{DESCRIPTION}
{Title of Invention} Photovoltaic Device and Process for
Producing same
{Technical Field}
{0001}
The present invention relates to a photovoltaic device
and a process for producing the same, and relates particularly
to a thin-film silicon stacked solar cell that uses silicon as
the photovoltaic layer.
{Background Art}
{0002}
The use of silicon-based thin-film photovoltaic devices
as photovoltaic devices such as solar cells is already known.
These photovoltaic devices generally comprise a transparent
electrode, a silicon-based semiconductor layer (a photovoltaic
layer), and a back electrode stacked sequentially on top of a
transparent substrate. The semiconductor layer has a pin
junction formed by p-type, i-type, and n-type semiconductor
materials. In those cases where the photovoltaic device is a
solar cell, this pin junction functions as the energy
conversion unit, converting the light energy from sunlight
into electrical energy.
Further, in a thin-film photovoltaic device, in order to

achieve a desired level of output, a plurality of solar cell
unit cells (photovoltaic cells) each having a transparent
electrode, a photovoltaic layer and a back electrode, and in
which a predetermined region is specified as a single unit,
are generally connected electrically in a series arrangement
to form an integrated structure.
{0003}
Patent Literature 1 discloses an integrated thin-film
solar cell module in which series-connected solar cell unit
cells are insulated by isolation slots to form a plurality of
sub-modules (a series array), and each of the sub-modules is
connected electrically in a parallel arrangement to common
electrodes provided at both ends of the panel. Employing this
type of structure means that if a faulty cell is contained
within one of the sub-modules, then by utilizing the other
parallel-connected good sub-modules, any reduction in the
overall output of the module caused by the faulty cell can be
significantly alleviated compared with the case where only a
single module is formed on a single substrate.
{0004}
Patent Literature 2 discloses a process in which, for a
structure comprising a plurality of photovoltaic cells
connected electrically in a series arrangement, by causing
electrical shorts by not completely isolating the cells at the
positive electrode and negative electrode, or cells positioned

close thereto, from the peripheral region with peripheral
isolation slots, but then, following completion of a water
cleaning step, removing these electrical shorts by forming a
complete peripheral isolation slot, short-circuits that occur
between the photovoltaic cell integrated region and the
peripheral region as a result of ion migration within the
peripheral isolation slots can be prevented.
Furthermore, in the water cleaning step for this
photovoltaic device, by conducting the water cleaning inside a
water cleaning chamber that is shielded from the light, the
solar cell is prevented from generating photovoltaic power
during the water cleaning step, thereby preventing short-
circuits caused by ion migration.
{Patent Literature}
{0005}
{PTL 1}
Japanese Unexamined Patent Application, Publication No.
Hei 11-312816 (paragraph [0009] and Fig. 1)
{PTL 2}
Japanese Unexamined Patent Application, Publication No.
Hei 10-209477 ([Example 1] and [Example 3])
{Summary of Invention}
{0006}

On the other hand, as illustrated in Fig. 2, in a solar
cell having a structure in which a plurality of solar cell
unit cells 5 are connected electrically in series from a
positive electrode 20 through to a negative electrode 22, a
side insulation slot (side insulation portion) 16 that
electrically insulates the solar cell layer in a central
region of the substrate from the solar cell layer formed on an
edge portion 24 of the substrate 1 is formed with a width of
approximately 50 to 100 um. Because positioning a mask
precisely on the surface of the substrate during the
production steps is a complex task, the solar cell layer on
the edge portion 24 of the substrate is formed when each of
the layers of the solar cell layer and the like are deposited
on the entire substrate, and is an unavoidable result of
targeting mass production.
The edge portion 24 of the substrate acts as a sealing
and bonding surface that is used for bonding, via an adhesive
filler sheet of EVA or the like, a backing sheet 21 that
functions as a protective sheet for protecting the solar cell
layer. Accordingly, the solar cell layer formed on the edge
portion 24 of the substrate is removed by grinding or blast
polishing.
However, because there are limits to the dimensional
precision of the polishing location during the removal of the
solar cell layer formed on the edge portion 24 of the

substrate, a solar cell layer having a width of several mm may
be left unpolished on the outside of the side insulation slot
16. If the protective sheet is bonded in this state, with a
portion of the solar cell layer remaining on the outside of
the side insulation slot 16, and the cell is then used for an
extended period of time, then the resulting deterioration in
the waterproofing performance of the bonded portion may allow
a small amount of water to penetrate the cell from the edge of
the protective sheet, or may allow moisture to gradually
penetrate into the cell in the form of water vapor. When
water W that penetrates between the protective sheet and the
substrate in this manner reaches the side insulation slot 16,
then as illustrated in Fig. 2, a short-circuit can occur
between the solar cell 5, which is isolated by the side
insulation slot 16 and functions as an electric power
generation region, and the solar cell layer remaining on the
outside of the side insulation slot 16, thereby forming an
electrical circuit that leads to the negative electrode 22.
When this occurs, then as illustrated in the enlarged view of
the vicinity of the corner of the negative electrode 22 shown
in Fig. 3, the metal (such as silver) used as the back
electrode of the solar cell unit cell 5 dissolves due to a
leakage current I arising from the electrical current
generated by the solar cell layer, causing deposition
(electrodeposition) 103 at the counter electrode. As this

electrodeposition 103 proceeds, the deposited metal causes a
short-circuit between the insulated portion produced by the
side insulation slot 16 and the edge portion 24, resulting in
a deterioration in the cell output performance of the solar
cell.
{0007}
Furthermore, the above type of electrodeposition within
the insulation slot may also occur during the production of
the solar cell. This is because, even during the production
steps, following formation of the solar cell layer, the inside
illumination used along the production line can cause electric
power generation to occur within the solar cell layer,
generating a photovoltaic force.
For example, following formation of the side insulation
slot 16, a substrate cleaning step is performed. The water
used during this cleaning step may adhere to the side
insulation slot 16, causing electrodeposition and increasing
the possibility of a short-circuit occurring from the
insulation portion.
Further, even in cases such as those described in PTL 2,
where the substrate cleaning step is performed after formation
of the isolation slot, water that adheres within the isolation
slot may still cause electrodeposition.
{0008}
Furthermore, in PTL 1, creating sub-modules and then

connecting these sub-modules in a parallel arrangement offers
the advantage that even if one sub-module contains a faulty
cell, the remaining healthy sub-modules can continue to be
used, but also suffers the drawback that the sub-module that
contains the faulty cell cannot be used as an electric power
generation region.
{0009}
Furthermore, even if, as in PTL 2, the positive electrode
or negative electrode cell is not isolated by the side
insulation slot, when the substrate cleaning step is
performed, in the case of a solar cell formed on a large
substrate, a voltage difference may still develop between
cells positioned in distant locations from the positive
electrode or negative electrode, meaning water that adheres in
the side insulation slots may still cause electrodeposition.
{0010}
Furthermore, in PTL2, although the solar cell water
cleaning step is conducted inside a chamber that is surrounded
by a light-blocking guard to prevent photovoltaic power from
being generated during the water cleaning step, blocking light
from entering the portions where the solar cell is transported
into and out of the cleaning apparatus is problematic, and
satisfactory prevention of ion migration (electrodeposition)
has proven difficult.
{0011}

Furthermore, in PTL 2, the side insulation slots 16 that
were initially formed by an incomplete cut must be cut
completely through following the cleaning step, which is not
particularly suited to a mass production process.
{0012}
The present invention has been developed in light of
these circumstances, and has an object of providing a
photovoltaic device which is capable of preventing
deterioration in the performance of a solar cell caused by
electrodeposition generated as a result of moisture
penetration, and is also capable of suppressing, as far as
possible, any deterioration in performance even when the
device includes a photovoltaic cell (solar cell unit cell)
that is unable to generate electric power, such as a faulty
cell.
Here, the term "faulty cell" refers to a cell that is
partially shielded from the light and therefore has a reduced
electric power generation current, a cell that suffers from a
low electric power generation current as an inherent cell
property, or a cell in which the resistance of the transparent
electrode or back electrode, or the contact resistance
thereof, is high within some portions, resulting in a larger
current collection loss.
{0013}
Further, the present invention also has an object of

providing a process for producing a photovoltaic device that
is capable of avoiding the possibility of short-circuits
caused by electrodeposition during the production steps.
{0014}
In order to achieve the above objects, a photovoltaic
device according to a first aspect of the present invention
employs the configuration described below.
In other words, a photovoltaic device of the present
invention comprises a plurality of photovoltaic cells, which
are formed on top of a substrate and are connected in series
in a first direction, and side insulation portions, which are
formed continuously in the vicinity of the sides of the
substrate that extend along the first direction and
electrically insulate the photovoltaic cells from an edge
portion of the substrate, wherein two or more intermediate
insulation portions that electrically insulate the
photovoltaic cells positioned adjacently in a second direction
that is substantially orthogonal to the first direction are
formed on the substrate center side of the side insulation
portions so as to extend in the first direction in a parallel
arrangement across the second direction, a conductive portion
that electrically connects the photovoltaic cells positioned
adjacently in the second direction is provided in a position
partway along each of the intermediate insulation portions,
and the photovoltaic cells where the conductive portion is

positioned are electrically insulated from a photovoltaic cell
positioned adjacently in the second direction by another of
the intermediate insulation portions positioned distant from
the conductive portion in the second direction.
{0015}
Because the intermediate insulation portions
(intermediate insulation slots) are provided on the substrate
center side of the side insulation portions, the photovoltaic
cells adjacent to the side insulation portions are limited in
size to the surface area from the side insulation portion to
the adjacent intermediate insulation portion. Accordingly,
even if a side insulation portion short-circuits as a result
of water penetration or the like, only an electric power
generation current equivalent to the surface area between the
side insulation portion and the intermediate insulation
portion leaks into the edge portion of the substrate. In this
manner, the intermediate insulation portions enable the
leakage current generated when a short-circuit occurs to be
reduced, meaning short-circuits caused by electrodeposition
can be dramatically suppressed.
There are no particular restrictions on the configuration
of the side insulation portions and the intermediate
insulation portions, as long as they provide reliable
electrical insulation between adjacent regions. Examples of
preferred configurations include, for example, insulation

slots, which can be generated following formation of the
photovoltaic cells by using laser processing to remove the
transparent electrode, the photovoltaic layer, and the back
electrode layer across a predetermined slot width.
{0016}
Furthermore, by providing the conductive portion in a
position partway along each intermediate insulation portion,
the adjacent photovoltaic cells on either side of this
position are electrically connected. This means that the
electric power generation current can also flow in the second
direction through this conductive portion, meaning the
electrical current can flow not only to the photovoltaic cell
positioned adjacently in the first direction, but also via the
conductive portion to the photovoltaic cell positioned
adjacently in the second direction. Accordingly, even if an
ineffective cell that does not contribute to electric power
generation exists in the first direction, another photovoltaic
cell positioned adjacently in the second direction can be
used, meaning deterioration in the performance of the
photovoltaic device can be prevented as far as possible.
There are no particular restrictions on the configuration
of the conductive portions, provided they generate a reliable
electrical connection. In a preferred configuration, each of
the intermediate insulation portions formed in the first
direction is divided at a position partway along the

intermediate insulation portion, and this position where the
intermediate insulation portion is not formed functions as a
conductive portion. Further, in the case of photovoltaic
cells formed by sequentially stacking a transparent electrode,
a photovoltaic layer (including single structures, tandem
structures and triple structures) and a back electrode layer
on a transparent substrate, the back electrode layer and the
transparent electrode layer preferably remain within the
conductive portion. However, a region in which only the back
electrode layer remains or a region in which only the
transparent electrode layer remains can also be used as the
conductive portion.
{0017}
Furthermore, the photovoltaic cells where a conductive
portion is positioned are electrically insulated from another
photovoltaic cell positioned adjacently in the second
direction due to another intermediate insulation portion. As
a result, photovoltaic cells having a comparatively large
surface area that are formed in a continuous manner from one
side insulation portion through to the other side insulation
portion can be avoided, thereby suppressing the size of the
electrical current that flows when a short-circuit occurs
within a side insulation portion as a result of water
penetration or the like, and largely avoiding short-circuits
caused by electrodeposition.

{0018}
Moreover, in the photovoltaic device of the present
invention, the intermediate insulation portions may include
two first intermediate insulation portions, each provided next
to one of the side insulation portions formed along both sides
of the substrate, and at least one second intermediate
insulation portion provided between the first intermediate
insulation portions.
{0019}
Because at least one second intermediate insulation
portion is provided between the two first intermediate
insulation portions, photovoltaic cells between the two first
intermediate insulation portions are partitioned into at least
two cells in the second direction. As a result, even if one
photovoltaic cell becomes a faulty cell due to the state of
the film deposition, the presence of shade, or the adhesion of
dirt or the like, the group of photovoltaic cells positioned
adjacently in the second direction and isolated by the second
intermediate insulation portion can continue to be utilized
for electric power generation, meaning any deterioration in
the performance of the photovoltaic device can be largely
suppressed.
Furthermore, even if a photovoltaic cell exists that has
become faulty due to the state of the film deposition, the
presence of shade, or the adhesion of dirt or the like, the

electric power generation current can still flow through the
conductive portion provided in the intermediate insulation
portion into the photovoltaic cell positioned adjacently in
the second direction, and therefore deterioration in the
performance of the photovoltaic device can be suppressed even
further.
{0020}
Moreover, the photovoltaic device of the present
invention may further comprise a protective sheet that covers
an entire surface of the substrate so as to protect the
photovoltaic cells formed on top of the substrate, wherein the
intermediate insulation portions are positioned not less than
20 mm distant from the side insulation portions.
{0021}
The protective sheet is installed on top of the substrate
to protect the photovoltaic cells. When the photovoltaic
device is used for an extended period of time, there is a
possibility that the edges of the protective sheet may peel
away from the substrate, or that the waterproofing and
moisture-proofing performance of the sealed portion may
deteriorate, allowing water or moisture from the outside
atmosphere to penetrate into the photovoltaic cells. If the
peeling of the edges of the protective sheet is minimal, then
the moisture is blocked by the side insulation portions.
However, if the peeling of the edges of the protective sheet

progresses and the waterproofing and moisture-proofing
performance of the sealed portion deteriorates further, then
moisture may cross the side insulation portion and penetrate
into the photovoltaic cells. In the present invention,
because the intermediate insulation portions are formed not
less than 20 mm distant from the side insulation portions,
even if moisture crosses a side insulation portion and
penetrates via the slot portion formed by the series
connection of the plurality of photovoltaic cells, the
adjacent intermediate insulation portion can block the
penetration of the moisture, and those photovoltaic cells
positioned on the inside of the intermediate insulation
portion can continue to be used. According to investigations
conducted by the inventors of the present invention and
others, provided that the intermediate insulation portion is
20 mm distant from the side insulation portion, then even in
those cases where the protective sheet peels as far as the
side insulation portion, the intermediate insulation portion
is able to block adverse effects to such an extent that 10 or
more years are required before short-circuits due to water
penetration or performance deterioration caused by cell
degeneration become problematic.
The protective sheet is preferably a waterproof backing
sheet that is bonded via an adhesive filler sheet such as EVA
(ethylene vinyl acetate copolymer). A three-layer structure

comprising a PET sheet, Al foil, and a PET sheet can be used
favorably as the backing sheet.
{0022}
Moreover, in the photovoltaic device of the present
invention, the photovoltaic cells may exist within a single
structure comprising a single photovoltaic layer, a tandem
structure comprising two stacked photovoltaic layers, or a
triple structure comprising three stacked photovoltaic layers.
{0023}
Further, the electric power generation current increases
with increasing size of the solar cell, and therefore in large
solar cells where the length along one side exceeds 1 m, the
present invention is effective even in single structures
having a single electric power generation layer.
Moreover, photovoltaic cells having a tandem structure
with two stacked photovoltaic layers or a triple structure
with three stacked photovoltaic layers have larger electric
power generation capacities than photovoltaic cells having a
single structure with one photovoltaic layer, and therefore
the potential leakage current is larger, which means there is
an increased chance of electrodeposition causing short-
circuits. Accordingly, in the case of photovoltaic cells
having a tandem structure or a triple structure, a
photovoltaic device comprising intermediate insulation
portions, such as the device of the present invention

described above, is particularly effective.
{0024}
A process for producing a photovoltaic device according
to the present invention comprises an insulation step of
forming an insulation portion that electrically insulates a
photovoltaic layer formed on a substrate from other regions,
and a cleaning step of cleaning the substrate following the
insulation step, wherein for a predetermined period including
the cleaning step, the photovoltaic layer is illuminated with
a red-colored light. This red-colored light is a red light
having a wavelength of not less than approximately 650 nm, and
preferably a wavelength of not less than 700 nm.
{0025}
When the substrate is cleaned with water in a cleaning
apparatus following completion of the insulation step, there
is a possibility that water may accumulate within an
insulation portion, causing the insulation portion to short-
circuit, and increasing the likelihood of electrodeposition
and subsequent short-circuits. In the present invention, for
a predetermined period including the cleaning step, the
photovoltaic layer is illuminated with a red-colored light,
and light of a wavelength that causes the photovoltaic cells
to contribute significantly to electric power generation is
excluded as far as possible, and therefore an electric
potential sufficient to cause electrodeposition is not

generated within those insulation portions that have been
short-circuited during the cleaning step. Accordingly, any
chance that electrodeposition may occur during the production
process for the photovoltaic device, causing a short-circuit,
can be effectively eliminated.
Here, the expression "predetermined period including the
cleaning step" means a period that includes, at least, the
period during which water supplied during the cleaning step
causes short-circuits of the insulation portions.
{0026}
Moreover, the process for producing a photovoltaic device
according to the present invention is preferably used for
producing one of the photovoltaic devices described above.
{0027}
The photovoltaic devices according to each of the aspects
of the present invention described above comprise intermediate
insulation portions in addition to the side insulation
portions, meaning there is an increased chance of
electrodeposition occurring within the insulation portions and
causing short-circuits, and therefore during the cleaning
step, maintaining a state of illumination that employs mainly
red-colored light, which enables operations inside the
cleaning apparatus to be inspected visually while offering
minimal contribution to electric power generation, is
particularly effective.
{Brief Description of Drawings}
{0028}
{Fig. 1} A plan view illustrating the structure of a
photovoltaic device according to an embodiment of the present
invention.
{Fig. 2} A plan view illustrating the structure of a
conventional photovoltaic device.
{Fig. 3} An enlarged view illustrating the corner portion of
the negative electrode in Fig. 2.
{Fig. 4} A plan view of a photovoltaic device illustrating a
comparative example of the present invention.
{Fig. 5} A longitudinal cross-sectional view illustrating a
photovoltaic device according to an embodiment of the present
invention.
{Fig. 6} A schematic view illustrating part of a process for
producing a solar cell panel according to an embodiment of the
present invention.
{Fig. 7} A schematic view illustrating part of a process for
producing a solar cell panel according to an embodiment of the
present invention.
{Fig. 8} A schematic view illustrating part of a process for
producing a solar cell panel according to an embodiment of the
present invention.
{Fig. 9} A schematic view illustrating part of a process for

producing a solar cell panel according to an embodiment of the
present invention.
{Fig. 10} A side sectional view illustrating a substrate
cleaning apparatus according to an embodiment of the present
invention.
{Fig. 11} A plan view illustrating a modified example of a
photovoltaic device according to an embodiment of the present
invention.
{Reference Signs List}
{0029}
1 Substrate
2 Transparent electrode layer
3 Photovoltaic layer
4 Back electrode layer
5 Solar cell unit cell (photovoltaic cell)
16 Side insulation slot (side insulation portion)
17 Intermediate insulation slot (intermediate insulation
portion)
18 Conductive portion
90 Solar cell (photovoltaic device)
{Description of Embodiments}
{0030}
An embodiment of the present invention is described below

with reference to the drawings.
Fig. 1 is a plan view illustrating a solar cell that
represents one embodiment of the photovoltaic device according
to this embodiment.
The solar cell comprises a plurality of solar cell unit
cells 5 (photovoltaic cells) on a substrate 1. The substrate
1 is a transparent substrate formed using glass or the like,
and has a dimension in the X-direction shown in the figure
(the second direction) of approximately 1.4 m, and a dimension
in the Y-direction (the first direction) of approximately 1.1
m.
A waterproof backing sheet (protective sheet) is bonded
to the upper surface of the solar cell unit cells 5 with an
adhesive filler sheet composed of EVA (ethylene vinyl acetate
copolymer) or the like disposed therebetween, so as to cover
the entire substrate 1.
{0031}
Each solar cell unit cell 5 is a single unit that acts as
an electric power generation region having a predetermined
size, and as described below, comprises a transparent
electrode layer, a photovoltaic layer and a back electrode
layer. A single structure, a tandem structure or a triple
structure may be used as the photovoltaic layer.
The solar cell unit cells 5 are connected in series in
the Y direction (the first direction) from a positive

electrode 20 towards a negative electrode 22. The Y-direction
dimension of each solar cell unit cell 5 is approximately 11
mm, meaning a total of approximately 100 solar cell unit cells
5 are connected in series. Accordingly, it should be noted
that in the figure, the dimensions of the solar cell unit
cells 5 have been shown larger than true size in order to
facilitate comprehension.
{0032}
Side insulation slots (side insulation portions) 16 for
achieving electrical insulation are formed in the vicinity of
the sides of the substrate 1 that extend along the Y-
direction. These side insulation slots 16 are provided in a
continuous manner along the sides of the substrate 1. The
side insulation slots 16 are slots in which the transparent
electrode layer, the photovoltaic layer and the back electrode
layer stacked on the substrate 1 have been removed, and the
width of these slots is approximately 50 to 100 urn. Although
not shown in the figure, insulation slots may also be formed
in positions in the vicinity of the sides of the substrate 1
that extend along the X-direction. However, because a film
polishing and removal treatment is performed to generate an
insulation portion 24, these insulation slots in the vicinity
of the sides that extend along the X-direction may be omitted.
The edge portion 24 that represents the region outside
the side insulation slots 16 is a region in which grinding or

the like is used to remove the transparent electrode layer,
the photovoltaic layer and the back electrode layer formed on
top of the substrate 1. However, performing removal of the
photovoltaic layer and the like on the edge portion 24 along
the side of the side insulation slots 16 having a width of
approximately 50 to 100 um is problematic in terms of
maintaining dimensional precision, and therefore although only
very small, portions of several mm of the transparent
electrode layer, the photovoltaic layer and the back electrode
layer tend to remain on the outside of the side insulation
slots 16 (namely, within the edge portion 24). Furthermore, a
film polishing and removal treatment of the edge portion 24
along the sides that extend in the X-direction is performed in
the same manner as the Y-direction. The edge portion 24 acts
as a bonding and sealing surface that is used for bonding the
above-mentioned filler sheet and the backing sheet 21, thereby
preventing moisture from penetrating the device from the
periphery of the substrate 1.
{0033}
Intermediate insulation slots (intermediate insulation
portions) 17 that extend in the Y-direction are formed on the
substrate center side of the side insulation slots 16. In a
similar manner to the side insulation slot 16, these
intermediate insulation slots 17 are slots in which the
transparent electrode layer, the photovoltaic layer and the

back electrode layer stacked on the substrate 1 have been
removed, and the width of these slots is approximately 50 to
100 µm. As a result of these intermediate insulation slots
17, solar cell unit cells 5 that are positioned adjacently in
the X-direction (the second direction) are electrically
insulated from each other.
A plurality of the intermediate insulation slots 17
(three in this particular embodiment) are formed in parallel
with a certain separation therebetween in the X-direction. In
other words, two first intermediate insulation slots 17a are
formed adjacent to the side insulation slots 16 formed at both
sides of the substrate 1, and a single second intermediate
insulation slot 17b is formed between these first intermediate
insulation slots 17a. Each of the first intermediate
insulation slots 17a is formed in a position at least 20 mm
distant, in the X-direction, from the adjacent side insulation
slot 16. In this embodiment a single second intermediate
insulation slot 17b is provided, but two or more of these
slots may also be used.
{0034}
The intermediate insulation slots 17 are each divided at
a position partway along the slot in the Y-direction. In
other words, in these positions where the intermediate
insulation slots 17 are divided, conductive portions 18 exist
where the transparent electrode layer, the photovoltaic layer

and the back electrode layer remain on the substrate.
Accordingly, within these conductive portions 18, solar cell
unit cells 5 that are positioned adjacently in the X-direction
are electrically connected. However, solar cell unit cells 5
where a conductive portion 18 is positioned remain
electrically insulated from another solar cell unit cell 5
positioned adjacently in the X-direction due to another
intermediate insulation slot 17 positioned distantly from the
conductive portion 18 in the X-direction. Specifically, a
solar cell unit 5a in Fig. 1 is electrically connected to a
solar cell unit cell 5b positioned adjacently in the X-
direction via a conductive portion 18a. On the other hand,
the solar cell unit cells 5a and 5b where the conductive
portion 18a is positioned remain electrically insulated from a
solar cell unit cell 5c positioned adjacently in the X-
direction (namely, the left direction in the figure) as a
result of the second insulation slot 17b. In this manner, the
conductive portions 18 are arranged so that no solar cell unit
cell 5 exists that extends from one side insulation slot 16 to
the other side insulation slot 16 (unlike the solar cell unit
cells 5 illustrated in Fig. 2). In other words, the
conductive portion 18 provided within each intermediate
insulation slot 17 is provided at a different position in the
Y-direction from the conductive portion 18 provided in the
adjacent intermediate insulation slot 17.

{0035}
Next is a description of the longitudinal cross-sectional
structure of the solar cell (photovoltaic device), based on
Fig. 5. In this figure, the filler sheet and backing sheet 21
that are stacked on the back electrode layer 4 are omitted.
The solar cell 90 is a silicon-based thin-film solar
cell, and comprises a transparent substrate 1, a transparent
electrode layer 2, a photovoltaic layer (or electric power
generation layer) 3 comprising a first cell layer (a top
layer ) 91 and a second cell layer (a bottom layer ) 92, and a
back electrode layer 4. In this embodiment, the first cell
layer 91 is a photovoltaic layer comprising mainly amorphous
silicon-based semiconductors, and the second cell layer is a
photovoltaic layer comprising mainly crystalline silicon-based
semiconductors.
{0036}
Here, the term "silicon-based" is a generic term that
includes silicon (Si), silicon carbide (SiC) and silicon
germanium (SiGe). Further, the term "crystalline silicon-
based" describes a silicon system other than an amorphous
silicon system, and includes both microcrystalline silicon and
polycrystalline silicon systems.
{0037}
An intermediate contact layer 93 formed from a
transparent conductive film may be provided between the first

cell layer 91 and the second cell layer 92.
The solar cell illustrated in Fig. 5 is a tandem
structure comprising two stacked electric power generation
layers composed of the first cell layer 91 and the second cell
layer 92, but the present invention is not limited to tandem
structures, and may also be used within single structures
comprising a single electric power generation layer and triple
structures comprising three stacked electric power generation
layers.
{0038}
Next is a description of a process for producing a solar
cell panel comprising the solar cell described above and a
backing sheet 21 and terminal box 23 connected to the solar
cell. The description focuses on an example in which a
photovoltaic layer comprising mainly amorphous silicon-based
semiconductors and a photovoltaic layer comprising mainly
crystalline silicon-based semiconductors are stacked
sequentially, as the photovoltaic layer 3, on top of a glass
substrate that functions as the substrate 1. Fig. 6 through
Fig. 9 are schematic views illustrating the process for
producing a solar cell and a solar cell panel according to
this embodiment.
{0039}
(1) Fig. 6(a)
A soda float glass substrate (1.4 m * 1.1 m * thickness:

4 mm) is used as the substrate 1. The edges of the substrate
are preferably subjected to corner chamfering or R-face
chamfering to prevent damage caused by thermal stress or
impacts or the like.
{0040}
(2) Fig. 6(b)
A transparent electrode layer 2 is formed on top of the
substrate 1, thereby forming a transparent electrode-bearing
substrate. In addition to the transparent electrode film, the
transparent electrode layer 2 may include an alkali barrier
film (not shown in the figure) formed between the substrate 1
and the transparent electrode film. The alkali barrier film
is formed by using a thermal CVD apparatus to deposit a
silicon oxide film (SiC>2) of not less than 50 nm and not more
than 150 nm at a temperature of approximately 500°C.
{0041}
(3) Fig. 6(c)
Subsequently, the substrate 1 is mounted on an X-Y table,
and the first harmonic of a YAG laser (1064 nm) is irradiated
onto the film surface of the transparent electrode film, as
illustrated by the arrow in the figure. The laser power is
adjusted to ensure an appropriate process speed, and the
transparent electrode film is then moved in a direction
perpendicular to the direction of the series connection of the
electric power generation cells 5 (the X-direction in Fig. 1),

thereby causing a relative movement of the substrate 1 and the
laser light, and conducting laser etching across a strip
having a predetermined width of not more than approximately 6
mm and not more than 12 mm to form a slot 10.
{0042}
(4) Fig. 6(d)
Using a plasma CVD apparatus under conditions including a
reduced pressure atmosphere of not less than 30 Pa and not
more than 150 Pa, a substrate temperature of approximately
200°C, and a plasma RF generation frequency of not less than
13 MHz and not more than 100 MHz, a p-layer, i-layer and n-
layer each formed from a thin film of amorphous silicon are
deposited sequentially as the first cell layer (the top
layer ) 91 of the photovoltaic layer 3. The first cell layer
91 is deposited on top of the transparent electrode layer 2
using SiH4 gas and H2 gas as the main raw materials. The p-
layer, i-layer and n-layer are stacked in this order, with the
p-layer closest to the surface from which incident sunlight
enters.
{0043}
In this embodiment, the p-layer of the first cell layer
91 is an amorphous B-doped SiC film generated by reaction of
SiH4, H2, CH4 and B2H6 gases using an RF plasma, and preferably
has a thickness of not less than 4 nm and not more than 16 nm.
The i-layer of the first cell layer 91 is preferably an

amorphous Si film generated by reaction of SiH4 and H2 using an
RF plasma, and preferably has a film thickness of not less
than 100 nm and not more than 400 nm. The n-layer of the
first cell layer 91 is a Si film containing a crystalline
component, generated by reaction of SiH4, H2 and PH3 gas using
an RF plasma, and preferably has a film thickness of not less
than 10 nm and not more than 80 nm. Furthermore, in order to
suppress band mismatch at the interface between the p-layer
(SiC film) and the i-layer (Si film), a substance with an
intermediate band gap may be inserted as a buffer layer (not
shown in the figure).
{0044}
Next, using a plasma CVD apparatus under conditions
including a reduced pressure atmosphere of not more than 3
kPa, a substrate temperature of approximately 200°C, and a
plasma RF generation frequency of not less than 40 MHz and not
more than 200 MHz, a microcrystalline p-layer,
microcrystalline i-layer and microcrystalline n-layer each
formed from a thin film of microcrystalline silicon are
stacked sequentially, as the second cell layer (the bottom
layer ) 92, on top of the first cell layer 91.
{0045}
In this embodiment, the p-layer of the second cell layer
92 is a Si film containing a crystalline component, generated
by reaction of SiH4, H2 and B2H6 gases using an RF plasma, and

preferably has a film thickness of not less than 10 nm and not
more than 60 nm. The i-layer of the second cell layer 92 is a
Si film containing a crystalline component, generated by
reaction of SiH4 and H2 using an RF plasma, and preferably has
a film thickness of not less than 1,200 nm and not more than
3,000 nm.
The n-layer of the second cell layer 92 is a Si film
containing a crystalline component, generated by reaction of
SiH4, H2 and PH3 gases using an RF plasma, and preferably has a
film thickness of not less than 10 nm and not more than 80 nm.
{0046}
During formation of the microcrystalline silicon thin
films, particularly the microcrystalline i-layer by plasma
CVD, the distance between the plasma discharge electrode and
the surface of the substrate 1 is preferably not less than 3
mm and not more than 10 mm. If this distance is less than 3
mm, then the precision of the various structural components
within the film deposition chamber required for processing
large substrates means that maintaining the distance at a
constant level becomes difficult, which increases the
possibility of the electrode getting too close and making the
discharge unstable. If the distance exceeds 10 mm, then
achieving a satisfactory film deposition rate (of not less
than 1 nm/s) becomes difficult, and the uniformity of the
plasma also deteriorates, causing a deterioration in the

quality of the film due to ion impact. The i-layer of the
second cell layer 92 is preferably deposited under conditions
including an RF frequency of not less than 40 MHz and not more
than 200 MHz, a gas pressure of not less than 0.5 kPa and not
more than 3 kPa, and a film deposition rate of not less than 1
nm/s and not more than 3 nm/s, and in this embodiment, film
deposition is conducted using an RF frequency of 60 MHz, a gas
pressure of 1.6 kPa, and a film deposition rate of 2 nm/s.
{0047}
With the objective of forming a semi-reflective film to
improve the contact properties and achieve electrical current
consistency between the first cell layer 91 and the second
cell layer 92, a ZnO-based film (such as a GZO (Ga-doped ZnO)
film) with a film thickness of not less than 0 nm and not more
than 90 nm may be deposited as an intermediate contact layer
93 using a sputtering apparatus.
{0048}
(5) Fig. 6(e)
The substrate 1 is mounted on an X-Y table, and the
second harmonic of a laser diode excited YAG laser (532 nm) is
irradiated onto the film surface of the photovoltaic layer 3,
as illustrated by the arrow in the figure. With the pulse
oscillation set to not less than 10 kHz and not more than 20
kHz, the laser power is adjusted so as to achieve a suitable
process speed, and laser etching is conducted at a target not+

less than approximately 100 µm and not more than 150 urn to the
side of the laser etching line within the transparent
electrode layer 2, so as to form a slot 11. Provided the
positions of the laser etching lines are not inverted, no
particular problems arise, but in consideration of positioning
tolerances, the target is preferably set to a numerical value
within the above range.
{0049}
(6) Fig. 7(a)
Using a sputtering apparatus, a Ag film is then deposited
as the back electrode layer 4 under a reduced pressure
atmosphere and at a temperature of approximately 150°C. In
this embodiment, the Ag film of the back electrode layer 4 is
deposited with a film thickness of not less than 150 ran, and
in order reduce the contact resistance between the n-layer and
the back electrode layer 4 and improve the reflectance, a ZnO-
based film (such as a GZO (Ga-doped ZnO) film) with a film
thickness of not less than 10 nm is provided between the
photovoltaic layer 3 and the back electrode layer 4 using a
sputtering apparatus.
{0050}
(7) Fig. 7(b)
The substrate 1 is mounted on an X-Y table, and the
second harmonic of a la ser diode excited YAG laser (532 nni) is
irradiated onto the substrate 1, as illustrated by the arrow

in the figure. The laser light is absorbed by the
photovoltaic layer 3, and by using the high gas vapor pressure
generated at this point, the back electrode layer 4 is removed
by explosive fracture. With the pulse oscillation set to not
less than 1 kHz and not more than 20 kHz, the laser power is
adjusted so as to achieve a suitable process speed, and laser
etching is conducted at a target not less than approximately
250 urn and not more than 400 urn to the side of the laser
etching line within the transparent electrode layer 2, so as
to form a slot 12. Provided the positions of the laser
etching lines are not inverted, no particular problems arise,
but in consideration of positioning tolerances, the target is
preferably set to a numerical value within the above range.
{0051}
Following removal of the back electrode layer 4,
substrate cleaning is performed using a substrate cleaning
apparatus 201 illustrated in Fig. 10. In those cases where
the generation of residues (such as deposits and burrs)
following removal of the back electrode layer 4 is minimal,
this substrate cleaning step may sometimes be omitted.
The inside of the substrate cleaning apparatus 201 is
configured so that light of a wavelength that causes the
photovoltaic layer to contribute significantly to electric
power generation is not irradiated onto the photovoltaic
layer, but rather only red-colored light is irradiated onto

the photovoltaic layer. This red-colored light is composed
mainly of a wavelength band in which the wavelength is not
less than approximately 650 nm, and preferably not less than
approximately 700 nm, and represents a wavelength band for
which a solar cell comprising amorphous silicon as the
photovoltaic layer exhibits only low photovoltaic sensitivity.
Accordingly, a state of illumination can be achieved that
enables operations inside the substrate cleaning apparatus 201
to be inspected visually, while suppressing electric power
generation by the photovoltaic layer. Even in the case of a
tandem solar cell in which the photovoltaic layer includes
both amorphous silicon and crystalline silicon, because the
electric power generation capability of the solar cell
containing the amorphous silicon is very low under the red-
colored light, electric power generation by the tandem solar
cell can also be suppressed.
{0052}
The substrate cleaning apparatus 201 has transport
rollers 25 for transporting the substrate housed inside a main
cover 33. Further, the substrate cleaning apparatus 201 also
comprises, inside the main cover 33 and in sequence from the
upstream side of the transport direction, an entrance section
31, a roller brush unit 26, a high-pressure shower unit 27, a
direct water rinse unit 28, and an air knife unit 29. The
roller brush unit 26 is sometimes not used in order to protect

the photovoltaic layer, particularly in the case of cleaning
deposited film surfaces.
{0053}
The main cover 33 enables a state to be achieved in which
red light represents the main illumination inside the
apparatus, meaning light of a wavelength that causes the
photovoltaic layer to contribute significantly to electric
power generation is not irradiated onto the photovoltaic layer
formed on the substrate being transported through the
substrate cleaning apparatus 201. Internal room light and
external light from entering the apparatus is blocked, and
This red light is preferably generated by providing an
illumination device that generates light of a wavelength band
in which the wavelength is not less than approximately 650 nm,
and preferably not less than approximately 700 nm. For
example, this type of setup can be realized favorably by
providing red-colored filters (sharp cut filters that block
short wavelength light) that transmit light in a wavelength
band of approximately 650 nm or greater, and preferably 700 nm
or greater, on windows or gaps of the main cover 33 through
which internal illumination or external light is able to
enter. Gaps where internal and external light is able to
enter the apparatus exist at the portions where the substrate
enters and exits the cleaning apparatus, but the amount of
light entering from these portions is minimal, and provided

the amount of light inside the substrate cleaning apparatus
201 is restricted to a target of not more than 0.15 W/cm2,
electric power generation by the photovoltaic layer can be
satisfactorily suppressed.
{0054}
The above-mentioned amount of light is calculated from
the number of atoms corresponding with the amount of
electrodeposited metal (such as Ag) that poses a danger of
short-circuiting the insulation slot when sunlight (white
light) is irradiated onto the solar cell for a predetermined
period of time.
Specifically, a numerical value for the upper limit for
the above amount of light is calculated using a formula
detailed below.
Namely, in order to ensure that the amount of Ag
deposition within the insulation slot is an amount that is
insufficient to cause a short-circuit, the amount of light is
preferably limited as follows:
Upper limit for amount of light < (charge amount required
for Ag deposition) -e- (charge amount generated per unit amount
of light)
In this formula:
(charge amount required for Ag deposition) = (film
thickness of Ag film * cell width * deposition length *
specific gravity/molecular weight * charge amount), and

(charge amount generated per unit amount of light) =
(generated electrical current / amount of light * time).
Using the above formulas, if calculations are conducted
assuming a Ag film thickness of 0.24 [nm] (the film thickness
when single molecules of Ag are aligned), a cell width of 10
[mm], a deposition length of 0.1 [mm] (so that a length less
than the insulation slot width is set as the amount of Ag
deposition that does not cause a short-circuit), a specific
gravity of 10.5 [g/cc], a molecular weight of 107.86 [g/mol],
a charge amount of 6E23 [number/mol] * 1.6E-19 [C], a
generated electrical current of 1.5 [A], an amount of light of
1,000 [W/m2], and a time of 100 [s] (the contact time with
water), then the following relationship can be obtained.
Upper limit for amount of light < 0.15 W/m2
Moreover, if the Ag deposition length is set to not more
than l/10th of the insulation slot width, then a more reliable
suppression effect is obtained. In other words, the target
for the amount of light is preferably set as follows
Upper limit for amount of light < 1.5 * 10"2 W/m2
{0055}
Roller brushes.are provided in the roller brush unit 26.
The roller brushes are provided both above and below the
substrate undergoing treatment. The roller brushes are
pressed against the substrate undergoing treatment, thereby
scrubbing and cleaning the surfaces of the substrate

undergoing treatment.
{0056}
Nozzles for spraying high-pressure water are provided in
the high-pressure shower unit 27. High-pressure water (for
example, having a pressure of 0.2 to 1.0 MPa) is sprayed from
these nozzles onto the substrate undergoing treatment. In
this manner, in the high-pressure shower unit 27, cleaning is
performed using water that is sprayed onto the substrate at
high pressure.
{0057}
Nozzles for spraying pure water are provided in the
direct water rinse unit 28. Pure water (having a resistivity
of not less than 10 MQ-cm) is sprayed from these nozzles onto
the substrate undergoing treatment.
{0058}
In the air knife unit 29, air is blown onto the substrate
undergoing treatment. This removes water from the substrate
undergoing treatment and dries the substrate.
{0059}
(8) Fig. 7(c)
The electric power generation region is then
compartmentalized, by using laser etching to remove the effect
wherein the serially connected portions within the edge
portion 24 of the substrate 1 (see Fig. 1) are prone to short-
circuits. The substrate 1 is mounted on an X-Y table, and the

second harmonic of a laser diode excited YAG laser (532 nm) is
irradiated onto the substrate 1. The laser light is absorbed
by the transparent electrode layer 2 and the photovoltaic
layer 3, and by using the high gas vapor pressure generated at
this point, the back electrode layer 4 is removed by explosive
fracture, thereby removing the back electrode layer 4, the
photovoltaic layer 3 and the transparent electrode layer 2.
With the pulse oscillation set to not less than 1 kHz and not
more than 10 kHz, the laser power is adjusted so as to achieve
a suitable process speed, and laser etching is conducted at a
point not less than approximately 5 mm and not more than 20 mm
from the edge of the substrate 1, so as to form a Y-direction
insulation slot 16. Fig. 7(c) represents a cross-sectional
view cut along the direction of the series connection of the
photovoltaic layer 3, and therefore the location in the figure
where the Y-direction insulation slot 16 is formed should
actually appear as an edge portion 24 in which the back
electrode layer 4, the photovoltaic layer 3 and the
transparent electrode layer 2 have been removed by film
polishing (see Fig. 8(a)), but in order to facilitate
description of the processing of the edges of the substrate 1,
the insulation slot formed in this location is described as a
Y-direction insulation slot 16.
Further, another method of forming the Y-direction
insulation slot 16 is described below. Namely, the substrate

1 is mounted on an X-Y table, and the first harmonic of a
laser diode excited YAG laser (1064 nm) is irradiated onto the
substrate 1. The laser light is absorbed by and vaporizes the
transparent electrode layer 2, and by using the high gas vapor
pressure generated at this point, even within the photovoltaic
layer 3, the back electrode layer 4 is removed by explosive
fracture, thereby removing the back electrode layer 4, the
photovoltaic layer 3 and the transparent electrode layer 2.
Subsequently, the second harmonic of a YAG laser (532 nm) is
irradiated onto the substrate 1 together with the above first
harmonic of the YAG laser, thereby removing any residues
(deposits or burrs) of the back electrode layer 4, the
photovoltaic layer 3 and the transparent electrode layer 2.
With the pulse oscillation set to not less than 1 kHz and not
more than 20 kHz, the laser power is adjusted so as to achieve
a suitable process speed, and laser etching is conducted at a
point not less than approximately 5 mm and not more than 15 mm
from the edge of the substrate 1, so as to form the Y-
direction insulation slot 16.
Completing the etching of the Y-direction insulation slot
16 at a position not less than 5 mm and not more than 10 mm
from the edge of the substrate 1 is preferred, as it ensures
that the Y-direction insulation slot 16 is effective in
inhibiting external moisture from entering the interior of the
solar cell module 6 via the edges of the solar cell panel.

Although the laser etching treatments up until this point
has been specified as using a YAG laser, a YV04 laser or fiber
laser or the like may also be used in a similar manner.
{0060}
In a similar manner to the Y-direction insulation slot
16, intermediate insulation slots 17 (see Fig. 1) are formed
in the Y-direction by laser etching. When forming the
intermediate insulation slots 17, a conductive portion 18 is
provided that divides the slot at a position partway along
each slot. The intermediate insulation slots 17 are
preferably not provided within the series-arranged solar cell
unit cells 5 positioned along the two edges of the solar cell
module 6. This ensures that when, in a subsequent step (see
(10) Fig. 8b), processing is performed to extract the
electrical power from each of these solar cell unit cells 5
along the two edges, even if some locations exist where a
favorable electrical contact cannot be ensured between the
current collecting copper foil and each of the solar cell unit
cells 5 along the two edges, current collection by the copper
foil can still be performed favorably due to the fact that the
back electrode layer 4 has not been divided for each of the
solar cell unit cells 5 along the two edges.
A side insulation slot need not be provided in the X-
direction in the same manner as the Y-direction insulation
slots 16, because a film polishing and removal treatment is

performed within the edge portion 24.
Examples of the method used for providing the conductive
portion 18 by dividing each of the intermediate insulation
slots 17 at a position partway along the slot include the
methods outlined below,
(i) Methods that employ a blocking mask to block the laser
Specifically, a blocking mask may be installed using one
of the methods (a) to (d) described below.
(a) The substrate 1 is mounted and positioned on a process
stage (X-Y table), and a blocking mask (composed of a
combination of metal foil and metal wire) is installed that
covers the entire surface of the module that is to be
irradiated with laser light. The blocking mask may be
positioned during the step of positioning the substrate.
(b) An adhesive tape is bonded to the laser incident side of
the substrate 1 for the purpose of blocking the laser light in
those portions that are to become the conductive portions 18.
The adhesive tape is removed following completion of the laser
processing and exit of the substrate form the processing
apparatus.
(c) A volatile liquid (such as water or alcohol) is dripped
onto the laser incident side of the substrate 1, within
blocking regions in which the conductive portions 18 are to be
formed, thereby scattering the laser light and weakening the
laser light to an energy level insufficient to effect etching.

The volatile liquid (such as water or alcohol) is eliminated
naturally over time, meaning a mask removal step is
unnecessary.
(d) A water-soluble substance (such as sodium bicarbonate) is
applied to blocking regions in which the conductive portions
18 are to be formed, thereby scattering the laser light. The
water-soluble substance can be removed in the cleaning
apparatus employed in a subsequent step.
(ii) Methods that block the laser light
Specific examples of methods of blocking the laser light
include the methods (a) to (c) described below.
(a) A mechanical shutter is inserted within the light path.
Alternatively, the optical system light axis is finely altered
using a reflective mirror or the like.
(b) The laser excitation pulse is blocked (to adjust the
oscillation of the intermittent pulse laser), and is
synchronized with the movement of the process stage.
(c) The focus lens is driven in synchronization with the
movement of the process stage so that the laser light density
at the processing surface is insufficient to effect film
etching.
{0061}
Following formation of the insulation slots 16 and 17 in
the manner described above, the substrate may be cleaned using
the substrate cleaning apparatus 201 illustrated in Fig. 10,

in an environment in which internal and external light is
blocked and red-colored light acts as the main illumination.
{0062}
(9) Fig. 8(a)
In order to ensure favorable adhesion and sealing of a
backing sheet 21 via EVA or the like in a subsequent step, the
stacked films within the edge portion 24 of the substrate 1
are removed, as they tend to be uneven and prone to peeling.
First, grinding or blast polishing or the like is performed to
remove the back electrode layer 4, the photovoltaic layer 3,
and the transparent electrode layer 2 from a region that is
not less than 5 mm and not more than 20 mm from the edge of
the substrate, and is closer to the substrate edge than the
insulation slots 16 provided in the step of Fig. 7(c)
described above.
{0063}
Following completion of polishing in the manner described
above, the substrate is cleaned using the substrate cleaning
apparatus 201 illustrated in Fig. 10, in an environment in
which internal and external light is blocked and red-colored
light acts as the main illumination.
{0064}
(10) Fig. 8(b)
An attachment portion for a terminal box 23 is prepared
by providing an open through-window in the backing sheet 21

and exposing a collecting plate. A plurality of layers of an
insulating material are provided in the open through-window
portion in order to prevent external moisture and the like
entering the solar cell.
Processing is conducted so as to enable current
collection, using a copper foil, from the series-connected
solar cell electric unit cell 5 at one end and the solar cell
unit cell 5 at the other end, and to enable electric power to
be extracted from a terminal box portion on the rear surface
of the solar cell panel. In order to prevent short-circuits
between the copper foil and the various portions, an
insulating sheet that is wider than the width of the copper
foil is provided.
Following arrangement of the collecting copper foil and
the like at predetermined positions, a sheet of a filling
material such as EVA (ethylene vinyl acetate copolymer) is
arranged so as to cover the entire substrate 1 but not
protrude beyond the substrate 1.
A backing sheet 21 with a- superior waterproofing effect
is positioned on top of the EVA. In this embodiment, in order
to achieve a superior waterproofing and moisture-proofing
effect, the backing sheet 21 is formed as a three-layer
structure comprising a PET sheet, Al foil, and a PET sheet.
The structure comprising the components up to and
including the backing sheet 21 arranged in predetermined

positions is subjected to internal degassing under a reduced
pressure atmosphere and pressing at approximately 150°C using
a laminator, thereby causing cross-linking of the EVA that
tightly seals the structure.
{0065}
(11) Fig. 9(a)
A terminal box 23 is attached to the rear surface 24 of
the solar cell module 6 using an adhesive.
{0066}
(12) Fig. 9(b)
The copper foil and an output cable from the terminal box
are connected using solder or the like, and the interior of
the terminal box is filled and sealed with a sealant (a
potting material). This completes the production of the solar
cell panel 50.
{0067}
(13) Fig. 9(c)
The solar cell panel 50 formed via the steps up to and
including Fig. 9(b) is then subjected to an electric power
generation test, as well as other tests for evaluating
specific performance factors. The electric power generation
test is conducted using a solar simulator that emits a
standard sunlight of AM 1.5 (1,000 W/m2) .
{0068}
(14) Fig. 9(d)

In tandem with the electric power generation test (Fig.
9(c)), a variety of specific performance factors including the
external appearance are evaluated.
{0069}
The production process outlined above describes a solar
cell using the example of a tandem solar cell having an
amorphous silicon-based photovoltaic layer as the top cell and
a crystalline (microcrystalline) silicon-based photovoltaic
layer as the bottom cell, but the present invention is not
limited to this example.
For example, the present invention can also be applied in
a similar manner to other types of thin-film solar cells,
including single solar cells containing only an amorphous
silicon-based photovoltaic layer as the photovoltaic layer,
single solar cells containing only a crystalline silicon-based
photovoltaic layer of microcrystalline silicon or the like,
and multi-junction solar cells in which either one, or two or
more, other photovoltaic layers are provided in addition to
the top cell and bottom cell described above.
{0070}
The effects of employing the solar cell and the
production process according to the embodiment described above
are described below.
Because the intermediate insulation slots 17 are provided
on the substrate center side of the side insulation slots 16,

the solar cell unit cells adjacent to a side insulation slot
16 are limited in area to the surface area from the side
insulation slot 16 to the adjacent intermediate insulation
slot 17. Accordingly, even if a short-circuit occurs within
the side insulation slot 16 as a result of water penetration
or the like, only an electric power generation current
equivalent to the surface area from the side insulation slot
16 to the intermediate insulation slot 17 is leaked into the
edge portion 24 of the substrate 1.
Specifically, even if moisture penetrates from the edge
of the substrate 1, either as a result of degradation over
time in the filler sheet and backing sheet 21 bonded to the
substrate 1, or as a result of a deterioration in the
waterproofing properties of the bonded portions, causing the
formation of water W within a side insulation slot 16 as
illustrated in Fig. 1, the leakage current that flows as a
result of the short-circuit caused by the water W is limited
to the electrical current accumulated in a solar cell unit
cell 5d compartmentalized by the first intermediate insulation
slot 17a. In contrast, in a solar cell described in the
background art and illustrated in Fig. 2, the electrical
current accumulated within a large surface area solar cell
unit cell that extends from the side insulation slot 16 on one
side of the module to the side insulation slot 16 on the other
side flows as a leakage current, meaning electrodeposition is

more likely to occur, thereby increasing the likelihood of
short-circuits. In this manner, in the embodiment of the
present invention, the provision of the intermediate
insulation slots 17 reduces the leakage current generated when
a short-circuit occurs, meaning short-circuits caused by
electrodeposition can be dramatically suppressed.
{0071}
Furthermore, by providing a conductive portion 18 in a
position partway along each intermediate insulation slot 17,
the adjacent solar cell unit cells 5 on either side of this
position are electrically connected. This means that the
electric power generation current can also flow in the X-
direction through this conductive portion 18, meaning the
electrical current can flow not only to the solar cell unit
cell 5 positioned adjacently in the Y-direction, but also via
the conductive portion 18 to the solar cell unit cell 5
positioned adjacently in the X-direction. Accordingly, even
if an ineffective cell that does not contribute to electric
power generation exists in the Y-direction, another solar cell
unit cell 5 positioned adjacently in the X-direction can be
used, meaning deterioration in the performance of the
photovoltaic device can be prevented as far as possible.
Specifically, as illustrated in a comparative example in
Fig. 4, a module can be prepared in which four sub-modules 7
are provided by forming three intermediate insulation slots 19
that are continuous in the Y-direction and include no
conductive portions. If water W is formed within the side
insulation slot 16 that forms one edge of a first sub-module
7a positioned on the right side in the figure, then the solar
cell unit cell 5d corresponding with this water W short-
circuits, causing a leakage current I to flow, and as a
result, no electric power generation current flows through the
first sub-module 7a. Furthermore, if, as illustrated within a
third sub-module 7c positioned third from the right side in
the figure, one of the solar cell unit cells 5f within the
sub-module is a faulty cell which, due to the state of the
film deposition or the presence of shade or dirt, is unable to
contribute to electric power generation, then no electric
power generation current will flow through the third sub-
module 7a. Accordingly, in the case of the solar cell
illustrated in Fig. 4, as illustrated by the dashed arrows in
the figure, electrical current is only able to flow through
the second sub-module 7b and the fourth sub-module 7d.
In contrast, in the embodiment of the present invention,
as illustrated in Fig. 1, even if a solar cell unit cell 5f
becomes a faulty cell due to the state of the film deposition
or the presence of shade or dirt, because a conductive portion
18 is provided upstream in the Y-direction from this faulty
solar cell unit cell 5f, the electric power generation current
is able to flow in the X-direction through this conductive

portion 18, thereby avoiding the faulty solar cell unit cell
5f (see the dashed arrows in Fig. 1). As a result, the solar
cell unit cells upstream in the Y-direction from the faulty
solar cell unit cell 5f can still be effectively utilized,
meaning any deterioration in the performance of the solar cell
can be largely suppressed.
As in the present embodiment, the back electrode layer 4
and the transparent electrode layer 2 preferably remain within
the conductive portion 18. However, a region in which only
the back electrode layer 4 remains or a region in which only
the transparent electrode layer 2 remains can also be used as
the conductive portion 18.
{0072}
Furthermore, the solar cell unit cells 5 where a
conductive portion 18 is positioned remain electrically
insulated from another solar cell unit cell 5 positioned
adjacently in the X-direction due to another intermediate
insulation slot 17. As a result, solar cell unit cells (such
as those illustrated in Fig. 2) having a comparatively large
surface area that are formed in a continuous manner from one
side insulation slot 16 through to the other side insulation
slot 16 can be avoided, thereby suppressing the size of the
electrical current that flows when a short-circuit occurs
within a side insulation slot 16 as a result of water
penetration or the like, and largely avoiding short-circuits

caused by electrodeposition.
{0073}
Furthermore, because the intermediate insulation slots 17
are formed not less than 20 mm distant from the side
insulation slots 16, even if moisture crosses a side
insulation slot 16 and penetrates into the module, the
adjacent intermediate insulation slot 17 can block any adverse
effects caused by the short-circuit, and those solar cell unit
cells 5 positioned on the inside of the intermediate
insulation slot 17 can continue to be used. According to
investigations conducted by the inventors of the present
invention and others, provided that the intermediate
insulation slots 17 are 20 mm distant from the side insulation
slots 16, then even in those cases where the protective sheet
degrades and water penetrates as far as the side insulation
slots 16, the intermediate insulation slots 17 are able to
block adverse effects caused by short-circuits to such an
extent that 10 or more years are required before short-
circuits due to water penetration or performance deterioration
caused by cell degeneration become problematic.
{0074}
Further, in large solar cells where the length along one
side exceeds 1 m, the present invention is effective even in
single structures having a single electric power generation
layer as it yields increased electric power generation

capacity.
Moreover, solar cells having a tandem structure with two
stacked electric power generation layers or a triple structure
with three stacked electric power generation layers have
larger electric power generation capacities than solar cells
having a single structure with one electric power generation
layer, and therefore the potential leakage current is larger,
meaning an increased chance of electrodeposition.
Accordingly, in the case of a solar cell having a tandem
structure or a triple structure, a solar cell comprising
intermediate insulation slots 17 and conductive portions 18,
such as the solar cell of the present embodiment, is
particularly effective.
{0075}
In the present invention, the pattern in which the
intermediate insulation slots 17 are formed is not restricted
to the pattern illustrated in Fig. 1.. For example, as
illustrated in Fig. 11, the intermediate insulation slots 17
may be formed in a regular repeating pattern that alternates
for each solar cell unit cell 5 in the Y-direction.
{0076}
Furthermore, the inside of the substrate cleaning
apparatus 201 used in the substrate cleaning step is
maintained in a state in which light of a wavelength that
causes the solar cell unit cells 5 to contribute significantly

to electric power generation is irradiated to the solar cell
5, with only red-colored light used for illumination. As a
result, not only is an electric potential sufficient to cause
electrodeposition not generated within those insulation
portions that have been short-circuited as a result of water
that has adhered during the cleaning step, but the red-colored
light enables operations inside the substrate cleaning
apparatus to be checked visually. Accordingly, any chance
that electrodeposition may occur during the production process
for the solar cell, causing a short-circuit, can be
effectively eliminated.

{CLAIMS}
{Claim 1}
A photovoltaic device comprising a plurality of
photovoltaic cells, which are formed on top of a substrate and
are connected in series in a first direction, and
side insulation portions, which are formed continuously
in a vicinity of sides of the substrate that extend along the
first direction, and electrically insulate the photovoltaic
cells from an edge portion of the substrate, wherein
two or more intermediate insulation portions that
electrically insulate the photovoltaic cells positioned
adjacently in a second direction that is substantially
orthogonal to the first direction are formed on a substrate
center side of the side insulation portions so as to extend in
the first direction in a parallel arrangement across the
second direction,
a conductive portion that electrically connects the
photovoltaic cells positioned adjacently in the second
direction is provided in a position partway along each of the
intermediate insulation portions, and
the photovoltaic cells where the conductive portion is
positioned are electrically insulated from a photovoltaic cell
positioned adjacently in the second direction by another of
the intermediate insulation portions positioned distant from
the conductive portion in the second direction.
{Claim 2}
The photovoltaic device according to claim 1, wherein the
intermediate insulation portions comprise:
two first intermediate insulation portions, each provided
next to one of the side insulation portions formed along both
sides of the substrate, and
at least one second intermediate insulation portion
provided between the first intermediate insulation portions.
{Claim 3}
The photovoltaic device according to claim 1 or 2,
further comprising a protective sheet that covers an entire
surface of the substrate so as to protect the photovoltaic
cells formed on top of the substrate, wherein
the intermediate insulation portions are positioned not
less than 20 mm distant from the side insulation portions.
{Claim 4}
The photovoltaic device according to any one of claims 1
to 3, wherein
the photovoltaic cells exist within a tandem structure
comprising two stacked photovoltaic layers, or within a triple
structure comprising three stacked photovoltaic layers.

{Claim 5}
A process for producing a photovoltaic device comprising:
an insulation step of forming an insulation portion that
electrically insulates a photovoltaic layer formed on a
substrate from other regions, and
a cleaning step of cleaning the substrate following the
insulation step, wherein
for a predetermined period including the cleaning step,
the photovoltaic layer is illuminated with a red-colored
light.
{Claim 6}
The process for producing a photovoltaic device according
to claim 5, wherein the photovoltaic device is the
photovoltaic device according to any one of claims 1 to 4.

A photovoltaic device that can prevent performance
degradation caused by electrodeposition generated as a result
of moisture penetration. In the photovoltaic device, two or
more intermediate insulation portions 17 that electrically
insulate solar cell unit cells 5 positioned adjacently in the
X-direction are formed on the substrate center side of side
insulation portions 16 so as to extend in the Y-direction in a
parallel arrangement across the X-direction, a conductive
portion 18 that electrically connects solar cell unit cells 5
positioned adjacently in the X-direction is provided in a
position partway along each of the intermediate insulation
portions 17, and the solar cell unit cells 5 where the
conductive portion 18 is positioned are electrically insulated
from a solar cell unit cell 5 positioned adjacently in the X-
direction by another of the intermediate insulation portions
17 positioned distant from the conductive portion 18 in the X-
direction.