JP2008192542A - Manufacturing method of chalcopyrite nanoparticle and photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing high-quality chalcopyrite nanoparticles, with their size, composition, shape and crystal structure controlled, at a low cost. <P>SOLUTION: The manufacturing method of chalcopyrite nanoparticles shown in Ib group metal-IIIb group metal-VIb group element by mixing Ib group metal compound, IIIb group metal compound, and VIb group compound of the periodic table, in an organic solvent and forming nanoparticles, is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing chalcopyrite nanoparticles and a photoelectric conversion element including a solar cell using chalcopyrite nanoparticles.

  In recent years, nanomaterials have been actively researched because of their unique properties different from bulk materials. When the size of a semiconductor is on the order of nanometers, a “quantum confinement effect” in which electron-hole pairs (excitons) are confined in a narrow region is observed. As an example, direct transition semiconductor nanoparticles such as CdS are called “quantum dots”, and it is well known that the emission wavelength and band gap can be controlled by the particle size. In addition, it is known that a semiconductor ultrathin film is cut in one direction by using a method such as electron beam lithography to form a linear quantum well structure, and a quantum size effect with a shape can be obtained. As described above, semiconductor nanoparticles capable of controlling an electronic state are expected to be applied to next-generation light-emitting materials, optical materials, or energy conversion materials.

As photoelectric conversion materials, compound semiconductors such as CdS, HgS, PbS, and PbSe are promising, but heavy metals such as Hg, Cd, and Pb are severely restricted by European RoHS directives, and these heavy metals There is a strong demand for the development of materials that do not contain.
On the other hand, many chalcopyrite compounds have been proposed as photoelectric conversion materials. The chalcopyrite-based compound has a band gap of ~ 1.5 eV for CuInS ₂ and ~ 1 eV for CuInSe ₂ and good matching with sunlight, and has a light absorption coefficient of 10 ⁵ cm ^{-1 in the} visible region. Since it is very large, it is very excellent as an absorption layer for solar cells. In addition, the constituent elements are relatively innocuous, and are expected to be applied to photoelectric conversion materials as alternative materials in harmony with the environment. Especially, if these compounds are obtained in the form of nanoparticles, it is considered that creation of devices such as photoelectric conversion devices is facilitated.

  Conventional methods for producing nanoparticles are roughly divided into a breakdown method (top-down method) and a build-up method (bottom-up method). The breakdown method is a method in which a bulk material is pulverized into fine particles, but the particle size is limited to the submicron level. The build-up method is further classified into three types: a solid phase method, a gas phase method, and a liquid phase method. The solid phase method takes a long time in the production process, and particle aggregation is remarkable and size control is difficult. Therefore, the solid phase method is not suitable for practical use, and the gas phase method and the liquid phase method are mainly used. . In the vapor phase method, the particle size, crystal structure, and the like can be controlled by selecting the concentration of vapor and reaction gas and the carrier gas type, and nanoparticles with a pure composition can be obtained, but they are not suitable for mass synthesis. In addition, since the obtained nanoparticles accumulate randomly on the substrate, it is difficult to form a device by arranging the nanoparticles in an ordered manner. On the other hand, the liquid phase method is advantageous in that it can be mass-produced and a device can be created by utilizing self-assembly of nanoparticles (Non-Patent Document 1).

In the liquid phase method, synthesis in a dilute solution has been tried for a long time (homogeneous liquid phase synthesis), and made a great contribution to the study of quantum dots in the early stage. In addition, the synthesis of nanoparticles using reverse micelles has been actively studied in recent years, and it has been shown that monodisperse nanoparticles can be synthesized in a relatively large amount (reverse micelle method). In such a research flow, the group of Bawendi and Alivissatos found a method for synthesizing very monodispersed semiconductor nanoparticles in a high-temperature polar solvent (hot soap method). In this method, the surfactant adsorbed on the surface of the particles controls particle growth and prevents aggregation, whereby monodispersed nanoparticles can be obtained. Unlike the reverse micelle method, this hot soap method is synthesized in a non-aqueous solvent, so it is less affected by oxidation and the like, and the surfactant inactivates dangling bonds on the surface. It is characterized by extremely high quantum efficiency compared to particles.
However, the hot soap method uses a dangerous raw material such as a metal alkoxide, and TOP / TOPO used as a surface protective agent is expensive and highly corrosive, so it is very difficult to scale up the production process. (Nonpatent literature 2, 3) There existed a fault.

Regarding the method of producing nanoparticles of chalcopyrite compounds, in Non-Patent Documents 4 and 5, high-grade chalcopyrite nanoparticles are produced using a special raw material “single precursor” (PPh ₃ ) ₂ CuIn (SEt) _4. Although it is synthesized, it has a drawback that there is no freedom of composition control. Non-Patent Document 6 has the disadvantages that the generated particles are coarse and a phase (solid solution) that does not have a chalcopyrite structure coexists.
On the other hand, the inventors and the group of Korgel have obtained copper sulfide nanoparticles by reacting a copper precursor with a thiol compound (Non-patent Documents 7 and 8), and reacting a metal precursor with a thiol compound. And a method for producing metal sulfide nanoparticles is proposed (Patent Document 1).

Kikuo Okumura, “The Forefront of Nanomaterials”, Chemistry Doujin, 2002 “Journal of the American Chemical Society (J. Am. Chem. Soc.)”, 1993, 115, p. 8706 "Journal of the American Chemical Society (J. Am. Chem. Soc.)", 1997, Vol. 119, p. 7019 "The Journal of Physical Chemistry B (J. Phys. Chem. B), 2004, Vol. 108, pp. 12429-12435. “Nano Letters”, 2006, Vol. 6, p. 1218 “Journal of the American Chemical Society”, 2006, Vol. 128, p. 2520 “Chem. Lett.”, 2004, Vol. 33, p. 352-353 "Journal of the American Chemical Society (J. Am. Chem. Soc.)", 2003, vol. 125, p. 5638 JP 2005-325016 A

As described above, at present, it has been difficult to inexpensively synthesize high-quality chalcopyrite nanoparticles with controlled size, controlled composition, controlled shape, and controlled crystal structure.
As a result of further intensive studies, the present inventors have found a method for producing high-quality chalcopyrite nanoparticles that solves the above problems.

  That is, the present invention provides a group Ib metal-group characterized in that a group Ib metal compound, a group IIIb metal compound, and a group VIb compound in the periodic table are mixed in an organic solvent to form nanoparticles. It relates to a method for producing chalcopyrite nanoparticles represented by Group IIIb metal-Group VIb element.

  In addition, the present invention also includes mixing a Group Ib metal compound and a Group VIb compound in an organic solvent in an organic solvent to form nanoparticles represented by a Group Ib metal-Group VIb element, and then the nanoparticles. Further, the present invention relates to a method for producing chalcopyrite nanoparticles represented by a Group Ib metal-Group IIIb metal-Group VIb element, which is doped with a Group IIIb metal.

  In the present invention, the Group Ib metal compound of the periodic table is a compound containing Cu or Ag, the Group IIIb metal compound is a compound containing In, Ga or Al, and the Group VIb compound is S or Se. It is related with the manufacturing method of the said chalcopyrite nanoparticle characterized by the above-mentioned.

  In the present invention, the chalcopyrite is characterized in that the Group Ib metal compound of the periodic table is a copper salt or a copper complex, and the Group VIb compound is a thiol compound in which sulfur is dissolved or a selenol compound in which selenium is dissolved. The present invention relates to a method for producing nanoparticles.

  Furthermore, this invention relates to the photoelectric conversion element using the chalcopyrite nanoparticle manufactured by said method.

  According to the present invention, high-quality chalcopyrite nanoparticles whose size is controlled, composition is controlled, shape is controlled, and crystal structure is controlled under mild conditions as compared with conventional synthesis methods are inexpensively synthesized. The chalcopyrite nanoparticles obtained can be applied to photoelectric conversion elements and other electronic devices.

Hereinafter, the present invention will be described in detail.
In the present invention, as the method for producing chalcopyrite nanoparticles represented by Group Ib metal-Group IIIb metal-Group VIb element, the following two methods, ie, the two-step synthesis method and the one-pot synthesis method are employed. can do.

First, the 2-step synthesis method will be specifically described.
In the 2step synthesis method, a group Ib metal compound and a group VIb compound in the periodic table are mixed in an organic solvent to form nanoparticles represented by a group Ib metal-group VIb element. This is a method for producing chalcopyrite nanoparticles by doping particles with Group IIIb metals.
In the present invention, S or Se is preferably used as the Group VIb element. Hereinafter, for convenience, the Group VIb element will be described as sulfur.

(1) Synthesis of Group Ib metal sulfide nanoparticles (Step 1)
Group Ib metal nanoparticles are synthesized by mixing a Group Ib metal compound and a Group VIb compound (hereinafter described as a sulfur compound) in an organic solvent.
Specifically, a Group Ib metal-amine complex (precursor metal complex) is used as the Group Ib metal compound. As the sulfur compound, a thiol compound solution in which sulfur is dissolved (hereinafter referred to as “sulfur / thiol solution”) is used. Group Ib metal sulfide nanoparticles are synthesized by mixing the precursor metal complex and a sulfur / thiol solution.

The precursor metal complex is prepared by bringing a metal salt containing a target metal (Group Ib metal) into contact with an amine compound in a solvent such as an ether compound, toluene, hexane, or the amine compound itself as a solvent. It can be prepared by adding a metal salt directly to the inside.
A metal-amine complex (precursor metal complex) is formed by the reaction between the metal salt and the amine compound.

  In the present invention, as the Group Ib metal salt, a compound of Cu or Ag is particularly preferably used, and acetate, acetylacetonate, metal halide, sulfate, nitrate, perchlorate, hydrochloride of such metal are used. Perchlorate, oxide, organic acid salt and the like are preferable, and acetate and acetylacetonate are particularly preferable. Specific examples include copper acetate, copper acetylacetonate, silver acetate, and silver acetylacetonate.

Metal sulfide nanoparticles can be obtained by reacting this metal-amine complex with a sulfur / thiol solution and sulfiding.
The sulfur / thiol solution is prepared by mixing sulfur and a thiol compound. When sulfur is dissolved in the thiol compound, it becomes hydrogen sulfide by the reducing ability of the thiol compound under the reaction formula (R) below (1), and the sulfur source of the target metal sulfide nanoparticles Become.
S + 2RSH → (RSH) ₂ S → H ₂ S + RSSR (1)

  The thiol compound is selected from an alkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a heterocyclic group containing at least one selected from nitrogen, sulfur and oxygen. Functional groups may be present. In addition to functioning as a sulfur reducing agent, the thiol compound also functions as a surface protecting agent.

Specific examples of the thiol compound having an alkyl group include ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-pentanethiol, octanethiol, decanethiol, and dodecanethiol. And pentadecanethiol. Moreover, dithiol, trithiol, etc. which have two or more thiol parts can also be used.
Specific examples of the thiol compound having an aryl group include thiophenol, 2-naphthalenethiol, 3-naphthalenethiol, dimethylbenzenethiol, and ethylbenzenethiol. Moreover, dithiol, trithiol, etc. which have two or more thiol parts can also be used.
Specific examples of the thiol compound having an aralkyl group include benzylthiol, 2-phenylethanethiol, and 3-phenylpropylthiol. Moreover, dithiol, trithiol, etc. which have two or more thiol parts can also be used.

Specific examples of the thiol compound having a heterocyclic group include 2-mercaptopyridine, 4-mercaptopyridine, 2-mercaptopyrimidine, 2-mercaptoimidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole and the like. Can do. Moreover, dithiol, trithiol, etc. which have two or more thiol parts can also be used.
Among the thiol compounds listed above, a thiol compound having an alkyl group is preferably used, and a thiol compound having an alkyl group having 6 or more carbon atoms is particularly preferably used.

  As a method for dissolving sulfur in the thiol compound, it is preferable to perform heating and stirring after mixing in order to promote dissolution of sulfur. The reaction time is about 10 minutes to 1 hour, and can be arbitrarily set depending on the reaction temperature. The reaction temperature ranges from room temperature to 200 ° C, preferably 50 ° C to 150 ° C.

  In the present invention, the precursor metal complex and the sulfur / thiol solution are mixed in an organic solvent. At this time, the mixing ratio of the precursor metal complex and the sulfur / thiol solution is not particularly limited, but the mixing is preferably performed so that the atomic ratio of metal to sulfur is the target metal sulfide nanoparticles.

Examples of the solvent that can be used include ethers, alcohols, halides, hydrocarbons, aromatics (toluene and benzene), amines, and the like. The reaction temperature is 0 ° C or higher, preferably room temperature or higher, 300 ° C or lower, preferably 200 ° C or lower.
The particle size can be controlled by the reaction temperature. Similarly, the shape of the particles can be controlled. In general, when the reaction temperature is increased, the formation of the metal-thiol complex in the initial process is accelerated and the amount of the core increases, so that the size of the finally formed nanoparticles tends to decrease. .

(2) Doping of Group IIIb metal into Group Ib metal sulfide nanoparticles (Step 2)
Next, the group Ib metal sulfide nanoparticles obtained above are doped with a group IIIb metal to produce the chalcopyrite nanoparticles of the present invention.
First, a Group IIIb metal salt and a thiol compound are mixed in an organic solvent, and heated for a predetermined time with stirring in an inert gas atmosphere to obtain a uniform solution (hereinafter referred to as Solution A). Here, as a thiol compound, the thing similar to what was mentioned above can be used. In addition, the same organic solvent as described above is used.
Next, the Group Ib metal sulfide nanoparticles obtained in Step 1 are dispersed in an organic solvent to obtain a sulfide nanoparticle dispersion (hereinafter referred to as Dispersion B). The obtained dispersion B is added to solution A and mixed with stirring.

  The mixing ratio of the solution A and the dispersion B may be charged with the group Ib metal sulfide nanoparticles and the group IIIb metal salt so that the element ratio of the target chalcopyrite nanoparticles is obtained. It can be arbitrarily adjusted according to the concentration of.

When stirring and mixing the solution A and the dispersion B, the mixing temperature is not particularly limited, but is usually room temperature or higher, preferably 100 ° C. or higher, and 300 ° C. or lower, preferably 260 ° C. or lower. The mixing time is not particularly limited, but is usually 0.5 to 2 hours.
By performing the above reaction, the Group Ib metal sulfide nanoparticles in the solution B are annealed, and the Group IIIb metal is doped into the Group Ib metal sulfide nanoparticles, so that the target chalcopyrite nanoparticle is obtained. Particles are obtained. The method for separating the obtained chalcopyrite nanoparticles from the reaction solution is not particularly limited. Usually, a method of adding ethanol or the like to agglomerate and then recovering by centrifugation is preferably employed.

Examples of the Group IIIb metal include Al, Ga, and In, and Ga and In are particularly preferable.
Further, the group IIIb metal salt is not particularly limited, but acetate, acetylacetonate salt, metal halide, sulfate, nitrate, perchlorate, hydrochloride, perchlorate, oxide, organic acid Examples thereof include salts and hydrides. Among them, acetate and acetylacetonate are preferable.
Specific examples of the Group IIIb metal salt include indium acetate, gallium acetate, aluminum acetate, indium acetylacetonate, gallium acetylacetonate, aluminum acetylacetonate, lithium aluminum hydride (LiAlH ₄ ), etc. Indium acetate and indium acetylacetonate are particularly preferred.

Although the above has been described for convenience with sulfur as the VIb group, selenium can also be suitably used in the same manner. As the Group VIb compound, a selenol compound in which selenium is dissolved is used.
Specific examples of the selenol compound include benzene selenol, butane selenol, hexane selenol and the like.

The chalcopyrite nanoparticles of the present invention can be produced by the above two-step synthesis method.
The size, shape, composition (group Ib metal / group IIIb metal molar ratio) and crystal structure of the chalcopyrite nanoparticles of the present invention are usually the size of the group Ib metal sulfide nanoparticles synthesized in step 1, It is influenced by the shape, composition, and crystal structure, and particularly greatly influenced by the composition of the Group Ib metal sulfide nanoparticles.
Further, the composition (group Ib metal / group IIIb metal molar ratio) and crystal structure of the chalcopyrite nanoparticles of the present invention are the reaction conditions of the solution A and the dispersion B, that is, the group Ib metal / group IIIb metal. It is affected by the charged molar ratio and annealing temperature (mixing temperature).

The composition of the resultant chalcopyrite nanoparticles 2step _{synthesis, Cu x In y S 2,} Cu x In y Se 2, Cu x Ga y S 2, Cu x Ga y Se 2, Cu x Al y S 2 ( wherein, x + y = 2,0 <x <2,0 < number in the range of _{y <2), CuIn 1-} X Ga X S 2, CuIn 1-X Ga X Se 2, CuIn 5 S 8 etc. Can be mentioned.

Next, the one-pot synthesis method will be described.
The one-pot synthesis method is a method of forming nanoparticles by mixing a Group Ib metal compound, a Group IIIb metal compound, and a Group VIb compound in an organic solvent. Mixing is usually performed in an inert gas atmosphere.
The mixing temperature and mixing time at this time are not particularly limited. Usually, the mixed solution is heated to about 100 ° C., stirred for 0.5 to 2 hours, and then the mixed solution is further heated to 200 to 300 ° C. The target chalcopyrite nanoparticles can be obtained by heating and stirring for 0.5 to 2 hours. A method for separating the obtained chalcopyrite nanoparticles from the reaction solution is not particularly limited, and there is usually a method in which ethanol or the like is added to agglomerate and then collected by a centrifugation method.

  As the Group Ib metal compound, a Group Ib metal salt is used, and acetate, acetylacetonate salt, metal halide, sulfate, nitrate, perchlorate, hydrochloride, perchlorate of the metal, Examples thereof include oxides and organic acid salts, and acetate salts and acetylacetonate salts are particularly preferable. Specific examples of the Group Ib metal salt include copper acetate, copper acetylacetonate, silver acetate, silver acetylacetonate and the like.

  As the Group IIIb metal compound, a Group IIIb metal salt is used, and acetate, acetylacetonate salt, metal halide, sulfate, nitrate, perchlorate, hydrochloride, perchlorate of the metal, Examples thereof include oxides and organic acid salts, and acetate salts and acetylacetonate salts are particularly preferable. Specific examples of the Group IIIb metal salt include indium acetate, gallium acetate, aluminum acetate, indium acetylacetonate, gallium acetylacetonate, aluminum acetylacetonate, etc., or a mixture of 1 to 3 thereof, and acetic acid. Preferable examples include indium and indium acetylacetonate.

  Examples of the Group VIb element include S and Se. Examples of the Group VIb element compound include thiols and selenols. Preferred examples include alkanethiol and selenol.

  The organic solvent used for the solvent is not particularly limited, but a low-coordinating solvent is preferable, and examples thereof include ethers, alcohols, halides, hydrocarbons, aromatics (toluene and benzene), amines, and the like.

The chalcopyrite nanoparticles of the present invention can be produced by the above one-pot synthesis method.
In the present invention, the atomic ratio of Group Ib metal / Group IIIb metal of chalcopyrite nanoparticles is governed by the charged molar ratio of Group Ib metal salt / Group IIIb metal salt / Group VIb element.
The composition of the resultant chalcopyrite nanoparticles one-pot synthesis _{method, Cu x In y S 2,} Cu x In y Se 2, Cu x Ga y S 2, Cu x Ga y Se 2, Cu x Al y S ₂ (wherein, x + y = 2,0 <x <2,0 <y < number 2 _{range), CuIn 1-X Ga X} S 2, CuIn 1-X Ga X Se 2, CuIn 5 S 8 etc. Can be mentioned.

  The photoelectric conversion device of the present invention is characterized by using an electrode in which the chalcopyrite nanoparticles obtained above are adsorbed on a semiconductor layer such as titanium oxide.

A solar cell which is a specific example of the photoelectric conversion element of the present invention will be described. As an example of a solar cell, the element which has the cross section shown in FIG. 1 can be mentioned, for example.
In this element, a semiconductor layer 3 in which metal sulfide nanoparticles that act as a light absorber are adsorbed is disposed on a transparent conductive substrate 1, and an electrolyte layer 4 is disposed between the semiconductor layer 3 and the counter electrode substrate 2. Is sealed with a sealing material 5. Note that the lead wire is connected to the conductive portion of the transparent conductive substrate 1 and the counter electrode substrate 2 so that electric power can be taken out.

  The transparent conductive substrate 1 is usually manufactured by laminating a transparent electrode layer on a transparent substrate. The transparent substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose.For example, colorless or colored glass, netted glass, glass blocks, etc. are used. A colorless or colored resin having transparency may be used. Specific examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. Etc. In addition, the transparency in this invention is having the transmittance | permeability of 10 to 100%. Moreover, the board | substrate in this invention has a smooth surface at normal temperature, The surface may be a plane or a curved surface, and may deform | transform by stress.

Further, the transparent conductive film for forming the conductive layer of the electrode is not particularly limited as long as it fulfills the object of the present invention. For example, a metal thin film such as gold, silver, chromium, copper, tungsten, or a metal oxide is used. And a conductive film. Examples of the metal oxide include Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)) obtained by doping a small amount of other metal elements with tin oxide or zinc oxide, or Fluorine doped Tin Oxide (FTO (SnO ₂ : F)). ), Aluminum doped Zinc Oxide (AZO (ZnO: Al)) and the like are preferably used.
The film thickness is usually 10 nm to 10 μm, preferably 100 nm to 2 μm. The surface resistance (resistivity) is appropriately selected depending on the use of the substrate of the present invention, but is usually 0.5 to 500 Ω / sq, preferably 2 to 50 Ω / sq.

  As an electrode of the counter electrode substrate 2, platinum, a carbon electrode, etc. can be normally used. The material of the counter electrode substrate 2 is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, colorless or colored glass, meshed glass, glass block, or the like is used. In addition, a colorless or colored resin having transparency may be used. Specifically, polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, polymethylpentene, and the like can be given. Moreover, a metal plate etc. can also be used as a board | substrate.

As the semiconductor layer 3 used in the solar cell is not particularly limited, for example, TiO _2, ZnO, such as a layer made of SnO _2, Nb ₂ O ₅ and the like, the layer preferably consists of among others TiO _2, ZnO. The semiconductor may be single crystal or polycrystalline. As the crystal system, anatase type, rutile type, brookite type and the like are mainly used, and anatase type is preferable.
A known method can be used to form the semiconductor layer 3. As a formation method of the semiconductor layer 3, it can obtain by apply | coating the said semiconductor nanoparticle dispersion liquid, a sol solution, etc. on a board | substrate by a well-known method. The coating method in this case is not particularly limited, and examples thereof include various printing methods including a screen printing method, in addition to a method obtained in a thin film state by a casting method, a spin coating method, a dip coating method, and a bar coating method. Can do.
The thickness of the semiconductor layer 3 is arbitrary, but is usually 0.5 μm or more and 50 μm or less, preferably 1 μm or more and 20 μm or less.

  In the present invention, a chalcopyrite nanoparticle layer is disposed on the semiconductor layer 3. A method for disposing the chalcopyrite nanoparticle layer on the semiconductor layer 3 is not particularly limited, but the semiconductor layer 3 is placed on a conductive glass substrate in a suspension in which chalcopyrite nanoparticles are dispersed in a solvent. It is common practice to immerse and adsorb the placed laminate. Preferably, after adsorption, drying or baking. The drying is usually performed at room temperature to about 200 ° C., and the baking is performed at 300 ° C. or more, preferably 300 to 500 ° C. in order to remove the remaining carbon source such as an alkyl group. The firing time is about 20 minutes to 2 hours.

The electrolyte layer 4 used in the present invention is not particularly limited, and may be either a liquid system or a solid system and desirably exhibits reversible electrochemical redox characteristics. Here, showing reversible electrochemical redox characteristics means that an electrochemical redox reaction can occur reversibly in the potential region where the photoelectric conversion element acts. Typically, it is usually desirable to be reversible in the potential region of −1 to +2 V vs NHE with respect to the hydrogen reference electrode (NHE).

The ionic conductivity of the electrolyte layer 4 is usually 1 × 10 ⁻⁷ S / cm or more at room temperature, preferably 1 × 10 ⁻⁶ S / cm or more, more preferably 1 × 10 ⁻⁵ S / cm or more. Is desirable.
The thickness of the electrolyte layer 4 is not particularly limited, but is preferably 1 μm or more, more preferably 10 μm or more, and preferably 3 mm or less, more preferably 1 mm or less.
The electrolyte layer 4 is not particularly limited as long as the above-described conditions are satisfied, and liquid and solid systems known in the art can be used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(1) Synthesis of copper sulfide nanoparticles (Step 1)
Copper acetate (79 mg) and oleylamine (1.9 ml) were mixed in dioctyl ether (20 ml), stirred for several minutes under an argon atmosphere, and then heated to 100 ° C. Next, sulfur (13 mg) was dissolved in dodecanethiol (2.5 ml), and this solution was added to a solution of copper acetate and oleylamine. After stirring at 100 ° C. for 30 minutes, the mixture was cooled, and then the intended copper sulfide nanoparticles were obtained with a centrifuge. The average particle diameter of the copper sulfide nanoparticles (Cu _1.8 S) was 5 nm.
(2) In doping of copper sulfide nanoparticles (Step 2)
Indium acetate (115 mg) and 1-dodecanethiol (1 ml) were mixed in trioctylamine (15 ml) and heated to 90 ° C. with stirring under an argon atmosphere (stirring for about 30 minutes). Next, copper sulfide nano-particles _(Cu 1.8 S, 0.2mmol) a material obtained by dissolving in trioctylamine (5 ml), and stirred for 30 minutes at 200 ° C. In addition to the above indium acetate solution. The obtained nanoparticles were aggregated by adding ethanol to the reaction solution and collected by centrifugation. The TEM, XRD, absorption and fluorescence spectrum measurement results of the obtained copper indium sulfide are shown (FIGS. 2 and 3).

<Example 2 (one-pot synthesis method)>
Copper acetate (74.9 mg: 0.4 mmol) and indium acetate (116.8 mg: 0.4 mmol) and 1-dodecanethiol (2.46 ml: 10 mmol) were mixed in trioctylamine (20 mmol), and under an argon atmosphere. The temperature was raised to 90 ° C. with stirring (stirring for about 30 minutes). Next, the solution was heated to 200 ° C. and stirred for 30 to 120 minutes. The obtained nanoparticles were aggregated by adding ethanol to the reaction solution and collected by centrifugation. The XRD, absorption and fluorescence spectrum measurement results of the obtained copper indium sulfide are shown (FIGS. 4 and 5).

<Example 3 (application to solar cell)>
The Cu _x In _y S ₂ nanoparticles obtained in Example 1 were mixed with titania paste (manufactured by Solaronics) and dispersed well, and then applied to a glass substrate with a conductive film. Drying (90 ° C.) and firing (450 ° C., 1 hour) were performed to obtain a mixed thin film of CuInS nanoparticles and titania nanoparticles.
Using this substrate as a photoelectric conversion layer, using conductive glass with a platinum layer formed on the counter electrode, facing the two substrates, sealing the periphery, and injecting an electrolyte for iodine redox between the substrates, A battery was produced.
When the obtained solar cell was irradiated with simulated sunlight (AM1.5) and the conversion efficiency was measured, an efficiency of 3.5% could be obtained. When this solar cell was allowed to stand at room temperature for 1000 hours and the conversion efficiency was measured, an efficiency of 3.4% could be obtained.

<Example 4 (application to solar cell)>
The Cu _x In _y S ₂ nanoparticles obtained in Example 2 were mixed with titania paste (manufactured by Solaronics) and dispersed well, and then applied to a glass substrate with a conductive film. Drying (90 ° C.) and firing (450 ° C., 1 hour) were performed to obtain a mixed thin film of CuInS nanoparticles and titania nanoparticles.
Using this substrate as a photoelectric conversion layer, using conductive glass with a platinum layer formed on the counter electrode, facing the two substrates, sealing the periphery, and injecting an electrolyte for iodine redox between the substrates, A battery was produced.
When the obtained solar cell was irradiated with simulated sunlight (AM1.5) and the conversion efficiency was measured, an efficiency of 3.2% could be obtained. When this solar cell was allowed to stand at room temperature for 1000 hours and the conversion efficiency was measured, an efficiency of 3.2% could be obtained.

It is an example of the cross section of a solar cell. The XRD spectrum of the copper indium sulfide obtained in Example 1 is shown. The absorption and fluorescence spectrum of the copper indium sulfide obtained in Example 1 are shown. The XRD spectrum of the copper indium sulfide obtained in Example 2 is shown. The absorption and fluorescence spectrum of the copper indium sulfide obtained in Example 2 are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent conductive substrate 2 Counter electrode substrate 3 Semiconductor layer impregnated with chalcopyrite nanoparticles 4 Electrolyte layer 5 Sealing material

Claims (5)

  A Group Ib metal-Group IIIb metal-Group VIb characterized in that a Group Ib metal compound, a Group IIIb metal compound, and a Group VIb compound are mixed in an organic solvent to form nanoparticles. A method for producing chalcopyrite nanoparticles represented by a group element.   A group Ib metal compound of the periodic table and a group VIb compound are mixed in an organic solvent to form nanoparticles represented by a group Ib metal-group VIb element, and then the group IIIb is added to the nanoparticles. A method for producing chalcopyrite nanoparticles represented by Group Ib metal-Group IIIb metal-Group VIb element obtained by doping a metal.   The group Ib metal compound of the periodic table is a compound containing Cu or Ag, the group IIIb metal compound is a compound containing In, Ga or Al, and the group VIb compound is a compound containing S or Se. The method for producing chalcopyrite nanoparticles according to claim 1 or 2, wherein:   The group Ib metal compound of the periodic table is a copper salt or a copper complex, and the group VIb compound is a thiol compound in which sulfur is dissolved or a selenol compound in which selenium is dissolved. A method for producing chalcopyrite nanoparticles.   The photoelectric conversion element using the chalcopyrite nanoparticle manufactured by the method of Claim 1 or 2.

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