JPH0519834B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to photovoltaic elements such as solar cells or optical sensors made of amorphous silicon used indoors and outdoors, and particularly to improvement of substrate materials thereof. Conventional configurations and their problems Recently, amorphous silicon (hereinafter referred to as a-Si) solar cells have been used alone or together with small secondary batteries as power sources for relatively small portable electronic devices used indoors and outdoors. Increasingly, they are being adopted in combination. This seems to be due to the need for battery replacement and the response to the times, such as the use of clean energy. A-Si solar cells, which are commonly used at present, use a transparent, colorless and insulating glass plate as a substrate. An example will be explained with reference to FIG. In the figure, 1 is a transparent substrate made of a colorless transparent glass plate with a thickness of about 1 mm, and a thin layer of indium oxide containing tin oxide (hereinafter referred to as ITO) or tin oxide is coated on one side by vapor deposition or other methods. A transparent electrode 2 is formed in a predetermined pattern. Next, silane gas (SiH ₄ ), etc. is decomposed using a plasma CVD device, etc., and p-i
- an a-Si layer 3 consisting of an n layer is deposited, and aluminum or the like is deposited on the top surface to form a back electrode 4;
Configure a solar cell. In order to protect the back electrode 4 and insulate it from the outside, an insulating paint or the like is applied and dried on the surface of the back electrode 4 to provide an insulating film 5 as necessary. In the a-Si solar cell configured as described above, light (hν) such as sunlight or electric lamp light enters through the glass transparent substrate 1, passes through the transparent electrode 2, and reaches the a-Si layer 3. Generate electricity. Therefore, when a solar cell is incorporated into a device, the glass plate side becomes the front surface, so it has a beautiful appearance and is easy to wipe off if it gets dirty, which is convenient in terms of design for small and thin portable electronic devices. However, since the substrate is a thin glass plate, it is easily damaged by falling impact or external force during transportation, and there are problems in that it requires careful attention in how to incorporate it into equipment and when handling the equipment. For this reason, methods such as forming a thin layer of polyimide resin on a thin metal plate such as stainless steel and using it as a substrate,
As disclosed in Publication No. 103839 and the like, solar cells using a film of polyimide or polyamideimide, which is a heat-resistant and hard resin, as a substrate are being considered. Since both are opaque substrates, the battery construction method is reversed from the case where a thin glass plate is used as a substrate. An example is shown in FIG. Reference numeral 11 denotes an opaque substrate having a polyimide insulating layer 11a provided on a polyimide film or stainless steel polished thin plate with a thickness of about 0.2 mm, and a metal film electrode 14, a-Si
A layer 13 and a transparent electrode 12 made of an ITO thin film are sequentially formed, and a transparent protective film 15 such as a transparent silicone resin is applied to insulate the transparent electrode 12 from the outside and protect the surface. In this type of solar cell, as can be seen from the figure, light is transmitted to the substrate 11.
In the opposite direction, transparent protective film 15, ITO transparent electrode 1
2 into the a-Si layer. The one shown in Fig. 2 uses a metal or resin film for the substrate, so it has the advantage of not being damaged by being dropped or slightly bent. However, since a transparent protective layer of resin is applied to the surface, it is difficult to obtain a smooth surface in terms of appearance, and the thickness tends to be uneven. As a result, there were problems in that the appearance deteriorated, the variation in output characteristics increased, and the commercial value decreased. If another transparent cover was placed on top of the battery, the appearance would improve somewhat, but this would not be sufficient, and the cover would reduce the photoelectric conversion efficiency of the battery. Additionally, as can be seen from Figure 2, since the output terminals (not shown) of each electrode are formed on the surface, there may be restrictions on installation and wiring to the equipment used, and the effective light-receiving area may be reduced. Ta. Various studies have been made to eliminate the drawbacks of the conventional examples described above. The idea of using tempered glass or hard glass for the glass substrate has little effect if the thickness is less than 1 mm. As an alternative to glass,
If there is a resin material that is transparent and has appropriate strength and flexibility, it can be substituted, but resin materials such as acrylic, polycarbonate, some Teflon materials, and polyester have almost no mechanical strength and light transmittance. However, at temperatures suitable for depositing the a-Si layer and forming the ITO film, there are problems such as melting, thermal deformation, etc., making it impossible to construct a battery, or only producing batteries with low photoelectric conversion efficiency. It was hot. Purpose of the Invention The present invention provides a transparent material that has strength and flexibility that can withstand heating, etching, solvents, etc. in the photovoltaic device construction process such as a-Si layer deposition, and is not damaged by external forces such as drop impact. By using polyether sulfon resin with good light transmittance as the substrate material and solving the problems of this substrate material when depositing the a-Si layer, we have succeeded in replacing conventional glass substrates (transparent) and polyimide films. The object of the present invention is to provide a highly practical photovoltaic device that has the features of both opaque substrates (flexibility) such as thin stainless steel plates and eliminates the drawbacks of both. Structure of the Invention The present invention uses a transparent film of polyether sulfon resin as a substrate material, which is subjected to vacuum heating and degassing treatment at a temperature that is the same as or slightly higher than the substrate heating temperature during a-Si layer deposition. It is something. Polyether sulfone (without reinforcing filler added, usually referred to as non-reinforced product) is as shown below. It is an amorphous thermoplastic resin with a molecular structure, and has features such as little strength loss after long-term use at high temperatures, little change in performance due to sudden temperature changes, and good light transmittance. It is. Its representative physical properties are shown below. Heat distortion temperature ~203℃ (18.6Kg load, ASTMD-648) Tensile strength: (according to ASTMD-638) 20℃...860 (K
g/ ^cm2 ) 150℃...580 (〃) 180℃...420 (〃) Flexural modulus; (according to ASTM D-590) 20℃...2650
0 (Kg/cm ² ) 150℃...25500 (〃) 180℃...23500 (〃) Resistant to hydrochloric acid and strong alkali. The coefficient of linear expansion hardly changes from room temperature to 200℃. Light transmittance ~88% (according to ASTM D-1003) In the present invention, a transparent film of polyether sulfon expressed by the above formula (1) is used as a substrate material. However, using this film, on its surface
When ITO transparent electrodes and a-Si layers are deposited, gaseous impurities generated from the film surface may deteriorate the film quality or make them non-uniform.
Furthermore, partial short circuits occur, making it difficult to produce a photovoltaic element with stable characteristics. As a result of intensive study on this problem, we found that in the vacuum degassing step as a pre-process, vacuum heating and degassing is performed at a temperature equal to or slightly higher than the substrate heating temperature during a-Si layer deposition, which allows the film to be adsorbed onto the film surface. By removing moisture, air, other gases, and impurities, the influence on film forming processes such as the above-mentioned a-Si layer deposition is eliminated. Using the substrate whose surface condition was stabilized in this way, an ITO transparent electrode, an a-Si layer, and a back electrode were sequentially formed.
The photovoltaic device is configured to generate electricity by incident light from the outer surface of a polyether sulfon film substrate. Description of Examples A polyether sulfon film (manufactured by ICI, UK, etc.) with a thickness of 0.1 to 0.5 mm was used as the substrate material.
Use a transparent one. Before forming the a-Si layer and the like, the film is placed in a vacuum heating furnace and adsorbed impurities such as moisture and air are degassed as described above. At this time, stable battery characteristics can be ensured by heating to a temperature that is the same as or slightly higher than the deposition temperature of the a-Si layer, which will be described later. The upper limit of the heating temperature at this time needs to be 200° C. in view of the heat resistance of the film. Next, an example of an a-Si solar cell constructed according to the present invention will be described with reference to FIG. In the figure, reference numeral 1 denotes a substrate made of a transparent film of polyether sulfon having a thickness of 0.2 mm and subjected to vacuum heating and degassing treatment at 195° C. by the method described above. ITO or SnO ₂ is deposited on one side of this substrate 1 by vacuum evaporation method (substrate temperature
180° C.) to form a transparent electrode 2 in a predetermined pattern. The thickness of the transparent electrode is 400 to 2000 Å in terms of translucency, flexibility, and resistance. Subsequently, monosilane gas (SiH ₄ ), diporane gas (B ₂ H ₆ ) as a p-layer doping material, and phosphine gas (PH ₃ ) as an n-layer doping material are decomposed by a known method using the glow discharge property of plasma CVD, and p-i -n layers are sequentially deposited to a predetermined thickness to form an a-Si layer 3 as an electromotive element. The substrate temperature at this time is 185 to 190°C. Next, a metal such as aluminum or chromium is deposited thereon to a thickness of 2000 to 5000 Å to form the back electrode 4. In order to insulate and protect the back electrode, an insulating film 5 may be provided on the upper surface excluding the terminal portion using a paint such as silicone resin or epoxy resin. Since an insulating polyether sulfon film is used for the substrate, the transparent electrode 2, the a-Si layer 3, and the back electrode 4 can be patterned on the same substrate in the same way as when using a conventional glass substrate. It is easy to configure multiple cells to obtain high voltage. As described above, the present invention uses a polyether sulfon film, which is transparent, has excellent thermal stability, and is flexible, and uses it as a substrate by subjecting it to vacuum heating and degassing treatment under the above-mentioned conditions. , which takes advantage of the features of conventional glass substrates and can be used as an alternative. Polycarbonate, polyester, acrylic, and the like are conceivable as transparent resin films with appropriate hardness and strength, but they have insufficient thermal properties as described above and cannot withstand the heating temperatures used in battery construction. That is, when depositing the a-Si layer 3,
A substrate temperature of 180 to 250°C is required; below that temperature, the film quality deteriorates and a battery with good photoelectric conversion characteristics cannot be obtained. Also, when forming the transparent electrode 2, 170
Heating to ~180°C or higher is necessary to lower the electrode surface resistance. However, the resin film mentioned above has a heat resistance temperature of 150-160°C.
C or below, which is the temperature required to form an a-Si layer, etc., it could not be used because it would begin to deform or melt. Next, the heat distortion temperature is 200
Using transparent and opaque resin films at temperatures above ℃,
When an a-Si deposition experiment was attempted, the following results were obtained.

[Table] As can be seen from this table, except for polyimide films, the polyether sulfon of the present invention is good at a substrate temperature of 180°C or higher, which is necessary to form a high-quality a-Si film. Well, the other two
Although seeds are said to have a high heat resistance, they begin to deform at relatively low temperatures. If the substrate material is deformed in this way, it is impossible to put it into practical use as a battery because it may cause short circuits or poor film quality, making it impossible to obtain good characteristics. In addition, when using polyether sulfon film as a substrate, it is necessary to heat the film to a temperature that is the same as or slightly higher than the substrate heating temperature during a-Si layer deposition, with an upper limit of approximately 200°C taking into account the film's heat resistance temperature. However, as mentioned above, moisture, air, and other impurities are adsorbed on the film surface during manufacturing and storage, and are released during ITO formation and a-Si deposition. This is to prevent pinholes and poor film quality from occurring, resulting in a decrease in yield and characteristics of the constructed battery.
To give an example, when the vacuum heating deaeration treatment of the present invention is applied, the defective battery characteristics are less than 0.5%.
Without treatment, 25 to 60% defects occurred. Furthermore, the heating temperature during the vacuum heating and degassing treatment is set to about 100% higher than the substrate heating temperature during a-Si layer deposition.
When the temperature is lowered by 10°C or more (for example, 170°C to 175°C), the effect of reducing the defective rate such as the above-mentioned defective battery characteristics decreases, and products with abnormal characteristics also appear (defective characteristics 2 to 175°C).
Ten%). In addition, in the photovoltaic device using the polyether sulfon film of the present invention as a substrate, the substrate thickness is
It is possible to make it less than 0.2 mm (approximately 0.08 to 0.2 mm), making it thinner and lighter than conventional glass substrates, making it advantageous for large-area solar cells, etc. can be made. In addition, as in the case of the glass substrate method, the output terminals (not shown) of each electrode are arranged on the back side of the element, so compared to the conventional method using an opaque substrate as explained in Fig. 2. Therefore, there is a large degree of freedom in patterning the output terminal portion of each electrode, and compatibility with equipment can be achieved without reducing the effective light-receiving area. Effects of the Invention The photovoltaic element of the present invention uses a method in which light enters from the transparent polyether sulfon film side, similar to the glass substrate type, so it has an excellent appearance when attached to electronic equipment, and is also thin and lightweight. In addition, since it has excellent flexibility and mechanical strength, it can overcome the conventional problems such as being able to sufficiently withstand falling and bending when being carried.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing the structure of an amorphous silicon solar cell, and FIG. 2 is a sectional view of a main part showing the structure of a conventional amorphous solar cell. 1... Substrate (transparent), 2, 12... Transparent electrode,
3, 13...a-Si layer (p-i-n, p-i, n
-i-p, etc.), 4... Back electrode, 5... Insulating film,
11...Substrate (metal or polyimide substrate),
11a...Insulating layer provided on the metal substrate, 14...
Metal thin film electrode, 15...Transparent protective film.

Claims (1)

[Claims] 1. While heating a transparent polyether sulfon resin film to a temperature that is the same as or slightly higher than the substrate heating temperature during deposition of the amorphous silicon layer,
A process of making a transparent substrate 1 by vacuum heating and degassing treatment, and providing a transparent electrode 2 on the treated substrate, and then heating the substrate at a temperature of approximately 185°C on its upper surface.
A substrate surface incident photovoltaic type amorphous silicon photovoltaic method comprising the steps of sequentially depositing a predetermined amorphous silicon layer 3 by plasma CVD at a temperature of ~190°C, and then forming a back electrode 4 thereon. Manufacturing method of electromotive force element.