U.S. patent application number 13/302838 was filed with the patent office on 2012-03-15 for photovoltaic module.
This patent application is currently assigned to Sanyo Electric Co., Ltd.. Invention is credited to Atsushi NAKAUCHI, Shingo Okamoto, Toshio Yagiura.
Application Number | 20120060894 13/302838 |
Document ID | / |
Family ID | 37946334 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120060894 |
Kind Code |
A1 |
NAKAUCHI; Atsushi ; et
al. |
March 15, 2012 |
PHOTOVOLTAIC MODULE
Abstract
A photovoltaic module capable of suppressing separation of a tab
electrode can be obtained. The photovoltaic module includes a
plurality of semiconductor layers including a photoelectric
conversion layer, a plurality of photovoltaic elements including a
finger electrode for collecting generated currents, formed on the
semiconductor layers on a side of a light receiving surface, and a
tab electrode for electrically connecting the plurality of
photovoltaic elements, in which the tab electrode is electrically
connected to the finger electrode in a region corresponding to a
power generation region of the photovoltaic element and bonded on
the light receiving surface through an insulating bonding
material.
Inventors: |
NAKAUCHI; Atsushi; (Osaka,
JP) ; Okamoto; Shingo; (Osaka, JP) ; Yagiura;
Toshio; (Kobe-shi, JP) |
Assignee: |
Sanyo Electric Co., Ltd.
Osaka
JP
|
Family ID: |
37946334 |
Appl. No.: |
13/302838 |
Filed: |
November 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11657131 |
Jan 24, 2007 |
|
|
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13302838 |
|
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Current U.S.
Class: |
136/244 |
Current CPC
Class: |
H01L 31/0201 20130101;
H01L 31/0747 20130101; H01L 31/1876 20130101; H01L 31/022433
20130101; H01L 31/022425 20130101; H01L 31/022475 20130101; H01L
31/0504 20130101; Y02E 10/50 20130101 |
Class at
Publication: |
136/244 |
International
Class: |
H01L 31/05 20060101
H01L031/05 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2006 |
JP |
2006-014917 |
Claims
1-18. (canceled)
19. A photovoltaic module comprising: a plurality of photovoltaic
elements each including a semiconductor layer including a
photoelectric conversion layer and a finger electrode for
collecting generated currents, formed on said semiconductor layer
on a side of a light receiving surface; and a tab electrode
electrically connected to said finger electrode for electrically
connecting adjacent said photovoltaic elements, wherein said finger
electrode has a divided region in a region in which said tab
electrode is arranged so as not to cross said region in which said
tab electrode is arranged.
20. The photovoltaic module according to claim 19, wherein said tab
electrode is bonded onto said light receiving surface through an
insulating bonding material in said divided region of said finger
electrode.
21. The photovoltaic module according to claim 19, wherein a
plurality of said finger electrodes are so formed as to be spaced
from each other at a prescribed interval in a direction
intersecting with said tab electrode.
22. The photovoltaic module according to claim 19, wherein said
finger electrode is divided into three by two said tab
electrodes.
23. The photovoltaic module according to claim 22, wherein a width
of each of said tab electrodes is narrower than a width of said
finger electrode divided by said tab electrodes.
24. The photovoltaic module according to claim 19, wherein said tab
electrode is bonded onto said semiconductor layer through a bonding
material.
25. The photovoltaic module according to claim 19, wherein said
photovoltaic elements each further include a translucent conductive
film formed on said semiconductor layer, and said tab electrode is
bonded onto said translucent conductive film through a bonding
material.
26. The photovoltaic module according to claim 19, wherein said tab
electrode is electrically connected to said finger electrode
through a solder material.
27. A photovoltaic module comprising: a plurality of photovoltaic
elements each including a plurality of semiconductor layers
including a photoelectric conversion layer and a finger electrode
for collecting generated currents, formed on said semiconductor
layer on a side of a light receiving surface; and a tab electrode
for electrically connecting said plurality of photovoltaic
elements, wherein a plurality of said finger electrodes are divided
into groups each including a prescribed number of said finger
electrodes, and said prescribed number of said finger electrodes
included in the same group in said groups are aggregated into one
finger electrode of said prescribed number of said finger
electrodes and electrically connect to said tab electrode.
28. The photovoltaic module according to claim 27, wherein said
groups consist of a plurality of groups.
29. The photovoltaic module according to claim 28, wherein said tab
electrode is electrically connected to said finger electrode
through a solder material.
30. The photovoltaic module according to claim 28, wherein said
finger electrodes are so formed as to extend in a first direction
and be spaced from each other at a prescribed interval in a second
direction intersecting with said first direction, said tab
electrode is so arranged as to extend in said second direction, and
a width in second direction of said finger electrode located in the
region in which said prescribed number of said finger electrodes
are aggregated into one finger electrode is substantially identical
with a width in second direction of said finger electrode located
in the region in which said prescribed number of said finger
electrodes are not aggregated into one finger electrode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a photovoltaic module, and
more particularly, it relates to a photovoltaic module including a
plurality of photovoltaic elements.
[0003] 2. Description of the Background Art
[0004] A photovoltaic module in which a plurality of photovoltaic
elements are serially connected with each other is known in
general, as disclosed in Japanese Patent Laying-Open No 10-65192
(1998), for example.
[0005] Each photovoltaic element constituting the conventional
photovoltaic module disclosed in the aforementioned Japanese Patent
Laying-Open No 10-65192 includes a finger electrode consisting of a
metallic wire for collecting generated currents, bonded to a
element surface through a conductive adhesive, and a bus bar
electrode consisting of foil or a metallic wire for aggregating
currents collected by the finger electrode consisting of a metallic
wire. The bus bar electrode of the conventional photovoltaic
element is so bonded to a surface of a non-light emitting region
other than a light emitting region of the photovoltaic element as
to be electrically connected to the finger electrode.
[0006] In the photovoltaic module disclosed in the aforementioned
Japanese Patent Laying-Open No 10-65192, the metallic wire is
employed as the finger electrode, and hence the conductive adhesive
for bonding the finger electrode and the element surface must be
disadvantageously provided independently of the finger
electrode.
[0007] On the other hand, a photovoltaic element in which a finger
electrode and a bus bar electrode are formed of conductive paste
has been proposed in general. In a case where a photovoltaic module
is formed from the conventional photovoltaic elements, a tab
electrode consisting of foil is bonded on the bus bar electrode
formed of the conductive paste of the photovoltaic elements
adjacent to each other by soldering, whereby the photovoltaic
elements are serially connected with each other. In a case where
this finger electrode formed of the conductive paste is employed,
the conductive paste has an adhesion function, and hence an
adhesive for bonding the finger electrode and the element surface
is not required to be provided dissimilarly to a case where the
finger electrode consisting of the metallic wire is employed.
[0008] In the aforementioned conventional photovoltaic module in
which the finger electrode and the bus bar electrode are formed of
the conductive paste and the tab electrode consisting of foil is
formed on the bus bar electrode, however, in a case where an
excessive tensile stress is applied to the bus bar electrode
through the tab electrode, the bus bar electrode is likely to be
separated from a surface of the photovoltaic element.
SUMMARY OF THE INVENTION
[0009] The present invention has been proposed in order to solve
the aforementioned problem, and an object of the present invention
is to provide a photovoltaic module capable of suppressing
separation of a tab electrode.
[0010] In order to attain the aforementioned object, a photovoltaic
module according to an aspect of the present invention comprises a
plurality of photovoltaic elements each including a plurality of
semiconductor layers including a photoelectric conversion layer and
a finger electrode for collecting generated currents, formed on the
semiconductor layers on a side of a light receiving surface and a
tab electrode for electrically connecting the plurality of
photovoltaic elements. The tab electrode is electrically connected
to the finger electrode and bonded on the light receiving surface
through an insulating bonding material in a region corresponding to
a power generation region of the photovoltaic element.
[0011] In the photovoltaic module according to this aspect, as
hereinabove described, the tab electrode is directly bonded on the
light receiving surface through the insulating bonding material in
the region corresponding to the power generation region of the
photovoltaic element, whereby a bonding strength between the
element and the tab electrode can be increased as compared with a
bonding strength between the element and the tab electrode (bus bar
electrode) in a case where the tab electrode is bonded on the light
receiving surface through the bus bar electrode formed of
conductive paste having no strong bonding force. Thus, separation
of the tab electrode from the element can be suppressed.
Consequently, also in a case where the finger electrode (collector)
forming of conductive paste is included, the separation of the tab
electrode can be suppressed. The tab electrode is bonded on the
light receiving surface without the bus bar electrode, whereby the
bus bar electrode can be omitted. Thus, an electrode structure can
be simplified. In the region corresponding to the power generation
region of the photovoltaic element, the tab electrode is bonded on
the light receiving surface through the insulating bonding
material, whereby a dark current can be inhibited from flowing
through the bonding material dissimilarly to a case where the tab
electrode is bonded on the light receiving surface through
conductive bonding material. Thus, reduction in a characteristic of
the photovoltaic module can be suppressed.
[0012] In the photovoltaic module according to the aforementioned
aspect, the insulating bonding material is preferably provided in a
region corresponding to the power generation region of the
photovoltaic element, in which the finger electrode is not formed.
According to this structure, the element and the tab electrode can
be bonded through the insulating bonding material in the region in
which the finger electrode is not formed, whereby the tab electrode
and the finger electrode can be easily electrically connected to
each other by a solder or the like.
[0013] In the photovoltaic module according to the aforementioned
aspect, a plurality of the finger electrodes are preferably so
formed as to extend in a first direction and be spaced from each
other at a prescribed interval in a second direction intersecting
with the first direction, the tab electrode is preferably so
arranged as to extend in the second direction, and the insulating
bonding material is preferably provided in a region in which the
tab electrode is arranged and the finger electrode is not formed.
According to this structure, the element and the tab electrode can
be bonded through the insulating bonding material in the region in
which the tab electrode is arranged without preventing electrical
connection of the tab electrode and the finger electrode.
[0014] In the aforementioned structure in which a plurality of the
finger electrodes are formed to be spaced from each other at a
prescribed interval in the second direction, the insulating bonding
materials may be provided in a plurality of regions located between
the finger electrodes adjacent in the second direction, in which
the tab electrode is arranged. According to this structure, a
bonding region of the element and the tab electrode can be
increased in the region in which the tab electrode is arranged
without preventing electrical connection of the tab electrode and
the finger electrode.
[0015] In the aforementioned structure in which a plurality of the
finger electrodes are formed to be spaced from each other at a
prescribed interval in the second direction, the plurality of
finger electrodes may be divided into a plurality of groups each
including a prescribed number of the finger electrodes, the
prescribed number of the finger electrodes included in the same
group may be so formed that a distance in the second direction
between the finger electrodes adjacent in a region in which the tab
electrode is arranged is smaller than a distance in the second
direction between the finger electrodes adjacent in a region in
which the tab electrode is not arranged, and the insulating bonding
materials may be provided in a plurality of regions located between
the groups adjacent in the second direction, in which the tab
electrode is arranged. According to this structure, the distance in
the second direction between the adjacent finger electrodes is
increased in the region in which the tab electrode is arranged,
whereby an area of a region to which the insulating bonding
material arranged between the adjacent finger electrodes is applied
can be increased. Thus, application of the insulating bonding
material to the light receiving surface can be easily
performed.
[0016] In the aforementioned structure in which a plurality of the
finger electrodes are formed to be spaced from each other at a
prescribed interval in the second direction, the plurality of
finger electrodes may be divided into a plurality of groups each
including a prescribed number of the finger electrodes, the
prescribed number of the finger electrodes included in the same
group may be aggregated into one finger electrode of the prescribed
number of the finger electrodes in a region in which the tab
electrode is arranged, and the insulating bonding materials may be
provided in a plurality of regions located in the groups adjacent
in the second direction, in which the tab electrode is arranged.
According to this structure, an area of a region in which the
finger electrode is not formed can be increased in the region in
which tab electrode is arranged, whereby an area of a bonding
region of the element and the tab electrode can be increased. Thus,
a bonding strength between the element and the tab electrode can be
increased.
[0017] In this case, an interval between the aggregated finger
electrodes of two of the groups adjacent to each other is
preferably larger than a distance between the finger electrodes
opposed to each other of two of the groups adjacent to each other.
According to this structure, an area of a region in which the
finger electrode is not formed can be increased in the region in
which tab electrode is arranged, whereby an area of a bonding
region of the element and the tab electrode can be increased.
[0018] In the aforementioned structure in which the prescribed
number of the finger electrodes included in the same group may be
aggregated into one finger electrode, a width in the second
direction of the aggregated finger electrode is preferably
substantially equal to a width in the second direction of each of
the finger electrodes located in regions in which the tab electrode
is not arranged. According to this structure, it is possible to
suppress increase in an area occupied by the aggregated finger
electrode in the region in which the tab electrode is arranged.
Thus, an area of a region in which the finger electrode is not
formed can be increased in the region in which tab electrode is
arranged, whereby an area of a bonding region of the element and
the tab electrode can be increased.
[0019] In the aforementioned structure in which the prescribed
number of the finger electrodes included in the same group may be
aggregated into one finger electrode, a width in the second
direction of the aggregated finger electrode located in the region
in which the tab electrode is arranged is preferably larger than a
width in the second direction of each of the finger electrodes
located in regions in which the tab electrode is not arranged.
According to this structure, a contact area of the tab electrode
and the finger electrode can be increased in the region in which
the tab electrode is arranged, whereby contact resistance between
the tab electrode and the finger electrode can be reduced.
[0020] In this case, a width in the second direction of the
aggregated finger electrode is preferably smaller than a distance
in the second direction between two of the finger electrodes
located at outermost positions in the group in a region in which
the tab electrode is not arranged. According to this structure, an
area of a region in which the finger electrode is not formed can be
increased in the region in which tab electrode is arranged, whereby
an area of a bonding region of the element and the tab electrode
can be increased.
[0021] In the photovoltaic module according to the aforementioned
aspect, the tab electrode is preferably electrically connected to
the finger electrode through a solder material. According to this
structure, the tab electrode and the finger electrode can be easily
electrically connected to each other by the solder material.
[0022] In this case, the solder materials are provided over
substantially entire regions in which the finger electrode and the
tab electrode are overlapped in plan view. According to this
structure, an area of an electrical connection portion of the
finger electrode and the tab electrode can be increased. Thus, the
finger electrode and the tab electrode can be inhibited from being
electrically disconnected to each other, and resistance of a
connection portion of the finger electrode and the tab electrode
can be reduced.
[0023] In the aforementioned structure in which the tab electrode
is electrically connected to the finger electrode through the
solder material, the solder material and the insulating bonding
material are preferably so provided as to be spaced at a prescribed
interval. According to this structure, the insulating bonding
material can be inhibited from protruding into the region in which
the solder material is provided. Thus, normal electrical connection
of the finger electrode and the tab electrode by the solder
material can be inhibited from being hindered due to the protruding
bonding material.
[0024] In the aforementioned structure in which the tab electrode
is electrically connected to the finger electrode through the
solder material, the finger electrode is preferably so formed as to
extend in a first direction, the tab electrode is preferably so
arranged as to extend in a second direction intersecting with the
first direction, and the finger electrode is preferably divided in
a region in which the tab electrode is arranged so as not to cross
the region in which the tab electrode is arranged. According to
this structure, the finger electrode is not formed in the region in
which the tab electrode is arranged, whereby the insulating bonding
material can be so provided as to extend continuously along the
second direction. Thus, an area of a bonding region of the element
and the tab electrode can be further increased, whereby a bonding
strength between the element and the tab electrode can be further
increased.
[0025] In the aforementioned structure in which the tab electrode
is so arranged as to extend in the second direction, the insulating
bonding material is preferably so provided in the region in which
the tab electrode is arranged as to extend continuously along the
second direction. According to this structure, an area of a bonding
region of the element and the tab electrode can be easily further
increased.
[0026] In the aforementioned structure in which the insulating
bonding material is so provided as to extend continuously along the
second direction, the solder material is preferably so provided in
portions of side surfaces in the first direction of the tab
electrode and the insulating bonding material as to electrically
connect the side surface of the tab electrode and an divided end of
the finger electrode. According to this structure, even if the
finger electrode is divided in the region in which the tab
electrode is arranged, the tab electrode and the finger electrode
can be easily electrically connected to each other through the
solder material.
[0027] In this case, the solder materials are preferably so
provided in portions of both side surfaces in the first direction
of the tab electrode and the insulating bonding material as to
electrically connect both side surfaces of the tab electrode and
both divided ends of the finger electrode. According to this
structure, an area of an electrical connection portion of the
finger electrode and the tab electrode can be increased. Thus,
normal electrical connection of the finger electrode and the tab
electrode by the solder material can be inhibited from being
hindered, and resistance of a connection portion of the finger
electrode and the tab electrode can be reduced.
[0028] In the photovoltaic module according to the aforementioned
aspect, the photovoltaic element preferably includes a translucent
conductive film formed closer to the light receiving surface than
the semiconductor layer, and the tab electrode is preferably bonded
to the translucent conductive film through the insulating bonding
material. According to this structure, the photovoltaic element and
the tab electrode can be easily bonded to each other.
[0029] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a sectional view showing a structure of a
photovoltaic module according to a first embodiment of the present
invention;
[0031] FIG. 2 is a plan view showing a photovoltaic element
constituting the photovoltaic module according to the first
embodiment shown in FIG. 1, to which tab electrodes are
connected;
[0032] FIG. 3 is a sectional view taken along a line 100-100 in
FIG. 2;
[0033] FIG. 4 is a sectional view taken along a line 200-200 in
FIG. 2;
[0034] FIG. 5 is a sectional view taken along a line 300-300 in
FIG. 2;
[0035] FIG. 6 is a plan view showing configuration of finger
electrodes of the photovoltaic element constituting the
photovoltaic module according to the first embodiment shown in FIG.
1;
[0036] FIG. 7 is a plan view showing the photovoltaic element
constituting the photovoltaic module according to the first
embodiment shown in FIG. 1, from which the tab electrodes are
removed;
[0037] FIG. 8 is a plan view showing configuration of finger
electrodes of a photovoltaic element constituting a photovoltaic
module according to a first modification of the first
embodiment;
[0038] FIG. 9 is a plan view showing the photovoltaic element
constituting the photovoltaic module according to the first
modification of the first embodiment, from which the tab electrodes
are removed;
[0039] FIG. 10 is a plan view showing configuration of finger
electrodes of a photovoltaic element constituting a photovoltaic
module according to a second modification of the first
embodiment;
[0040] FIG. 11 is a plan view showing the photovoltaic element
constituting the photovoltaic module according to the second
modification of the first embodiment, from which the tab electrodes
are removed;
[0041] FIG. 12 is a plan view showing configuration of finger
electrodes of a photovoltaic element constituting a photovoltaic
module according to a third modification of the first
embodiment;
[0042] FIG. 13 is a plan view showing the photovoltaic element
constituting the photovoltaic module according to the third
modification of the first embodiment, from which the tab electrodes
are removed;
[0043] FIG. 14 is a plan view showing a photovoltaic element
constituting a photovoltaic module according to a second embodiment
of the present invention, to which tab electrodes are
connected;
[0044] FIG. 15 is a sectional view taken along a line 400-400 in
FIG. 14;
[0045] FIG. 16 is a sectional view taken along a line 500-500 in
FIG. 14;
[0046] FIG. 17 is a sectional view taken along a line 600-600 in
FIG. 14;
[0047] FIG. 18 is a plan view showing configuration of finger
electrodes of a photovoltaic element constituting a photovoltaic
module according to the second embodiment shown in 14; and
[0048] FIG. 19 is a plan view showing the photovoltaic element
constituting the photovoltaic module according to the second
embodiment shown in FIG. 14, from which the tab electrodes are
removed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Embodiments of the present invention will be hereinafter
described with reference to the drawings.
First Embodiment
[0050] A structure of a photovoltaic module according to a first
embodiment will be now described with reference to FIGS. 1 to
7.
[0051] The photovoltaic module according to the first embodiment
includes a plurality of photovoltaic elements 1 as shown in FIG. 1
and has a structure in which the plurality of photovoltaic elements
1 are electrically connected through tab electrodes 2. The tab
electrodes 2 electrically connecting the plurality of photovoltaic
elements 1 are so arranged as to be electrically connected to
finger electrodes 18(19) serving as after-mentioned collectors and
extend in a direction Y perpendicular to a direction X (direction
in which the finger electrodes 18(19) extend), as shown in FIGS. 1
and 2. The tab electrodes 2 consist of copper foil having a
thickness of about 200 .mu.m to about 400 .mu.m and a width of
about 1 mm to about 2 mm. A filler 3 consisting of EVA (ethylene
vinyl acetate) covers the plurality of photovoltaic elements 1 as
shown in FIG. 1. A surface protector 4 consisting of a glass is
provided on an upper surface of the filer 3, and a back surface
protector 5 consisting of PVF (poly vinyl fluoride) is provided on
a lower surface of the filler 3.
[0052] According to each photovoltaic element 1 of the first
embodiment, a substantially intrinsic i-type amorphous silicon
layer 12 having a thickness of about 5 nm to about 20 nm and a
p-type amorphous silicon layer 13 having a thickness of about 5 nm
to about 20 nm are successively formed on an upper surface of an
n-type single-crystalline silicon substrate 11 having a thickness
of about 180 .mu.m to about 300 .mu.m, as shown in FIGS. 3 to 5.
The n-type single-crystalline silicon substrate 11 is an example of
the "photoelectric conversion layer" and the "semiconductor layer"
in the present invention, and the i-type amorphous silicon layer 12
and the p-type amorphous silicon layer 13 are examples of the
"semiconductor layer" in the present invention. An ITO (indium tin
oxide) film 14 as a translucent conductive film having a thickness
of about 30 nm to about 150 nm is formed on the p-type amorphous
silicon layer 13. According to the first embodiment, a surface of
the ITO film 14 opposite to the n-type single-crystalline silicon
substrate 11 is a light receiving surface 1a on a front surface
side.
[0053] An i-type amorphous silicon layer 15, an n-type amorphous
silicon layer 16 and an ITO film 17 are successively formed on a
lower surface of the n-type single-crystalline silicon substrate
11. Thicknesses of the i-type amorphous silicon layer 15, the
n-type amorphous silicon layer 16 and the ITO film 17 are about 5
nm to about 20 nm, about 5 nm to about 20 nm and about 30 nm to
about 150 nm, respectively. The i-type amorphous silicon layer 15
and the n-type amorphous silicon layer 16 are examples of the
"semiconductor layer" in the present invention. According to the
first embodiment, a surface of the ITO film 17 opposite to the
n-type single-crystalline silicon substrate 11 is a light receiving
surface 1b on a back surface side.
[0054] According to each photovoltaic element 1 of the first
embodiment, regions formed with respective semiconductor layers
(12, 13, 15 and 16) on the upper and lower surfaces of the n-type
single-crystalline silicon substrate 11 in plane view are power
generation regions. In other words, the light receiving surface 1a
constituted by the surface of the ITO film 14 formed on the p-type
amorphous silicon layer 13 and the light receiving surface 1b
constituted by the surface of the ITO film 17 formed on the n-type
amorphous silicon layer 16 are arranged in regions corresponding to
the power generation region of the photovoltaic element 1.
[0055] As shown in FIGS. 4 and 5, the finger electrodes 18 each
having a thickness of about 10 .mu.m to about 50 atm and consisting
of a conductive material formed by conductive paste consisting of
epoxy resin or the like prepared by incorporating fine powder of
silver (Ag) are formed in prescribed regions on the light receiving
surface 1a of the front surface side (surface of the ITO film 14
opposite to the n-type single-crystalline silicon substrate 11).
The finger electrodes 18 have a function of collecting generated
currents. A plurality of the finger electrodes 18 are so formed as
to extend in the direction X and be spaced from each other at
intervals of about 2 mm in the direction Y (direction in which the
tab electrodes 2 extend) perpendicular to the direction X, as shown
in FIG. 6. Each finger electrode 18 has a width of about 100 .mu.m
in the Y direction.
[0056] A plurality of the finger electrodes 19 having similar
configuration to the finger electrodes 18 on the front surface side
and consisting of, for example, similar materials to the finger
electrodes 18 on the front surface side are formed also in
prescribed regions on the light receiving surface 1b of the back
surface side (surface of ITO film 17 opposite to the n-type
single-crystalline silicon substrate 11), as shown in FIGS. 4 and
5. The collectors of each photovoltaic element 1 of the first
embodiment are constituted only by the aforementioned finger
electrodes 18 and 19. In other words, bus bar electrodes for
aggregating currents collected by the finger electrodes 18 and 19
are not provided in the photovoltaic element 1 of the first
embodiment.
[0057] In the photovoltaic module according to the first
embodiment, each tab electrode 2 is directly bonded to the light
receiving surface 1a through an insulating bonding layer 6
consisting of acrylic thermosetting resin in a region corresponding
to the power generation region on the front surface side of the
photovoltaic element 1, as shown in FIGS. 3 and 5. According to the
first embodiment, each insulating bonding layer 6 bonding the light
receiving surface 1a and the tab electrode 2 is provided in the
region corresponding to the power generation region of the
photovoltaic element 1 in which the finger electrode 18 is not
formed, as shown in FIG. 7. More specifically, according to the
first embodiment, the insulating bonding layer 6 is provided in
each region located between the finger electrodes 18 adjacent in
the direction Y, in which the tab electrode 2 is arranged.
[0058] According to the first embodiment, in each region in which
the tab electrode 2 is arranged, a solder layer 7 consisting of
Sn--Ag--Cu is provided on an upper surface of each of a plurality
of the finger electrodes 18, as shown in FIGS. 5 and 7. The solder
layers 7 are provided over substantially entire regions in which
the finger electrode 18 and the tab electrode 2 are overlapped in
plan view. The tab electrodes 2 and the finger electrodes 18 are
electrically connected to each other by the solder layers
respectively. As shown in FIGS. 5 and 7, the solder layers 7 are so
provided as to be spaced from the insulating bonding layers 6 at
prescribed intervals.
[0059] A method of connecting the tab electrodes 2 on the back
surface side of each photovoltaic element 1 is similar to the
aforementioned method of connecting the tab electrodes 2 on the
front surface side of each photovoltaic element 1, as shown in
FIGS. 3 to 5. More specifically, each tab electrode 2 is directly
bonded to the light receiving surface 1b through insulating bonding
layer 6 in a region corresponding to the power generation region on
the back surface side of the photovoltaic element 1. The tab
electrodes 2 are electrically connected to the finger electrodes 19
through the solder layers 7, respectively.
[0060] According to the first embodiment, as hereinabove described,
the tab electrodes 2 are directly bonded to the light receiving
surface 1a through the insulating bonding layers 6 in the region
corresponding to the power generation region of the front surface
side of the photovoltaic element 1, whereby a bonding strength
between the light receiving surface 1a and the tab electrodes 2 can
be increased as compared with a bonding strength between the light
receiving surface 1a and the tab electrodes 2 in a conventional
case where the tab electrodes 2 are bonded through bus bar
electrodes formed of conductive paste on the light receiving
surface 1a without using the insulating bonding layers 6. Thus,
separation of the tab electrodes 2 from the light receiving surface
1a can be suppressed. Consequently, also in a case where the finger
electrodes (collectors) 18 consisting of conductive paste are
included, the separation of the tab electrodes 2 can be
suppressed.
[0061] According to the first embodiment, as hereinabove described,
the tab electrodes 2 are bonded to the light receiving surface 1a
without bus bar electrodes, whereby the bus bar electrodes can be
omitted. Thus, an electrode structure can be simplified.
[0062] According to the first embodiment, as hereinabove described,
in the region corresponding to the power generation region on the
front surface side of each photovoltaic element 1, the tab
electrodes 2 are bonded to the light receiving surface 1a through
the insulating bonding layers 6, whereby a dark current can be
inhibited from flowing to the tab electrodes 2 through the bonding
layers 6 dissimilarly to a case where the tab electrodes 2 are
bonded to the light receiving surface 1a through conductive bonding
layers. Thus, reduction in a characteristic of the photovoltaic
module can be suppressed.
[0063] According to the first embodiment, as hereinabove described,
each insulating bonding layer 6 is provided in the region in which
the tab electrode 2 is arranged and the finger electrode 18 is not
formed, whereby the light receiving surface 1a and each tab
electrode 2 can be bonded through the insulating bonding layer 6 in
the region in which the tab electrode 2 is arranged without
preventing electrical connection of the tab electrode 2 and the
finger electrode 18. In this case, the insulating bonding layer 6
is provided in each region located between the finger electrodes 18
adjacent in the direction Y, in which the tab electrode 2 is
arranged, a bonding region between the light receiving surface 1a
and each tab electrode 2 can be increased in the region in which
the tab electrodes 2 is arranged.
[0064] According to the first embodiment, as hereinabove described,
the tab electrodes 2 and the finger electrodes 18 are electrically
connected to each other through the solder layers 7 respectively,
whereby the tab electrodes 2 and the finger electrodes 18 can be
easily connected to each other by the solder layers 7
respectively.
[0065] According to the first embodiment, as hereinabove described,
connection of the tab electrodes 2 on the back surface side of each
photovoltaic element 1 is performed in a similar manner to the
connection of the tab electrodes 2 on the front surface side of
each photovoltaic element 1, whereby separation of the tab
electrodes 2 can be suppressed also in the back surface side of the
photovoltaic element 1.
[0066] According to the first embodiment, as hereinabove described,
the solder layers 7 are provided over the substantially entire
regions in which the finger electrode 18 and the tab electrode 2
are overlapped in plan view, whereby an area of each electrical
connection portion of the finger electrodes 18 and the tab
electrodes 2 can be increased. Thus, the finger electrodes 18 and
the tab electrodes 2 can be inhibited from being electrically
disconnected to each other, and resistance of the connection
portions of the finger electrodes 18 and the tab electrodes 2 can
be reduced.
[0067] According to the first embodiment, as hereinabove described,
the solder layers 7 are so provided as to be spaced from the
insulating bonding layers 6 at prescribed intervals, whereby the
insulating bonding layers 6 can be inhibited from protruding into
the regions in which the solder layer 7 is provided. Thus, normal
electrical connection of the finger electrodes 18 and the tab
electrodes 2 by the solder layers 7 can be inhibited from being
hindered due to the protruding bonding layers 6.
[0068] A process of fabricating the photovoltaic module according
to the first embodiment will be now described with reference to
FIGS. 1 to 7.
[0069] The i-type amorphous silicon layer 12 having a thickness of
about 5 nm to about 20 nm and the p-type amorphous silicon layer 13
having a thickness of about 5 nm to about 20 nm are successively
formed on the n-type single-crystalline silicon substrate 11 having
a thickness of about 180 .mu.m to about 300 .mu.m by plasma CVD
(chemical vapor deposition) as shown in FIGS. 3 to 5. Thereafter,
the i-type amorphous silicon layer 15 having a thickness of about 5
nm to about 20 nm and the n-type amorphous silicon layer 16 having
a thickness of about 5 nm to about 20 nm are successively formed on
the lower surface of the n-type single-crystalline silicon
substrate 11 by plasma CVD. Then, after the ITO film 14 having a
thickness of about 30 nm to about 150 nm are formed on the p-type
amorphous silicon layer 13 by sputtering, the ITO film 17 having a
thickness of about 30 nm to about 150 nm is formed also on an lower
surface of the n-type amorphous silicon layer 16.
[0070] The conductive paste consisting of epoxy resin or the like
prepared by incorporating fine powder of Ag is applied to
prescribed regions on the ITO film 14 by screen printing, as shown
in FIGS. 4 and 5. Thereafter, the conductive paste is hardened,
thereby forming the finger electrodes 18 on the front surface side
consisting of the conductive material each having a thickness of
about 10 .mu.m to about 50 .mu.m in the prescribed regions on the
ITO film 14. At this time, a plurality of the finger electrodes 18
on the front surface side are so formed as to extend in the
direction X and be spaced from each other at intervals of about 2
mm in the direction Y perpendicular to the direction X, as shown in
FIG. 6. Thereafter, a plurality of the finger electrodes 19 on the
back surface side having similar configuration to the finger
electrodes 18 on the front surface side are formed also in the
prescribed regions on the lower surface of the ITO film 17 by a
forming process similar to the aforementioned forming process of
the finger electrodes 18 on the front surface side. Thus, the
photovoltaic elements 1 constituting the photovoltaic module
according to the first embodiment are formed.
[0071] As shown in FIG. 7, a bonding material consisting of
insulating resin paste for forming the bonding layer 6, consisting
of acrylic thermosetting resin is applied to each region located
between the finger electrodes 18 adjacent in the direction Y on the
ITO film 14, in which the tab electrode 2 on the front surface side
is arranged, by screen printing. Solder paste consisting of
Sn--Ag--Cu for forming the solder layer 7 is applied to the upper
surface of each of a plurality of the finger electrodes 18 in the
regions where the tab electrode 2 on the front surface side is
arranged, by screen printing.
[0072] Thereafter the tab electrodes 2 each consisting of copper
foil having a thickness of about 200 .mu.m to about 400 .mu.m and a
width of about 1 mm to about 2 mm are pressed against the regions
to which the aforementioned resin paste and solder paste are
applied. Heat treatment is performed under a condition of a
temperature of about 150.degree. C. to about 200.degree. C. for
about 10 minutes to about 60 minutes by hot air heating in this
state, thereby hardening the resin paste. Therefore, the resin
paste becomes the bonding layers 6 and the surface (light receiving
surface 1a) of the ITO film 14 and the tab electrodes 2 are bonded
through the bonding layers 6. Thereafter, heat treatment is
performed under a condition of a temperature of about 230.degree.
C. to about 260.degree. C. by hot air heating, thereby hardening
the solder paste. Therefore, the solder paste becomes the solder
layers 7 and the tab electrodes 2 and the finger electrodes 18 are
electrically connected to each other through the solder layers 7
respectively. Thus, the tab electrodes 2 are connected to the front
surface of the photovoltaic element 1 as shown in FIG. 2.
[0073] The tab electrodes 2 are connected also to the back surface
of each photovoltaic element 1 by a connecting process similar to
the aforementioned connecting process of the tab electrodes 2 on
the front surface side. In other words, the tab electrodes 2 are
bonded to the light receiving surface 1b through the insulating
bonding layers 6, and electrically connected to the finger
electrodes 19 through the solder layers 7 respectively.
[0074] Finally, an EVA sheet for forming the filler 3, a plurality
of the photovoltaic elements 1 connected by the tab electrodes 2,
an EVA sheet for forming the filler 3, and the back surface
protector 5 consisting of PVF are successively deposited on the
surface protector 4 consisting of glass, as shown in FIG. 1.
Thereafter, the photovoltaic module according to the first
embodiment are formed by performing a vacuum laminating process
while heating.
[0075] With reference to FIGS. 8 and 9, a structure of a
photovoltaic module according to a first modification of the first
embodiment will be now described. In a photovoltaic element 21
according to the first modification of the first embodiment,
collectors constituted only by the finger electrodes 28a are formed
in prescribed regions on the light receiving surface 1a of the
front surface side similarly to the aforementioned first
embodiment. A plurality of the finger electrodes 28a serving as the
collectors are so formed as to extend in the direction X and be
spaced at prescribed intervals in the direction Y (direction in
which the tab electrodes 2 extend) perpendicular to the direction
X. Each finger electrode 28a has a thickness of about 10 .mu.m to
about 50 .mu.m and a width of about 100 .mu.m in the direction Y,
and consists of a conductive material formed by conductive paste
consisting of epoxy resin or the like prepared by incorporating
fine powder of Ag.
[0076] According to the first modification of the first embodiment,
a plurality of the finger electrodes 28a are divided into a
plurality of groups 28 each including three finger electrodes 28a
as shown in FIG. 8. The three finger electrodes 28a in the same
group 28 are so formed that a distance L1 in the direction Y
between the finger electrodes 28a adjacent in the regions in which
the tab electrode 2 is arranged is smaller than a distance L2 in
the direction Y between the finger electrodes 28a adjacent in the
regions in which the tab electrode 2 is not arranged.
[0077] According to the first modification of the first embodiment,
a plurality of the finger electrodes having similar configuration
to the finger electrodes 28a on the front surface side and
consisting of similar materials to the finger electrodes 28a on the
front surface side are formed also in prescribed regions on a light
receiving surface of the back surface side (not shown).
[0078] In the photovoltaic module according to the first
modification of the first embodiment, each tab electrode 2 is
directly bonded to the light receiving surface 1a through
insulating bonding layer 26 consisting of acrylic thermosetting
resin in a region corresponding to the power generation region on
the front surface side of the photovoltaic element 21, as shown in
FIG. 9. According to the first modification of the first
embodiment, each insulating bonding layer 26 bonding the light
receiving surface 1a and the tab electrode 2 is provided in the
region corresponding to the power generation region of the
photovoltaic element 21 in which the finger electrode 28a is not
formed. More specifically, according to the first modification of
the first embodiment, the insulating bonding layer 26 is provided
in each region located between the adjacent groups 28 each
including the three finger electrodes 28a in the direction Y, in
which the tab electrode 2 is arranged.
[0079] According to the first modification of the first embodiment,
in each region in which the tab electrode 2 is arranged, a solder
layer 27 consisting of Sn--Ag--Cu is provided on an upper surface
of each of a plurality of the finger electrodes 28a. The tab
electrodes 2 and the finger electrodes 28a are electrically
connected to each other by the solder layers 27 respectively.
[0080] A method of connecting the tab electrodes 2 on the back
surface side of the photovoltaic element 21 is similar to the
aforementioned method of connecting the tab electrodes 2 on the
front surface side of the photovoltaic element 21.
[0081] According to the first modification of the first embodiment,
as hereinabove described, the three finger electrodes 28a in the
same group 28 are so formed that a distance L1 in the direction Y
between the adjacent finger electrodes 28a in the regions in which
the tab electrode 2 is arranged is smaller than a distance L2 in
the direction Y between the adjacent finger electrodes 28a in the
regions in which the tab electrode 2 is not arranged, and the
insulating bonding layer 26 is provided in each region located
between the adjacent groups 28 in the direction Y in which the tab
electrode 2 is arranged. Therefore, the distance in the direction Y
between the adjacent groups 28 is increased in each region in which
the tab electrode 2 is arranged, whereby an area of a region to
which the bonding layer 26 arranged between the groups 28 is
applied can be increased. Thus, application of the insulating
bonding layers 26 to the light receiving surface 1a can be easily
performed.
[0082] Remaining effects of the first modification of the first
embodiment are similar to those of the aforementioned first
embodiment.
[0083] A structure of a photovoltaic module according to a second
modification of the first embodiment will be now described with
reference to FIGS. 10 and 11. In a photovoltaic element 31
according to the second modification of the first embodiment,
collectors constituted only by the finger electrodes 38a are formed
in prescribed regions on the light receiving surface 1a of the
front surface side similarly to the aforementioned first
embodiment. A plurality of the finger electrodes 38a serving as the
collectors are so formed as to extend in the direction X and be
spaced at prescribed intervals in the direction Y (direction in
which the tab electrodes 2 extend) perpendicular to the direction
X. Each finger electrode 38a has a thickness of about 10 .mu.m to
about 50 .mu.m and a width of about 100 .mu.m in the direction Y,
and consists of a conductive material formed by conductive paste
consisting of epoxy resin or the like prepared by incorporating
fine powder of Ag.
[0084] According to the second modification of the first
embodiment, a plurality of the finger electrodes 38a are divided
into a plurality of groups 38 each including three finger
electrodes 38a as shown in FIG. 10. The three finger electrodes 38a
included in the same group 38 are aggregated into one finger
electrode 38a of the three finger electrodes 38a in each region in
which the tab electrode 2 is arranged. According to the second
modification of the first embodiment, a width W1 in the direction Y
of each aggregated finger electrode 38a located in the region in
which the tab electrode 2 is arranged is substantially identical
with a width W2 (about 100 .mu.m) in the direction Y of each finger
electrode 38a located in the region in which the tab electrode 2 is
not arranged.
[0085] An interval D1 between the aggregated finger electrodes 38a
of the two groups 38 adjacent to each other is larger than a
distance D2 between the finger electrodes 38a opposed to each other
of the two groups 38 adjacent to each other.
[0086] According to the second modification of the first
embodiment, a plurality of the finger electrodes having similar
configuration to the finger electrodes 38a on the front surface
side and consisting of, for example, similar materials to the
finger electrodes 38a on the front surface side are formed also in
prescribed regions on the light receiving surface on the back
surface side (not shown).
[0087] In the photovoltaic module according to the second
modification of the first embodiment, each tab electrode 2 is
directly bonded to the light receiving surface 1a through an
insulating bonding layer 36 consisting of acrylic thermosetting
resin in a region corresponding to the power generation region on
the front surface side of the photovoltaic element 31, as shown in
FIG. 11. According to the second modification of the first
embodiment, each insulating bonding layer 36 bonding the light
receiving surface 1a and the tab electrode 2 is provided in the
region corresponding to the power generation region of the
photovoltaic element 31 in which the finger electrode 38a is not
formed. More specifically, according to the second modification of
the first embodiment, the insulating bonding layer 36 is provided
in each region located between the adjacent groups 38 each
including the three finger electrodes 38a in the direction Y, in
which the tab electrode 2 is arranged.
[0088] According to the second modification of the first
embodiment, in the regions in which the tab electrode 2 is
arranged, solder layers 37 consisting of Sn--Ag--Cu are provided on
upper surfaces of a plurality of the finger electrodes 38a. The tab
electrodes 2 and the finger electrodes 38a are electrically
connected to each other by the solder layers 37 respectively.
[0089] A method of connecting the tab electrodes 2 on the back
surface side of the photovoltaic element 31 is similar to the
aforementioned method of connecting the tab electrodes 2 on the
front surface side of the photovoltaic element 31.
[0090] According to the second modification of the first
embodiment, as hereinabove described, the three finger electrodes
38a included in the same group 38 are aggregated into one finger
electrode 38a of the three finger electrodes 38a in each region in
which the tab electrode 2 is arranged, and the insulating bonding
layer 36 is provided in each region located between the adjacent
groups 38 in the direction Y in which the tab electrode 2 is
arranged. Therefore, an area of each region in which the finger
electrode 38a is not formed can be increased in the region in which
tab electrode 2 is arranged, whereby an area of a bonding region of
the light receiving surface 1a and each tab electrode 2 can be
increased. Thus, a bonding strength between the light receiving
surface 1a and the tab electrodes 2 can be increased.
[0091] Remaining effects of the second modification of the first
embodiment are similar to those of the aforementioned first
embodiment.
[0092] A structure of a photovoltaic module according to a third
modification of the first embodiment will be now described with
reference to FIGS. 12 and 13. In a photovoltaic element 41
according to the third modification of the first embodiment,
collectors constituted only by the finger electrodes 48a are formed
in prescribed regions on the light receiving surface 1a of the
front surface side similarly to the aforementioned first
embodiment. A plurality of the finger electrodes 48a serving as the
collectors are so formed as to extend in the direction X and be
spaced at prescribed intervals in the direction Y (direction in
which the tab electrodes 2 extend) perpendicular to the direction
X. Each finger electrode 48a has a thickness of about 10 .mu.m to
about 50 .mu.m and a width of about 100 .mu.m in the direction Y,
and consists of a conductive material formed by conductive paste
consisting of epoxy resin or the like prepared by incorporating
fine powder of Ag.
[0093] According to the third modification of the first embodiment,
a plurality of the finger electrodes 48a are divided into a
plurality of groups 48 each including three finger electrodes 48a
as shown in FIG. 12. The three finger electrodes 48a included in
the same group 48 are aggregated into one finger electrode 48a of
the three finger electrodes 48a in each region in which the tab
electrode 2 is arranged. According to the third modification of the
first embodiment, a width W11 (about 300 .mu.m to about 1 mm) in
the direction Y of each aggregated finger electrode 48a located in
the region in which the tab electrode 2 is arranged is larger than
a width W12 (about 100 .mu.m) in the direction Y of each finger
electrode 48a located in the region in which the tab electrode 2 is
not arranged and is smaller than a distance L11 between the finger
electrodes 48a located at outermost positions of the three finger
electrodes 48a included in the same group 48.
[0094] An interval D11 between the aggregated finger electrodes 48a
in the two groups 48 adjacent to each other is larger than a
distance D12 between the finger electrodes 48a opposed to each
other of the two groups 48 adjacent to each other.
[0095] According to the third modification of the first embodiment,
a plurality of the finger electrodes having similar configuration
to the finger electrodes 48a on the front surface side and
consisting of similar materials to the finger electrodes 48a on the
front surface side are formed also in prescribed regions on the
light receiving surface of the back surface side (not shown).
[0096] In the photovoltaic module according to the third
modification of the first embodiment, each tab electrode 2 is
directly bonded to the light receiving surface 1a through an
insulating bonding layer 46 consisting of acrylic thermosetting
resin in a region corresponding to the power generation region on
the front surface side of the photovoltaic element 41, as shown in
FIG. 13. According to the third modification of the first
embodiment, each insulating bonding layer 46 bonding the light
receiving surface 1a and the tab electrode 2 is provided in the
region corresponding to the power generation region of the
photovoltaic element 41 in which the finger electrode 48a is not
formed. More specifically, according to the third modification of
the first embodiment, the insulating bonding layer 46 is provided
in each region located between the adjacent groups 48 each
including the three finger electrodes 48a in the direction Y, in
which the tab electrode 2 is arranged.
[0097] According to the third modification of the first embodiment,
in the regions in which the tab electrode 2 is arranged, solder
layers 47 consisting of Sn--Ag--Cu are provided on upper surfaces
of the finger electrodes 48a each having the larger width W11 (see
FIG. 12) in the direction Y. The tab electrodes 2 and the finger
electrodes 48a are electrically connected to each other by the
solder layers 47 respectively.
[0098] A method of connecting the tab electrodes 2 on the back
surface side of the photovoltaic element 41 is similar to the
aforementioned method of connecting the tab electrodes 2 on the
front surface side of the photovoltaic element 41.
[0099] According to the third modification of the first embodiment,
as hereinabove described, the three finger electrodes 48a included
in the same group 48 are aggregated into one finger electrode 48a
of the three finger electrodes 48a in each region in which the tab
electrode 2 is arranged, and the insulating bonding layer 46 is
provided in each region located between the adjacent groups 48 in
the direction Y in which the tab electrode 2 is arranged. Thus, an
area of a bonding region of the light receiving surface 1a and each
tab electrode 2 can be increased similarly to the second
modification of the aforementioned first embodiment, whereby a
bonding strength between the light receiving surface 1a and the tab
electrodes 2 can be increased.
[0100] According to the third modification of the first embodiment,
as hereinabove described, the width W11 in the direction Y of each
aggregated finger electrode 48a located in the region in which the
tab electrode 2 is arranged is larger than the width W12 in the
direction Y of each finger electrode 48a located in the region in
which the tab electrode 2 is not arranged. Thus, a contact area of
each tab electrode 2 and the finger electrode 48a can be increased
in the region in which the tab electrode 2 is arranged, whereby
contact resistance between the tab electrodes 2 and the finger
electrode 48a can be reduced.
[0101] Remaining effects of the third modification of the first
embodiment are similar to those of the aforementioned first
embodiment.
Second Embodiment
[0102] According to a second embodiment of the present invention, a
case where finger electrodes are divided in regions where a tab
electrode is arranged will be now described with reference to FIGS.
14 to 19, dissimilarly to the aforementioned first embodiment.
[0103] In a photovoltaic module according to the second embodiment,
tab electrodes 52 electrically connecting a plurality of
photovoltaic elements 51 are so arranged as to be electrically
connected to finger electrodes 58(59) serving as after-mentioned
collectors and extend in a direction Y perpendicular to a direction
X (direction in which the finger electrodes 58(59) extend), as
shown in FIG. 14. Each tab electrode 52 consists of copper foil
having a thickness of about 200 .mu.m to about 400 .mu.m and a
width of about 1 mm to about 2 mm.
[0104] In the photovoltaic elements 51 according to the second
embodiment, as shown in FIGS. 15 to 17, the i-type amorphous
silicon layer 12, the p-type amorphous silicon layer 13 and the ITO
film 14 are successively formed on the n-type single-crystalline
silicon substrate 11 similarly to the photovoltaic elements 1
according to the aforementioned first embodiment. The i-type
amorphous silicon layer 15, the n-type amorphous silicon layer 16
and the ITO film 17 are successively formed on the lower surface of
the n-type single-crystalline silicon substrate 11.
[0105] According to the second embodiment, a surface of the ITO
film 14 opposite to the n-type single-crystalline silicon substrate
11 is a light receiving surface 1a on a front surface side and a
surface of the ITO film 17 opposite to the n-type
single-crystalline silicon substrate 11 is a light receiving
surface 1b on a back surface side, similarly to the aforementioned
first embodiment. The light receiving surfaces 1a and 1b are
arranged in regions corresponding to the power generation
regions.
[0106] As shown in FIG. 16, the finger electrodes 58 each having a
thickness of about 10 .mu.m to about 50 .mu.m and consisting of a
conductive material formed by conductive paste consisting of epoxy
resin or the like prepared by incorporating fine powder of Ag are
formed in prescribed regions on the light receiving surface 1a of
the front surface side. A plurality of the finger electrodes 58 are
so formed as to extend in the direction X and be spaced from each
other at intervals of about 2 mm in the direction Y (direction in
which the tab electrodes 52 extend) perpendicular to the direction
X, as shown in FIG. 18. Each finger electrode 58 has a width of
about 100 .mu.m in the Y direction.
[0107] In the photovoltaic elements 51 according to the second
embodiment, the finger electrodes 58 are divided in the region in
which the tab electrode 52 is arranged so as not to cross the
regions in which the tab electrode 52 is arranged. In other words,
according to the second embodiment, each finger electrode 58
extending in the direction X is divided into three.
[0108] A plurality of the finger electrodes 59 having similar
configuration to the finger electrodes 58 on the front surface side
and consisting of similar materials to the finger electrodes 58 on
the front surface side are formed also in prescribed regions on the
light receiving surface 1b of the back surface side, as shown in
FIG. 16. The collectors of each photovoltaic element 51 of the
second embodiment are constituted only by the aforementioned finger
electrodes 58 and 59. In other words, bus bar electrodes for
aggregating currents collected by the finger electrodes 58 and 59
are not provided in the photovoltaic element 51 of the second
embodiment.
[0109] In the photovoltaic module according to the second
embodiment, each tab electrode 52 is directly bonded to the light
receiving surface 1a through insulating bonding layer 56 consisting
of acrylic thermosetting resin in a region corresponding to the
power generation region on the front surface side of the
photovoltaic element 51, as shown in FIGS. 15 to 17. According to
the second embodiment, each insulating bonding layer 56 bonding the
light receiving surface 1a and the tab electrode 52 is provided in
the region corresponding to the power generation region of the
photovoltaic element 51 in which the finger electrode 58 is not
formed, as shown in FIG. 19. More specifically, according to the
second embodiment, the insulating bonding layer 56 is so provided
in each region in which the tab electrode 52 is arranged so as
extend continuously along the direction Y (direction in which the
tab electrodes 52 extend).
[0110] According to the second embodiment, solder layers 57
consisting of Sn--Ag--Cu are provided on both sides in the
direction X of the region in which the tab electrode 52 on the
light receiving surface 1a is provided as shown in FIGS. 16 and 19.
Each solder layer 57 electrically connect a part of both side
surfaces 52a of the tab electrode 52 and divided both ends 58a of
the finger electrode 58 in portions of the both side surfaces in
the direction X of the tab electrode 52 and the insulating bonding
layer 56, as shown in FIG. 16.
[0111] A method of connecting the tab electrodes 52 on the back
surface side of the photovoltaic element 51 is similar to the
aforementioned method of connecting the tab electrodes 52 on the
front surface side of the photovoltaic element 51, as shown in
FIGS. 15 to 17. More specifically, each tab electrode 52 is
directly bonded to the light receiving surface 1b through the
insulating bonding layer 56 in a region corresponding to the power
generation region on the back surface side of the photovoltaic
element 51. The tab electrodes 52 are electrically connected to the
finger electrodes 59 through the solder layers 57,
respectively.
[0112] Remaining structures of the second embodiment are similar to
those of the aforementioned first embodiment.
[0113] According to the second embodiment, as hereinabove
described, the tab electrodes 52 are directly bonded to the light
receiving surface 1a through the insulating bonding layers 56 in
the region corresponding to the power generation region of the
front surface side of the photovoltaic element 51, whereby a
bonding strength between the light receiving surface 1a and the tab
electrodes 52 can be increased as compared with a bonding strength
between the light receiving surface 1a and the tab electrodes 52 in
a conventional case where the tab electrodes 52 are bonded through
bus bar electrodes formed of conductive paste on the light
receiving surface 1a. Thus, separation of the tab electrodes 52
from the light receiving surface 1a can be suppressed.
Consequently, also in a case where the finger electrodes
(collectors) 58 consisting of conductive paste are included,
separation of the tab electrodes 52 can be suppressed.
[0114] According to the second embodiment, as hereinabove
described, each finger electrode 58 is divided in the region in
which the tab electrode 52 is arranged, whereby the finger
electrode 58 is not formed in the region in which the tab electrode
52 is arranged. Therefore, the insulating bonding layers 56 can be
so provided as to extend continuously along the direction Y. Thus,
an area of a bonding region of the light receiving surface 1a and
each tab electrode 52 can be increased, whereby a bonding strength
between the light receiving surface 1a and each tab electrode 52
can be increased. In this case, the side surfaces of the tab
electrodes 52 and the divided ends of the finger electrodes 58 are
electrically connected to each other in the portions of the both
side surfaces in the direction X of the tab electrodes 52 and the
insulating bonding layers 56 through the solder layers 57. Thus,
even if the finger electrodes 58 are divided in the regions in
which the tab electrode 52 is arranged, the tab electrodes 52 and
the finger electrodes 58 can be easily electrically connected to
each other through the solder layers 57, respectively.
[0115] According to the second embodiment, as hereinabove
described, the tab electrodes 52 on the back surface side of the
photovoltaic element 51 are connected in a similar manner to the
tab electrodes 52 on the front surface side of the photovoltaic
element 51, whereby separation of the tab electrodes 52 and
reduction in the power generation region can be suppressed also on
the back surface side of the photovoltaic element 51.
[0116] Remaining effects of the second embodiment are similar to
those of the aforementioned first embodiment.
[0117] A process of fabricating the photovoltaic module according
to the second embodiment will be now described with reference to
FIGS. 14 to 19.
[0118] The ITO films 14 and 17 are formed by a similar fabrication
process to the aforementioned first embodiment as shown in FIGS. 15
to 17.
[0119] Then, the conductive paste consisting of epoxy resin or the
like prepared by incorporating fine powder of Ag is applied to
prescribed regions on the ITO film 14 by screen printing, as shown
in FIG. 16. Thereafter, the conductive paste is hardened, thereby
forming the finger electrodes 58 on the front surface side
consisting of the conductive material each having a thickness of
about 10 .mu.m to about 50 .mu.m in the prescribed regions on the
ITO film 14. At this time, the finger electrodes 58 on the front
surface side are so formed as to extend in the direction X without
crossing the regions in which the tab electrode 52 is arranged, as
shown in FIG. 18. In addition, a plurality of the finger electrodes
58 on the front surface side are so formed as to be spaced from
each other at intervals of about 2 mm in the direction Y
perpendicular to the direction X. Thereafter, a plurality of the
finger electrodes 59 on the back surface side having similar
configuration to the finger electrodes 58 on the front surface side
are formed also in the prescribed regions on the lower surface of
the ITO film 17 by a forming process similar to the aforementioned
forming process of the finger electrodes 58 on the front surface
side. Thus, the photovoltaic elements 51 constituting the
photovoltaic module according to the second embodiment are
formed.
[0120] As shown in FIG. 19, insulating resin paste for forming the
bonding layer 56, consisting of acrylic thermosetting resin is
applied to the ITO film 14 in each region in which the tab
electrode 52 on the front surface side is arranged so as to extend
continuously along the direction Y, by screen printing. Solder
paste consisting of Sn--Ag--Cu for forming the solder layer 57 is
applied to the both sides in the X direction of each region in
which the tab electrode 52 on the ITO film 14 of the front side is
arranged so as to come in contact with ends of each finger
electrode 58 on sides of the regions in which the tab electrode 52
is arranged, by screen printing.
[0121] Thereafter, the tab electrodes 52 each consisting of copper
foil having a thickness of about 200 .mu.m to about 400 .mu.m and a
width of about 1 mm to about 2 mm are pressed against the regions
to which the aforementioned resin paste is applied. Heat treatment
is performed under a condition of a temperature of about
150.degree. C. to about 200.degree. C. for about 10 minutes to
about 60 minutes by hot air heating in this state, thereby
hardening the resin paste. Therefore, the resin paste becomes the
bonding layers 56 and the surface (light receiving surface 1a) of
the ITO film 14 and the tab electrodes 52 are bonded through the
bonding layers 56 respectively. Thereafter, heat treatment is
performed under a condition of a temperature of about 230.degree.
C. to about 260.degree. C. by hot air heating, thereby hardening
the solder paste. Therefore, the solder paste becomes the solder
layers 57 and the tab electrodes 52 and the finger electrodes 58
are electrically connected to each other through the solder layers
57 respectively. Thus, the tab electrodes 52 are connected to the
front surface of the photovoltaic element 51 as shown in FIG.
14.
[0122] The tab electrodes 52 are connected also to the back surface
of the photovoltaic element 51 by a connecting process similar to
the aforementioned connecting process of the tab electrodes 52 on
the front surface side. In other words, the tab electrodes 52 are
bonded to the light receiving surface 1b through the insulating
bonding layers 56, and electrically connected to the finger
electrodes 59 through the solder layers 57 respectively.
[0123] Subsequent processes of fabricating the photovoltaic module
according to the second embodiment is similar to the processes
after the tab electrodes 2 of the aforementioned first embodiment
are connected.
[0124] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
[0125] For example, while the insulating resin paste consisting of
acrylic thermosetting resin is employed as the bonding material for
bonding the tab electrodes in the aforementioned first and second
embodiments, the present invention is not restricted to this but
insulating resin paste consisting of thermosetting resin other than
acrylic thermosetting resin may be alternatively employed. The
thermosetting resin other than acrylic thermosetting resin includes
silicon thermosetting resin or epoxy thermosetting resin, for
example. Alternatively, insulating resin paste consisting UV
curable resin or UV-thermosetting resin may be also employed. When
the insulating resin paste consisting UV curable resin or
UV-thermosetting resin is hardened, the process is preferably
performed in the following UV irradiation condition. In other
words, the preferable UV irradiation condition is a UV irradiation
intensity of about 100 mW/cm.sup.2 to about 600 mW/cm.sup.2, UV
irradiation time of about 1 minute to about 5 minutes. When the
insulating resin paste consisting of UV-thermosetting resin is
hardened, heat treatment may be performed under a condition of a
temperature of about 100.degree. C. to about 180.degree. C. for
about 10 minutes to about 90 minutes without UV irradiation.
[0126] While the resin paste and the solder paste are applied to
the surface of the ITO film by screen printing in the
aforementioned first and second embodiments, the present invention
is not restricted to this but the resin paste and the solder paste
may be alternatively formed on the surface of the ITO film by a
formation method other than the screen printing as far as formation
in a minute (fine) region can be performed. For example, the resin
paste and the solder paste may be alternatively applied to the
surface of the ITO film by dispenser.
[0127] While the resin paste and the solder paste are hardened by
hot air heating in the aforementioned first and second embodiments,
the present invention is not restricted to this but the resin paste
and the solder paste may be alternatively hardened by a method
other than hot air heating. A method other than hot air heating
includes reflow heating, beam irradiation heating and laser
irradiation heating, for example.
[0128] While the tab electrodes consisting of copper foil are
employed in the aforementioned first and second embodiments, the
present invention is not restricted to this but tab electrodes of
foil consisting of material other than copper may be alternatively
employed, or tab electrodes of wire may be alternatively employed.
Alternatively, the tab electrodes of foil or wire coated with
solders in advance may be employed.
[0129] While the surface of the ITO film is the light receiving
surface by forming the ITO film on the semiconductor layer in the
aforementioned first and second embodiments, the present invention
is not restricted to this but the present invention may be applied
to elements not formed with the ITO film on the semiconductor
layer. Alternatively, other transparent conductive film may be
employed instead of the ITO film.
[0130] While the photovoltaic elements each having a structure in
which the i-type amorphous silicon layers are formed between the
n-type single-crystalline silicon substrate and the p-type
amorphous silicon layer and between the n-type single-crystalline
silicon substrate and the n-type amorphous silicon layer are
employed as photovoltaic elements constituting a photovoltaic
module in the aforementioned first and second embodiments, the
present invention is not restricted to this but the present
invention can be applied to a photovoltaic module employing various
types of photovoltaic elements such as single-crystalline
photovoltaic elements, amorphous photovoltaic elements and
microcrystalline photovoltaic elements.
[0131] While the tab electrodes are bonded on the surface of the
ITO film on the semiconductor layer through the insulating bonding
layers in the aforementioned first and second embodiments, the
present invention is not restricted to this but the tab electrodes
may alternatively be bonded on the surface of the semiconductor
layer through the insulating bonding layers without forming the ITO
film on the semiconductor layer. Alternatively, the ITO film may be
so formed on the semiconductor layer as to expose a part of the
surface of the semiconductor layer, and the tab electrodes may be
alternatively bonded on the exposed surface of the semiconductor
layer through the insulating bonding layers. According to this
structure, a bonding strength of the element and each tab electrode
can be enhanced as compared with a case where the tab electrodes
are bonded on the surface of the ITO film through the insulating
bonding layers.
[0132] While the resin paste and the solder paste are hardened by
different heat treatment processes respectively in the
aforementioned first and second embodiments, the present invention
is not restricted to this but the resin paste and the solder paste
may be alternatively hardened by the same heat treatment
processes.
[0133] While the tab electrodes and the finger electrodes are
electrically connected to each other through the solder layers
respectively in the aforementioned first embodiment, the present
invention is not restricted to this but the tab electrodes may be
brought into contact with the finger electrodes without the solder
layers, thereby electrically connecting the tab electrodes and the
finger electrodes.
* * * * *