WO2013008512A1 - Compound semiconductor solar cell material, and solar cell using same - Google Patents

Compound semiconductor solar cell material, and solar cell using same Download PDF

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Publication number
WO2013008512A1
WO2013008512A1 PCT/JP2012/060951 JP2012060951W WO2013008512A1 WO 2013008512 A1 WO2013008512 A1 WO 2013008512A1 JP 2012060951 W JP2012060951 W JP 2012060951W WO 2013008512 A1 WO2013008512 A1 WO 2013008512A1
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solar cell
compound semiconductor
selenide
metal
group
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PCT/JP2012/060951
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French (fr)
Japanese (ja)
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尚起 吉本
宮本　真
雅人 針替
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株式会社日立製作所
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0749—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
    • H01L31/035281—Shape of the body
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0392—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03923—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including AIBIIICVI compound materials, e.g. CIS, CIGS
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/541—CuInSe2 material PV cells

Definitions

  • the present invention relates to a compound semiconductor solar cell material having a core-shell structure and a solar cell using the same.
  • Solar cells using inorganic compounds have a high light absorption intensity, and can be used to obtain sufficient light absorption even when thinned.
  • a compound semiconductor having a chalcopyrite type crystal structure such as CuInSe2 (hereinafter referred to as CIS) made of copper indium selenium, CuInGaSe2 (hereinafter referred to as CIGS) made of copper indium gallium selenium, and the like are excellent solar cell materials.
  • CIS and CIGS solar cells can be formed into a thin film by a printing process using fine particle dispersed ink as a raw material.
  • a conventional large-scale apparatus such as vapor deposition or sputtering is not required, and the entire manufacturing process can be simplified, so that the manufacturing cost can be reduced.
  • the melting point of CIS and CIGS crystals reaches close to 1000 ° C., even when a fine particle dispersed ink is prepared, the particles are not sufficiently fused with each other, and as a result, a phenomenon such as film peeling tends to occur.
  • a metal selenide for example, copper selenide (for example, the characteristic formula Cu2Se) and indium selenide (for example, the characteristic expression In2Se3) are mixed, and the diffusion and reaction of copper and indium which are metal elements are reacted.
  • a uniform CIS thin film has been formed using a thermochemical reaction utilizing selenium rich in nature (Patent Document 1).
  • thermochemical reaction there is also a method in which a thin film is formed with ink prepared by dispersing fine particles of metal oxide and thermochemical reaction is performed with hydrogen selenide gas (Patent Document 2).
  • Patent Document 2 the reactivity of selenization can be made uniform by using gas reaction, but hydrogen selenide gas is toxic, and the reaction is caused by the complicated equipment design for ensuring safety and the difference in element diffusion coefficient. Cannot be solved.
  • a compound semiconductor having a chalcopyrite structure formed by using a printing process has been difficult to form a uniform thin film without compositional segregation due to a mismatch in diffusion coefficient of elements and a problem of thermochemical reaction of selenization.
  • the object of the present invention is to prevent segregation of a low resistance Group I metal selenide even when a Group I metal (such as Cu) selenide and Group III metal (such as In) selenide are used.
  • An object of the present invention is to provide a compound semiconductor solar cell material capable of forming a uniform thin film and a high-efficiency solar cell using the same.
  • a group III metal selenide in the form of fine particles disposed in the center, and a group I metal selenide formed so as to cover the surface of the group III metal selenide The compound semiconductor solar cell material is characterized in that a chalcopyrite crystal structure can be expressed by heating.
  • a solar cell comprising a substrate and a compound semiconductor layer having a chalcopyrite crystal structure formed by heating an ink containing the compound semiconductor solar cell material on the substrate.
  • a substrate a first electrode provided on the substrate, a compound including a group I metal, a group III metal, and selenium provided on the first electrode and having a chalcopyrite crystal structure, and the group I metal
  • a material for a compound semiconductor solar battery capable of forming a uniform thin film without composition segregation of a selenide of a low resistance group I metal (such as Cu) and a high-efficiency solar battery using the same.
  • the present invention has a selenide of a group III metal such as indium selenide at the center to obtain a thin film having a chalcopyrite crystal structure, and the outer periphery thereof is selenide. It was found that the uniformity of the reaction can be obtained by preparing ink with fine particles integrated with a core / shell structure coated with copper fluoride.
  • a thin film having a chalcopyrite crystal structure is composed of four elements, for example, copper indium gallium selenium CuInGaSe2, the alloy selenide of indium gallium is at the center and the outer periphery is coated with copper selenide.
  • the produced ink can be produced to obtain a solar cell.
  • a chalcopyrite structure has a structure in which crystals of a group III metal selenide are mixed. With this structure, it is possible to efficiently react copper selenide that causes a short circuit into the chalcopyrite structure.
  • the present invention defines raw materials necessary for producing a thin film solar cell made of a compound semiconductor having a chalcopyrite crystal structure in a printing process, and has the effect of producing a compound semiconductor having high-performance semiconductor physical properties. Further, manufacturing advantages such as simplification of the manufacturing process and effective use of raw materials by printing can be obtained.
  • the solar cell produced by the present invention can reduce the content of copper selenide that causes a short circuit as compared with conventional products, and has an effect of obtaining a highly efficient solar cell.
  • FIG. 1 is an example of a cross-sectional view of fine particles of a compound semiconductor solar cell material having a core / shell structure according to the present embodiment.
  • the radius of the entire fine particle is represented by r2
  • the radius of the core portion 101 is represented by r1.
  • the core part 101 is a selenide of a group III metal, and examples thereof include indium selenide including In 2 Se 3.
  • Indium selenide forms a composition ratio such as InSe or In3Se7 in addition to In2Se3, but is not limited to a specific composition ratio.
  • the energy level can be controlled by the composition ratio of the group III metal element.
  • the composition ratio of the group III metal element For example, when using a selenide in which gallium is added at an arbitrary ratio in addition to indium such as InGaSe3, Higher performance solar cells can be produced.
  • the shell part 102 can use a selenide containing a group I metal such as copper selenide.
  • group I metal silver and an alloy of copper and silver can be used in addition to copper, and there is no particular limitation as long as it is a group I metal.
  • the radius r1 of the core portion and the radius r2 of the entire fine particle are defined by the density of the substance used and the molar ratio of Group I metal to Group III metal.
  • Core-shell fine particles used in this example a fine group III-group metal selenide disposed in the center and a group I metal selenide formed over the surface of the group III metal selenide) ) Is used to produce a solar cell, the compound semiconductor layer having a chalcopyrite crystal structure preferably forms a p-type semiconductor.
  • a compound semiconductor having a chalcopyrite crystal structure has a molar ratio of copper to group III metal (Cu / III group metal ratio) of 0.6 or more and less than 1.0, and more preferably 0.7 or more and 0.9 or less.
  • a p-type semiconductor is shown. Even if the molar ratio of copper to group III metal (Cu / group III metal ratio) is less than 0.6, the function of the solar cell is satisfied. Therefore, r1 / r2 may be defined so that this molar ratio can be realized.
  • the shell thickness d2 may be designed such that, for example, the average particle diameter of the core, which is indium selenide, is used, and the copper selenide constituting the shell is completely segregated without compositional segregation.
  • composition segregation of a selenide of a low resistance group I metal that has conventionally caused a short circuit does not occur.
  • Indium selenide is surrounded by CIS, and only CIS is in contact with the electrode, so that the resistance can be reduced.
  • Indium selenide is surrounded by CIS and does not come into contact with the electrode, so it may remain unreacted (composition segregation).
  • the optimum value of r1 / r2 is defined as 0.843.
  • the optimum value of r1 / r2 is defined as 0.786.
  • the optimum ratio of r1 / r2 is 0.7 or more and less than 1.0.
  • r2 corresponding to the radius of the entire fine particle is 100 nm or less, and more preferably 50 nm or less.
  • the film thickness of the light absorption layer of the thin film solar cell formed in this example is 5 ⁇ m or less, and the fine particle radius r2 is 1/25 or less of the thin film thickness in consideration of the filling structure of fine particles and the fusion between the fine particles.
  • 1/100 or less is more desirable.
  • the size of the fine particles varies. Variations in the radius r2 of the entire fine particles in the system affect the filling structure of the fine particles, so that a better quality thin film can be formed when the variation is smaller. Based on this requirement, various syntheses have been proposed in which the variation in the fine particle radius is reduced.
  • the fine particles used in this example may follow these synthesis methods, and there are no restrictions on the raw material synthesis.
  • the shell formation corresponds to the surface area of the fine particles, so even if there are variations in the fine particle radius in the system, Correspondingly, it is possible to coat the shell material with a uniform wall thickness.
  • Fine particles having a core / shell structure can be obtained by washing fine particles coated with copper selenide with alcohol such as methanol and repeating fine particle precipitation by centrifugation.
  • the ink is prepared by dispersing the synthesized fine particles according to this example in various solvents.
  • Ink can be produced by dispersing the synthesized fine particles in a solvent that is easy to disperse.
  • the solvent include alcohols such as ethanol, 2-propanol, and 1-butanol, and aromatics such as toluene and p-xylene. It is selected in consideration of the viscosity and boiling point of the solvent, volatility, wettability with the fine particle interface, and the like.
  • the solvent is not particularly limited as long as it satisfies these conditions, and other solvents than those described can be applied.
  • the group I metal such as Cu
  • the group III metal selenide having a low resistance
  • a compound semiconductor solar cell material capable of forming a uniform thin film without segregation of selenide composition can be provided.
  • Example 2 a method for manufacturing a solar battery cell using the fine particles of the compound semiconductor solar battery material having the core-shell structure described in Example 1 and its features will be described. Note that the matters described in the first embodiment but not described in the present embodiment can be applied to the present embodiment as long as there is no particular circumstance.
  • FIG. 2 shows a schematic cross-sectional view of the solar cell according to this example.
  • the schematic diagram shown in FIG. 2 is an example of the embodiment, and is not limited to the configuration of FIG.
  • reference numeral 201 denotes a substrate
  • reference numeral 202 denotes a metal electrode
  • reference numeral 203 denotes a compound semiconductor layer having a chalcopyrite crystal structure
  • reference numeral 204 denotes a buffer layer
  • reference numeral 205 denotes a non-doped zinc oxide layer
  • reference numeral 206 denotes a transparent electrode.
  • FIG. 3 schematically shows a production flow chart for forming FIG.
  • a manufacturing method will be described with reference to the flowchart of FIG.
  • the back electrode of the solar cell is composed of a substrate 201 and a metal electrode 202. Since it is effective to dope the compound semiconductor layer having a chalcopyrite crystal structure with sodium element, a substrate 201 such as a stainless substrate or a polyimide substrate coated with soda lime glass or sodium silicate is used. In this example, a stainless steel substrate coated with soda lime glass was used. Since a sintering process is involved in forming a compound semiconductor layer having a chalcopyrite crystal structure, a material having high heat resistance is desirable.
  • the metal electrode 202 is placed in contact with the substrate 201.
  • a material that secures adhesion to the compound semiconductor layer 203 having a chalcopyrite crystal structure and is excellent in durability even when the surface of the metal electrode is selenized is desirable, such as molybdenum. Also in this example, molybdenum was used.
  • a p-type compound semiconductor layer 203 having a chalcopyrite crystal structure in contact with the metal electrode 202 is formed.
  • the thickness of the compound semiconductor layer 203 is 1 ⁇ m, but can be 1 to 3 ⁇ m.
  • the compound semiconductor layer 203 is first printed by various methods using the ink shown in Example 1 as a precursor. Examples of the printing method include screen, blade coating, gravure, ink jet, and slit coating, but there is no particular limitation. In this embodiment, it is formed by a screen printing method. The printed ink is dried until the solvent is volatilized and then sintered. Examples of the sintering method include infrared lamp heating and heating wire heating, but are not particularly limited. In this example, an infrared lamp was used. The sintering temperature is adjusted between 400 ° C. and 700 ° C. depending on the metal selenide of the ink material.
  • the buffer layer 204 that defines a junction structure (pn junction or pin junction) with the compound semiconductor layer 203 is formed.
  • the buffer layer 204 can be formed by an existing method such as a solution growth method (Chemical Bath Deposition, CBD).
  • Materials such as cadmium sulfide CdS, indium sulfide InS, and zinc sulfide / zinc hydroxide mixture ZnS ⁇ Zn (OH) 2 can be selected in consideration of consistency with the energy level of the compound semiconductor layer 203, and the thickness is about 50 nm. Is desirable. In this embodiment, cadmium sulfide is used.
  • the non-doped zinc oxide layer 205 is placed in contact with the buffer layer by an existing method such as sputtering or solution growth. It is installed for preventing a short circuit with the transparent electrode 206, and there is no particular limitation as long as the thickness is 100 nm or less.
  • the transparent electrode 206 can be prepared by sputtering an existing material such as ITO.
  • the thickness of the transparent electrode is not particularly limited as long as a sufficiently low electric resistance can be realized as an electrode, but is generally between 300 nm and 500 nm.
  • a solar cell produced using ink containing fine particles having a core / shell structure by the above production method is completed.
  • a highly efficient solar cell could be obtained without short-circuiting.
  • a peak indicating the presence of a selenide of a group III metal is obtained in addition to the chalcopyrite structure.
  • indium selenide in the core portion is dispersed in the thin film of chalcopyrite crystal formed. Since this core part remains, it becomes possible to produce a solar cell that completely consumes low resistance copper selenide and prevents a short circuit of the cell. Thereby, the manufacturing yield of a solar cell can be improved significantly.
  • this solar cell can be manufactured at low cost, it can also be applied to consumer use.
  • a high efficiency solar cell is obtained by using fine particles of a compound semiconductor solar cell material having a group III metal selenide as a core and a group I metal selenide as a shell. Can be provided.
  • this invention is not limited to the above-mentioned Example, Various modifications are included.
  • the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
  • a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.
  • 101 Core portion containing group III metal selenide, 102... Shell part containing group I metal selenide, 201 ... substrate, 202 ... Metal electrode, 203 ... Compound semiconductor layer having chalcopyrite crystal structure, 204 ... buffer layer, 205 ... non-doped zinc oxide layer, 206: Transparent electrode.

Abstract

In order to provide a compound semiconductor solar cell material which enables the formation of an even thin film without the compositional segregation of low-resistance group I metal selenides, even when group I metal (Cu or similar) selenides and group III metal (In or similar) selenides are used, and in order to provide a high efficiency solar cell using the material, a compound semiconductor solar cell material, capable of attaining a chalcopyrite crystal structure upon heating, comprises a group III metal selenide (core section (101)), arranged in a central section and having a micro-particle shape, and a group I metal selenide (shell section (102)), formed so as to cover the surface of the group III metal selenide.

Description

化合物半導体太陽電池材料およびそれを用いた太陽電池Compound semiconductor solar cell material and solar cell using the same
　本発明は、コア・シェル構造を持つ化合物半導体太陽電池材料およびそれを用い太陽電池に関する。 The present invention relates to a compound semiconductor solar cell material having a core-shell structure and a solar cell using the same.
　無機化合物を用いた太陽電池は光吸収強度が大きく、薄膜化しても十分な光吸収が得られることや多様な作製工程を駆使して製造コストの低減が図れる等の利便性を持つため、注目されている。特にカルコパイライト型結晶構造を有する化合物半導体、たとえば銅インジウムセレンからなるＣｕＩｎＳｅ２（以下、ＣＩＳ）や銅インジウムガリウムセレンからなるＣｕＩｎＧａＳｅ２（以下、ＣＩＧＳ）などは優れた太陽電池材料である。 Solar cells using inorganic compounds have a high light absorption intensity, and can be used to obtain sufficient light absorption even when thinned. Has been. In particular, a compound semiconductor having a chalcopyrite type crystal structure, such as CuInSe2 (hereinafter referred to as CIS) made of copper indium selenium, CuInGaSe2 (hereinafter referred to as CIGS) made of copper indium gallium selenium, and the like are excellent solar cell materials.
　ＣＩＳやＣＩＧＳ太陽電池は微粒子分散インクを原料にして、印刷工程で薄膜形成することが可能である。従来の蒸着やスパッタリングなどの大掛かりな装置が不要となり、全体の作製工程も簡略化できるため、製造コストの低減が可能となる。しかしながら、ＣＩＳやＣＩＧＳの結晶は融点が１０００℃近くに達するため、微粒子分散インクを作製しても粒子同士の融着が不十分となり、結果として膜剥がれなどの現象を起こしやすかった。そこで、従来の微粒子分散技術では金属セレン化物、たとえばセレン化銅（たとえば示性式Ｃｕ２Ｓｅ）とセレン化インジウム（たとえば示性式Ｉｎ２Ｓｅ３）を混合して、金属元素である銅やインジウムの拡散と反応性に富むセレンを利用した熱化学反応を用いて均一なＣＩＳ薄膜を形成してきた（特許文献１）。 CIS and CIGS solar cells can be formed into a thin film by a printing process using fine particle dispersed ink as a raw material. A conventional large-scale apparatus such as vapor deposition or sputtering is not required, and the entire manufacturing process can be simplified, so that the manufacturing cost can be reduced. However, since the melting point of CIS and CIGS crystals reaches close to 1000 ° C., even when a fine particle dispersed ink is prepared, the particles are not sufficiently fused with each other, and as a result, a phenomenon such as film peeling tends to occur. Therefore, in the conventional fine particle dispersion technology, a metal selenide, for example, copper selenide (for example, the characteristic formula Cu2Se) and indium selenide (for example, the characteristic expression In2Se3) are mixed, and the diffusion and reaction of copper and indium which are metal elements are reacted. A uniform CIS thin film has been formed using a thermochemical reaction utilizing selenium rich in nature (Patent Document 1).
　しかし、従来のセレン化銅とセレン化インジウムの微粒子分散で作製したインクではセレン化銅とセレン化インジウムの偏析部分では、どちらか一方が未反応物質として薄膜内に残留し、特にセレン化銅は低抵抗物質であるために作製した太陽電池が短絡しやすいとの課題があった。また、金属元素である銅とインジウムの拡散係数が異なるため、十分に反応させるためには拡散係数の小さな元素に合わせた反応時間の設定が必要となるため、タクトタイムが長くなるなどの影響があった。 However, in the conventional ink prepared by dispersing fine particles of copper selenide and indium selenide, one of the segregated portions of copper selenide and indium selenide remains in the thin film as an unreacted substance. There existed a subject that the solar cell produced since it was a low resistance substance was easy to short-circuit. Also, since the diffusion coefficients of copper and indium, which are metallic elements, are different, it is necessary to set a reaction time according to an element with a small diffusion coefficient in order to react sufficiently, which has the effect of increasing the tact time. there were.
　熱化学反応の不均一性を補填するため、金属酸化物の微粒子分散で作製したインクで薄膜形成し、セレン化水素ガスで熱化学反応する方法もある（特許文献２）。この場合、セレン化の反応性はガス反応の利用により均一化できるが、セレン化水素ガスが有毒であり、安全性確保の装置設計が複雑化すること、元素拡散係数の違いが原因である反応の長時間化は解決できない。 In order to compensate for non-uniformity of thermochemical reaction, there is also a method in which a thin film is formed with ink prepared by dispersing fine particles of metal oxide and thermochemical reaction is performed with hydrogen selenide gas (Patent Document 2). In this case, the reactivity of selenization can be made uniform by using gas reaction, but hydrogen selenide gas is toxic, and the reaction is caused by the complicated equipment design for ensuring safety and the difference in element diffusion coefficient. Cannot be solved.
特表２００９－５０７３６９号公報Special table 2009-507369 米国特許第５９８５６９１号明細書US Pat. No. 5,985,691
　以上のように、印刷工程を用いて形成するカルコパイライト構造を有する化合物半導体は元素の拡散係数の不一致およびセレン化の熱化学反応の問題から組成偏析のない均一な薄膜形成が困難であった。 As described above, a compound semiconductor having a chalcopyrite structure formed by using a printing process has been difficult to form a uniform thin film without compositional segregation due to a mismatch in diffusion coefficient of elements and a problem of thermochemical reaction of selenization.
　本発明の目的は、I族金属（Ｃｕ等）のセレン化物とIII族金属（Ｉｎ等）のセレン化物とを用いた場合であっても、低抵抗なI族金属のセレン化物の組成偏析がない、均一な薄膜形成が可能な化合物半導体太陽電池用材料およびそれを用いた高効率太陽電池を提供することにある。 The object of the present invention is to prevent segregation of a low resistance Group I metal selenide even when a Group I metal (such as Cu) selenide and Group III metal (such as In) selenide are used. An object of the present invention is to provide a compound semiconductor solar cell material capable of forming a uniform thin film and a high-efficiency solar cell using the same.
　上記目的を達成するための一実施形態として、中心部に配置された微粒子状のIII族金属のセレン化物と、前記III族金属のセレン化物の表面を覆って形成されたI族金属のセレン化物とを有し、加熱によってカルコパイライト結晶構造を発現できることを特徴とする化合物半導体太陽電池材料とする。 As one embodiment for achieving the above object, a group III metal selenide in the form of fine particles disposed in the center, and a group I metal selenide formed so as to cover the surface of the group III metal selenide The compound semiconductor solar cell material is characterized in that a chalcopyrite crystal structure can be expressed by heating.
　また、基体と、上記化合物半導体太陽電池材料を含むインクが前記基体上で加熱されることにより形成されたカルコパイライト結晶構造を有する化合物半導体層と、を有することを特徴とする太陽電池とする。 Also, a solar cell comprising a substrate and a compound semiconductor layer having a chalcopyrite crystal structure formed by heating an ink containing the compound semiconductor solar cell material on the substrate.
　また、基板と、前記基板上部に設けられた第１電極と、前記第１電極上部に設けられ、カルコパイライト結晶構造を有するI族金属とIII族金属とセレンとを含む化合物及び前記I族金属とIII族金属とセレンとを含む化合物に覆われたIII族金属のセレン化物とを有する化合物半導体層と、前記化合物半導体層上部に設けられた第２電極と、を有することを特徴とする太陽電池とする。 Further, a substrate, a first electrode provided on the substrate, a compound including a group I metal, a group III metal, and selenium provided on the first electrode and having a chalcopyrite crystal structure, and the group I metal And a compound semiconductor layer having a group III metal selenide covered with a compound containing a group III metal and selenium, and a second electrode provided on the compound semiconductor layer. Use batteries.
　中心部に配置された微粒子状のIII族金属のセレン化物と、前記III族金属のセレン化物の表面を覆って形成されたI族金属のセレン化物とを有する（コア・シェル構造）ことにより、低抵抗なI族金属（Ｃｕ等）のセレン化物の組成偏析がない、均一な薄膜形成が可能な化合物半導体太陽電池用材料およびそれを用いた高効率太陽電池を提供することができる。 By having a finely divided group III metal selenide disposed in the center and a group I metal selenide formed over the surface of the group III metal selenide (core-shell structure), There can be provided a material for a compound semiconductor solar battery capable of forming a uniform thin film without composition segregation of a selenide of a low resistance group I metal (such as Cu) and a high-efficiency solar battery using the same.
本発明の第１の実施例に係るコア・シェル構造を持つ化合物半導体太陽電池材料の断面模式図の一例である。It is an example of the cross-sectional schematic diagram of the compound semiconductor solar cell material which has a core shell structure which concerns on the 1st Example of this invention. 本発明の第２の実施例に係る太陽電池の断面図の一例である。It is an example of sectional drawing of the solar cell which concerns on the 2nd Example of this invention. 本発明の第２の実施例に係る太陽電池の作製工程を説明したフロー図の一例である。It is an example of the flowchart explaining the preparation process of the solar cell which concerns on the 2nd Example of this invention.
　上記課題を解決するための検討を行なった結果、本発明はカルコパイライト結晶構造を有する薄膜を得るためにセレン化インジウムをはじめとするIII族金属のセレン化物を中心部に持ち、その外周をセレン化銅で被覆したコア・シェル構造で一体化した微粒子でインクを作製することによって反応の均一性を得ることができることを見出した。 As a result of investigations to solve the above problems, the present invention has a selenide of a group III metal such as indium selenide at the center to obtain a thin film having a chalcopyrite crystal structure, and the outer periphery thereof is selenide. It was found that the uniformity of the reaction can be obtained by preparing ink with fine particles integrated with a core / shell structure coated with copper fluoride.
　本発明によれば、カルコパイライト結晶構造を有する薄膜が４元素系、たとえば銅インジウムガリウムセレンＣｕＩｎＧａＳｅ２で構成される場合、インジウムガリウムの合金セレン化物を中心部に持ち、その外周をセレン化銅で被覆したインクを作製して太陽電池を得ることができる。 According to the present invention, when a thin film having a chalcopyrite crystal structure is composed of four elements, for example, copper indium gallium selenium CuInGaSe2, the alloy selenide of indium gallium is at the center and the outer periphery is coated with copper selenide. The produced ink can be produced to obtain a solar cell.
　本発明によれば、カルコパイライト構造中にIII族金属のセレン化物の結晶が混在する構造を有する。この構造によって、短絡原因となるセレン化銅を効率よくカルコパイライト構造へ反応することが可能となる。 According to the present invention, a chalcopyrite structure has a structure in which crystals of a group III metal selenide are mixed. With this structure, it is possible to efficiently react copper selenide that causes a short circuit into the chalcopyrite structure.
　本発明はカルコパイライト結晶構造を有する化合物半導体からなる薄膜太陽電池を印刷工程で作製するために必要な原料を規定するものであり、高性能な半導体物性を有する化合物半導体を作製できる効果を有する。また、作製工程の簡略化、印刷による原料の有効利用など製造面の優位性を得ることができる。本発明によって作製された太陽電池は従来品と比較して、短絡原因となるセレン化銅の含有率を減少させることが可能であり、高効率な太陽電池を得ることができる効果を有する。 The present invention defines raw materials necessary for producing a thin film solar cell made of a compound semiconductor having a chalcopyrite crystal structure in a printing process, and has the effect of producing a compound semiconductor having high-performance semiconductor physical properties. Further, manufacturing advantages such as simplification of the manufacturing process and effective use of raw materials by printing can be obtained. The solar cell produced by the present invention can reduce the content of copper selenide that causes a short circuit as compared with conventional products, and has an effect of obtaining a highly efficient solar cell.
　以下、本発明を実施するための形態を実施例に沿って説明する。なお、以下の実施例は本発明を実施するための一例であって、実施例で述べている詳細な材料構成、寸法、実施条件等によって、本発明の効果が何ら制限されることは無い。 Hereinafter, modes for carrying out the present invention will be described according to examples. The following examples are examples for carrying out the present invention, and the effects of the present invention are not limited by the detailed material configuration, dimensions, working conditions, etc. described in the examples.
　本実施例では、カルコパイライト結晶構造を有する化合物半導体を作製することができるコア・シェル構造の微粒子の規定とそのインク作製方法の一例について示す。
  図１は、本実施例に係るコア・シェル構造を持つ化合物半導体太陽電池材料の微粒子断面図の一例である。微粒子全体の半径をｒ２、コア部１０１の半径をｒ１として現している。 In this embodiment, an example of the definition of core / shell structure fine particles capable of producing a compound semiconductor having a chalcopyrite crystal structure and an ink preparation method thereof will be described.
FIG. 1 is an example of a cross-sectional view of fine particles of a compound semiconductor solar cell material having a core / shell structure according to the present embodiment. The radius of the entire fine particle is represented by r2, and the radius of the core portion 101 is represented by r1.
　コア部１０１はIII族金属のセレン化物であり、たとえばＩｎ２Ｓｅ３をはじめとするセレン化インジウムなどが挙げられる。セレン化インジウムはＩｎ２Ｓｅ３以外にもＩｎＳｅ，Ｉｎ３Ｓｅ７などの組成比を形成するが、特定の組成比に限定されない。 The core part 101 is a selenide of a group III metal, and examples thereof include indium selenide including In 2 Se 3. Indium selenide forms a composition ratio such as InSe or In3Se7 in addition to In2Se3, but is not limited to a specific composition ratio.
　本実施例で用いたIII族金属のセレン化物の場合、III族金属元素の組成比によってエネルギーレベルが制御できるため、たとえばＩｎＧａＳｅ３などインジウム以外にガリウムを任意の割合で添加したセレン化物を用いると、より高性能な太陽電池を作製できる。 In the case of the selenide of the group III metal used in this example, the energy level can be controlled by the composition ratio of the group III metal element. For example, when using a selenide in which gallium is added at an arbitrary ratio in addition to indium such as InGaSe3, Higher performance solar cells can be produced.
　シェル部１０２はセレン化銅をはじめとするI族金属を含有するセレン化物を用いることができる。Ｉ族金属としては銅のほか、銀および銅と銀の合金なども用いることができ、Ｉ族金属であれば特に制限は無い。 The shell part 102 can use a selenide containing a group I metal such as copper selenide. As the group I metal, silver and an alloy of copper and silver can be used in addition to copper, and there is no particular limitation as long as it is a group I metal.
　コア部分の半径ｒ１と微粒子全体の半径ｒ２（コア部分の半径ｒ１、シェルの肉厚ｄ２の総和）は用いる物質の密度とＩ族金属とIII族金属のモル比で規定される。本実施例で用いたコア・シェル構造の微粒子（中心部に配置された微粒子状のIII族金属のセレン化物と、III族金属のセレン化物の表面を覆って形成されたI族金属のセレン化物）を用いて太陽電池セルを作製する場合には、カルコパイライト結晶構造を有する化合物半導体層はｐ型半導体を形成することが望ましい。カルコパイライト結晶構造を有する化合物半導体は銅とIII族金属のモル比（Ｃｕ／III族金属比）が０．６以上１．０未満で、さらに望ましくは０．７以上０．９以下あれば良好なｐ型半導体を示す。なお、銅とIII族金属のモル比（Ｃｕ／III族金属比）が０．６未満であったとしても、太陽電池の機能を満たす。  
したがって、このモル比が実現できるようにｒ１／ｒ２を規定すればよい。言い換えると、シェルの肉厚ｄ２は、例えば、インジウムセレン化物であるコアの平均粒径を用い、シェルを構成する銅セレン化物が組成偏析せず完全にＣＩＳとなるように設計すればよい。これにより、従来短絡の原因となっていた低抵抗なＩ族金属（Ｃｕ等）のセレン化物の組成偏析は生じることがない。また、インジウムセレン化物はＣＩＳに取り囲まれており、ＣＩＳのみが電極に接触するため、抵抗を低減できる。なお、インジウムセレン化物はＣＩＳに取り囲まれ、電極と接触することがないため未反応で残っても（組成偏析しても）よい。 The radius r1 of the core portion and the radius r2 of the entire fine particle (the sum of the radius r1 of the core portion and the thickness d2 of the shell) are defined by the density of the substance used and the molar ratio of Group I metal to Group III metal. Core-shell fine particles used in this example (a fine group III-group metal selenide disposed in the center and a group I metal selenide formed over the surface of the group III metal selenide) ) Is used to produce a solar cell, the compound semiconductor layer having a chalcopyrite crystal structure preferably forms a p-type semiconductor. A compound semiconductor having a chalcopyrite crystal structure has a molar ratio of copper to group III metal (Cu / III group metal ratio) of 0.6 or more and less than 1.0, and more preferably 0.7 or more and 0.9 or less. A p-type semiconductor is shown. Even if the molar ratio of copper to group III metal (Cu / group III metal ratio) is less than 0.6, the function of the solar cell is satisfied.
Therefore, r1 / r2 may be defined so that this molar ratio can be realized. In other words, the shell thickness d2 may be designed such that, for example, the average particle diameter of the core, which is indium selenide, is used, and the copper selenide constituting the shell is completely segregated without compositional segregation. Thereby, composition segregation of a selenide of a low resistance group I metal (Cu or the like) that has conventionally caused a short circuit does not occur. Indium selenide is surrounded by CIS, and only CIS is in contact with the electrode, so that the resistance can be reduced. Indium selenide is surrounded by CIS and does not come into contact with the electrode, so it may remain unreacted (composition segregation).
　例えば、Ｉ族金属のセレン化物としてＣｕ２Ｓｅ，III族金属のセレン化物としてＩｎ２Ｓｅ３を用いた場合、ｒ１／ｒ２の最適値は０．８４３と規定される。また、I族金属のセレン化物にＣｕＳｅ，III族金属のセレン化物にＩｎ２Ｓｅ３を用いた場合はｒ１／ｒ２の最適値は０．７８６と規定される。種々のI族金属、III族金属の密度と組成比を考慮すると、最適なｒ１／ｒ２の比は０．７以上１．０未満である。０．７未満の場合はシェル部分の肉厚が厚過ぎて、シェル部分のI族金属のセレン化物が残留するため、太陽電池を作製した際に低抵抗成分となり、太陽電池セルが短絡する。一方、ｒ１／ｒ２＝１．０はすべてコア部分であること（ｄ２＝０と同値）を意味するので、太陽電池として機能しない。 For example, when Cu2Se is used as the selenide of the group I metal and In2Se3 is used as the selenide of the group III metal, the optimum value of r1 / r2 is defined as 0.843. When CuSe is used as the selenide of the group I metal and In2Se3 is used as the selenide of the group III metal, the optimum value of r1 / r2 is defined as 0.786. Considering the density and composition ratio of various Group I metals and Group III metals, the optimum ratio of r1 / r2 is 0.7 or more and less than 1.0. If it is less than 0.7, the shell portion is too thick and selenide of the Group I metal in the shell portion remains, so that when the solar cell is produced, it becomes a low resistance component and the solar cell is short-circuited. On the other hand, r1 / r2 = 1.0 means that all are core parts (same value as d2 = 0), and thus does not function as a solar cell.
　実施するに当たって、微粒子全体の半径に相当するｒ２は１００ｎｍ以下であることが望ましく、さらに５０ｎｍ以下であれば最適である。本実施例で形成される薄膜太陽電池の光吸収層の膜厚が５μｍ以下であり、微粒子の充填構造や微粒子同士の融着を考慮すると、微粒子半径ｒ２は薄膜膜厚の１／２５以下が望ましく、さらに充填率を高めるために１／１００以下がより望ましい。 In carrying out, it is desirable that r2 corresponding to the radius of the entire fine particle is 100 nm or less, and more preferably 50 nm or less. The film thickness of the light absorption layer of the thin film solar cell formed in this example is 5 μm or less, and the fine particle radius r2 is 1/25 or less of the thin film thickness in consideration of the filling structure of fine particles and the fusion between the fine particles. Desirably, in order to further increase the filling rate, 1/100 or less is more desirable.
　微粒子の合成方法にもよるが、微粒子の大きさにはばらつきが生じる。微粒子全体の半径ｒ２の系内でのばらつきは微粒子の充填構造に影響を及ぼすため、ばらつきが小さい方がより良質な薄膜が形成できる。この要求に基づき、微粒子半径のばらつきが少なくなる種々の合成が提案されており、本実施例で用いる微粒子はそれら合成法を踏襲すればよく、原料合成に関して何ら制限は無い。 Depends on the method of fine particle synthesis, the size of the fine particles varies. Variations in the radius r2 of the entire fine particles in the system affect the filling structure of the fine particles, so that a better quality thin film can be formed when the variation is smaller. Based on this requirement, various syntheses have been proposed in which the variation in the fine particle radius is reduced. The fine particles used in this example may follow these synthesis methods, and there are no restrictions on the raw material synthesis.
　微粒子の直径ばらつきによって、形成されるシェルの肉厚にもばらつきが生じると予想できるが、シェル形成は微粒子の表面積に対応するため、仮に系内の微粒子半径にばらつきがあったとしても、表面積に対応して均一な肉厚でシェル物質を被覆することが可能である。 Although it can be expected that the thickness of the shell formed will vary due to the variation in the diameter of the fine particles, the shell formation corresponds to the surface area of the fine particles, so even if there are variations in the fine particle radius in the system, Correspondingly, it is possible to coat the shell material with a uniform wall thickness.
　図１に示すコア・シェル構造を有する微粒子の合成方法は種々挙げられるため、特に制限は無い。一例としてセレン化ナトリウムと金属塩との反応で形成する方法について説明する。コア部分の微粒子合成はたとえばヨウ化インジウム（III）とセレン化ナトリウムをメタノール中で混合することによって、式（１）に示す反応でコア微粒子が形成できる。
  
２ＩｎＩ３　＋　３Ｎａ２Ｓｅ　→　Ｉｎ２Ｓｅ３　＋　６ＮａＩ　　　　式（１）  
  
コア微粒子が分散している状態でｉｎ　ｓｉｔｕでよう化銅(I)ＣｕＩを添加すると、セレン化インジウム微粒子を被覆する形でセレン化銅が形成される。 Since there are various methods for synthesizing the fine particles having the core / shell structure shown in FIG. 1, there is no particular limitation. As an example, a method of forming by reaction of sodium selenide and a metal salt will be described. In the fine particle synthesis of the core portion, for example, indium (III) iodide and sodium selenide are mixed in methanol, whereby the core fine particles can be formed by the reaction shown in the formula (1).

2InI3 + 3Na2Se → In2Se3 + 6NaI Formula (1)

When copper iodide (I) CuI is added in situ in a state where the core fine particles are dispersed, copper selenide is formed so as to cover the indium selenide fine particles.
　セレン化銅で被覆された微粒子はメタノールなどのアルコールで洗浄、遠心分離による微粒子沈殿を繰り返すことによって、コア・シェル構造を有する微粒子を得ることができる。 Fine particles having a core / shell structure can be obtained by washing fine particles coated with copper selenide with alcohol such as methanol and repeating fine particle precipitation by centrifugation.
　他に、ジチオカルバメート誘導体の熱分解を利用した形成方法やソルボサーマル法を利用した形成法などが挙げられるが、いずれの方法でも本実施例に係る微粒子を合成することが可能である。 Other examples include a formation method using thermal decomposition of a dithiocarbamate derivative and a formation method using a solvothermal method, and it is possible to synthesize the fine particles according to this example by any method.
　本実施例に係る合成した微粒子を種々の溶媒に分散してインクを作製する。合成した微粒子を分散しやすい溶媒に分散処理することによってインクを作製することができ、溶媒としてはエタノール、２－プロパノール、１－ブタノールなどのアルコール系、トルエン、ｐ－キシレンなどの芳香族系など溶媒の粘度や沸点、揮発性、微粒子界面との濡れ性などを考慮に入れて選定される。これら条件を満たした溶媒であれば特に制限は無く、説明した溶媒以外でも適用することができる。 The ink is prepared by dispersing the synthesized fine particles according to this example in various solvents. Ink can be produced by dispersing the synthesized fine particles in a solvent that is easy to disperse. Examples of the solvent include alcohols such as ethanol, 2-propanol, and 1-butanol, and aromatics such as toluene and p-xylene. It is selected in consideration of the viscosity and boiling point of the solvent, volatility, wettability with the fine particle interface, and the like. The solvent is not particularly limited as long as it satisfies these conditions, and other solvents than those described can be applied.
　以上の構成によって、コア・シェル構造の微粒子とそれを用いたインクを作製することが可能である。
  以上示したように、本実施例によれば、III族金属のセレン化物をコアとし、I族金属のセレン化物をシェルとする微粒子とすることにより、低抵抗なＩ族金属（Ｃｕ等）のセレン化物の組成偏析がない、均一な薄膜形成が可能な化合物半導体太陽電池用材料を提供することができる。 With the above configuration, it is possible to produce core-shell structured fine particles and ink using the same.
As described above, according to the present example, the group I metal (such as Cu) having a low resistance can be obtained by forming fine particles having a group III metal selenide as a core and a group I metal selenide as a shell. A compound semiconductor solar cell material capable of forming a uniform thin film without segregation of selenide composition can be provided.
　第２の実施例について図２、図３を用いて説明する。実施例２では実施例１で説明したコア・シェル構造を持つ化合物半導体太陽電池材料の微粒子を用いた太陽電池セルの作製方法とその特長について説明する。なお、実施例１に記載され本実施例に未記載の事項は特段の事情が無い限り本実施例にも適用することができる。 The second embodiment will be described with reference to FIGS. In Example 2, a method for manufacturing a solar battery cell using the fine particles of the compound semiconductor solar battery material having the core-shell structure described in Example 1 and its features will be described. Note that the matters described in the first embodiment but not described in the present embodiment can be applied to the present embodiment as long as there is no particular circumstance.
　図２に本実施例に係る太陽電池の断面模式図を示す。以下、図２を作製するための構成、条件等について記述する。なお、図２に示した模式図は実施例の一例であって、図２の構成で何ら制限されるものではない。図２において、符号２０１は基板、符号２０２は金属電極、符号２０３はカルコパイライト結晶構造を有する化合物半導体層、符号２０４はバッファ層、符号２０５はノンドープ酸化亜鉛層、符号２０６は透明電極を示す。 FIG. 2 shows a schematic cross-sectional view of the solar cell according to this example. Hereinafter, a configuration, conditions, and the like for manufacturing FIG. 2 will be described. The schematic diagram shown in FIG. 2 is an example of the embodiment, and is not limited to the configuration of FIG. In FIG. 2, reference numeral 201 denotes a substrate, reference numeral 202 denotes a metal electrode, reference numeral 203 denotes a compound semiconductor layer having a chalcopyrite crystal structure, reference numeral 204 denotes a buffer layer, reference numeral 205 denotes a non-doped zinc oxide layer, and reference numeral 206 denotes a transparent electrode.
　図２を形成するための作製フロー図を模式的に示したものが図３である。以下、図３のフロー図に従って、作製方法を説明する。 FIG. 3 schematically shows a production flow chart for forming FIG. Hereinafter, a manufacturing method will be described with reference to the flowchart of FIG.
　太陽電池の裏面電極は基板２０１および金属電極２０２から構成される。基板２０１はカルコパイライト結晶構造を有する化合物半導体層にナトリウム元素をドーピングするのが効果的であるため、ソーダライムガラスやケイ酸ソーダなどをコーティングしたステンレス基板やポリイミド基板などが用いられる。本実施例ではソーダライムガラスをコーティングしたステンレス基板を用いた。カルコパイライト結晶構造を有する化合物半導体層を形成する際に焼結工程を伴うため、耐熱性の高い材質が望ましい。金属電極２０２は基板２０１に接して設置される。カルコパイライト結晶構造を有する化合物半導体層２０３との密着性を確保し、金属電極表面がセレン化されても耐久性などに優れている材質が望ましく、たとえばモリブデンなどが挙げられる。本実施例においてもモリブデンを用いた。 The back electrode of the solar cell is composed of a substrate 201 and a metal electrode 202. Since it is effective to dope the compound semiconductor layer having a chalcopyrite crystal structure with sodium element, a substrate 201 such as a stainless substrate or a polyimide substrate coated with soda lime glass or sodium silicate is used. In this example, a stainless steel substrate coated with soda lime glass was used. Since a sintering process is involved in forming a compound semiconductor layer having a chalcopyrite crystal structure, a material having high heat resistance is desirable. The metal electrode 202 is placed in contact with the substrate 201. A material that secures adhesion to the compound semiconductor layer 203 having a chalcopyrite crystal structure and is excellent in durability even when the surface of the metal electrode is selenized is desirable, such as molybdenum. Also in this example, molybdenum was used.
　金属電極２０２に接する形でカルコパイライト結晶構造を有するｐ形の化合物半導体層２０３が形成される。本実施例では化合物半導体層２０３の膜厚は１μｍとしたが、１～３μｍとすることができる。化合物半導体層２０３はまず前駆体となる実施例１で示したインクを種々の方法で印刷する。印刷方法はスクリーン、ブレードコート、グラビア、インクジェット、スリットコートなどが挙げられるが、特に制限は無い。本実施例ではスクリーン印刷法で形成した。印刷したインクは溶媒が揮発するまで乾燥し、その後焼結する。焼結方法は赤外線ランプ加熱、電熱線加熱などが挙げられるが、特に制限は無い。本実施例では赤外線ランプを用いた。焼結温度は４００℃から７００℃の間で、インク材料の金属セレン化物によって調整される。 A p-type compound semiconductor layer 203 having a chalcopyrite crystal structure in contact with the metal electrode 202 is formed. In this embodiment, the thickness of the compound semiconductor layer 203 is 1 μm, but can be 1 to 3 μm. The compound semiconductor layer 203 is first printed by various methods using the ink shown in Example 1 as a precursor. Examples of the printing method include screen, blade coating, gravure, ink jet, and slit coating, but there is no particular limitation. In this embodiment, it is formed by a screen printing method. The printed ink is dried until the solvent is volatilized and then sintered. Examples of the sintering method include infrared lamp heating and heating wire heating, but are not particularly limited. In this example, an infrared lamp was used. The sintering temperature is adjusted between 400 ° C. and 700 ° C. depending on the metal selenide of the ink material.
　次いで、化合物半導体層２０３との間の接合構造（ｐｎ接合やｐｉｎ接合）を規定するバッファ層２０４を形成する。バッファ層２０４は溶液成長法（Ｃｈｅｍｉｃａｌ　Ｂａｔｈ　Ｄｅｐｏｓｉｔｉｏｎ，ＣＢＤ）などの既存の方法によって形成することができる。材質は硫化カドミウムＣｄＳ、硫化インジウムＩｎＳ、硫化亜鉛／水酸化亜鉛混合体ＺｎＳ・Ｚｎ（ＯＨ）２などが化合物半導体層２０３のエネルギーレベルとの整合性を考慮して選択でき、厚さは５０ｎｍ程度が望ましい。本実施例では硫化カドミウムを用いて形成した。 Next, a buffer layer 204 that defines a junction structure (pn junction or pin junction) with the compound semiconductor layer 203 is formed. The buffer layer 204 can be formed by an existing method such as a solution growth method (Chemical Bath Deposition, CBD). Materials such as cadmium sulfide CdS, indium sulfide InS, and zinc sulfide / zinc hydroxide mixture ZnS · Zn (OH) 2 can be selected in consideration of consistency with the energy level of the compound semiconductor layer 203, and the thickness is about 50 nm. Is desirable. In this embodiment, cadmium sulfide is used.
　バッファ層に接して、ノンドープ酸化亜鉛層２０５をスパッタリングや溶液成長法などの既存の方法で設置する。透明電極２０６との短絡防止のために設置するものであって、厚さは１００ｎｍ以下であれば特に制限は無い。 The non-doped zinc oxide layer 205 is placed in contact with the buffer layer by an existing method such as sputtering or solution growth. It is installed for preventing a short circuit with the transparent electrode 206, and there is no particular limitation as long as the thickness is 100 nm or less.
　透明電極２０６はＩＴＯなどの既存の材料をスパッタリングなどの方法で作製することができる。透明電極の厚さは電極として十分に低い電気抵抗が実現できれば特に制限は無いが、一般的に３００ｎｍから５００ｎｍの間である。 The transparent electrode 206 can be prepared by sputtering an existing material such as ITO. The thickness of the transparent electrode is not particularly limited as long as a sufficiently low electric resistance can be realized as an electrode, but is generally between 300 nm and 500 nm.
　以上の作製方法でコア・シェル構造を持つ微粒子を含むインクを用いて作製した太陽電池セルが完成する。その結果、短絡することなく高効率の太陽電池を得ることができた。この太陽電池のＸ線回折分析を行うと、カルコパイライト構造のほかに、III族金属のセレン化物の存在を示すピークが得られる。本実施例によると、焼結の熱化学反応後、コア部分のセレン化インジウムが生成したカルコパイライト結晶の薄膜中に分散して存在する。このコア部分が残留するために、低抵抗のセレン化銅を完全に消費し、セルの短絡を防止した太陽電池を作製することが可能となる。これにより、太陽電池の製造歩留まりを大幅に向上することができる。また、本太陽電池は低コストで製造ができるため、民生用にも適用することができる。 A solar cell produced using ink containing fine particles having a core / shell structure by the above production method is completed. As a result, a highly efficient solar cell could be obtained without short-circuiting. When the X-ray diffraction analysis of this solar cell is performed, a peak indicating the presence of a selenide of a group III metal is obtained in addition to the chalcopyrite structure. According to this example, after the thermochemical reaction of sintering, indium selenide in the core portion is dispersed in the thin film of chalcopyrite crystal formed. Since this core part remains, it becomes possible to produce a solar cell that completely consumes low resistance copper selenide and prevents a short circuit of the cell. Thereby, the manufacturing yield of a solar cell can be improved significantly. Moreover, since this solar cell can be manufactured at low cost, it can also be applied to consumer use.
　以上示したように、本実施例によれば、III族金属のセレン化物をコアとし、I族金属のセレン化物をシェルとする化合物半導体太陽電池用材料の微粒子を用いることにより、高効率太陽電池を提供することができる。 As described above, according to this example, a high efficiency solar cell is obtained by using fine particles of a compound semiconductor solar cell material having a group III metal selenide as a core and a group I metal selenide as a shell. Can be provided.
　なお、本発明は上記した実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることも可能であり、また、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
１０１…III族金属セレン化物を含有するコア部、  
１０２…I族金属セレン化物を含有するシェル部、  
２０１…基板、  
２０２…金属電極、  
２０３…カルコパイライト結晶構造を有する化合物半導体層、  
２０４…バッファ層、  
２０５…ノンドープ酸化亜鉛層、  
２０６…透明電極。 101... Core portion containing group III metal selenide,
102... Shell part containing group I metal selenide,
201 ... substrate,
202 ... Metal electrode,
203 ... Compound semiconductor layer having chalcopyrite crystal structure,
204 ... buffer layer,
205 ... non-doped zinc oxide layer,
206: Transparent electrode.

Claims (12)

  1. 　中心部に配置された微粒子状のIII族金属のセレン化物と、前記III族金属のセレン化物の表面を覆って形成されたI族金属のセレン化物とを有し、
      加熱によってカルコパイライト結晶構造を発現できることを特徴とする化合物半導体太陽電池材料。     A group III metal selenide in the form of fine particles disposed in the center, and a group I metal selenide formed over the surface of the group III metal selenide,
    A compound semiconductor solar cell material characterized in that a chalcopyrite crystal structure can be developed by heating.
  2. 　請求項１記載の化合物半導体太陽電池材料において、
      微粒子状の前記III族金属のセレン化物の半径をｒ１、前記I族金属のセレン化物で覆われた微粒子全体の半径をｒ２とした場合、ｒ１／ｒ２の比は、０．６以上１．０未満であることを特徴とする化合物半導体太陽電池材料。     The compound semiconductor solar cell material according to claim 1,
    When the radius of the selenide of the group III metal in the form of fine particles is r1, and the radius of the entire fine particles covered with the selenide of the group I metal is r2, the ratio of r1 / r2 is 0.6 or more and 1.0. The compound semiconductor solar cell material characterized by being less than.
  3. 　請求項１記載の化合物半導体太陽電池材料において、
      前記加熱の温度は、４００℃以上７００℃未満であることを特徴とする化合物半導体太陽電池材料。     The compound semiconductor solar cell material according to claim 1,
    The compound semiconductor solar cell material, wherein the heating temperature is 400 ° C. or higher and lower than 700 ° C.
  4. 　請求項３記載の化合物半導体太陽電池材料において、
      前記温度での加熱により、カルコパイライト結晶構造とIII族金属のセレン化物結晶を含有することを特徴とする化合物半導体太陽電池材料。     In the compound semiconductor solar cell material according to claim 3,
    A compound semiconductor solar cell material comprising a chalcopyrite crystal structure and a group III metal selenide crystal by heating at the above temperature.
  5. 　基体と、
      請求項１記載の化合物半導体太陽電池材料を含むインクが前記基体上で加熱されることにより形成されたカルコパイライト結晶構造を有する化合物半導体層と、を有することを特徴とする太陽電池。     A substrate;
    A compound semiconductor layer having a chalcopyrite crystal structure formed by heating an ink containing the compound semiconductor solar cell material according to claim 1 on the substrate.
  6. 　請求項５記載の太陽電池において、
      微粒子状の前記III族金属のセレン化物の半径をｒ１、前記I族金属のセレン化物で覆われた微粒子全体の半径をｒ２とした場合、ｒ１／ｒ２の比は、０．６以上１．０未満であることを特徴とする太陽電池。     The solar cell according to claim 5, wherein
    When the radius of the selenide of the group III metal in the form of fine particles is r1, and the radius of the entire fine particles covered with the selenide of the group I metal is r2, the ratio of r1 / r2 is 0.6 or more and 1.0. A solar cell characterized by being less than.
  7. 　請求項５記載の太陽電池において、
      前記加熱の温度は、４００℃以上７００℃未満であることを特徴とする太陽電池。     The solar cell according to claim 5, wherein
    The heating temperature is 400 ° C or higher and lower than 700 ° C.
  8. 　請求項７記載の太陽電池において、
      前記温度での加熱により、カルコパイライト結晶構造とIII族金属のセレン化物結晶を含有することを特徴とする太陽電池。     The solar cell according to claim 7, wherein
    A solar cell comprising a chalcopyrite crystal structure and a group III metal selenide crystal by heating at the above temperature.
  9. 　基板と、
      前記基板上部に設けられた第１電極と、
      前記第１電極上部に設けられ、カルコパイライト結晶構造を有するI族金属とIII族金属とセレンとを含む化合物と、前記I族金属とIII族金属とセレンとを含む化合物に覆われたIII族金属のセレン化物とを有する化合物半導体層と、
      前記化合物半導体層上部に設けられた第２電極と、を有することを特徴とする太陽電池。     A substrate,
    A first electrode provided on the substrate;
    A group III covered with a compound including a group I metal having a chalcopyrite crystal structure, a group III metal, and selenium, and a compound including the group I metal, the group III metal, and selenium provided on the first electrode. A compound semiconductor layer having a metal selenide,
    And a second electrode provided on the compound semiconductor layer.
  10. 　請求項９記載の太陽電池において、
      前記化合物半導体層は、銅を含むことを特徴とする太陽電池。     The solar cell according to claim 9, wherein
    The said compound semiconductor layer contains copper, The solar cell characterized by the above-mentioned.
  11. 　請求項９記載の太陽電池において、
      前記化合物半導体層は、インジウムを含むことを特徴とする太陽電池。     The solar cell according to claim 9, wherein
    The said compound semiconductor layer contains indium, The solar cell characterized by the above-mentioned.
  12. 　請求項１１記載の太陽電池において、
      前記化合物半導体層は、ガリウムを更に含むことを特徴とする太陽電池。     The solar cell according to claim 11, wherein
    The solar cell, wherein the compound semiconductor layer further contains gallium.
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