JPH0358190B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention integrates a photoelectric conversion device that generates electrons and holes through light irradiation with redox (reduction-oxidation reaction solution), thereby flattening output, storing power, and reducing power usage at night. It is something that we will do. BACKGROUND ART Conventional photoelectric conversion devices, particularly solar cells, can generate photovoltaic force by irradiation with light. However, this solar cell produces output only when it is irradiated with sunlight and is proportional to the irradiation intensity, so the output fluctuates greatly depending on whether it is sunny or cloudy. When installed on the roof of a general household, there are drawbacks such as no photovoltaic power being generated when illuminating at night, which is a major problem for practical use in civilian use. A method of using a secondary battery to compensate for these problems is known. However, secondary batteries have major drawbacks, such as being expensive and requiring additional equipment space. The present invention is characterized in that it compensates for these drawbacks by providing a redox system that is integrated into the solar cell and has a power storage effect only in the area that is irradiated with light. That is, for example, light transmitted through glass, which is a light-transmitting substrate, is caused to generate a photovoltaic force by a first semiconductor having a PIN junction. The P or N layer provided on one surface is taken out to the outside through ITO, a multilayer film of ITO and tin oxide, or other transparent conductive film provided between the glass and the semiconductor. On the other hand, the N or P layer provided on the back side is in contact with the redox,
Provide electrons or holes to this redox.
Then, in terms of the charge relationship, we change the number of charges as follows: R ⁿ⁺ →R ⁽ⁿ⁺ 〓 ⁾⁺ ……(1) Q ^m+ →Q ^(m+ 〓 ⁾⁺ ……(2) One increases the n value to n + α value, and the other increases the m value to m
- By reducing the valence to β, it is intended to be stored as electrical energy. In particular, a redox in which R=Q n=m=2 α=β=1 is practically preferable. For example, Fe′ (bipyridine) ²⁺ _3, (ClO ₄ ) ^2- ₂ (simply called FBP) Fe (phenanthroline) ²⁺ _3, (ClO ₄ ) ^2- ₂ Ru (bipyridine) ²⁺ _3, (ClO ₄ ) ^{2 -} (Simply referred to as RBP) Ru (phenanthroline) ²⁺ _3, (ClO ₄ ) ^2- ₂ is preferred. In particular, RBP is superior in terms of physical properties, but FBP, which is inexpensive and non-toxic, is preferred from a practical standpoint. In addition, propylene carbonate is used as a solvent for this redox.

[Formula] (hereinafter simply referred to as PPK, or acetonitrile (CH ₃ -CN) is a typical anhydride, that is, a stable non-toxic solvent with little electrode reaction. Of course, the semiconductor using the PIN junction of the present invention can be used as an electrode. Water as a redox in the system used as
A chromium bath solution or a mixture of the above-mentioned iron bath solution and chromium solution may also be used. Particularly when water is used, semiconductors are exposed to redox N.
For example, when the layers are in contact with each other, hydrogen is generated, and oxygen is released on the P layer side, which receives holes or releases electrons. Therefore, it was possible to separate and generate oxygen and hydrogen by integrating it with a photoelectric conversion device using a non-single crystal semiconductor having a PIN junction, particularly an amorphous or semi-amorphous semiconductor. Furthermore, the present invention has a significant difference compared to conventional redox systems using platinum titanium monoxide semiconductor electrode systems. That is, since titanium oxide has an energy band width of about 4 eV, only the ultraviolet rays of the irradiated light can effectively create electron-hole pairs and separate them. For this reason, sunlight etc.
The efficiency is extremely low for continuous light centered around 500mm. Therefore, in the present invention, we use non-single crystal silicon with Eg (energy band width) of 1.0 to 2.5 eV, especially to generate electrons and holes with irradiation light. It is a feature. In other words, this silicon, especially amorphous or semi-amorphous silicon, has a light absorption coefficient for light, especially sunlight, at a short wavelength of 3500 to 5000 Å, which is 10 to 30 times larger than that of single crystal silicon. The thickness of the I layer (intrinsic or substantially intrinsic conductivity type) is typically 0.3 to 1 μm.
0.5 μm is sufficient, and for P or N layer,
SixC _1-X (0≦X≦1) In particular, the optical energy band width of
1.9 eV typically can be set wider than 1.7 to 1.8 eV. Therefore, this P or N layer is 50
It is possible to make the semiconductor extremely thin, ~500 Å, by irradiating light from the side of the transparent substrate, especially the glass substrate. This made it possible to place the redox in close contact with the window surface of this semiconductor. FIG. 1 is a vertical sectional view A of a redox system in a titanium oxide system showing the conventionally known Honda-Fujishima effect, and a corresponding energy band diagram B. In the drawing, a semiconductor 5 made of titanium oxide is provided on a metal substrate 6, a counter electrode 4, and a redox 1, such as water, is filled between the two electrodes. When light, especially ultraviolet light, is irradiated here, the first
As shown in FIG. B, electrons and holes are generated in the titanium oxide 5, and in the case of N-type titanium oxide, the holes react with water to generate oxygen at the redox interface 9. Furthermore, the interface 11 of this counter electrode 4
Conversely, hydrogen is generated and a photochemical reaction using a so-called semiconductor electrode can be accomplished. However, in this conventionally known system, the optical energy band width (referred to as Eg) is 3 to 3.5 eV, although the semiconductor is an oxide and therefore does not dissolve in redox.
Therefore, only the ultraviolet rays of sunlight can be used. For this reason, the efficiency with which the incident light energy is effectively used for oxidation/reduction reactions (simply referred to as redox reactions) is less than 0.1%, which is extremely inefficient and completely impossible to put into practical use. The present invention eliminates such drawbacks and utilizes irradiated light effectively by using amorphous amorphous (amorphous), semi-amorphous amorphous having crystallinity with a size of 5 to 100 Å, or microcrystalline with a size of 30 to 3000 Å. A material in which a non-single-crystal semiconductor made of a certain micro-polycrystal is used as a product, and 0.1 to 30 mol% of hydrogen or a halogen element such as fluorine or chlorine is added to these non-single-crystal semiconductors to neutralize recombination centers is used. It is characterized by its use. Another feature is that the semiconductor in contact with the redox surface uses SixC _1-X (O≦X≦1) (hereinafter simply referred to as silicon carbide), which is difficult to dissolve. In addition, this semiconductor material allows a PIN junction to be provided, with the P and N layers having a thickness of 50 to 500 Å.
Another feature is that it has a wide Eg of 3.0 eV and uses silicon, germanium, or SixGe _1-X (O≦X≦1), which has an intrinsic or substantially intrinsic conductivity type. Semiconductors with such PIN junctions have a non-single crystal structure, so the light absorption coefficient is 10~10 compared to that of a single crystal structure.
It is 30 times larger and uses 1.5 to 1.8 eV, which is optimal for generating electron-hole pairs with irradiation light.
It was possible to absorb more than 70% of sunlight with a semiconductor thickness of 0.3 to 1 μm. This makes it possible to store energy in the redox system using irradiated light with an efficiency of more than 10%, which is an extremely significant feature. The present invention will be illustrated below with reference to the drawings. In FIG. 2, a redox 1 is disposed in contact with a non-single crystal semiconductor 12 having a PIN junction according to the present invention and its N or P layer 16, and a counter electrode 28 is further provided. In this figure, unlike the conventional semiconductor electrode reaction using redox, the incident light 10 is performed from the transparent substrate 30 side, and electrons or holes generated in this semiconductor 12 are given at the interface 9 with the redox 1. produced a redox reaction. Particularly in this case, the semiconductor 15 is made of non-single crystal silicon made by plasma CVD as an intrinsic or substantially intrinsic semiconductor, and the P or N layer 14, the
Alternatively, carbon or silicon carbide having SixC _1-X (0X<1) is used for the P layer 16 to improve the melting resistance as the semiconductor surface. Especially P or N on the incident light side
In order to reduce the absorption loss of the irradiated light, the layer 14 is extremely important to have a voltage of 1.6 to 3 eV, typically 1.8 to 2.3 eV, and its thickness should be 50 to 30 eV.
200 Å was sufficient. The electrode 20 in this example is ITO
(a mixture of indium oxide and tin oxide) or a double structure with tin oxide formed on its upper surface to a thickness of 100 to 300 Å, or a translucent electrode made of tin oxide was used. In addition, the I layer has a thickness of 0.3 to 1 μm, typically 0.4 to 1 μm.
A semiconductor mainly composed of silicon having a non-single crystal structure, particularly an amorphous or semi-amorphous structure with a thickness of 0.6 μm was used. To this, SixGe _1-X (0<X<
The semiconductor shown in 1) may also be used. Furthermore, for the N or P layer 16, the thickness is 50 to 500 Å.
carbon or silicon carbide having a thickness of . This semiconductor has an Eg of 1.7 to 3.0eV, typically
SixC _1-X (0X<1) had x=0.1 to 0.8. The semiconductor having this electrode interface 9 is hardly soluble due to redox reaction, and if the redox substance is an oxide such as water, it is extremely important that it does not oxidize and become an insulating film. Therefore, the use of silicon carbide or carbon instead of silicon is a major feature in the practical application of the present invention. In particular, silicon is typically used in general semiconductors, but such silicon is not preferred because it forms an oxide, which is an insulator, on the surface. Further, in FIG. 2A, an aqueous solution, typically water, is used as the redox. Furthermore, tin oxide was formed on the surface as a counter electrode 28 to form an electrode. Then, 16 of the semiconductors can be made N-type and serve as a cathode, and a counter electrode can be provided as an anode. With this structure, both the semiconductor electrode and the counter electrode are stable, hydrogen is released from 43 on the cathode side, and oxygen is released from 44 on the anode side 28.
It can be released more easily. In such a structure, since hydrogen is emitted from the semiconductor side, the semiconductor electrode does not melt, and since the tin oxide on the anode side is an oxide, it does not deteriorate even when oxygen is generated, resulting in extremely high reliability. I was able to have it. Especially in this structure, since the irradiated light does not pass through the aqueous solution,
It is no longer reflected on the water surface and can now be decomposed into oxygen and hydrogen using electrical energy generated by solar cells and stored.
The conversion efficiency is not less than 1% as conventionally known, and in particular, a load of 25 is required to generate oxygen and hydrogen.
It can be turned on by setting it to 0Ω. In that case, a conversion efficiency of 10 to 18% could be obtained. Furthermore, in terms of cost, the semiconductor is a non-single-crystal semiconductor, and it is provided on the transparent electrode on the substrate 30 using the plasma CVD method, so it is difficult to make a semiconductor with a 10 cm PIN layer.
It could be manufactured for 100 to 300 yen, and its contribution to industry was extremely large. FIG. 3 shows the energy band diagram at FIG. 2 A-A'. The numbers correspond to FIG. 2A. FIG. 2B shows another embodiment of the invention. That is, the transparent electrode 20 is placed on the transparent substrate 30,
It consists of a semiconductor 12, a P or N layer 14, an I layer 15, an N or P layer 16, and a counter electrode 28, which are made of the same materials as in FIG. 2A. The redox 1 has a semipermeable membrane, for example, an ion conversion membrane 7 in its center,
A redox 2 on the semiconductor electrode side and a redox 3 on the counter electrode side are provided. If the irradiated light 10 is used as an output as it is, the load 24 may be used, and in order to cause a redox reaction and store energy in the redox 1, the load 25 may be set to 0Ω and a current turned on may be caused to flow. Moreover, the load 23 may be used to release the stored energy at night or the like. In this FIG. 2B, a non-aqueous solution was used. In particular, the solutes are Fe (bipyridine) ²⁺ _3, (ClO ₄ ) ^3- ₂ (FBP) Fe (phenanthroline or phenanthroline) ²⁺ _3, (ClO ₄ ) ^2- ₂ Ru (bipyridine) ²⁺ _3, (ClO ₄ ) ^2- ₂ Ru (Fenacerorin) ²⁺ _3, (ClO ₄ ) ^2- ₂ was used, and propylene carbonate was used as a solvent.

[Formula] Acetonitrile CH ₃ −CH was used. Especially due to its low cost and non-toxicity
FBP was used. Although expensive, RBP has higher efficiency. In particular, FBP has extremely high solubility in the solvent propylene carbonate.
A large amount of energy can be stored in a small volume. By doing so, in the general formula R ⁿ⁺ →R ⁽ⁿ⁺ 〓 ⁾⁺ anode Q ^m+ →Q ^(m+ 〓 ⁾⁺ cathode, in particular, the reaction where R=Q=FBP n=m=2 α=β=1, That is, the reaction of FBP ²⁺ →FBP ³⁺ anode FBP ²⁺ →FBP ¹⁺ cathode could be carried out. In this case, the load 25 should be turned on close to 0Ω. In addition, when releasing the accumulated energy, load 23
We were able to perform the reverse reaction using Also, if used simply as the output of a photophore conversion device,
The circuit system of the load 24 may be used. The electrode 15 on the semiconductor was made of tin oxide or the like in a comb shape. In this way, energy can be stored in a non-aqueous solution, especially on the back side of a photoelectric conversion device installed on a roof, etc., which is convenient for supplying power for nighttime lighting in general households, and further stabilizes the output power. It has the great feature of being able to be supplied with FIG. 4 shows another embodiment of the present invention in which the redox reaction system using a non-aqueous solution shown in FIG. 2B is further developed. In the drawing, it has a complementary structure in which semiconductor electrodes are used on the cathode side and the anode side. That is, in one semiconductor electrode 12, the N layer 19 and the I
It consists of a layer 18 and a P layer 17. In this complementary structure, the semi-permeable membrane, particularly the ion conversion membrane 7 is used, and in order to store energy by light irradiation, the load 22 should be brought close to 0Ω and the switch 26 should be turned on. Then the irradiation light 10
Therefore, in the redox 1, reactions similar to those shown in FIG. 2B occur on the cathode side 2 and the anode side 3. If the stored energy is to be used, the load 23 may be used. An energy band diagram corresponding to the cross section taken along line A-A' in this drawing is shown in FIG. 5 with corresponding numbers. In the drawing, electrodes 20, 2 in contact with the semiconductor
1 is a transparent conductive electrode, and electrodes 28 for emission,
29 is made using, for example, tin oxide. As this extraction electrode, not only tin oxide but also tungsten oxide, niobium oxide, strontium titanate, titanium oxide, iron oxide, iron titanate, and P or N type silicon carbide can be used. This electrode material can be similarly applied to 28 or 43 in FIG. Others are shown in Figure 2 A.
Or the same as in case B. FIG. 6 shows another embodiment of the invention. In this drawing, semiconductor electrodes are provided with comb-shaped electrodes as in FIG. 2B, and a semi-permeable membrane 7 is provided as a complementary structure. The redox reaction is generated by turning on the switch 16, and used as a photoelectric conversion device by the loads 35 and 34.
The release of stored energy can be utilized using a load 23. Of course, the discharge of the stored energy may be performed using the electrodes 46, 47 instead of the electrodes 28, 29. FIG. 7 shows a further development of the semiconductor device of FIG. 2B. That is, the semiconductor 12 provides electrons or holes to one of the redoxes 1 by the irradiation light 10, and provides holes or electrons to the electrode 13. When this electrode 13 becomes an anode or a cathode, it may be made of P- or N-type silicon carbide, and is preferably made in the same manner as the semiconductor 12 by providing non-single-crystal silicon carbide on a metal plate by plasma vapor phase method. It was. Thus, the redox reaction could be carried out by bringing the load 22 close to 0Ω. Also, if this irradiation light is sufficient, new redox is supplied from 41 and 42,
For example, FBP can be supplied and the reacted redox can be stored in other storage tanks as FBP and FBP from 43 and 44, respectively. By storing such a redox reaction solution in another storage tank, energy storage could be achieved over a long period and on a large scale. Discharging may be performed via the load 23. This technique can also be applied to the embodiments of FIGS. 2B and 3. Furthermore, in the present invention, a non-single crystal semiconductor having a PIN structure is used, and the fact that the redox is in contact with the N or P layer of this semiconductor is a major feature in terms of increasing the efficiency of the reaction current. However, even if the entire surface of this semiconductor is coated with titanium oxide, tin oxide, etc., a redox reaction can be caused in the same way. In particular, since tin oxide and titanium oxide are N-type, it is convenient to form them on the N-type semiconductor surface of the PIN junction.

[Brief explanation of drawings]

FIG. 1 shows a semiconductor device for redox reaction using a conventional semiconductor device and its energy band diagram. FIGS. 2A and 2B show an outline of the semiconductor device of the present invention. FIG. 3 is an energy band diagram corresponding to FIG. 2A. FIG. 4 shows another semiconductor device of the present invention. FIG. 5 is an energy band diagram corresponding to FIG. 4. 6 and 7 show other semiconductor devices of the present invention.

Claims (1)

[Claims] 1. On a transparent substrate, a first electrode and a P or N layer on the electrode are SiC _1-X (0
≦X≦1);
A redox reaction solution is provided in contact with the P or N layer of the semiconductor, and a counter electrode corresponding to the semiconductor is provided in contact with the redox reaction solution, passing through the first electrode from the light-transmitting substrate side. A semiconductor device characterized in that a redox reaction is caused by a photovoltaic force generated when the semiconductor having the PIN junction is irradiated with the light. 2 On the transparent substrate, the first electrode and the electrode
A semiconductor having a PIN junction, having a non-single crystal structure doped with a halogen element such as hydrogen or fluorine, and made of silicon, germanium, silicon carbide, carbon, or a mixture thereof, and the semiconductor or an electrode on the semiconductor. A redox reaction solution is provided in contact with the first electrode, and a counter electrode corresponding to the semiconductor is provided in contact with the redox reaction solution, so that light passing through the first electrode from the light-transmitting substrate side is directed to the semiconductor having the PIN junction. 1. A semiconductor device characterized in that a redox reaction is caused by a photovoltaic force generated by being irradiated with a semiconductor device.