JP4896490B2 - Photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion device that can be suitably used, for example, as a solar cell, an optical sensor, a hydrogen generation device based on a photoelectric conversion principle, or the like.

  In recent years, in order to reduce the cost of the solar cell and the like, dye-sensitized photoelectric conversion devices have been actively researched and developed for practical use. As a dye-sensitized photoelectric conversion device, a photoexciter that generates electrons and holes by photoelectric conversion, and the photoexciter supported thereon, for transporting electrons generated by photoelectric conversion in the photoexciter, Filled in the space between the counter electrode and the electron transport layer, an electron transport layer made of titanium oxide or the like, a counter electrode disposed in a non-contact state with the electron transport layer, and facing the counter electrode In addition, a material including an electrolyte layer for transporting holes generated by photoelectric conversion in a photoexciter to the counter electrode is generally used (see, for example, Patent Document 1).

  The dye-sensitized photoelectric conversion device is a batch that becomes a bottleneck for improving productivity in the manufacturing process because the material itself forming each part is inexpensive, can be used without purifying each material to high purity. It has the characteristics that almost no vacuum device of the type is used and the manufacturing process is a low-temperature process, and there is an advantage that it can be manufactured at low cost with high productivity.

Conventionally, organic dyes such as metal complex dyes have been used as photoexciters (therefore, there is a name of dye-sensitized type). However, recently, in order to improve the weather resistance of the dye-sensitized photoelectric conversion device and maintain good photoelectric conversion characteristics over a longer period of time, instead of the organic dye, for example, Nanoparticles made of a sulfide inorganic semiconductor, such as cadmium sulfide (CdS), lead sulfide (PbS), silver sulfide (Ag ₂ S), antimony sulfide (Sb ₂ S ₃ ), bismuth sulfide (Bi ₂ S ₃ ), The use as a photoexciter was studied (for example, see Non-Patent Documents 1 to 3).

Further, for example, a photoelectric semiconductor having a structure in which a porous semiconductor layer and an inorganic semiconductor layer made of a compound semiconductor are stacked via an organic material layer made of a monomolecular film of a sensitizing dye, as described in Patent Document 2. Indium copper sulfide (CuInS ₂ , sometimes abbreviated as “CIS”), which is used as a compound semiconductor in the conversion device, is one of the sulfide inorganic semiconductors, and absorbs light in the visible light range. Since it has characteristics such as a large coefficient and is suitable as a photoexciter, it has been studied to make it into nanoparticles and use it as a photoexciter in a dye-sensitized photoelectric conversion device.
U.S. Pat. No. 4,927,721 US Pat. No. 6,653,701 Ralf Vogel et al., "Sensitization of highly porous porous TiO2 electrodes by quantum sized CdS", Chemical Physics Letter, 241-246 (1990) Ralf Vogel et al., "Quantum-sized PbS, CdS, Ag2S, Sb2S3, and Bi2S3 Particles as Sensitizers for Various Nanoporous Wide-Bandgap Semiconductors", Journal of Physical Chemistry, 98, 3183-3188 (1994) RK Pandey et al., "Comparative study of performance of CdTe, CdSe and CdS thin films-based photoelectrochemical solar cells", Solar Energy Materials & Solar Cells, 59-72 (2000)

In a conventional dye-sensitized photoelectric conversion device, an electrolyte layer is formed using an aqueous electrolyte solution in which an electrolyte is dissolved in water. Specifically, an aqueous electrolyte solution is sealed in the space between the counter electrode and the electron transporter layer, or gelled at an arbitrary stage before and after filling the space with the aqueous electrolyte solution. Thus, an electrolyte layer is formed. Further, as the electrolyte used for the aqueous electrolyte, ferrocyanide, sulfides that form soluble polysulfide species in the electrolyte, and the like are generally used. The latter sulfide undergoes a sulfide / polysulfide reaction [S ²⁻ / S _x ²⁻ (x = 2 to 5)] in the electrolytic solution, and holes are formed by the redox couple generated at that time. It works to transport to the counter electrode.

  However, according to the inventor's study, as the electrolyte, an aqueous electrolyte containing the former ferrocyanide is combined with a sulfide inorganic semiconductor such as CIS to assemble a dye-sensitized photoelectric conversion device, and light irradiation However, almost no power was generated. For example, the photoelectric conversion efficiency when CIS was combined with an aqueous electrolyte containing potassium ferrocyanide was less than 0.03%.

  On the other hand, when a dye-sensitized photoelectric conversion device is assembled by combining a water-based electrolyte containing the latter sulfide as an electrolyte with a sulfide inorganic semiconductor such as CIS, it is possible to generate power by light irradiation. However, even in the dark without light irradiation, a slight current (dark current) was generated, and it was found that the sulfide inorganic semiconductor was corroded by the aqueous electrolyte containing sulfide. From this, the combination of the aqueous electrolyte containing sulfide and the sulfide inorganic semiconductor has a low reliability of the photoelectric conversion device and maintains good photoelectric conversion characteristics over a long period of time. It was confirmed that it was difficult.

  An object of the present invention is to use a dye-sensitized photoelectric conversion that uses a sulfide inorganic semiconductor as a photoexciter and is more reliable than before and can maintain good photoelectric conversion characteristics over a long period of time. To provide an apparatus.

A photo-exciter made of a sulfide inorganic semiconductor and generating electrons and holes by photoelectric conversion;
The excitation body is supported, and an electron transport layer for transporting electrons generated by photoelectric conversion in the light excitation member,
A counter electrode disposed to face the electron transporter layer in a non-contact state;
Wherein the counter electrode is filled between the electron transport layer, holes generated by photoelectric conversion in the light excitation body, wherein for transporting the counter electrode, a layer of electrolyte containing an electrolyte solution of the non-aqueous The electrolytic solution comprises a solvent and an electrolyte, and the electrolyte forms a soluble polysulfide species in the electrolytic solution, Na ₂ S, Li ₂ S, K ₂ S And (NH ₄ ) ₂ S. At least one sulfide selected from the group consisting of (NH ₄ ) ₂ S.

According to a second aspect of the present invention, the electron transporter layer is formed in a porous structure, and CuInS ₂ particles having a particle size of 20 nm or less as the photoexciter are pores of the porous structure of the electron transporter layer. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is carried on a surface including an inner surface .

According to a third aspect of the invention, the electrolytic solution of the nonaqueous is a photoelectric conversion device according to claim 1 or 2, characterized in that it contains alcohol as the solvent.

The invention according to claim 4 is the photoelectric conversion device according to claim 3, wherein the alcohol is ethanol.

In the first aspect of the present invention, since a non-aqueous electrolytic solution containing no water is used as the electrolytic solution, the photoexciter made of a sulfide inorganic semiconductor is prevented from being corroded by the electrolytic solution. Can do. Therefore, according to the first aspect of the present invention, a sulfide inorganic semiconductor is used as a photoexciter, which is more reliable than before and can maintain good photoelectric conversion characteristics over a long period of time. A sensitized photoelectric conversion device can be provided.
In the first aspect of the present invention, as the electrolyte constituting the electrolytic solution, to form a soluble polysulfide species in the electrolyte _{solution, Na 2 S, Li 2 S} , K 2 S, and _{(NH 4) 2} By using at least one sulfide selected from the group consisting of S, holes injected from the sulfide inorganic semiconductor can be quickly and efficiently transported to the counter electrode by the above mechanism. . In addition, since the sulfide easily exchanges holes with the sulfide inorganic semiconductor, the amount of holes injected from the sulfide inorganic semiconductor into the sulfide as an electrolyte is increased. You can also. Therefore, the photoelectric conversion characteristics of the photoelectric conversion device can be improved.

According to the second aspect of the present invention, as described above, CuInS ₂ (CIS) suitable as a photoexciter is used as the sulfide inorganic semiconductor, and the CIS is a porous structure of the porous structure. by Rukoto is carried on the surface including the inside surface of the hole, it is possible to improve the photoelectric conversion characteristics of the photoelectric conversion device. According to the invention described in claim 3, by using alcohol as the solvent, the photoexciter is prevented from corroding while being prevented from being corroded as in the case of using an aqueous electrolyte. The amount of holes injected into the electrolyte as the hole transporter can be increased to the same level as or more than when an aqueous electrolyte is used, and the photoelectric conversion characteristics of the photoelectric conversion device can be improved. As the alcohol, ethanol is preferable as described in claim 4 in consideration of further improving the effect.

The photoelectric conversion device of the present invention comprises a sulfide inorganic semiconductor, a photoexciter that generates electrons and holes by photoelectric conversion,
The excitation body is supported, and an electron transport layer for transporting electrons generated by photoelectric conversion in the light excitation member,
A counter electrode disposed to face the electron transporter layer in a non-contact state;
Wherein the counter electrode is filled between the electron transport layer, holes generated by photoelectric conversion in the light excitation body, wherein for transporting the counter electrode, a layer of electrolyte containing an electrolyte solution of the non-aqueous The electrolytic solution comprises a solvent and an electrolyte, and the electrolyte forms a soluble polysulfide species in the electrolytic solution, Na ₂ S, Li ₂ S, K ₂ S And at least one sulfide selected from the group consisting of (NH ₄ ) ₂ S.

  FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a photoelectric conversion device of the present invention. Referring to FIG. 1, a photoelectric conversion device 1 of this example includes a substrate 2 and an electron transport layer 4 that carries a photoexciter (not shown) that is laminated on one surface of the substrate 2 via an electrode layer 3. A counter substrate 5 disposed to face the electron transport layer 4 in a non-contact state, and a counter electrode layer 6 formed on a surface of the counter substrate 5 facing the electron transport layer 4. And an electrolyte layer 7 containing a non-aqueous electrolyte filled in a space between the counter electrode layer 6 and the electron transport layer 4, and a non-aqueous electrolyte contained in the electrolyte layer 7 In order to protect, the transparent substrate 2 and the counter substrate 5 are bonded to each other at the outer peripheral edge portion, and a sealing material 8 for sealing the space between them from the outside is provided.

  The photoelectric conversion device 1 of this example, which includes the above-described parts, is configured so that either the substrate 2 side or the counter substrate 5 side transmits the light irradiated to the sulfide inorganic semiconductor as a photoexciter. It is necessary for the inorganic semiconductor to be transparent to light in a wavelength region where the sensitivity is high. That is, at least one of the substrate 2 and the counter substrate 5 is a transparent substrate that is transparent to the light in the wavelength range, and of the electrode layer 3 and the counter electrode layer 6 on the transparent substrate side. Similarly, the electrode layer needs to be a transparent electrode layer that is transparent to light in the wavelength range.

  Examples of the transparent substrate include a glass substrate, a plastic substrate (plate, sheet, film, etc.), an inorganic crystal substrate, and the like that are transparent to light in the wavelength range. Moreover, you may perform the process which prevents reflection of light, such as forming a texture structure in at least one surface of the said transparent substrate. Further, the substrate opposite to the light transmitting side may or may not be transparent with respect to the light in the wavelength range, and examples of the substrate that is not transparent include metal substrates (plates, films, etc.). And opaque plastic substrates (plates, sheets, films, etc.), ceramic substrates, and the like. Further, as the substrate, a substrate made of a sufficiently low resistance material can be used, and an electrode layer formed on one surface thereof can be omitted.

As the transparent electrode layer, for example, a tin compound such as tin oxide (SnO ₂ ) doped with fluorine (F) or antimony (Sb), tin oxide (SnO ₂ ), manganese (Mn), or molybdenum (Mo) is doped. Examples thereof include a thin film made of a transparent conductive material such as an indium compound such as indium oxide (In ₂ O ₃ ) or an indium-tin composite oxide (ITO) such as In ₄ Sn ₃ O ₁₂ . Since the transparent conductive material has a high transmittance for light in the wavelength region in which the sulfide inorganic semiconductor as a photoexciter has sensitivity, particularly in the visible light region, it is easy to form a low-resistance thin film. Preferred as a transparent electrode layer. The transparent electrode layer can be formed by vacuum film-forming methods such as sputtering, vacuum deposition, ion plating, CVD, etc., and vacuum devices such as spray pyrolysis, paste, dip coating, etc. The film can be easily formed even by a film forming method that does not use.

  In consideration of improving the photoelectric conversion characteristics of the photoelectric conversion device 1, the transparent electrode layer preferably has a sheet resistance of 20Ω / □ or less, particularly 10Ω / □ or less, and in order to achieve this, the transparent electrode layer is transparent. The electrode layer includes a continuous layer made of the transparent conductive material, silver (Ag), aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), iron (Fe), zinc (Zn), and molybdenum. (Mo), tungsten (W), and alloys or alloys thereof, and a laminated structure in which a network-shaped extraction electrode layer made of a low-resistance material and having a through hole for transmitting light is laminated. You may form in.

  The electrode layer on the side opposite to the light transmission side may or may not be transparent to the light in the wavelength range, but considering that the photoelectric conversion characteristics of the photoelectric conversion device 1 are improved, Similar to the transparent electrode layer, the sheet resistance is preferably 20 Ω / □ or less, particularly preferably 10 Ω / □ or less. In order to achieve this, the electrode layer is made of the same low resistance as the extraction electrode layer. It is preferable to form the material. Similarly to the transparent electrode layer, the electrode layer may be formed in a laminated structure in which a continuous layer made of a transparent conductive material and a network-shaped extraction electrode layer made of a low resistance material are laminated. Further, as described above, as the substrate opposite to the light transmitting side, a sufficiently low resistance material, for example, a substrate made of the same material as the extraction electrode layer is used, and the electrode layer is omitted. You can also

  The electron transport layer 4 can be formed of various electron transport materials capable of transporting electrons generated by photoelectric conversion in the photoexciter. The electron transport layer 4 can be formed in an arbitrary shape, but supports as much photoexciter as possible, or contacts the supported photoexciter with the electrolyte contained in the electrolyte layer 7 as wide as possible. Considering contact with the area, etc., it is preferable to form a porous structure. In order to form the electron transporter layer 4 in a porous structure, an electrode layer is prepared by mixing a powder of an electron transporting material that is the basis of the electron transporter layer 4 with polyethylene glycol, water, or the like. The method of baking after apply | coating on 3 is mentioned. Further, as described in Patent Document 1, for example, the electron transport layer 4 may be formed in a layered structure with a roughened surface in contact with the electrolyte layer 7.

Examples of the electron transport material forming the electron transport layer 4 include indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), and titanium oxide (TiO ₂ ). ), Niobium oxide (Nb ₂ O ₅ ), zirconium oxide (ZrO ₂ ), tantalum oxide (Ta ₂ O ₅ ), silver oxide (Ag ₂ O), manganese oxide (MnO ₂ ), copper oxide (Cu ₂ O ₃ ) , Iron oxide (Fe ₂ O ₃ ), vanadium oxide (V ₂ O ₅ ), chromium oxide (Cr ₂ O ₃ ), nickel oxide (NiO), strontium-titanium composite oxide (SrTiO ₃ ), potassium-niobium composite oxide object (K ₄ NbO ₁₇₎ such, and one or more compounds having an electron transporting property. In particular, the electron transport performance is excellent, the manufacturing process for forming the electron transporter layer 4 having a porous structure is simple, and the electron transporter layer 4 having a large area can be easily formed. Of these, TiO ₂ and ZnO are preferable.

  For example, a dense oxide semiconductor layer that does not transmit electrolyte may be inserted between the electron transporter layer 4 and the electrode layer 3 therebelow. Thereby, the leakage current between both the electrode layers 3 and 6 can be reduced, and the open circuit voltage value in the state which does not connect the load of the photoelectric conversion apparatus 1 can be improved. The oxide semiconductor layer is preferably formed of the same electron transport material as that forming the electron transport layer 4 in consideration of reducing the interface resistance with the electron transport layer 4.

  The sulfide inorganic semiconductor supported on the electron transport layer 4 as a photoexciter has an energy level at the bottom of the conduction band of 0.1 to 0 with respect to the electron transport material forming the electron transport layer 4. It is preferable to use a sulfide inorganic semiconductor located on the high energy side at about 0.4 eV, particularly around 0.2 eV. When the potential difference between the energy levels of both components is less than the above range, the internal electric field is reduced and the amount of electron movement is reduced. Therefore, in the sulfide inorganic semiconductor, electrons generated by light irradiation are reduced. There is a possibility that charges cannot be smoothly transferred to the electron transport layer 4. Conversely, when the potential difference between the energy levels of both components exceeds the above range, the band offset becomes too large, and the injection efficiency of electrons generated by light irradiation into the electron transport layer 4 is increased. On the other hand, there is a possibility that the electrons cannot be smoothly transferred to the electron transporter layer 4.

When the electron transport material forming the electron transport layer 4 is TiO ₂ or ZnO described above, CuInS ₂ (CIS) is preferably used as the sulfide inorganic semiconductor. The CIS is a compound semiconductor having a chalcopyrite type crystal structure with a band gap of about 1.5 eV, and has a large light absorption coefficient in the visible light region as described above, and is therefore suitable as a photoexciter. .

Moreover, since the energy order of the bottom of the conduction band is about 0.1 to 0.4 eV relative to ZnO on the high energy side, CIS is an electron transporter layer made of ZnO in terms of electron transfer. 4, the energy matching of the conduction band is good, and electrons generated by light irradiation can be smoothly transferred to the electron transport layer 4. Also, CIS is the energy level of the bottom of the conduction band, for TiO _2, before and after 0.2 eV, because they are located on the higher energy side, in terms of electron transfer, and the TiO ₂ electron-transporting layer 4 The energy matching of the conduction band is particularly good, and electrons generated by light irradiation can be transferred to the electron transport layer 4 more smoothly and smoothly.

Therefore, the photoelectric conversion characteristics of the photoelectric conversion device 1 can be improved by using CIS as the sulfide inorganic semiconductor and combining the CIS with the electron transport layer 4 made of TiO ₂ or ZnO. CIS is a range in which optical characteristics and electrical characteristics as a photoexciter are not significantly deteriorated, for example, CuIn ₅ S ₈ , CuIn ₅ S ₉ , Cu _1.70 In _0.05 S, CuIn ₁₁ S ₁₇ , Cu _2. S, it may contain one or more of such an in ₂ S _3.

As the sulfide inorganic semiconductor, other sulfide inorganic semiconductors other than CIS can also be used. Examples of the other sulfide inorganic semiconductors include CdS, PbS, Ag ₂ S, Sb ₂ S ₃ , Bi ₂ S _{3 and the} like. In order to smoothly transfer electrons generated by light irradiation to the electron transporter layer 4 using the sulfide inorganic semiconductor, as described above, the conduction band of the sulfide inorganic semiconductor is reduced. What is necessary is just to select the electron transport material which forms the electron transport body layer 4 to combine so that the energy level of a bottom part may be about 0.1-0.4 eV, especially about 0.2 eV and may be located in the high energy side.

  The photoexciter made of a sulfide inorganic semiconductor is in the form of fine particles, and the surface of the electron transporter layer 4 (in the case of the electron transporter layer 4 having a porous structure, not only the outer surface shown in the figure but also the porous body) It is preferably carried on the entire surface including the internal surface of the pores of the structure. In particular, the particulate photoexciter preferably includes nanoparticles capable of exhibiting a quantum size effect, and the radius of the nanoparticles is more preferably equal to or less than the effective Bohr radius. For example, in the case of the CIS, the particle diameter of the nanoparticles is preferably 20 nm or less (radius is 10 nm or less).

  The method of supporting the fine particle-like photoexciter containing nanoparticles on the electron transporter layer 4 is roughly divided into a gas phase method and a liquid phase method. In particular, the porous structure described above is used. In order to carry the photoexciter to every corner of the inner surface of the hole of the electron transport layer 4, it is preferable to adopt a liquid phase method. In the vapor phase method, the entrance of the hole of the electron transport layer 4 is blocked by the sulfide inorganic semiconductor deposited on the surface of the electron transport layer 4 in the initial stage of the supporting process, and the inner surface of the hole There is a possibility that the photoexciter cannot be supported sufficiently.

  On the other hand, in the liquid phase method, in a state where the liquid containing the component that is the basis of the sulfide inorganic semiconductor is sufficiently infiltrated into the inner part of the hole of the electron transport layer 4, the liquid and the electron Due to the interaction between the transporter layer 4 and the inner surface of the hole, not only the outer surface of the electron transporter layer 4 but also the corners of the inner surface of the inner part of the hole are separated from the sulfide inorganic semiconductor. Thus, a fine particulate photoexciter can be supported. Moreover, the coverage of the photoexciter with respect to the porous electron transporter layer 4 can also be improved. Further, in the liquid phase method, since the photoexciter can be supported at a lower temperature than in the gas phase method, each layer from the substrate 2 to the electron transporter layer 4 is damaged by the thermal history. , You can also prevent as much as possible. In particular, in the case where the electrode layer 3 is a transparent electrode layer, it is possible to prevent the composition from being changed due to the thermal history, thereby reducing the conductivity and the transparency.

  Examples of the liquid phase method include a chemical precipitation method such as a colloid method, a uniform precipitation method, an alkoxide method, a hydrothermal synthesis method, and a microemulsion method, and a solvent evaporation method such as a freeze drying method, a spray drying method, and a spray pyrolysis method. Is mentioned. In addition, the reverse micelle method and the hot soap method can be adopted as a method excellent in controlling the particle size of the particulate photoexciter to be formed, and a method using a microcapsule or a microtube as a reaction field is also preferably adopted. can do.

  The electrolyte layer 7 filled in the space between the electron transporter layer 4 carrying a photoexciter made of a sulfide inorganic semiconductor and the counter electrode layer 6 is conventional except that it contains a non-aqueous electrolyte. It is formed similarly. That is, the electrolyte layer 7 is formed before or after the non-aqueous electrolyte solution is sealed in the space between the counter electrode layer 6 and the electron transport layer 4 or the non-aqueous electrolyte solution is filled in the space. It is formed by gelling at any stage.

  The non-aqueous electrolyte contained in the electrolyte layer 7 is constituted by dissolving the electrolyte in a solvent that does not substantially contain water. As described above, alcohol is preferable as the solvent that constitutes the nonaqueous electrolytic solution and does not substantially contain water. The non-aqueous electrolyte containing alcohol as a solvent has no fear of corroding the photoexciter unlike the aqueous electrolyte, and the amount of electrons injected from the photoexciter into the electron transporter layer, and from the photoexciter, It is possible to improve the photoelectric conversion characteristics of the photoelectric conversion device by increasing the amount of holes injected into the electrolyte as the hole transporter to the same level as or more than when the aqueous electrolyte is used.

  Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, Lower alcohols such as 2-hexanol, 3-hexanol, heptanol, octanol, 1,2-butanediol, 1,3-propanediol, 1,5-pentanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene Examples include one or more polyhydric alcohols such as glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and 3-mercapto-1,2-propanediol. Considering the effect that does not corrode Okoshitai, lower alcohols, among which ethanol is preferred.

The electrolyte is at least one selected from the group consisting of Na ₂ S, Li ₂ S, K ₂ S, and (NH ₄ ) ₂ S as a sulfide that forms a soluble polysulfide species in the electrolytic solution. Are used. The sulfide undergoes a sulfide / polysulfide reaction [S ²⁻ / S _x ²⁻ (x = 2 to 5)] in the electrolytic solution, and transports holes by a redox pair generated at that time. Thus, holes injected from the sulfide inorganic semiconductor can be quickly and efficiently transported to the counter electrode. In addition, since the sulfide easily exchanges holes with the sulfide inorganic semiconductor, the amount of holes injected from the sulfide inorganic semiconductor into the sulfide as an electrolyte is increased. You can also. Therefore, the photoelectric conversion characteristics of the photoelectric conversion device can be improved .

When sulfur (S) is added to the electrolyte, in the presence of sulfur ions (S ²⁻ ), the formula (1):
yS + S ^2- → S _{y + 1} ^2- (1)
(Y = 1-4)
Since many polysulfide species are generated by this reaction, the hole transport efficiency based on the above sulfide / polysulfide reaction can be improved. Therefore, the photoelectric conversion characteristics of the photoelectric conversion device can be further improved. Further, when a reducing agent such as sodium sulfite (Na ₂ SO ₃ ) is added to the electrolytic solution, the reducing agent reacts quickly with the holes in the photoexciter generated by photoexcitation, thereby forming the photoexciter. The light dissolution of the sulfide inorganic semiconductor can be suppressed, and the reliability of the photoelectric conversion device can be improved.

  When the electrolytic solution is gelled, the reliability of the photoelectric conversion device can be improved. In order to gel the electrolytic solution, for example, a mixture obtained by adding a host polymer or a precursor thereof and, if necessary, a cross-linking agent of the host polymer or a polymerization initiator of the precursor to the electrolytic solution is used. The mixture is prepared and heated at any stage before and after filling the space between the counter electrode layer 6 and the electron transport layer 4 or irradiated with ultraviolet rays, ionizing radiation (electron beam) or the like. To do.

  Then, when the mixture includes a precursor, the precursor is polymerized to form a host polymer, whereby the electrolytic solution is gelled. When the mixture contains a host polymer, the host polymer undergoes a two-dimensional or three-dimensional crosslinking reaction, whereby the electrolyte solution is gelled. The host polymer formed by polymerizing the precursor may be further subjected to a two-dimensional or three-dimensional crosslinking reaction. Examples of the host polymer include one or more of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, polyacrylamide and the like. Moreover, you may make it gelatinize physically by adding the gelatinizer which gelatinizes electrolyte solution near room temperature by physical interaction.

  The sealing material 8 is preferably one that has corrosion resistance to a non-aqueous electrolyte, has low hygroscopicity and water permeability, and can adhere the substrate 2 and the counter substrate 5 more firmly. The sealing material 8 is preferably various adhesives such as thermoplastic, thermosetting, and ultraviolet curable. The resin forming the adhesive is, for example, ethylene-vinyl acetate copolymer (EVA). , Ethylene-ethyl acrylate copolymer (EEA), fluororesin, epoxy resin, acrylic resin, saturated polyester resin, amino resin, phenol resin, polyamideimide resin, silicone resin, fluororesin, urethane resin, etc. Examples of the compound include two or more kinds or two or more kinds of composites.

<< Examination of solvent for electrolyte >>
A nonaqueous electrolytic solution was prepared by adding Na ₂ S · 9H ₂ O as an electrolyte and Na ₂ SO ₃ as a reducing agent to the various solvents shown in Table 1. The concentration of Na ₂ S · 9H ₂ O was 3.6 M (mol / L), and the concentration of Na ₂ SO ₃ was 0.3 M. For comparison, an aqueous electrolyte was prepared by adding 3.6 M Na ₂ S · 9H ₂ O and 0.6 M Na ₂ SO ₃ to pure water.

After adding commercially available CIS [CuInS ₂ , purity 99%, manufactured by Kojundo Chemical Laboratories Co., Ltd.] to each of the electrolytes, mixing and allowing to stand to precipitate CIS, and filtering the supernatant, The concentrations of Cu and In eluted in the supernatant were measured by inductively coupled plasma emission (ICP) analysis. The amount of CIS input to the electrolytic solution is 0.3 g for about 7 ml of the electrolytic solution in the case of a non-aqueous electrolytic solution, and 1 g for about 12 ml of the electrolytic solution in the case of an aqueous electrolytic solution. did. The results are shown in Table 1. In addition, “<5” in the table indicates that it was below the detection limit by ICP analysis. Further, “(dehydration)” indicates that a commercially available solvent that has been dehydrated is used, and other than that, a commercially available solvent is used without being dehydrated.

  From the table, it was confirmed that if a non-aqueous electrolyte was used, the elution amount of Cu and In could be reduced and corrosion of CIS could be prevented as compared with the aqueous electrolyte. Further, comparing non-aqueous electrolytes, it was confirmed that lower alcohols can reduce the elution amount of Cu and In and can prevent CIS corrosion more reliably than polyhydric alcohols. It was.

<< Production of photoelectric conversion device >>
<Example 1, Comparative Example 1>
On the FTO transparent conductive film of the glass substrate on which FTO (Fluorine-doped Tin Oxide) transparent conductive film is formed on one side, TiO ₂ powder (average particle size 20 μm) as an electron transport material, A paste prepared by mixing 40 parts by weight of polyethylene glycol and water with 100 parts by weight of the TiO ₂ powder was applied, dried, and then fired to form an electron transporter layer having a porous structure. Formed. Next, a photoexciter composed of fine particles of CIS was supported on the entire surface of the electron transport layer including the inner surface of the porous pores by a liquid phase method, and then subjected to vacuum annealing.

As the counter substrate and the counter electrode layer, the same glass substrate as described above in which an FTO transparent conductive film was formed on one side was used. Then, a pair of glass substrates are arranged so that the electron transport layer and the FTO transparent conductive film as the counter electrode face each other in a non-contact state, and a non-aqueous electrolyte ( After impregnating Example 1) or an aqueous electrolyte solution (Comparative Example 1), the periphery of both glass substrates was sealed with an epoxy resin to produce a photoelectric conversion device. As the non-aqueous electrolyte, a solution obtained by adding 3.6 M Na ₂ S · 9H ₂ O and 0.3 M Na ₂ SO ₃ to ethanol was used. As the aqueous electrolyte, a solution obtained by adding 3.6 M Na ₂ S · 9H ₂ O and 0.3 M Na ₂ SO ₃ to pure water was used.

Short-circuit current density J _SC (mA / cm ² ), open-circuit voltage value V _OC (V), fill factor FF in the produced photoelectric conversion device in the light-irradiated state (photo) and the light-irradiated state (dark) (Fill factor) and a parameter η (%) indicating battery characteristics were obtained. The results are shown in Table 2.

  From Table 2, it can be seen that the photoelectric conversion device of Comparative Example 1 using the aqueous electrolyte generates dark current, and the sulfide inorganic semiconductor is corroded by the aqueous electrolyte containing sulfide. It was. On the other hand, it was confirmed that the photoelectric conversion device of Example 1 using a non-aqueous electrolyte solution did not generate dark current and exhibited characteristics equivalent to or higher than those of Comparative Example 1 when irradiated with light. It was.

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a photoelectric conversion device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric converter 4 Electron transporter layer 6 Counter electrode 7 Electrolyte layer

Claims (4)

A photo-exciter made of a sulfide inorganic semiconductor and generating electrons and holes by photoelectric conversion;
The excitation body is supported, and an electron transport layer for transporting electrons generated by photoelectric conversion in the light excitation member,
A counter electrode disposed to face the electron transporter layer in a non-contact state;
Wherein the counter electrode is filled between the electron transport layer, holes generated by photoelectric conversion in the light excitation body, wherein for transporting the counter electrode, a layer of electrolyte containing an electrolyte solution of the non-aqueous The electrolytic solution comprises a solvent and an electrolyte, and the electrolyte forms a soluble polysulfide species in the electrolytic solution, Na ₂ S, Li ₂ S, K ₂ S And (NH ₄ ) ₂ S. At least one sulfide selected from the group consisting of (NH ₄ ) ₂ S. The electron transporter layer is formed in a porous structure, and CuInS ₂ particles having a particle size of 20 nm or less as the photoexciter are supported on the surface including the inner surface of the porous structure of the electron transporter layer. The photoelectric conversion device according to claim 1, wherein: The electrolyte of the non-aqueous system, the photoelectric conversion device according to claim 1 or 2, characterized in that it contains alcohol as the solvent. The photoelectric conversion device according to claim 3, wherein the alcohol is ethanol.

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