of the connecting
electrode 630 may produce steps that face towards the outside
(i.e., face towards the second finger electrodes 640).
[0046] FIG. 8 is a plan view of a front electrode according to
another embodiment of the invention. As shown in FIG. 8, the front
electrode includes a bus bar electrode 710, an auxiliary bus bar
electrode 730, connecting electrodes 750, first finger electrodes
720, second finger electrodes 760, and a third finger electrode
740. In this instance, the first finger electrodes 720 are directly
connected to the bus bar electrode 710 to have intersections
therebetween. The auxiliary bus bar electrode 730 is extended from
the bus bar electrode 710 and has a width smaller than the bus bar
electrode 710. The third finger electrode 740 is connected to the
auxiliary bus bar electrode 730 and is nearer to an edge of the
solar cell than the first and second finger electrodes 720 and 760.
The third finger electrode 740 is farthest from the bus bar
electrode 710 as compared to the first and second finger electrodes
720 and 760. Since the auxiliary bus bar electrode 730 is connected
to the third finger electrode 740 that are fewer in number than the
first and second finger electrodes 720 and 760, the auxiliary bus
bar electrode 730 can have a width smaller than a width of the
first bus bar 710. In embodiments of the invention, the auxiliary
bus bar electrode 730 may extend parallel to the bus bar electrode
710, but may alternatively extend non-parallel to the bus bar
electrode 710. Also, a plurality of auxiliary bus bar electrodes
730 may be connected to the bus bar electrode 710. The third finger
electrode 740 may be connected to the auxiliary bus bar electrode
730 in a non-perpendicular manner in other embodiments.
[0047] The embodiment of the invention includes the auxiliary bus
bar electrode 730 and the third finger electrodes 740 disposed at a
space between the connecting electrodes 750 as auxiliary
electrodes. That is, a surface area available for light incidence
can be sufficiently procured by the space between the connecting
electrodes 750, and the current generated at the space between the
connecting electrodes 750 can be collected by the auxiliary bus bar
electrode 730. The third finger electrodes 740 connected to the bus
bar electrode 730 allows the current generated at the space between
the connecting electrodes 750 to be collected even more. That is,
in the embodiment of the invention, the current generated at the
portion between the connecting electrodes 750 can be effectively
collected while surface available for light incidence can be
sufficiently procured at the portion where the ribbon 143 is not
attached.
[0048] The auxiliary bus bar electrode 730 and the third finger
electrodes 740 may be disposed apart from the connecting electrodes
750 and the second finger electrodes 760 so that the current
collected by the auxiliary bus bar electrode 730 and the third
finger electrodes 740 can flow to the bus bar electrode 710 through
a shortest path.
[0049] In FIG. 8, a single third finger electrode 740 is shown as
an example. However, embodiments of the invention are not limited
thereto. For example, some finger electrodes that are disposed far
away from the bus bar electrode 710 may be the third finger
electrodes 740. Also, in FIG. 8, the third finger electrode 740 and
the auxiliary bus bar electrode 730 form a T shape. In another
embodiment of the invention, the third finger electrode 740 may be
bent at an intersection with the auxiliary bus bar electrode 730,
and thus, the third finger electrode 740 and the auxiliary bus
electrode 730 may have a Y shape. In this instance, the path from
the third finger electrodes 740 to the auxiliary bus bar electrode
730 can be reduced even more. Also, the third finger electrode 740
and the auxiliary bus electrode 730 may have a cross shape (+).
[0050] The second finger electrodes 760 have intersections with the
connecting electrodes 750, and are connected to the bus bar
electrode 710 through the connecting electrodes 750. The connecting
electrodes 750 include a first region 751 having an intersection
with the second finger electrodes 760 and a second region 753
connecting the second finger electrodes 760 and the bus bar
electrode 710. The first region 751 of the connecting electrodes
750 is apart from the bus bar electrode 710, and the second region
753 is bent toward the bus bar electrode 710. In this instance,
when the second region 753 has an angle of 45 degrees with the
first region 751 (as in the instance that a distance between one
connecting electrode 750 and the bus bar electrode 710, and another
distance between another connecting electrode 750 and the bus bar
electrode 710 are the same each other), the length of the
connecting electrodes 750 can be minimized. Considering a tolerance
(or a margin of error), the angle between the second region 753
with the first region 751 may be in a range of about 40 to about 50
degrees. Other angles may be used.
[0051] The first region 751 of the connecting electrode 750 has
intersections 770 with the plurality of the second finger
electrodes 760. The width of the first region 751 may increase as
the number of the second finger electrodes 760 connected to the
connecting electrodes 750 increases. That is, as the number of the
intersections 770 with the second finger electrodes 760
accumulates, the cross section of the connecting electrodes 750
increases, either gradually or in steps. Since the cross section or
the thickness of the connecting electrode 750 is adjusted as
discussed above, the resistance by the connecting electrodes 750
can be maintained below a predetermined value, regardless of the
number of the second finger electrodes 760 connected to the
connecting electrodes 750. That is, the first region 751 may have a
cross section decreasing as a distance from the bus bar 710
increases. Although not required, the first region 751 of the
connecting electrode 750 may be parallel to the bus bar electrode
710, while the second region 753 of the connecting electrode 750 is
non-parallel to the bus bar electrode 710.
[0052] In addition, the second finger electrodes 760 connected to
the connecting electrode 750 may be bent at a portion adjacent to
the intersections 770 with the connecting electrodes 750 in order
to shorten the path formed by the second finger electrodes 760 to
the connecting electrodes 750. In this instance, in order to
minimize the path, a bent angle may be about 40 to about 50 degrees
(for example, 45 degrees), as discussed above.
[0053] FIG. 9 is a plan view of a front electrode according to
still another embodiment of the invention. In the embodiment shown
in FIG. 9, finger electrodes 830 are directly connected to
connecting electrodes 820 or a bus bar electrode 810. In this
instance, two connecting electrodes 820 are connected to one bus
bar electrode 810. The connecting electrodes 820 may be inclined
with respect to the bus bar electrode 810 toward the finger
electrodes 830 in a range that lengths of the finger electrodes 830
are not too short. Bent angles, the lengths, and widths of the
connecting electrodes 820 may be adjusted considering an amount of
a metal paste that is used for forming the front electrode and the
efficiency of the solar cell due to an area of the light incident
surface.
[0054] Unlike the embodiment of the invention described in
referring to FIGS. 7 and FIG. 8, the finger electrodes 830 are not
bent in the embodiment described referring to FIG. 9. Thus, the
finger electrodes 830 (specifically, the finger electrodes 830
connected to the connecting electrodes 820) may have a stripe
shape. In this instance, because the connecting electrodes 820 are
inclined with respect to the bus bar electrode 810, and are bent
toward the finger electrodes 830, the length of the finger
electrodes 830 can decrease.
[0055] Instead of removing the end of the bus bar electrode 810,
the connecting electrodes 820 are connected to the finger
electrodes 830. Thus, the shading loss due to the bus bar electrode
810 can be reduced or prevented, and the metal paste for forming
the electrodes can be reduced. Also, considering a possibility of
short-circuit at one of the connecting electrodes 820, a bridge
electrode 850 connecting both of the connecting electrodes 820 may
be included as an auxiliary electrode. In addition, the cross
section of the connecting electrodes 820 may gradually decrease as
the distance from the bus bar electrode 810 increases, considering
the number of the finger electrodes 830 that are connected to the
connecting electrodes 820 is smaller as the distance from the bus
bar electrode 810 increases. The cross section of the connecting
electrodes 820 may be adjusted by controlling the width or the
thickness of the connecting electrodes 820.
[0056] In embodiments of the invention, the bridge electrode 850
and the connecting electrodes 820 may have an A shape arrangement.
Also, when a plurality of bridge electrodes 850 are used, lengths
of the plurality of bridge electrodes 850 may be different.
Additionally, increase in the cross section of the connecting
electrode 820 may produce steps that face towards the outside
(i.e., face towards the finger electrodes 830).
[0057] According to the embodiments of the invention, by improving
a pattern of a front electrode, the shading loss due to the front
electrode formed on the light incident surface of the solar cell
can be reduced, and thus, the efficiency of the solar cell can be
enhanced. Also, the material cost for forming the front electrode
can be also reduced.
[0058] Certain embodiments of the invention have been described.
However, the invention is not limited to the specific embodiments
described above; various modifications of the embodiments are
possible by those skilled in the art to which the invention belongs
without departing from the scope of the invention defined by the
appended claims. Also, modifications of the embodiments should not
be understood individually from the technical principles or
prospects of the invention.
* * * * *