JPH0551189B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a photoelectric conversion device that uses a colorless and transparent polyimide film as a substrate and improves photoelectric conversion efficiency by irradiating light from the substrate side. (b) Prior art Photoelectric conversion devices that convert light energy into electrical energy using amorphous silicon thin films, etc. are useful for low-cost solar cells (solar cells are also included in photoelectric conversion devices in the present invention), optical sensors, etc. It is applied. Photoelectric conversion devices, such as solar cells, have conventionally been produced by sequentially depositing p-type, i-type, and n-type amorphous silicon thin films on a metal plate such as stainless steel foil, and then layering a light-transmitting conductive thin film. Structures such as those with a structure in which a light-transmissive conductive film and p-type, i-type, and n-type amorphous silicon thin films are sequentially deposited on a glass plate, and a conductive thin film such as aluminum is further laminated. has been put into practical use. In the case of a metal substrate such as stainless steel, the sheet resistance of the substrate is sufficiently low, so a single solar cell can be formed on one substrate, and a large output current can be obtained from a fixed area of the substrate. On the other hand, when using an insulating substrate such as glass, 2
It is convenient to arrange the above-mentioned photoelectric conversion elements adjacent to each other and easily connect them in series with a conductor to obtain a voltage of twice or more. Currently, efforts are being made to reduce the cost of amorphous silicon solar cells by improving their photoelectric conversion efficiency as well as improving materials and production processes. As part of this, a thin film of stainless steel or other material is provided on a heat-resistant plastic film such as polyimide film, an amorphous silicon thin film is deposited on top of the film, and indium tin monoxide (hereinafter referred to as
A transparent conductive thin film such as tin oxide (abbreviated as ITO conductive thin film) or tin oxide has been proposed (for example, JP-A-54-149489, JP-A No. 55-4994, JP-A No. 55-29154). Publications and Publications No. 57-103839, etc.). These materials have low material costs, and have a great advantage in terms of production costs because the substrate is flexible and can be rolled into a roll for continuous processing.Furthermore, the shape can be arbitrarily selected, so they can be used in a wide range of applications.
It is expected to have many uses. However, although amorphous silicon solar cells based on polyimide films currently hold great promise, they have not yet been put into practical use. This is because the photoelectric conversion efficiency is generally much lower than that of substrates made of stainless steel foil or glass plates, and they lack stability over time and stability against bending stress. One of the reasons for these drawbacks is that the temperature 250℃~350℃
When an amorphous silicon thin film is deposited on a substrate under conditions of Another reason is that the substrate film and the stainless steel thin film for electrodes, etc. The point is that strain remains at the interface. As a method to improve these, a method has been proposed in which the substrate is preheated before depositing an amorphous silicon thin film (Japanese Patent Publication No. 1983-
Publication No. 53178). (c) Problems to be solved by the invention The method of preheating a substrate described above is extremely excellent in that it alleviates the essential problem of the substrate, but it is not suitable as a method for improving the photoelectric conversion efficiency of solar cells. has not become a fundamental improvement measure. In other words, solar cells using a polyimide film as a substrate have traditionally been made by forming a stainless steel sputter thin film on a non-transparent polyimide film, sequentially depositing an amorphous silicon thin film on top of this, and then laminating an ITO conductive thin film. It has a structure that Then, light is irradiated from the side opposite to the substrate, that is, from the ITO film side, and the light energy is converted into electrical energy. By the way, the deposition state of an amorphous silicon thin film is
Corresponding to the smoothness of the base substrate, in other words, it grows while forming domains along the minute irregularities on the surface, and as a result, the film thickness of the amorphous silicon thin film is about 1 to 2 μm. The thicker the film, the more structural defects the film generally has. In addition, electrons and holes mainly generated in the intrinsic layer are likely to recombine at locations where there are many structural defects in the thin film, and it is thought that photocurrent loss is large at these locations. Therefore, it is assumed that the photoelectric conversion efficiency becomes worse the further away from the substrate, that is, closer to the surface opposite to the substrate side. When irradiating from the thin film side, the polyimide film has a higher surface roughness than the one using a polyimide film as the substrate, and the one using a mirror-finished stainless steel foil, so the photoelectric conversion efficiency will be worse with the polyimide film. Possible (there is a limit to the surface smoothness of polyimide film). (d) Means for solving the problem Therefore, the present inventors developed a colorless and transparent polyimide film that has excellent heat resistance, and created a photoelectric conversion device using this as a substrate. As a result of investigating the photoelectric conversion efficiency by irradiating light from the substrate side, it was found that absorption of light by the substrate is unavoidable in this type of photoelectric conversion device, but surprisingly, despite this, conventional polyimide substrates The present inventors have discovered that the photoelectric conversion efficiency is significantly improved compared to conventional solar cells, and have completed the present invention. That is, the present invention provides a photoelectric conversion device in which a photoelectric conversion element for converting light energy into electrical energy is provided on a substrate, wherein the substrate has a general formula and/or [However, in formula (), X ₁ is O, SO ₂ ,
CH ₂ or CO, and in formula (), X ₂ is
_SO2 , C( _CH3 ) ₂ or C( _CF3 ) ₂ . ] It is formed from a polyimide film whose main component is polyimide having the repeating unit shown in
Further, the present invention is characterized in that it is configured to irradiate light from the substrate side. The present invention will be explained in detail below. In the present invention, the photoelectric conversion device refers to a device that converts light energy into electrical energy, and can be applied to any device provided with a photoelectric conversion element on a substrate. Specifically, for example, Examples include solar cells and optical sensors. The most significant feature of the present invention is that a colorless and transparent light-transmitting polyimide film is used as the substrate. And this colorless and transparent means visible light (500nm) for a polyimide film with a film thickness of 50±5μm.
Transmittance is 70% or more and yellowness index is 40 or less. Although polyimide film is heat resistant, there has been no colorless and transparent polyimide film, which was completed as a result of research by the present inventors. The colorless and transparent polyimide film used in the present invention has the general formula and/or [However, in formula (), X ₁ is O, SO ₂ ,
CH ₂ or CO, and in formula (), X ₂ is
_SO2 , C( _CH3 ) ₂ or C( _CF3 ) ₂ . ] It is formed from a polyimide film whose main component is polyimide having the repeating unit shown below. The colorless and transparent polyimide used in the present invention has the general formula () Biphenyltetracarboxylic dianhydride and general formulas () and () shown by [In formulas () and (), X ₁ and X ₂ are formulas (),
As shown in (). ] Obtained by reaction with an aromatic diamino compound represented by: The above-mentioned biphenyltetracarboxylic dianhydride includes the following 3,3',4,4'-biphenyltetracarboxylic dianhydride. 2,3,3',4'-biphenyltetracarboxylic dianhydride Examples include. Further, among the aromatic diamino compounds having an amino group at the meta position, the following are representative examples of the aromatic dinuclear diamine represented by the general formula (). 3,3'-diaminodiphenyl ether 3,3'-diaminodiphenyl sulfone 3,3'-diaminodiphenyl thioether 3,3'-diaminodiphenylmethane 3,3'-diaminobenzophenone Also, representative examples of aromatic tetranuclear diamines include:
The following may be mentioned. 4,4'-di-(3-aminophenoxy)diphenyl sulfone 4,4'-di-(3-aminophenoxy)diphenylpropane 4,4'-di-(3-aminophenoxy)diphenylhexafluoropropane (hereinafter referred to as "3,3'-
(abbreviated as "BAPF") The aromatic dinuclear diamine and the aromatic tetranuclear diamine may each be used alone or in appropriate combinations. By combining the above biphenyltetracarboxylic dianhydride with an aromatic dinuclear diamine and/or an aromatic tetranuclear diamine having an amino group in the meta position,
A colorless and transparent polyimide whose main component is a repeating unit represented by and/or () can be obtained. Here, the term "main component" is intended to include cases where the whole consists only of the above general formula () and/or (). In this case, in the polyimide thus obtained, the higher the content of the polyimide represented by the repeating unit represented by the above general formula () and/or the repeating unit represented by the above general formula (), the more the obtained polyimide is obtained. The colorless transparency of polyimide film increases. However, if the repeating unit represented by the above general formula () and/or the polyimide of the repeating unit represented by the general formula () is contained in an amount of 70 mol% or more, at least the colorless transparency required by this invention can be ensured. Therefore, within the range, other aromatic tetracarboxylic dianhydrides other than the above-mentioned biphenyltetracarboxylic dianhydride and other than the above-mentioned aromatic di-nuclear/tetra-nuclear diamine having an amino group at the meta position are used. cyamino compounds can be used. That is, the preferable range of the polyimide represented by the repeating unit represented by the above general formula () and/or the repeating unit represented by the general formula () is 70 mol% or more, and the most preferable range is 95 mol% or more. be. Examples of the other aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3', 4,
4'-benzophenonetetracarboxylic dianhydride,
4,4'-oxydiphthalic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoro Propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride Anhydrides are mentioned, and these can be used alone or in combination. In addition, other diamino compounds include 4,
4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,
4'-diaminodiphenylpropane, paraphenylenediamine, metaphenylenediamine, benzidine, 3,3'-dimethylbenzidine, 4,4'-diaminodiphenylthioether, 3,3'-dimethoxy-4,4'- Diaminodiphenylmethane, 3,
3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 2,2-bis[4-(4-aminophenoxy)
phenyl]-hexafluoropropane, 1,3-
Bis(aminophenoxy)benzene is mentioned,
These can be used alone or in combination. The colorless and transparent polyimide film used in the present invention can be obtained by heating the above-mentioned aromatic tetracarboxylic dianhydride and diamino compound in an organic polar solvent at temperature
A polyimide precursor solution is prepared by polymerizing at 80°C or lower, and a shaped body of a desired shape is formed using a method such as casting or roll coating using this polyimide precursor solution. It is obtained by evaporating and removing the organic polar solvent and simultaneously dehydrating and ring-closing the polyimide precursor in an active gas at a temperature of 50 to 350°C and a pressure of normal pressure or reduced pressure. Alternatively, instead of the above method, the polyimide precursor can be obtained by a method such as using a benzene solution of pyridine and colorless acetic acid, and removing the solvent and imidizing the polyimide precursor to form a polyimide. As the organic polar solvent, dimethylformamide, dimethylacetamide, diglyme, cresol, halogenated phenol, etc. are suitable, and dimethylacetamide is particularly preferred because it is a good solvent and has an extremely low boiling point. These organic polar solvents may be used alone, or alternatively, two or more of them may be used in combination without any problem. As organic polar solvents, each of the solvents exemplified above has a low boiling point, so they do not cause problems such as decomposition during dehydration and ring closure by heating, and the decomposed products remain in the polyimide and color the polyimide. be. However, high-boiling polymerization solvents such as N
The above disadvantages can be eliminated by dissolving the produced polyimide precursor in a suitable solvent as exemplified above by solvent substitution after synthesizing the polyimide precursor using -methyl-2-pyrrolidone. In this case, the suitable solvent exemplified above is a diluting solvent. In producing the above polyimide film, the polymerization solvent and the diluting solvent may be of different types, and the polyimide precursor produced may be dissolved in the diluting solvent by solvent substitution. In addition, when using the suitable organic polar solvents exemplified above, solvents such as ethanol, toluene, benzene, xylene, dioxane, tetrahydrofuran, and hydrobenzene may be added to this solvent without impairing the colorless transparency of the polyimide film. Even within the range, one type or two or more types may be used as a mixture as appropriate. As described above, when producing a colorless and transparent polyimide film, the logarithmic viscosity of the polyimide precursor solution (0.5 in N-methyl-2-pyrrolidone solvent)
(measured at 30℃ at a concentration of g/100ml) is 0.3~
It is preferable to adjust to a range of 5.0.
More preferred is 0.4 to 2.0. If the logarithmic viscosity is too low, the resulting polyimide film will have low mechanical strength, which is not preferable. On the other hand, if the logarithmic viscosity is too high, it is not preferable because it becomes difficult to cast the polyimide precursor solution into an appropriate shape, making the work difficult. Further, from the viewpoint of workability, it is desirable to set the concentration of the polyimide precursor solution to 5 to 30% by weight, preferably 15 to 25% by weight. Note that the above-mentioned logarithmic viscosity is calculated by the following formula, and the viscosity in the formula is measured by a capillary viscometer. Logarithmic viscosity = natural logarithm (viscosity of solution) / (viscosity of solvent) / concentration of polymer in solution To obtain a polyimide film with excellent in-place transparency using a polyimide precursor solution, a glass plate,
The above polyimide precursor solution is cast onto a mirror surface such as a stainless steel plate to a certain thickness, and heated at 100 to 350℃.
The polyimide precursor is imidized by gradual heating at a temperature of 100 to 100% to cause dehydration and ring closure, followed by imidization of the polyimide precursor. In forming a polyimide film from a polyimide precursor solution, heating for removing the organic polar solvent and imidizing the polyimide precursor may be performed continuously, or these steps may be performed under reduced pressure or in an inert gas atmosphere. It's good to wear. Furthermore, the properties of the produced polyimide film can be improved by finally heating it to around 400°C for a short time. In addition, other methods of forming polyimide films include
The above polyimide precursor solution is cast onto a glass plate, heated and dried at 100 to 150°C for 30 to 120 minutes to form a film, and this film is removed by immersing it in a benzene solution of pyridine and acetic anhydride. This is a method in which an imidization reaction is carried out with a solvent to form a polyimide film from the film, and a colorless and transparent polyimide film can also be obtained by this method. The thickness of the polyimide film thus obtained is preferably set to about 7 to 550 μm. If the thickness exceeds 550 μm, the light transmittance deteriorates and it lacks flexibility, making it difficult to continuously wind it into a roll, which causes problems in productivity. If the temperature is lower than that, sufficient mechanical strength will not be obtained and the temperature when depositing the amorphous silicon thin film (250°C to 350°C)
This is not preferable because the substrate cannot withstand thermal stress and the substrate may be deformed by this thermal stress. This polyimide film is colorless and transparent and is not colored yellow or yellowish brown as in conventional films, so it has extremely good colorless transparency even if it is a relatively thick film. When polyimide is produced by imidizing a polyimide precursor solution as described above, the resulting polyimide has a logarithmic viscosity (97% by weight) from the viewpoint of properties.
(measured at 30℃ at a concentration of 0.5g/dl in sulfuric acid)
It is preferable to set it within the range of 0.3 to 5.0. The most preferred range is 0.4-4.0. The polyimide film thus obtained is completely different from conventional films, and is colorless and transparent with extremely high transparency. In particular, aromatic dinuclear diamines and aromatic tetranuclear diamines represented by general formulas () and () have excellent colorless transparency and are most suitable for substrates used in the present invention, in which X ₁ and X ₂ are SO ₂ is used. The polyimide film obtained using this material not only has excellent colorless transparency but also excellent heat resistance and low heat shrinkage. A photoelectric conversion device is formed by depositing photoelectric conversion elements on the polyimide film substrate thus obtained. In the present invention, first, step A is performed in which a light-transmitting conductive thin film such as an ITO film or a tin oxide thin film is laminated on a substrate by a vapor deposition method or a sputtering method. The thickness of the conductive thin film is preferably 0.01 to 1.0 μm; if it is less than 0.01 μm, the desired conductivity (surface resistance of 1000Ω/□ or less) cannot be obtained;
If it exceeds 1.0 μm, the transparency of the conductive thin film of the polyimide film will be impaired, which is not preferable. In the present invention, next step B is performed in which a photoelectric conversion element is deposited on the conductive thin film. The photoelectric conversion element may include an amorphous silicon thin film deposited on the conductive thin film in the order of p-i-n or n-i-p; Examples include photoelectric conversion elements formed by depositing an amorphous silicon carbide thin film, an i-type amorphous silicon thin film, and an n-type amorphous silicon thin film in this order. The deposition methods for p-type amorphous silicon thin film, i-type amorphous silicon thin film, and n-type amorphous silicon thin film include sputtering method, glow discharge method,
Various methods such as optical CVD method and ion plating method can be employed. For example, in the case of glow discharge method, the temperature is 200 to 350℃.
A substrate with a transparent conductive thin film formed on one side is held in a heated substrate holder, and the substrate holder is used as one electrode.
Provides 13.56MHz high frequency power. For example, to form an n-type amorphous silicon thin film, phosphine (PH ₃ ) is mixed into silane, while to form a p-type amorphous silicon thin film, diborane (B ₂ H ₆ ) is mixed into silane. All you have to do is introduce the . Further, the above-mentioned amorphous silicon thin film refers to hydrogenated amorphous silicon and fluorine amorphous silicon. In the present invention, a thin film of metal such as aluminum, nickel, titanium, chromium, iron, stainless steel, nickel-chromium alloy, etc. is formed on the thus obtained photoelectric conversion element by an appropriate method such as vapor deposition or sputtering. For example, in the vapor deposition method, the degree of vacuum
The deposition is carried out under conditions of 10 ^-4 to 1 torr, and the deposition source temperature is around the melting point of the material used. (e) Effect When depositing an amorphous silicon thin film on a substrate,
When the film thickness is 1 to 2 μm, the film quality deteriorates as the film thickness increases due to the influence of the smoothness of the substrate surface (structural defects increase). This tendency is independent of the presence or absence of a metal thin film for electrodes at the boundary between the substrate and the amorphous silicon thin film. A non-transparent plastic film is used as a substrate.
In contrast to conventional amorphous silicon solar cells, which have a structure in which a photoelectric conversion element and a transparent conductive thin film are deposited via metal thin film electrodes, light is irradiated from the surface opposite to the substrate with good film quality. Then,
Whereas the one with poorer film quality is irradiated with light,
In the case of an amorphous silicon solar cell using a colorless and transparent polyimide film as a substrate according to the present invention, light is irradiated from the substrate side with good film quality, whereby electrons and holes mainly generated in the intrinsic silicon thin film are It is presumed that the rate of recombination and loss at locations with many structural defects is suppressed as much as possible. In other words, in the photoelectric conversion device of the present invention, since light is irradiated from the side with better film quality (the side with fewer structural defects), in other words, from the substrate side, there is a high rate of recombination of electrons and holes generated upon receiving light. This is thought to have the effect of significantly increasing the photoelectric conversion efficiency by lowering the photoelectric conversion efficiency. (f) Example Production of colorless and transparent polyimide film Using dimethylacetamide as a solvent,
3,3'-diaminodiphenyl sulfone 1 mol
1 mol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was reacted with the mixture to obtain a solution of a polyimide precursor. This solution was cast onto a glass plate to form a film, this film was dried with hot air, and finally heated at 300°C for 5 hours to complete the imidization reaction, yielding a polyimide film with a thickness of 50 μm. . Light transmittance of this film (wavelength 500nm)
is 85%, and the surface roughness is 80Å on both sides, and the temperature is 350%.
The heat shrinkage rate at °C was 2% or less. Production Example 1 of Amorphous Silicon Solar Cell The colorless and transparent polyimide film obtained above with a thickness of 50 μm was used as a substrate. An ITO conductive thin film with a thickness of 600 Å was provided on one side of the substrate by sputtering, and the substrate with the ITO conductive thin film was held in a holder equipped with a heater in an internal electrode type high frequency (13.56 MHz) glow discharge device. , after being kept at around 250℃, heated with hydrogen.
Silane diluted to 10 mol% and diborane diluted to 5000 ppm with hydrogen were mixed (B ₂ H ₆ / (SiH ₄ +
B ₂ H ₆ ) = 0.5 mol%) was introduced into a glow discharge device, and 10 W of high-frequency power was applied in a vacuum atmosphere of 0.2 Torr to dope boron on the substrate.
A p-type amorphous silicon layer with a thickness of 1.5 Å was provided. Subsequently, the above hydrogen diluted silane was introduced and the same reaction was performed to deposit a non-doped i-type amorphous silicon thin film with a thickness of 4500 Å.
Phosphine (PH ₃ ) diluted to 5000 ppm was mixed (PH ₃ / (SiH ₄ + PH ₃ ) = 0.5 mol%) and introduced into a glow discharge device to form a phosphorus-doped 500 Å film on an i-type amorphous silicon thin film. An n-type amorphous silicon thin film was provided. That is, on a colorless and transparent polyimide film substrate, p-type, i-type, and n-type
A photoelectric conversion element consisting of a shaped amorphous silicon thin film was fabricated. Next, this is held in a vacuum evaporation apparatus, and a thickness is deposited on the n-type amorphous silicon thin film by a conventional evaporation method.
A 0.1 μm aluminum conductive thin film was laminated. The photoelectric conversion efficiency of the solar cell thus obtained is
It was measured using a solar simulator with AM=1100mW/cm ² . In this case, light was irradiated from the substrate side. The results are shown in Table 1. Comparative Example 1 In order to compare the characteristics with Example 1, the thickness was 50 μm.
A conventional amorphous silicon solar cell was fabricated using a non-transparent polyimide film (Kapton H manufactured by DuPont) as a substrate and having a surface roughness of 80 Å. Note that the basic structure of this battery is the same as in Example 1. The specific method for creating it is as follows. That is, a conductive thin film made of stainless steel with a thickness of 5000 Å was provided on one side of the substrate by sputter deposition. Next, using the same apparatus and under the same conditions as in Example 1, a phosphorus-doped film was coated on the conductive thin film.
A photoelectric conversion element was formed by sequentially depositing an n-type amorphous silicon thin film of 500 Å, an undoped i-type amorphous silicon thin film of 4500 Å thick, and a 200 Å thick p-type amorphous silicon thin film doped with boron. Further, p-type amorphous silicon thin films were sequentially deposited to form a photoelectric conversion element. Furthermore, on the p-type amorphous silicon thin film, a thickness of 600 mm was deposited by sputter deposition.
An ITO conductive thin film of Å was provided. Next, the photoelectric conversion efficiency of this battery was measured in the same manner as in Example 1. In this case, light was applied from the side opposite to the substrate, that is, from the side of the ITO conductive thin film. Reference Example 1 An amorphous silicon solar cell having the same structure as in Example 1 was manufactured, except that Pyrex glass with a thickness of 1.0 mm was used as the substrate, and the photoelectric conversion efficiency was measured in the same manner as in Example 1. Example 2 An ITO conductive thin film was formed on one side of the colorless and transparent polyimide film substrate obtained above in the same manner as in Example 1, and the temperature inside the glow discharge device was maintained at around 250°C as in Example 1. After that, a mixture of silane, ethylene and diporane diluted with hydrogen to 10 mol%, 10 mol% and 5000 ppm respectively (B ₂ H ₆ /(SiH ₄ +C ₂ H ₄ ) = 0.5 mol%, C ₂ H ₄ /
(SiH ₄ + C ₂ H ₄ ) = 0.8 mol%) gas was introduced, and 10 W of high-frequency power was applied in an atmosphere with a degree of vacuum of 0.2 Torr to form a 200 Å thick p-type non-conductor doped with boron on the substrate. A crystalline silicon carbide thin film was provided. Next, by the same operation as in Example 1, a non-doped i-type amorphous silicon thin film with a thickness of 4500 Å and a phosphorus-doped n-type amorphous silicon thin film with a thickness of 5000 Å were provided. That is, a photoelectric conversion element consisting of a p-type amorphous silicon carbide thin film, an i-type amorphous silicon thin film, and an n-type amorphous silicon thin film was formed via an ITO conductive thin film. Next, a thickness of 0.1μ was obtained using the same method as in Example 1.
A conductive thin film made of aluminum was provided. The photoelectric conversion efficiency of this solar cell is AM=1100m
It was measured using a solar simulator at W/cm ² . In this case, light was irradiated from the substrate side. The results are shown in Table 1. Comparative Example 2 In order to compare the characteristics with Example 2, the thickness was 50 μm.
A conventional amorphous silicon solar cell was fabricated using a non-transparent polyimide film substrate with a surface roughness of 80 Å. Note that the basic structure of this battery is the same as in Example 1. The specific method for making this battery is as follows. As in Comparative Example 1, a conductive thin film made of stainless steel with a thickness of 5000 Å was placed on the substrate, and a conductive thin film doped with phosphorus was placed on the substrate with a thickness of 500 Å.
An n-type amorphous silicon thin film with a thickness of 4500 Å and a non-doped i-type amorphous silicon thin film with a thickness of 4500 Å were each deposited. Furthermore, in the same manner as in Example 2, a p-type amorphous silicon carbide thin film doped with boron and having a thickness of 200 Å was deposited on the i-type amorphous silicon thin film, and then ITO was deposited on the p-type amorphous silicon carbide film. A conductive thin film was deposited. The photoelectric conversion efficiency of this cell was measured in the same manner as in Example 2, and the results are shown in Table 1. Reference Example 2 An amorphous silicon solar cell having the same structure as in Example 2 was manufactured, except that Pyrex glass with a thickness of 0.5 mm was used as the substrate, and the photoelectric conversion efficiency was measured in the same manner as in Example 2. Example 3 An ITO conductive thin film was formed on one side of the colorless and transparent polyimide film substrate obtained above in the same manner as in Example 1, and this was held in a holder in the same glow discharge device as in Example 1. After maintaining the temperature at around 250℃, using the same raw material gas as in Example 1, the vacuum degree was
The thickness of the above ITO conductive thin film doped with phosphorus by applying 10 W of high frequency power in an atmosphere of 0.2 Torr
After forming a 200 Å thick n-type amorphous silicon thin film, a non-doped i-type amorphous silicon thin film 4500 Å thick and a boron-doped p-type amorphous silicon thin film 500 Å thick were sequentially deposited. That is, n-type, i-type, and p-type are formed on a colorless and transparent polyimide film substrate through an ITO conductive thin film.
A photoelectric conversion element consisting of a shaped amorphous silicon thin film was fabricated. Next, as in Example 1, an aluminum conductive thin film having a thickness of 0.1 μm was provided on the p-type amorphous silicon thin film. The photoelectric conversion efficiency of this solar cell is AM=1100m
It was measured using a solar simulator at W/cm ² . In this case, light was irradiated from the substrate side. Table 1 shows the photoelectric conversion efficiency of this battery. Comparative Example 3 In order to compare the characteristics with Example 3, the thickness was 50 μm.
We fabricated a conventional amorphous silicon solar cell using a non-transparent polyimide film substrate with a surface roughness of 80 Å. Note that the basic structure of this battery is the same as in Example 1. The method for manufacturing this battery is as follows. On the above substrate, there is a stainless steel conductive thin film with a thickness of 5000 Å, a boron-doped p-type amorphous silicon thin film with a thickness of 500 Å, an undoped i-type amorphous silicon thin film with a thickness of 4500 Å, and a phosphorus-doped thin film with a thickness of 200 Å. A photoelectric conversion element was formed by sequentially depositing n-type amorphous silicon thin films. Further, a conductive thin film of ITO having a thickness of 600 Å was laminated on the n-type amorphous silicon thin film. The photoelectric conversion efficiency of this solar cell was measured in the same manner as in Example 3. In this case, light was applied from the ITO conductive thin film side. The results are shown in Table 1. Reference Example 3 An amorphous silicon solar cell having the same structure as in Example 3 was manufactured except that Pyrex glass with a thickness of 0.5 mm was used as the substrate, and the photoelectric conversion efficiency of the cell was measured in the same manner as in Example 3. The results are shown in Table 1.

【table】

[Table] From Table 1, solar cells that use a colorless and transparent polyimide film as a substrate and irradiate light from the side of the substrate use a non-transparent polyimide film substrate and irradiate light from the side opposite to the substrate. It is recognized that the photoelectric conversion efficiency is significantly higher than that of the one in which light is irradiated from the outside. Although the above embodiments have been described with respect to solar cells, the present invention can also be applied to optical sensors and the like instead. (g) Effect The photoelectric conversion device of the present invention uses a colorless and transparent polyimide film as its substrate, and the light is irradiated from the substrate side, that is, the side with better film quality, so that the photoelectric conversion efficiency is higher than that of conventional devices. This can be significantly improved. In addition, since the substrate is made of a colorless and transparent polyimide film and is flexible, photoelectric conversion devices can be manufactured continuously by continuously pulling out the substrate wound into a roll. As a result, productivity is increased. It is possible to reduce the manufacturing cost while improving the performance, and since the material is inexpensive, the manufacturing cost can also be reduced from this point of view. Furthermore, since polyimide film is used for the substrate, it is heat resistant and has a low thermal shrinkage rate, so there is less distortion due to temperature changes, and as a result, photoelectric conversion elements deposited on the substrate will not crack or chip due to temperature changes. There are fewer problems. In particular, since the substrate is made of a colorless and transparent polyimide film and is electrically insulating, it is difficult to directly connect multiple solar cell elements on the same substrate when forming a solar cell using the substrate. Parallel connections are possible, and various types of solar cells can be manufactured easily.

Claims (1)

[Claims] 1. A photoelectric conversion device in which a photoelectric conversion element for converting light energy into electrical energy is provided on a substrate, wherein the substrate has a general formula and/or [However, in formula (), X ₁ is O, SO ₂ ,
CH ₂ or CO, and in formula (), X ₂ is
_SO2 , C( _CH3 ) ₂ or C( _CF3 ) ₂ . ] It is formed from a polyimide film whose main component is polyimide having the repeating unit shown in
A photoelectric conversion device characterized in that the device is configured to irradiate light from the substrate side.