JPH0330269B2 - - 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 a new installation location. 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 passing through glass, which is a transparent 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.
In terms of the charge relationship, this redox is changed as follows: R ⁿ⁺ →R ⁽ⁿ⁺ 〓 ⁾⁺ …(1) Q ^m+ →Q ^(m- 〓 ⁾⁺ …(2) increases the n value to n+α value, and the other increases the m value to m
-β, thereby storing it 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 referred to as EBP) Fe (phenanthroline) ²⁺³ , (ClO) ^2-2 Ru (bipyridine) ²⁺³ , (ClO ₄ ) ^2-2 (Simply referred to as RBP) Ru (phenanthroline) ²⁺³ and (ClO ₄ ) ^2-2 are 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 an anhydride, which is a typical stable non-toxic solvent with little electrode reaction. Of course, as a redox in a system using a semiconductor using the PIN junction of the present invention as an electrode,
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 the conventionally known redox system using a platinum-titanium oxide semiconductor electrode system. 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 at 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 A, 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) in 0.3-1μ, typically 0.5μ
and for the P or N layer,
SixC _1-X (0X1) In particular, the optical energy band width of X = 0.2 to 0.7 is 1.8 to 2.8eV and the I layer is 1.0 to
1.9 eV can be set wider than typically 1.7 to 1.8 eV. Therefore, this P or N layer
It is possible to make it very thin at 50 to 500A, so for the first time, light is irradiated from the side of the transparent substrate, especially the glass substrate, and the semiconductor with the PIN junction provided on the electrode of this substrate has a total thickness of 0.3 to 1μ. Since it does not need to be thin, the redox can be placed closely on 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, less than 0.1% of the incident light energy is effectively used for oxidation/reduction reactions (simply referred to as redox reactions), which is extremely inefficient and completely impossible to put into practical use. The present invention eliminates such drawbacks and effectively utilizes irradiated light by using amorphous amorphous, semi-amorphous amorphous with crystallinity of 5 to 100 A, or microcrystalline of 30 to 3000 A. A material whose main component is a non-single-crystal semiconductor made of certain micro-polycrystals, and in which 0.1 to 30 mol% of hydrogen or a halogen element such as fluorine or chlorine is added to the non-single-crystal semiconductor to neutralize recombination centers. It is characterized by its use. Another feature is that the semiconductor in contact with the redox surface uses SixC _1-X (0X1) (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 1.6~50~500A.
Another feature is that it has a wide Eg of 3.0 eV and uses silicon, germanium, or SixGe _1-X (0X1), 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.
We were able to absorb more than 70% of sunlight with a semiconductor thickness of 0.3 to 1μ. Therefore, energy can be accumulated in the redox system by irradiation light.
An extremely significant feature is that it has been made possible with an efficiency of over 10%. 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 drawing, 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 to the interface 9 with the redox 1, causing the redox to react. caused a 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 a semiconductor surface. In particular, in order to reduce the absorption loss of the light irradiated on the P or N layer 14 on the incident light side, it is extremely important to set it to 1.6 to 3 eV, typically 1.8 to 2.3 eV, and furthermore, the thickness of the P or N layer 14 is 50
~200A was sufficient. The electrode 20 in this example is
A translucent electrode made of ITO (a mixture of indium oxide and tin oxide) or a double structure on which tin oxide was formed to a thickness of 100 to 300 A or tin oxide was used. The thickness of the I layer is typically 0.4 to 0.6μ.
A semiconductor mainly composed of silicon having a non-single-crystal structure, particularly an amorphous or semi-amorphous structure with a thickness of . A semiconductor represented by SixGe _1-X (0<X<1) may be used for this purpose. Furthermore, 50 to 500A for N or P layer 16
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 such a structure, both the semiconductor electrode and the counter electrode are stable, and hydrogen is absorbed by 4 at the cathode side.
3, and oxygen can also be released from 44 on the anode side 28. 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, in order to generate oxygen and hydrogen, the load 25 is reduced to 0.
It is sufficient to turn it on by setting it to Ω. In that case, a conversion efficiency of 10 to 18% could be obtained. Furthermore, in terms of cost, since the semiconductor is a non-single crystal semiconductor and is provided on the transparent electrode on the substrate 30 using the plasma CVD method, it is possible to manufacture a semiconductor with a 10 cm square PIN layer 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 turned on to 0Ω and the electrodes 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 include: Fe (bipyridine) ²⁺³ , (ClO ₄ ) ^2-2 (FBP) Fe (phenanthroline or phenanthroline) ²⁺³ , (ClO ₄ ) ^2-2 Ru (bipyridine) ^{2+ 3} , (ClO ₄ ) ^2-2 (RBP) Ru (phenanthroline) ²⁺³ , (ClO ₄ ) ^2-2 and propylene carbonate as a solvent.

[Formula] Acetonitrile CH ₃ −CN 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 this, in the general formula R ⁿ⁺ →R ⁽ⁿ⁺ 〓 ⁾⁺ anode Q ^m+ →Q ^(m- 〓 ⁾⁺ cathode, especially the reaction where R=Q=FBP n=m=2 α=β=1 , that is, the reaction of FBP ²⁺ →FBP ³⁺ anode and FBP ²⁺ →FBP ¹⁺ cathode could be carried out. In this case, the load 25 should be turned on while approaching 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 photoelectric 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 power supply for night 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 cycled. 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, an electrode 20 in contact with the semiconductor,
21 is a transparent conductive electrode, and the electrode 2 for emission
8 and 29 are 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 second
This is the same as in Figure A or 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 it is preferable to use it by providing non-single-crystal silicon carbide on a metal plate by plasma vapor phase method in the same manner as the semiconductor 12. 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. Further, the discharge 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 surface of the N-type semiconductor 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. A first semiconductor having a PIN junction having a first transparent electrode and a P layer on the substrate side on a transparent substrate;
A second light-transmitting electrode and a second semiconductor having a PIN junction having an N layer on the substrate side are provided on the substrate, and the N layer of the first semiconductor and the P layer of the second semiconductor are provided.
A redox reaction solution is provided in such a way that only the electrodes on the semiconductor layer or each layer are in contact with each other and not the transparent substrate, and in the redox reaction solution there is a diaphragm separating the two semiconductors, and each semiconductor separated by the diaphragm. First and second electrodes are provided corresponding to the first and second semiconductors in contact with the redox reaction solution, and the first and second semiconductors generate photovoltaic force due to light passing through the light-transmitting substrate. . A semiconductor device, characterized in that a redox reaction is carried out using photovoltaic forces generated in the first and second semiconductors. 2. In claim 1, the photovoltaic force generated by the first and second semiconductors causes the redox reaction solution to become R ⁿ⁺ →R ⁽ⁿ⁺ 〓 ⁾⁺ Q ^m+ →Q ^(m- 〓 ⁾⁺ However, R and Q are molecules, n and m are ion valences, α and β are valences that were changed by light irradiation, causing a reaction expressed by the formula, and stopping or weakening the light irradiation to the first and second semiconductors. 1. A semiconductor device characterized in that a reverse reaction occurs when an electrical output is taken out from first and second electrodes. 3 In claim 2, R and Q
1. A semiconductor device characterized in that a propylene carbonate solvent contains a solute in which is Fe (bipyridine), n and m are divalent, and α and β are monovalent. 4. In claim 1, in the semiconductor having a PIN junction, the P layer and the N layer have an optical energy band width of 1.6 to 3.0 eV, and the layer having an intrinsic or substantially intrinsic conductivity type has an optical energy band width of 1.6 to 3.0 eV. A semiconductor device comprising a non-single crystal semiconductor having a voltage of 1.0 to 1.9 eV. 5. A semiconductor device according to claim 4, wherein the layer has silicon or germanium as a main component, and the P or N layer has SiXC _1-x (0≦X<1) as a main component.