JPH10209476A - Film-like solar cell excellent in environmental resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film board-type solar cell excellent in environmental resistance. SOLUTION: An amorphous silicon thin film is formed as a photovoltaic element on a flexible film board for the formation of a solar cell, wherein a heat-resistance synthetic resin film, which is 15 to 100μm in average thickness and provided with a surface whose surface roughness (Ra) is 4nm or below in center line average height and that has coarse projections of 0.273 to 0.546μm in height being at most 200 pieces per 100cm<2> , and projections of at least 0.546μm in height being 20 pieces per 100cm<2> , is used as the film board. By this setup, a formed amorphous silicon layer is protected against damage caused by an dimensional change in a solder cell due to an environmental change, so that the solar cell can stably keep a high performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell in which an amorphous silicon thin film is provided as a photovoltaic element on a flexible film substrate.

[0002]

2. Description of the Related Art A solar cell in which an amorphous silicon thin film is provided on a substrate such as a stainless steel plate or a glass plate is disclosed in JP-A-52-149489 and JP-A-55-499.
4 and JP-A-55-29154.

[0003] In addition, those using an aramid film or a polyimide film as a substrate are disclosed in Japanese Patent Application Laid-Open No. 54-149.
No. 489, JP-A-55-4994, JP-A-55-29
No. 154, JP-A-55-82474, JP-A-56-1
69372, JP-A-57-103839, JP-A-5
9-34677, JP-A-59-88874, JP-A-59-108368, JP-A-59-158571,
JP-A-60-130867, JP-A-60-25718
No. 3, JP-A-61-7624, JP-A-63-2363.
No. 72, JP-A-1-19072, JP-A-1-309
385, JP-A-5-281167, JP-A-7-69
No. 182, Japanese Unexamined Patent Publication No. Hei 7-131038 and the like.

An advantage of the method using a film as a substrate is that while the film is sent out from a roll, processed and then wound up again on a roll, necessary layers such as an amorphous silicon layer are continuously vacuum-deposited, sputter-deposited or plasma glow-discharged. It can be formed by the method described above. Also, unlike the conventional solar cell using a glass substrate or the like, the obtained film solar cell can be bent freely, and its application can be expected to expand.

In the case where a film is used as a substrate and an amorphous silicon layer or the like is formed thereon, 250 to 35
Since the film is exposed to a high temperature of 0 ° C., a polyimide film or an aramid film having excellent heat resistance is used as described above. However, in reality, even with these methods, the amorphous silicon layer formed on the film is partially peeled off from the film substrate during the manufacturing process or during the subsequent processing and use,
Many destructive phenomena occur, which lowers the yield of solar cells or causes breakdown.

As a method for solving these problems, as disclosed in Japanese Patent Application Laid-Open No. 56-169372, the heat shrinkage is 0.7% or less at 250 ° C., and the elastic modulus of the film at the production temperature is 200 kg / mm. The curl of the film caused by thermal stress based on the difference of the thermal expansion coefficient between the film and the amorphous silicon layer at the time of manufacture by using an aramid film with a crosslinked structure of ² or more, using a film with a low heat shrinkage ratio, There is also proposed an improvement method of overcoming with the strength of the waist.

However, even with this method, the above problem has not been completely solved. That is, due to the heat applied to the film when the amorphous silicon layer is formed, the strain remaining in the film is released, and then the amorphous silicon layer is formed, so that the magnitude of the heat shrinkage does not directly show an improvement effect, Also, the waist strength of the film is
On the contrary, it was found that the strain stress between the film and the amorphous silicon layer was maintained, and peeling and destruction of the amorphous silicon layer occurred.

Further, according to JP-A-1-309385, it is proposed to use an aramid film having a coefficient of thermal expansion of -5 to 10 × 10 ^-6.
In addition, JP-A-131038 proposes to use a substrate film whose center surface roughness (SRa) is as smooth as 10 nm or less, and a considerable improvement effect is obtained. Japanese Patent Application Laid-Open No. 59-88874 and others propose a method of reinforcing a substrate by providing a metal layer on the back surface of a film. However, this method requires a complicated process and a thermal expansion coefficient with an amorphous silicon layer. However, there remains such a problem that the amorphous silicon layer is distorted due to a large difference between the two.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a solar cell using a film as a substrate, and the amorphous silicon layer is partially peeled from the film and destroyed in response to an environmental change exposed during the manufacturing and processing and use thereof. It is an object of the present invention to provide a film-shaped solar cell with less trouble.

[0010]

Means for Solving the Problems The present inventors have further studied the solar cell disclosed in Japanese Patent Application Laid-Open No. Hei 7-131308, which has shown that solar cell performance may be degraded due to environmental changes. Has been found to be due to the presence of fine surface smoothness and coarse projections on the base film surface, and the present invention has been completed.

That is, the present invention relates to a solar cell in which an amorphous silicon thin film is provided as a photovoltaic element on a flexible film substrate.
The surface of the film has a center surface roughness (SRa) measured at a cutoff wavelength of 25 μm of 4 nm or less, and has 200 or less coarse projections having a height of 0.273 to 0.546 μm per 100 cm ^2. 0.546 μm
A film-shaped amorphous silicon solar cell, characterized by using a heat-resistant synthetic resin film having 20 or less coarse projections having a height of 100 cm ² or less.

[0012] Generally, in the handling of the film, fine particles are mixed in the film to impart slipperiness,
It is customary to adjust the surface smoothness by providing fine irregularities on the surface. In carrying out the present invention, it has been found that the smoothness of the surface of the film is also an important factor.
That is, the surface roughness on the side on which the amorphous silicon thin film is provided should be 4 nm or less, more preferably 3 nm or less, as expressed in terms of the center plane roughness (SRa). The formed amorphous silicon layer is easily peeled.

Furthermore, in addition to the fine irregularities on the surface, there are coarse projections due to aggregates of lubricant particles, undissolved resin and other foreign substances, which are important factors for damage to the amorphous silicon layer due to environmental changes. It turned out to be. That is, as film conditions for achieving the object of the present invention, the number of coarse projections having a height of 0.273 to 0.546 μm is 200 or less per 100 cm ² , more preferably 100 or less, and 0.546 μ or more. 20 or less coarse projections per 100 cm ² , preferably 10
Or less, more preferably 3 or less,
In a film having coarse protrusions more than this, the performance of the solar cell is greatly reduced due to an environmental change.

The film used in the present invention is required to have heat resistance to withstand the high temperature received when forming the amorphous silicon layer. As a measure of the heat resistance, if the heat shrinkage at 200 ° C. is 2% or less, The object of the present invention is achieved. In carrying out the present invention, the coefficient of thermal expansion of the film is 10 × 10 ⁻⁶ , more preferably 7 × 10 ^−6.
It is preferred that: Here, the coefficient of thermal expansion is represented by an average value between room temperature and 300 ° C. If the coefficient of thermal expansion is larger than this, when the formed amorphous silicon layer is cooled to room temperature, a dimensional difference from the film substrate becomes large and a strain stress is generated, so that peeling may occur. Although a film having a negative coefficient of thermal expansion smaller than 0 can be produced, it is not preferable that the negative coefficient of expansion is too large for the same reason.
It is preferably 10 ^-6 or more, more preferably 0 or more.

The strength of the film used is 20 kg / m
m ² or more, preferably 25 kg / mm ² or more,
It is preferable that there is little breakage during handling when processing or using the film-like solar cell. The elastic modulus of the film is also important when processing and handling film-like solar cells.
It is important to prevent unnecessary deformation due to the force applied to the solar cell and to prevent destruction of the amorphous silicon layer.
A material of 0 kg / mm ² or more, preferably 800 kg / mm ² or more is preferably used.

The properties of these films should be satisfied in both the longitudinal direction and the width direction, but they do not necessarily have to be the same, and can be either a balance type or a uniaxial tension type. Is also good. Further, the film may also contain a coloring agent such as a dye or a pigment, a flame retardant, an antistatic agent, an antioxidant, and other modifiers as long as they do not contradict the purpose of the present invention. . As a film satisfying these characteristics, a part of a film made of an aramid resin or a polyimide resin can be used.

The aramid resin used in the present invention is a resin substantially composed of a unit selected from the group consisting of the following structural units. —NH—Ar ₁ —NH— (1) —CO—Ar ₂ —CO— (2) —NH—Ar ₃ —CO— (3) where Ar ₁ , Ar ₂ and Ar ₃ are at least one aromatic ring And may be the same or different, and representative examples thereof include those of the following formulas.

[0018]

Embedded image

Further, those in which a part of hydrogen on the ring of these aromatic rings is substituted by a halogen group, a nitro group, an alkyl group, an alkoxy group, or the like are also included. X is -O
_{-, - CH 2 -, -} SO 2 -, - S -, - CO- , and the like. In particular, an aramid resin in which 80 mol% or more of all the aromatic rings are bonded at the para position is preferable for producing a film used in the present invention. The polyimide resin used in the present invention contains at least one aromatic ring and at least one imide group in the repeating unit of the polymer, and is represented by the following general formula (2) or (3).

[0020]

Embedded image

[0021]

Embedded image Here, Ar ₄ and Ar ₆ contain at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This A
r ₄ is derived from an aromatic tetracarboxylic acid or its anhydride. As a representative example, there is the following formula.

[0022]

Embedded image Wherein Y is, -O -, - CO -, - CH 2 -, - S-,
—SO ₂ — and the like.

Ar ₆ is derived from tricarboxylic anhydride or its halide. The following are typical examples.

Embedded image

Ar ₅ and Ar ₇ contain at least one aromatic ring and are derived from aromatic diamines and aromatic isocyanates. The following are typical examples of Ar ₅ or Ar ₇ .

Embedded image

Here, those in which a part of hydrogen on the ring of these aromatic rings is substituted with a halogen group, a nitro group, an alkyl group, an alkoxy group or the like are also included. Z is -O-,-
CH ₂ —, —S—, —SO ₂ —, and —CO—. In particular, a polyimide resin in which 80% or more of Ar ₅ and Ar ₇ are aromatic rings bonded to the para position is preferable for producing a film used in the present invention. Further, the aramid resin or the polyimide resin of the present invention contains a lubricant, an antioxidant, other additives, and other polymers, as long as the physical properties of the film are not impaired or the purpose of the present invention is not adversely affected. Is also good.

The method for producing the film of the present invention is not particularly limited, and a production method suitable for each resin may be adopted. First, as for the aramid resin, in the case of those soluble in an organic solvent, it is polymerized directly in a solvent, or once isolated and redissolved to form a solution, and then formed into a film by a dry method or a wet method, Further, those which are hardly soluble in organic solvents such as polyparaphenylene terephthalamide (PPTA) are dissolved in concentrated sulfuric acid or the like to form a solution, and then formed into a film by a dry method or a wet method.

On the other hand, as for the polyimide resin, a tetracarboxylic anhydride is reacted with an aromatic diamine in an organic solvent to obtain a polyamic acid, and this solution is directly or once subjected to a ring-closing treatment to obtain a polyimide. The solution is obtained by dissolving, and they are formed into a film by a dry method or a wet method. In the dry method, the solution is extruded from a die, cast on a support such as a metal drum or an endless belt, and the drying or imidization reaction proceeds until the cast solution forms a self-supporting film.

In the wet method, the solution is extruded directly from a die into a coagulating liquid, or cast on a metal drum or an endless belt as in the dry method, and then guided into the coagulating liquid and coagulated. Next, these films are washed with a solvent or an inorganic salt and subjected to processing such as stretching, drying and heat treatment. The film having a smooth surface used in the present invention is manufactured by mixing fine particles as a lubricant in a solution of an aramid resin or a polyamic acid which is a polyimide or a precursor of a polyimide, and forming this solution into a film. Often.

The fine particles include an organic compound and an inorganic compound. Usually, for example, SiO ₂ , TiO ₂ , Zn
O, Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaC
Inorganic compounds such as O ₃ , carbon black, zeolite, and other metal powders are used. Particle size is 5-150n
m, the addition amount is often selected to be 0.005% by weight or more and less than 5% by weight, preferably 1% by weight or less.

For obtaining the flat-surface film of the present invention, the dispersion of fine particles is important. Fine particles cannot be achieved in a sufficiently dispersed state by directly adding only fine particles to the resin solution, and should be avoided. The fine particles are preferably dispersed in a low-viscosity liquid, and are pre-dispersed in a solvent used for the polymerization of the resin, or when the resin is redissolved, are pre-dispersed in a solution used for dissolution, or a solvent. The resin solution is adjusted by, for example, removing a part of the mixture, dispersing the fine particles, adding the mixture to the solution, and mixing.

As a method for dispersing the fine particles, various homogenizers may be used. In particular, an ultrasonic homogenizer is recommended because of its excellent dispersing power. As a method of improving the dispersion state of the fine particles, a method of decomposing an organic silicon compound in an organic solvent to form a fine particle sol or colloidal fine particles has also been proposed. It should be noted that the desired effect may be difficult to achieve.

In practicing the present invention, the average agglomeration degree of the fine particles in the resin solution is about 1 to 10, more preferably 1 to 10.
In many cases, good results are obtained when the particles are dispersed to about 5 to 5, which is a preferred embodiment of the present invention.
As means for realizing such a dispersed state of fine particles,
A method in which fine particles are dispersed alone in a colloidal state is used, and a method of performing stirring under sufficient stirring such as a stirring homogenizer or an ultrasonic homogenizer is used so that aggregation does not occur upon dilution in a solvent.

The fine particle dispersion preliminarily dispersed in a low-viscosity solvent can be filtered for undispersed or agglomerated fine particles before being used for polymerization, dissolution of a resin, or the like. This is a preferred embodiment for setting the range. In addition, fine particles that are finely dispersed once often aggregate with time, and it is preferable to use the fine particles immediately after dispersion. It is also preferable that the surface roughness of the side on which the amorphous silicon layer is provided is within the range of the present invention, and the roughness of the back surface is larger than that.

To manufacture the solar cell of the present invention, a first conductive layer is formed on a film to a thickness of 0.01 to 20 μm. For the conductive layer, stainless steel, nickel-chromium alloy, and nickel, iron, chromium, niobium, zirconium, titanium alone or their alloys, or oxides such as tin oxide, indium oxide, indium tin oxide, and cadmium oxide are deposited It can be formed by a method or a sputtering method.

Next, an amorphous silicon layer is formed by a method such as a glow discharge method, a sputtering method, or an ion plating method. For example, in the case of glow discharge,
In a vacuum reactor maintained at 1 to 0.01 Torr, the film wound in a roll is pulled out, and 200 to 400 ° C.
On the heated supporting electrode. S in the vacuum reactor
A DC voltage or a high frequency voltage of 1 to several tens of MHz is applied between the electrode facing the support electrode and the iH ₄ gas while sending iH ₄ gas to cause a glow discharge, and the inside of the vacuum reactor is brought into a plasma state to thereby produce SiH _4. Decompose to form an amorphous silicon layer on the film. At this time, SiH ₄
At the same time, p-type silicon layer is formed when B ₂ H ₆ is fed by 0.5 to 5% by weight, and n-type silicon layer is formed when PH ₃ is sent together with SiH ₄ .

Next, for example, in the case of a Schottky junction cell, platinum, gold, palladium or the like is formed as a Schottky barrier electrode to a thickness of about 100 Å by sputtering or vacuum evaporation. In the case of a hetero-coupled cell, an indium oxide, tin oxide, indium tin oxide, and cadmium oxide layer is formed to a thickness of about 200 to 3000 angstroms by a sputtering method or a vacuum evaporation method.

Next, a collector electrode is provided on the Schottky barrier metal and the hetero electrode, and an amorphous silicon solar cell is completed. These processes, such as vacuum deposition, sputtering, and glow discharge, can be performed while the film is continuously moved from roll to roll, or can be processed batchwise for a film of a certain size. It may be.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In the examples,% not particularly indicated is% by weight. [Method of measuring characteristics] The method of measuring characteristic values according to the present invention is as follows. (1) Method of measuring film thickness, strength, elongation, and elastic modulus The film thickness is measured with a dial gauge having a measurement surface having a diameter of 2 mm. The strength, elongation, and elastic modulus were measured using a constant-speed elongation-type high-elongation measuring instrument at a measurement length of 100 mm and a pulling speed of 50 mm / min.

(2) Method of Measuring Heat Shrinkage A 2 cm × 5 cm sample piece was cut out from a film, and 4 c
The mark is made by making a mark with a knife at intervals of m.
After leaving for 72 hours in an atmosphere of 5% RH, the distance between the labels was read and measured with a microscope, and then left in a hot air oven at 200 ° C. for 2 hours without restraining, then again at 23 ° C. and 55% RH. After leaving for 72 hours in the atmosphere of
The distance between the labels was read and measured with a microscope. (3) Measurement method of thermal expansion coefficient Thermodynamic property measuring device (TMA, TM7 manufactured by Vacuum Riko Co., Ltd.)
000 type), a sample with a width of 5 mm was attached, and a load of 0.
After removing the residual strain of the sample by raising the temperature once to 300 ° C. under 3 g, the sample was cooled under a nitrogen stream, and the temperature was lowered from 300 ° C. to 30 ° C.
The dimensional change of the film up to ° C. is measured, and the coefficient of thermal expansion during this period is determined as an average value.

(4) Measurement method of center plane average roughness (SRa) The definition of SRa is described in, for example, “Measurement of Surface Roughness,
Evaluation method ”(Sogo Gijutsu Center, 1983), and a method of calculating and obtaining an interference image of an interference phase contrast microscope was used. In other words, New View of ZYGO
Using a 100 type surface roughness measuring device, objective lens magnification 4
SRa was measured at any three points of the film at 0 times, with a camera resolution of 550 μm, and a cut-off of 25 μm, and the average was represented.

(5) Coarse projections Al was uniformly vacuum-deposited to a thickness of 20 nm on the surface of the film, and halogen monochromatic light having a wavelength of 0.546 μm was used.
Any 3c at 200x magnification using optical multiplex interference microscope
By observing the film surface of m squares, one interference fringe generated with respect to the protrusion of the protrusion was determined to be 0.273 to 0.546 μm.
As a coarse projection having a height of m (hereinafter abbreviated as H1),
Those having two or more interference fringes are counted as coarse projections having a height of 0.546 μm or more (hereinafter abbreviated as H2), and the number of projections in the visual field converted to 100 cm ² is 1
Expressed as the average of zero observations. (6) Photoelectric conversion characteristics The photoelectric conversion characteristics were measured by a solar simulator manufactured by Oriel, whose conversion efficiency was adjusted to AM = 1.

[0042]

Example 1 40% colloidal silica particles of 80 nm
Mix the dispersion with distilled water with sufficient stirring
A dilute solution having a silica concentration of 10% by weight was prepared. From a branch pipe of a pipe in which 100.6% of concentrated sulfuric acid was circulated at a speed of 100 m / min, silica was supplied at a ratio of 0.06% by volume / min to total concentrated sulfuric acid. The diluent was fed and mixed. PPTA was dissolved using concentrated sulfuric acid containing 0.035% of silica thus adjusted so that the polymer concentration became 12.5%, and PPTA was dissolved.
Was adjusted. The dope reflects light irregularly during stirring,
In addition, observation under an optical microscope revealed that the liquid crystal was in a liquid crystal state, such as exhibiting optical anisotropy that makes the dark field of the crossed Nicols of the polarizing microscope a bright field.

The PPTA dope was filtered through a 5 μm-cut filter made of sintered stainless steel nonwoven fabric, and then cast from a die onto an endless belt at a draft rate of 1.2. Next, the dope is heated and absorbed simultaneously with moisture to convert the dope from a liquid crystal phase to an isotropic phase. The dope is coagulated in 30% sulfuric acid at 10 ° C., neutralized and washed with water. After stretching 1 time, the film is stretched 1.1 times in the transverse direction by a clip tenter, dried with hot air while maintaining a fixed length state, and then heat-treated at 430 ° C while holding the film with the tenter, and then at 350 ° C. After free heat treatment, it was wound up.

The obtained PPTA film has a thickness of 50 μm, and the physical properties of the film in the longitudinal direction and the width direction are strength 36 and 37 kg / mm ² , elongation 40 and 38%, respectively.
Elastic modulus 960, 970 kg / mm ² , 200 ° C. heat shrinkage 0.07, 0.05%, thermal expansion coefficient 4.3 × 10 ⁻⁶ ,
4.2 × 10 ⁻⁶ , the average degree of aggregation of silica is 2.4,
SRa was 2.0 nm, H1 of the coarse protrusion was 30, and H2 was 0.

[0045]

Comparative Example 1 Polyparaphenylene terephthalamide (P
PTA) was dissolved in 99.8% concentrated sulfuric acid in which 40 nm silica particles were previously dispersed by an ultrasonic stirrer so as to be 0.3% by weight with respect to PPTA, and the dope was filtered through a 10 μm-cut filter. A PPTA film was produced in the same manner as in Example 1 except for the above. The obtained PP
The TA film has a thickness of 50 μm, and has a strength of 35, 37 kg / mm ² and an elongation of 4 in the longitudinal direction and the width direction, respectively.
0, 37%, elastic modulus 950, 980 kg / mm ² , 20
0 ° C. heat shrinkage 0.06, 0.05%, coefficient of thermal expansion 4.2
× 10 ⁻⁶ , 4.0 × 10 ⁻⁶ , the average agglomeration degree of silica was 21, SRa 4.7 nm, 350 large projections H1,
H2 was 80 pieces.

[0046]

Comparative Example 2 A PPTA film was produced in the same manner as in Comparative Example 1 except that dispersion of silica particles was carried out with a stirring homogenizer. P obtained
The PTA film has a thickness of 50 μm, and has a strength of 36, 36 kg / mm ² and an elongation of 3 in the longitudinal direction and the width direction, respectively.
9, 38%, elasticity 955, 970 kg / mm ² , 20
0 ° C. heat shrinkage 0.06, 0.06%, coefficient of thermal expansion 4.2
× 10 ^-6 , 4.1 × 10 ^-6 , the average degree of aggregation of silica was 40, SRa 6.5 nm, 450 coarse projections H1,
H2 was 150 pieces.

[0047]

Example 2 A solar cell was manufactured using the films of Example 1 and Comparative Examples 1 and 2 under the following conditions, and the performance was compared. A 1000 angstrom thick stainless steel layer was formed on the film from a stainless steel target using a sputtering apparatus.

Next, the above-mentioned treated film was set on the supporting electrode in the vacuum reactor, and the inside of the reactor was once cooled to 10 ^-5 Torr.
After raising the temperature of the supporting electrode to 300 ° C., an argon gas was introduced into the vessel while applying a high-frequency voltage of 30 W and 13.56 MHz to the counter electrode and the supporting electrode, and the pressure was increased to 1 Torr.
r under argon atmosphere, then pre-sputtered, then diluted with hydrogen gas to 10% SiH ₄ , similarly hydrogen gas with 1%
A diluted PH ₃ gas is introduced, and a 200 Å n-type amorphous silicon layer is formed on the film in an atmosphere of 0.8 Torr.

Subsequently, only SiH ₄ was introduced, and a thickness of 6
A 2,000 angstrom p-type amorphous silicon layer is deposited, and a layer containing 1% B ₂ H ₆ in SiH ₄ gas is introduced.
A type amorphous silicon layer was formed. Then this pi
The film on which the n-type amorphous silicon semiconductor layer is formed is set in a vacuum evaporation apparatus, and 100 nm is formed by an electron beam method.
An indium tin oxide layer having a thickness of 0 Å was deposited to form a heteroface layer. Finally, a thickness of 1000
Angstrom palladium layer is vacuum-deposited in a comb shape,
A film solar cell was constructed.

When the photoelectric conversion characteristics of each of the obtained film solar cells were measured, it was 4.7 according to the present invention.
% In Comparative Example 1 and 3.0% in Comparative Example 2. Observation of each amorphous silicon layer with a scanning electron microscope revealed that in the solar cell of Comparative Example 2, peeling from the film surface was observed, and it was presumed that this deteriorated the photoelectric conversion characteristics. Next, after leaving each film-shaped solar cell in an environment of 80 ° C. and 80% RH for one week, the film-shaped solar cell was heated at 20 ° C. and 55% RH for 24 hours.
After standing, the photoelectric conversion efficiency was measured again to be 4.6%. 3.5% and 2.9%. According to the observation with a scanning microscope, exfoliation of the amorphous silicon layer was remarkably observed except for those of the present invention.

[0051]

According to the present invention, in manufacturing a flexible film solar cell, an amorphous silicon layer or the like formed on the film is exposed during a manufacturing process or during subsequent processing or use. It does not cause partial peeling or destruction from the film substrate during environmental changes, high yield in solar cell manufacturing, and application processing utilizing flexibility, and a decrease in photoelectric conversion efficiency in use. Since a film-shaped solar cell with less number of cells can be provided, the cost of the solar cell can be reduced, and its application range can be expanded.

Claims (3)

[Claims] 1. A solar cell having an amorphous silicon thin film provided as a photovoltaic element on a flexible film substrate, the average thickness of the film substrate is 15 to 100 μm, and the film surface is measured at a cutoff wavelength of 25 μm. The center plane average roughness (SRa) is 4 nm or less;
100 coarse protrusions with a height of 0.273 to 0.546 μm
cm ² 200 per below, the film-like amorphous silicon solar cell coarse protrusions of a height of more than 0.546μm is characterized by using a heat-resistant synthetic resin film is less than 20 per 100 cm ^2. 2. The film substrate has a strength of 20 kg / m.
m ² or more, elastic modulus 600 kg / mm ² or more, 200 ° C.
Has a thermal shrinkage of 2% or less and a coefficient of thermal expansion of 10
× 10 ^-6 or less, the film-like amorphous silicon solar cell according to claim 1, which comprises using a heat-resistant synthetic resin film is -2 × 10 ^-6 or more. 3. A film substrate having an average particle size of 5 nm or more.
2. A heat-resistant synthetic resin film comprising 150 to 150% by weight of inert fine particles dispersed in an average cohesion of 1 to 10 in a range of 1 to 10. 3. The film-shaped amorphous silicon solar cell according to 2.