JPH0456475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amorphous solar cell formed on the inner wall of a transparent hollow body, and particularly to stabilization thereof.

Amorphous solar cells are attracting attention as a new energy conversion material. However, its energy conversion efficiency decreases over time. Conventionally, solar cells have been formed by placing their substrates in expensive equipment for forming amorphous semiconductors. For example, a glow discharge tank of glow discharge equipment, a sputtering tank of sputtering equipment, a CVD tank of CVD equipment, etc. are used, and a substrate is placed in these, and an amorphous semiconductor is formed using each method. As a result, the solar cells are exposed to the outside, and it is difficult to protect them, especially to stabilize them against moisture.

Various stabilization methods have been studied from this point of view, and for example, a method of embedding an amorphous solar cell in a case using an epoxy resin has been proposed.

One of the objects of the present invention has been made in view of this point, and is to provide a stabilized amorphous solar cell without using these embedding resins or cases.

Furthermore, another object of the present invention is to provide a technique for simplifying the amorphous silicon layer forming means in the process of forming the amorphous silicon layer.

According to the present invention, there is no need for the above-mentioned expensive equipment, and the substrate of the solar cell itself becomes a reactor, and can be used as a glow discharge tank and a pyrolysis tank, for example, as shown in FIG. A stable amorphous silicon solar cell can also be easily produced by introducing a semiconductor raw material gas and performing glow discharge and thermal discharge.

That is, in the present invention, electrodes and photovoltaic regions are formed on the inner wall of a transparent hollow body in the order of a transparent first electrode, a photovoltaic region, and a second electrode, and the inside of the hollow body is substantially dry. and the photovoltaic region is an amorphous silicon solar cell comprising an amorphous silicon layer formed by pyrolysis.

In the amorphous silicon solar cell of the present invention, a substantially dry state is a state in which gas with a moisture content of 5 ppm or less is enclosed, particularly preferably hydrogen or an inert gas with a moisture content of 3 ppm or less is enclosed. It is something.

FIG. 1 is an example of an external view of a preferable amorphous silicon solar cell of the present invention, and FIG.
-A schematic diagram showing an example of a cross-sectional view taken along line A. In FIG. 2, 1 is a transparent hollow body, 2 is a first electrode formed on the inner wall of the transparent hollow body 1, 3 is a photovoltaic region, 4 is a second electrode, and 5 is an internal space of the hollow body. It shows. In FIG. 1, 6 and 7 are external lead wires, which are connected to the first electrode 2, respectively.
and is connected to the second electrode 4.

The transparent hollow body is not limited to having a circular cross section as shown in Figure 2, but may also be square, rectangular, oval, etc., and is not particularly limited; however, from the viewpoint of manufacturing and handling, it is preferable that the cross section is circular. preferable. In short, the hollow body may have any shape as long as it can maintain a substantially dry state in the interior space of the hollow body, and the hollow body may be a single piece or may be composed of parts. In FIG. 1, the device is composed of a hollow cylinder 1 as a transparent hollow body and sealing materials 8 and 9. The hollow cylinder and the sealing material are integrated by welding or adhesion. The gas introduction or evacuation portions are sealed by heat sealing, for example, as shown in 13 and 14. The material of the sealing members 8 and 9 is not particularly limited, but from the viewpoint of manufacturing and maintenance, it is preferable that the material is the same as or similar to that of the transparent hollow body 1.

The first electrode 2 is a light-transmitting conductor.
For example, ITO (Indium−Tin−Oxide), In ₂ O ₃ ,
It is made of a thin film such as SnO ₂ . Of course, the second electrode 4 can be formed using the electrode material used for the first electrode, but an opaque metal electrode can also be effectively used. When a light-transmitting conductor is used as the second electrode, the light that has passed through the photovoltaic region on the light irradiation side can reach the photovoltaic region on the opposite side to the light irradiation side, so sunlight This is preferable in terms of effective utilization.

The photovoltaic region consisting of an amorphous silicon layer is SiH ₄ ,
Gaseous silicon compounds such as Si ₂ H ₆ and Si ₃ H ₈ ,
It is formed by glow discharge or thermal decomposition in an atmosphere of a raw material gas with or without addition of gases such as PH ₃ , B ₂ H ₆ , AsH ₃ , CH ₄ , C ₂ H ₆ , NH _{3 ,} etc. as appropriate. One of the features of the present invention is this deposition method. That is, while conventional deposition methods require expensive equipment to generate glow discharge and thermal decomposition, this is not necessarily necessary in the present invention. For example, in the case of glow discharge, a hollow body is heated, the inside thereof is connected to a vacuum means and a raw material gas introduction means, and the raw material gas is introduced while being evacuated, and a high frequency electric field is applied. In the case of thermal decomposition, the silicon compound decomposes even under normal pressure by heating the hollow body to about 300° C. or higher. As a result, amorphous silicon is deposited on the inner wall of the hollow body, and a photovoltaic region can be easily formed.

The amorphous silicon layer is formed by depositing, for example, p-type, i-type, and n-type silicon layers in this order from the first electrode side. The thickness of the i-type layer is the same as the thickness of the p-type layer and the n-type layer.
Requires 10-100x. Therefore, the time required to form the amorphous silicon layer is determined by the time required to form the i-type layer. The i-type layer is preferably Si ₂ H ₆ or
Formed by thermal decomposition of higher order silicon compounds such as Si ₃ H ₈ . In higher-order silicon compounds, thermal decomposition proceeds at 300-500℃ and atmospheric pressure.
The deposition rate of the amorphous silicon layer is higher than under decomposition conditions under reduced pressure. Furthermore, the above temperature range is such that hydrogen can exist in the amorphous silicon to compensate for dangling bonds in the amorphous silicon. That is, it is not necessary to perform H ₂ plasma annealing after forming the amorphous silicon layer, which is convenient because the process can be simplified.

The thickness of the p-type amorphous silicon layer is 50 to 1000 Å. The p-type amorphous silicon layer contains p-type impurity gas,
For example, it is formed by glow discharge by mixing B ₂ H ₆ with a gaseous silicon compound at a ratio of 10 ^-4 to 10 ^-1 .

As described above, the i-type amorphous silicon layer is formed by thermal decomposition (chemical vapor deposition). Therefore, a deposition rate of 50 Å/sec or more can be easily achieved, and an i-type amorphous silicon layer with a thickness of 5000 Å to 1 μm can be formed within a few minutes. The gaseous silicon compound for forming the i-type amorphous silicon layer is preferably a high-order silicon compound such as Si ₃ H ₆ or Si ₃ H ₈ as described above. SiH ₄ is 300~
Separation does not occur at 500°C; high temperatures of 600°C or higher are required. Since hydrogen desorbs from the amorphous silicon layer at this temperature, the amorphous silicon layer must be annealed in an H ₂ plasma atmosphere after forming the amorphous silicon layer. Furthermore, at high temperatures of 600°C or higher, the materials that can be used for transparent hollow bodies are limited.

The n-type layer has a film thickness of 50 to 1000 Å and is formed by glow discharge of an n-type impurity gas such as PH ₃ or AsH ₃ at a ratio of 10 ^-4 to 10 ^-1 to a gaseous silicon compound. be done. The deposition of these amorphous silicon layers can also be carried out in an atmosphere in which a gas such as He, Ar, _H2, etc. is added in an amount of 0 to 1000 times the amount of a gaseous silicon compound.

A second electrode is deposited on top of the amorphous silicon. Glow discharge or vacuum evaporation means can be effectively used for the deposition. For example, it is useful to introduce a gaseous tin compound and an oxygen-containing gas after depositing amorphous silicon and deposit tin oxide by glow discharge, or to deposit aluminum by heating it in a vacuum. . As the external lead wire, it goes without saying that wires and plates made of aluminum, copper, silver, etc. can be effectively used, but it is also convenient to use conductive paint, such as silver paste. After connecting the external lead wires to the first and second electrodes, the process moves to H ₂ gas introduction and sealing steps. For example, in FIG. 4, the gas introduction section 11 and the vacuum exhaust section 1
2 are connected to gas introduction means 15 and evacuation means 16, respectively, to perform evacuation and introduction of H ₂ . Preferably, evacuation and introduction are performed three or more times, and then the inside of the hollow body is vacuumed to below atmospheric pressure, preferably
The gas inlet and gas outlet are sealed in a vacuum of 100 Torr.

When the photovoltaic region has a large area, a thin film electrode for current collection can be provided between the first electrode and the inner wall or on the second electrode.

Another feature of the present invention is that the solar cell of the present invention has no distinction between front and back, and a photovoltaic region exists over almost the entire surface. Therefore, not only directly incident light but also transmitted light, scattered light, and reflected light can be effectively used. Naturally, it is also useful as a solar cell for condensing light.

As described above, in the present invention, the electrodes and photovoltaic region are sealed inside a transparent hollow body, which is not only isolated from the outside world, but also kept in an H ₂ or inert gas atmosphere, so it is protected from water and corrosion from the outside. Not only does it prevent the intrusion of toxic gases and oxidizing gases, making its performance extremely stable, but it also has excellent manufacturing methods and photoelectric conversion efficiency.

A more specific explanation will be given below with reference to Examples.

Embodiment In FIG. 3, a transparent hollow body 1 whose inner wall is coated with ITO and SnO ₂ is evacuated by evacuation means 18, a flange 19 having a water cooling means (not shown) having a movable source gas introduction means 17, and 20
(The flange 19 has a flange 21 that serves as a mask to prevent amorphous silicon from being deposited) through an O-ring. Furthermore, heating means 2
2. An electric field applying means 23 for glow discharge is added. The glass cylinder was heated to 300° C. by the heating means 22 while flowing hydrogen gas. B ₂ H ₆ /
Introducing a mixed gas of SiH ₄ = 1/100 (volume ratio),
P-type amorphous silicon layer to 100Å by glow discharge
formed to a thickness of Then heat the glass cylinder to 400℃
heated to. Furthermore, Si ₂ H ₆ /He = 1/4 (capacity ratio)
A 5000 Å thick i-type layer was formed without glow discharge. Next, heat the glass cylinder to 300℃.
PH ₃ /SiH ₄ =1/1000 (capacity ratio) was added to form an n-type layer with a thickness of 150 Å by glow discharge. Furthermore, SnCl ₂ and O ₂ gas were introduced, and a SnO ₂ layer was deposited by glow discharge to form a second electrode.
As shown in FIG. 4, the external lead wire 6 is connected with silver paste to the portion 24 where the first electrode exists in a bare state. A grit-like current collecting electrode is provided on the second electrode and an external lead wire 7 is connected to this current collecting electrode using silver paste. The external lead wires are taken out to the outside of the sealing materials 8 and 9, and the sealing material and the glass cylinder are bonded and integrated with epoxy resin. Next, the gas introduction section 11 and vacuum exhaust section 12 of the sealing material are connected to the gas introduction means 1.
5 and vacuum evacuation means 16. After drawing a vacuum below 10 ^-2 , hydrogen gas is introduced. After repeating this three times, the gas introduction part and the vacuum exhaust part were melt-sealed with an oxyhydrogen flame while the pressure was reduced to 1 Torr. It was confirmed that the thus obtained solar cell had hydrogen gas sealed inside and was isolated from the outside world, and its performance was stabilized.

[Brief explanation of the drawing]

FIG. 1 is an example of an external view of a preferable amorphous silicon solar cell of the present invention, and FIG.
-A schematic diagram showing an example of a cross-sectional view taken along line A. FIG. 3 is a schematic diagram of an apparatus in which a vacuum means and a gas introduction means are attached to a transparent hollow body.
FIG. 4 is a diagram showing an example of the state of the solar cell at the time of gas introduction and fusing. 1... Transparent hollow body, 2... First electrode, 3...
Photovoltaic region, 4... second electrode, 5... internal space of transparent hollow body.

Claims (1)

[Claims] 1. An electrode and a photovoltaic region are formed on the inner wall of an integrally formed cylindrical transparent hollow body, and from the side in contact with the inner wall, a translucent first electrode, a photovoltaic region, and a second
The inside of the hollow body is filled with hydrogen gas or inert gas and is in a substantially dry state, and at least the i-type layer in the photovoltaic region is formed by thermal decomposition of higher-order silane. An amorphous silicon solar cell comprising an amorphous silicon layer formed by.