JP2011124468A - Organic thin film solar cell and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic thin film solar cell which allows a cathode to be formed on a flexible substrate through a coating and low-temperature process, and has superior energy conversion efficiency, optical durability, and thermal shelf stability, and a method of manufacturing the same. <P>SOLUTION: The organic thin film solar cell has at least an anode, a photoelectric conversion layer, an electron transport layer, and the cathode, on a substrate. The cathode is formed from a coating liquid including at least a silver compound and a reducing agent, and at least one electron transport layer adjoins the cathode and includes organic alkali metal salt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an organic thin film solar cell and a method for manufacturing the same.

  Organic solar cells are attracting attention as solar cells suitable for mass production because they can be formed by a coating method, and many research institutions are actively researching them. In organic solar cells, the so-called bulk heterojunction structure in which an organic donor material and an organic acceptor material are mixed improves charge separation efficiency, which has been a problem (see, for example, Patent Document 1). As a result, the energy conversion efficiency has been improved to the 5% level, and it can be said that this field has been developed to a practical level at once.

  Conventionally, in the cathode formation method, the coated cathode is advantageous from the viewpoint of manufacturing cost compared to the vacuum deposition process, but the coated cathode requires high-temperature firing in order to provide high conductivity, and is difficult to form on a flexible substrate. there were. A metal such as Ag or Al is often used for the cathode, but it is common to use Al, which is an ohmic junction with the electron transport layer and has a low cost. However, Al is easily oxidized, and even if sealing is performed, the function as an electrode is likely to deteriorate. However, when a metal having a deeper work function and strong oxidation, such as Ag, is used, the durability is good, but the work function bonding with the electron transport layer is poor and the efficiency of extracting carriers to the electrode is lowered. There was also.

  Furthermore, in order to improve the bonding between the electron transport layer and the cathode, an alkali metal layer is generally formed by vapor deposition, but the electron transport layer can be applied, but the cathode needs to be formed by a vacuum deposition process. was there.

  In response to these problems, an invention of a thin-film solar cell in which an alloy layer containing Ag as a main component and added with an easily oxidizable metal element is laminated to form a conductive reflective film is disclosed (for example, see Patent Document 2). In this invention, it adds in order to increase the adhesiveness with a transparent conductive layer by oxidizing an oxidizable metal intentionally in oxygen presence. However, this technique cannot solve the problem of obtaining a metal electrode that is excellent in durability and satisfies an electrical ohmic junction with the electron transport layer.

  Patent Document 3 discloses a configuration in which a conductive polymer is applied as a cathode that can be formed by a low-temperature process. However, conductive polymers have higher resistance than metals and have low conversion efficiency (particularly fill factor FF). Further, the light reflection effect on the photoelectric conversion layer is small, and the conversion efficiency (particularly the short-circuit current density Jsc) is low. In addition, the conductive polymer is significantly deteriorated by heat and humidity, and there is a problem in terms of storage stability.

  Patent Document 4 discloses a method of reducing resistance by further adding a rod or needle-like metal to a conductive polymer, but the resistance reduction is still insufficient.

  Patent Document 5 discloses a method for improving electrical bonding by inserting an electron transport layer containing a metal oxide or a material capable of forming a metal oxide between a photoelectric conversion layer and a metal electrode. Moisture is required to form the film, and there is a concern about deterioration of durability due to corrosion of the cathode.

US Pat. No. 5,331,183 JP 2004-335991 A International Publication No. 04 / 051756A3 Pamphlet US Patent Application Publication No. 2008/0236657 Special table 2009-502028

  The present invention has been made in view of the above problems, and its purpose is to provide an organic material that can form a cathode on a flexible substrate by a coating / low-temperature process, has excellent energy conversion efficiency, and has excellent light durability and heat storage stability. The object is to provide a thin film solar cell and a method for manufacturing the same.

  The above object of the present invention is achieved by the following configurations.

  1. An organic thin film solar cell having at least an anode, a photoelectric conversion layer, an electron transport layer and a cathode on a substrate, wherein the cathode is formed from a coating solution containing at least a silver compound and a reducing agent, and the electron transport layer At least one layer is a layer adjacent to the cathode, and contains an organic alkali metal salt.

  2. 2. The organic thin film solar cell according to 1 above, wherein the silver compound is a paste containing silver oxide fine particles.

  3. 3. The organic thin film solar cell according to 2 above, wherein the silver compound is a paste further containing an organic silver compound.

  4). 4. The organic thin film solar cell according to any one of 1 to 3 above, wherein the organic alkali metal salt is an alkali metal salt of an aliphatic carboxylic acid.

  5. Any one of the above 1 to 4, wherein the electron transport layer comprises a plurality of layers, and the electron transport layer on the cathode side has a higher concentration of the organic alkali metal salt than the electron transport layer on the photoelectric conversion layer side. 2. The organic thin film solar cell according to item 1.

  6). 6. The organic thin film solar cell as described in 5 above, wherein the electron transport layer closest to the photoelectric conversion layer does not contain an organic alkali metal salt.

  7. A method for producing an organic thin film solar cell in which at least an anode, a photoelectric conversion layer, an electron transport layer, and a cathode are laminated on a substrate, wherein the cathode is reduced to at least one or more of silver oxide and organic silver. And a solution containing a charge transport material doped with an organic alkali metal salt, wherein the electron transport layer is at least between the photoelectric conversion layer and the cathode. A method for producing an organic thin-film solar cell, characterized by being formed by applying

  8). 8. The organic thin film solar cell according to 7, wherein a layer not doped with an organic alkali metal salt is formed on the photoelectric conversion layer, a doped layer is formed, and then a cathode is formed. Production method.

  INDUSTRIAL APPLICABILITY According to the present invention, a cathode can be formed on a flexible substrate by a coating / low temperature process, and an organic thin film solar cell excellent in energy conversion efficiency, light durability, and heat storage stability and a method for producing the same can be provided. It was.

It is a schematic sectional drawing which shows the basic structure of a bulk heterojunction type organic thin film type solar cell. It is sectional drawing of the basic structure of a bulk heterojunction type organic thin film type solar cell.

  As a result of intensive studies in view of the above problems, the inventors of the present invention are organic thin-film solar cells having at least an anode, a photoelectric conversion layer, an electron transport layer, and a cathode on a substrate, wherein the cathode is at least a silver compound. And an organic thin film solar cell characterized in that at least one of the electron transport layers is a layer adjacent to the cathode and contains an organic alkali metal salt. As a result, the present inventors have found that an organic thin-film solar cell that can form a cathode on a flexible substrate by coating and low-temperature processes, has excellent energy conversion efficiency, and has excellent light durability and heat storage properties can be obtained. It is.

  That is, by forming a cathode composed of silver oxide and a reducing agent and an electron transport layer doped with an organic metal in the vicinity of the cathode, the cathode can be formed not only at a low temperature, but also between the organic metal doped layer and the cathode. The electrical junction was improved, and a configuration excellent in the energy conversion efficiency of the solar cell could be obtained.

  Furthermore, since the carrier movement is smooth compared with the conventional coated silver cathode, it is excellent in durability during light irradiation. Further, since no hydrolysis reaction is required, there is no adverse effect on durability due to moisture.

  Hereinafter, configurations that can be preferably used in the present invention will be described in detail.

[Organic thin film solar cells]
The organic thin film solar cell of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the basic structure of an organic thin film solar cell according to the present invention.

  In FIG. 1, an organic thin film solar cell includes an anode 12 and a photoelectric conversion layer 13 having a bulk heterojunction structure (a structure in which a p-type semiconductor and an n-type semiconductor are mixed) on one surface of a substrate 11 (hereinafter referred to as a bulk heterojunction layer). The bulk heterojunction structure will be described as an example, but the present invention is not limited to this, and a stacked structure of a p-type semiconductor layer and an n-type semiconductor layer can also be preferably used.) As shown in FIG. Furthermore, an intermediate layer may be provided between the anode 12 and the photoelectric conversion layer 13 and / or between the photoelectric conversion layer 13 and the cathode 14. As a preferred form of the intermediate layer, a hole transport layer is preferably laminated between the photoelectric conversion layer 13 and the anode 12, and an electron transport layer is preferably laminated between the photoelectric conversion layer 13 and the cathode 14. The present invention is characterized in that a cathode made of silver oxide and a reducing agent and an electron transport layer doped with an organic metal are coated and laminated in the vicinity of the cathode.

  The method for producing the organic thin film solar cell of the present invention will be described in detail with reference to FIG. An anode 22 is formed on a substrate 21, a hole transport layer 23, a photoelectric conversion layer 24 containing a p-type semiconductor and an n-type semiconductor material, and an electron transport layer 25 are sequentially stacked thereon, and a cathode is further formed thereon. It is preferable to form an organic thin film type solar cell by forming 26. The electron transport layer 23 may be a plurality of layers.

〔cathode〕
The cathode of the present invention is an electrode that plays a role of receiving electrons from a photoelectric conversion layer or an electron transport layer and flowing them to an external circuit. On the other hand, the anode refers to an electrode that plays the role of flowing holes to an external circuit opposite to the cathode.

  For the cathode, a metal having a small work function (less than 4.5 eV) is generally used in order to obtain an electrical connection with the photoelectric conversion layer or the electron transport layer, but such a metal is influenced by moisture in the atmosphere. Therefore, it is necessary to have an advanced sealing technique in which a moisture getter is packed, and a cathode having high durability against moisture has been demanded.

  On the other hand, when a metal having a large work function is used for the cathode, there is a problem that the durability is good but the connection with the electron transport layer is bad and the conversion efficiency is lowered, and it is difficult to achieve both the durability and the conversion efficiency. It was. On the other hand, the present inventors are characterized in that the cathode is formed from a coating solution containing at least a silver compound and a reducing agent, preferably the silver compound is a paste containing silver oxide fine particles, more preferably, It was found that by forming the cathode as a paste containing an organic silver compound, the silver compound can form an organic thin-film solar cell having excellent durability and excellent conversion efficiency.

  The cathode of the present invention is formed from a solution containing at least a silver compound and a reducing agent. Here, the silver compound is a solid particulate compound having the property of being reduced to metal silver in the presence of a reducing agent. Specific examples of the silver compound include organic silver compounds such as silver oxide, silver carbonate, silver formate, silver acetate, and propion silver, and these may be used in combination of two or more. As this silver compound, those produced industrially can be used as they are or after classification, and they can also be used after classification after pulverization. Moreover, you may use what was obtained by the liquid phase method and vapor phase method which are mentioned later.

  The average particle diameter of the silver compound is preferably in the range of 0.01 to 10 μm, and can be appropriately selected according to the reduction reaction conditions, for example, the heating temperature, the reducing power of the reducing agent, and the like. In particular, it is preferable to use a silver compound having an average particle diameter of 0.5 μm or less because the speed of the reduction reaction is increased.

  In addition, those having an average particle size of 0.5 μm or less are those produced by the reaction of a silver compound with another compound, for example, an aqueous solution of sodium nitrate or the like added dropwise to an aqueous solution of silver nitrate with stirring to cause oxidation. It can be produced by a liquid phase method for obtaining silver. In this case, it is desirable to add a dispersion stabilizer to the solution to prevent aggregation of the precipitated silver compound. In this liquid phase method, the particle diameter can be controlled by changing the silver compound concentration, the dispersion stabilizer concentration, and the like.

  In order to obtain a fine silver compound having an average particle size of 0.1 μm or less, a vapor phase method in which silver halide and oxygen are heated in a gas phase and thermally oxidized to synthesize silver oxide can be used. .

  The reducing agent used in the present invention reduces the above-mentioned silver compound, and it is preferable that the by-product after the reduction reaction is a gas or a highly volatile liquid and does not remain in the generated conductive film. . Specific examples of such a reducing agent include one or a mixture of two or more of ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol diacetate and the like.

  The reducing agent is used in an amount of 20 mol or less, preferably 0.5 to 10 mol, and more preferably about 1 to 5 mol with respect to 1 mol of the silver compound. Considering reaction efficiency and volatilization due to heating, it is desirable to add more than an equimolar amount, but even if it exceeds 20 mol at the maximum, the amount is wasted.

  In addition, a dispersion medium is used to disperse or dissolve the silver compound and the reducing agent to obtain a liquid conductive composition. As the dispersion medium, water, alcohols such as ethanol, ethanol and propanol, and organic solvents such as isophorone, terpineol, triethylene glycol monobutyl ether and butyl cellosolve acetate are used.

  Further, if the reducing agent is liquid and disperses the silver compound, the reducing agent can also serve as a dispersion medium, and examples thereof include ethylene glycol and diethylene glycol.

  The selection of the type of dispersion medium and the amount used vary depending on the silver compound and the film forming conditions, for example, screen printing mesh roughness and print pattern fineness, and are adjusted as appropriate so that optimum film formation can be achieved. The

  In the present invention, the cathode is preferably formed by printing an ink containing at least one or more of silver oxide and organic silver and a reducing agent.

  Moreover, it is preferable to add a dispersing agent to disperse a silver compound having an average particle size of 1 μm or less well and prevent secondary aggregation of the silver compound. Hydroxypropyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, etc. are used for this dispersing agent, and the usage-amount is 0-300 mass parts with respect to 100 mass parts of silver compounds.

  The coating solution used for forming the cathode of the present invention comprises at least the silver compound and reducing agent described above. The average particle diameter of the silver compound used here is not limited to a small one, and there is no particular problem as long as it is in the range of 0.01 to 10 μm, and the reduction reaction proceeds smoothly even with particles of 1 μm or more.

  Moreover, although the viscosity of this electroconductive composition changes with film forming conditions, about 30-300 poise is preferable, for example in the case of screen printing.

  The cathode of the present invention can be formed by simply heating the coating liquid described above after applying it by an appropriate means. The heating temperature is 150 to 200 ° C. due to the presence of the reducing agent, and the heating time is about 10 seconds to 120 minutes. Naturally, the surface of the object is kept clean.

  In the cathode of the present invention thus obtained, the silver compound is reduced, and the reduced metallic silver particles are fused together to form a continuous thin coating of metallic silver. When observed with a scanning electron microscope, it can be seen that the film is a continuous film of metallic silver. In order to form a good cathode with few voids on the surface, it is only necessary to appropriately control the heating temperature. It was found that a highly conductive cathode with few voids can be obtained by heating at about 120 to 150 ° C. .

For this reason, the volume resistivity of the cathode of the present invention shows a value ranging from 3 to 8 × 10 ⁻⁶ Ω · cm, which is on the same order as the volume resistivity of metallic silver.

  Furthermore, since the heating temperature for forming the cathode is sufficient at 120 to 150 ° C., it can be applied to an object such as a plastic film such as polyethylene terephthalate having low heat resistance, and a highly conductive cathode can be formed. At the same time, it does not cause thermal degradation of the object.

Furthermore, since the volume resistivity of the cathode of the present invention is extremely low, sufficient conductivity can be obtained even if the thickness is reduced. The thickness can be reduced by an amount corresponding to the decrease in volume resistivity with respect to the conventional conductive paste. For example, when a silver paste of 5 × 10 ⁻⁵ Ω · cm is used and the specification requires a cathode having a thickness of 50 μm, a volume resistivity of 3 × 10 ⁻⁶ Ω · cm is realized according to the present invention. Thus, the thickness can be 3 μm.

  In addition, in order to form a good cathode with few voids on the surface, the heating temperature may be controlled appropriately, and heating at about 120 to 150 ° C. can provide a highly conductive cathode with few voids. I understood.

(Electron transport layer)
The present invention is characterized in that at least one of the electron transport layers is a layer adjacent to the cathode and contains an organic alkali metal salt. By inserting an electron transport layer doped with an organic alkali metal salt between the photoelectric conversion layer and the cathode, electrical connection with the Ag electrode formed by coating is improved. As a result, the conversion efficiency (particularly the short-circuit current density Jsc and the fill factor FF) is improved. When light is irradiated, charge-up at the interface is suppressed, and as a result, deterioration of the organic material can be suppressed.

  There are no particular restrictions on the type of organic alkali metal salt, but formate, acetate, propionic acid, butyrate, valerate, capronate, enanthate, caprylate, oxalate, malonic acid Salt, succinate, benzoate, phthalate, isophthalate, terephthalate, salicylate, pyruvate, lactate, malate, adipate, mesylate, tosylate, benzenesulfone Acid salts, preferably formate, acetate, propionate, butyrate, valerate, caprate, enanthate, caprylate, oxalate, malonate, succinate, benzoate Preferred are alkali metal salts of aliphatic carboxylic acids such as acid salts, more preferably formate, acetate, propionate, butyrate, etc., and the number of carbon atoms of the aliphatic carboxylic acid is preferably 4 or less. Most preferred is acetate.

  The type of alkali metal of the organic alkali metal salt is not particularly limited, and examples thereof include Na, K, and Cs, preferably K, Cs, and more preferably Cs. Examples of the organic alkali metal salt include a combination of the organic substance and the alkali metal, and preferably Li formate, K formate, Na formate, C formate, Li acetate, K acetate, Na acetate, Cs, Li propionate, propion. Acid Na, propionic acid K, propionic acid Cs, oxalic acid Li, oxalic acid Na, oxalic acid K, oxalic acid Cs, malonic acid Li, malonic acid Na, malonic acid K, malonic acid Cs, succinic acid Li, succinic acid Na Succinic acid K, succinic acid Cs, benzoic acid Li, benzoic acid Na, benzoic acid K, benzoic acid Cs, more preferably acetic acid Li, acetic acid K, sodium acetate, acetic acid Cs, most preferably acetic acid Cs.

  Since the concentration of the organic alkali metal salt affects the life of the organic thin film solar cell, the content of the organic alkali metal salt is preferably 1.5 to 35% by mass with respect to the added electron transport layer. Yes, more preferably 3 to 25% by mass, and most preferably 5 to 15% by mass.

  Further, the electron transport layer is composed of a plurality of layers, and the electron transport layer on the cathode side is preferably higher in concentration of the organic alkali metal salt than the electron transport layer on the photoelectric conversion layer side, and the electron transport closest to the photoelectric conversion layer is performed. It is preferred that the layer does not contain an organic alkali metal salt.

  This is because when an organic alkali metal salt is doped throughout the electron transport layer, carriers (holes and electrons) are recombined at the doped site on the side close to the photoelectric conversion layer, which may lead to a decrease in conversion efficiency. The organic alkali metal salt has a concentration distribution, particularly in the vicinity of the cathode, and the concentration is high, and the photoelectric conversion layer side is as low as possible (0 is preferable), so that recombination is suppressed.

  From the same point of view, as a method of manufacturing an organic thin film solar cell, an electron transport layer that is not doped with an organic alkali metal salt is formed on a photoelectric conversion layer, and then a doped electron transport layer is formed, and then a cathode Is preferably formed.

  The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron extraction layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers. In the case of a single electron transport layer and multiple layers, the electron transport material used for the electron transport layer adjacent to the cathode side of the photoelectric conversion layer (also serves as a hole blocking material) is generated in the photoelectric conversion layer As long as it has a function of transmitting the generated electrons to the cathode, any material selected from known compounds such as those conventionally used in organic electroluminescence devices (OLEDs) should be used. For example, octaazaporphyrin, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid An n-type semiconductor material such as acid diimide can be used. A layer made of a single n-type semiconductor material used for the bulk heterojunction layer can also be used.

  Other examples include nitro-substituted fluorene derivatives, dibenzofuran derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of the oxadiazole ring is substituted with a sulfur atom, or a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

Metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq) ₃ , tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material.

  The electron transport layer can be formed by thinning the electron transport material by a known method such as a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a structure composed of one or more of the above materials in one layer.

  Further, an electron transport layer having a high n property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  Preferred examples of the electron transport material include the following structures.

  These compounds are disclosed in JP 2007-288035 A, Chem. Mater. , 2008, 20, 5951, Experimental Chemistry Course 5th Edition (Edited by the Chemical Society of Japan), etc.

〔substrate〕
The substrate is a member that holds the anode, the photoelectric conversion layer, and the cathode that are sequentially stacked. In the present embodiment, it is desirable that the substrate be transparent with respect to the wavelength of light to be photoelectrically converted so that light that is photoelectrically converted from at least the anode can enter. For example, a glass substrate, a resin substrate, and the like are preferably used, but it is desirable to use a transparent resin film from the viewpoint of lightness and flexibility.

  There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things. For example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~780nm), can be preferably applied to a transparent resin film according to the present invention. Among these, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy-adhesion layer in order to ensure the wettability and adhesion of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer. When the transparent resin film is a biaxially stretched polyethylene terephthalate film, by making the refractive index of the easy adhesion layer adjacent to the film 1.57-1.63, the interface reflection between the film substrate and the easy adhesion layer can be achieved. Since it can reduce and can improve the transmittance | permeability, it is more preferable. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion. Moreover, the barrier coat layer may be formed in advance on the transparent substrate, or the hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred.

〔anode〕
The anode 12 is preferably an electrode that transmits light having a wavelength of 300 to 800 nm. As materials, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires, carbon nanotubes, and conductive polymers are used. it can.

  In the bulk heterojunction organic thin film solar cell 10 shown in FIG. 1, the photoelectric conversion layer 13 is sandwiched between the anode 12 and the cathode 13, but a pair of comb-like electrodes is provided on one side of the photoelectric conversion layer 13. The back contact type organic thin film solar cell 10 may be configured to be disposed.

[Photoelectric conversion layer]
The photoelectric conversion layer 13 is a layer that converts light energy into electric energy, and preferably has a so-called bulk heterojunction structure in which a p-type semiconductor material and an n-type semiconductor material are uniformly mixed. The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which when electrons are absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which don't just donate or accept electrons like an electrode, but donate or accept electrons by photoreaction.

  Examples of the p-type semiconductor material used in the present invention include various condensed polycyclic aromatic compounds and conjugated polymers / oligomers.

  Examples of the condensed polycyclic aromatic low molecular compound include pentacene and derivatives thereof, porphyrin and phthalocyanine, copper phthalocyanine and derivatives thereof.

  Examples of the conjugated polymer include polythiophene such as poly-3-hexylthiophene (P3HT) and oligomers thereof, polythiophene-thienothiophene copolymer, polythiophene-diketopyrrolopyrrole copolymer, polythiophene-thiazolothiazole copolymer, Nature Mat. , Vol. 6 (2007), p497 described in PCPDTBT, etc., polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane.

  As the condensed polycyclic aromatic compound, for example, anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, sarkham anthracene, bisanthene, zestrene, heptazelene, Examples thereof include compounds such as pyranthrene, violanthene, isoviolanthene, cacobiphenyl, anthradithiophene, and derivatives and precursors thereof.

  Examples of the conjugated compound include polythiophene and its oligomer, polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, tetrathiafulvalene compound, quinone Compounds, cyano compounds such as tetracyanoquinodimethane, fullerenes and derivatives or mixtures thereof.

  In particular, among polythiophene and oligomers thereof, thiophene hexamer α-seccithiophene α, ω-dihexyl-α-sexualthiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3- An oligomer such as butoxypropyl) -α-sexithiophene can be preferably used.

  Other examples of the polymer p-type semiconductor include polyacetylene, polyparaphenylene, polypyrrole, polyparaphenylene sulfide, polythiophene, polyphenylene vinylene, polycarbazole, polyisothianaphthene, polyheptadiyne, polyquinoline, polyaniline, and the like. JP-A-2006-36755, etc., substituted-unsubstituted alternating copolymer polythiophene, JP-A-2007-51289, JP-A-2005-76030, J. Pat. Amer. Chem. Soc. , 2007, p4112, J.A. Amer. Chem. Soc. , 2007, p7246, etc., polymers having a condensed ring thiophene structure, WO2008 / 000664, Adv. Mater. , 2007, p4160, Macromolecules, 2007, Vol. Examples thereof include thiophene copolymers such as 40 and p1981.

  Furthermore, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF) -perchloric acid complex, BEDTTTF-iodine complex, TCNQ-iodine complex, etc. Organic molecular complexes, fullerenes such as C60, C70, C76, C78, and C84, carbon nanotubes such as SWNT, dyes such as merocyanine dyes and hemicyanine dyes, and σ-conjugated polymers such as polysilane and polygerman Organic / inorganic hybrid materials described in 2000-260999 can also be used.

  Among these π-conjugated materials, at least one selected from the group consisting of condensed polycyclic aromatic compounds such as pentacene, fullerenes, condensed ring tetracarboxylic acid diimides, metal phthalocyanines, and metal porphyrins is preferable. Further, pentacenes are more preferable.

  Examples of pentacenes include substituents described in International Publication No. 03/16599, International Publication No. 03/28125, US Pat. No. 6,690,029, Japanese Patent Application Laid-Open No. 2004-107216, and the like. A pentacene derivative described in U.S. Patent Application Publication No. 2003/136964 and the like; Amer. Chem. Soc. , Vol. 127. No. And substituted acenes described in 14.4986 and the like and derivatives thereof.

  Among these compounds, compounds that have high solubility in organic solvents to the extent that solution processing is possible, can form a crystalline thin film after drying, and can achieve high mobility are preferable. Such compounds include those described in J. Org. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. No. 9, 2706 and the like, acene-based compounds substituted with a trialkylsilylethynyl group, a pentacene precursor described in U.S. Patent Application Publication No. 2003/136964, etc., and Japanese Patent Application Laid-Open No. 2007-224019 Examples include precursor type compounds (precursors) such as porphyrin precursors. Since the precursor type becomes insoluble after conversion, the bulk heterojunction layer dissolves when a hole transport layer, electron transport layer, hole block layer, electron block layer, etc. are formed on the bulk heterojunction layer by a solution process. Therefore, the material constituting the layer and the material forming the bulk heterojunction layer are not mixed.

  Examples of n-type semiconductor materials include fullerene, octaazaporphyrin, p-type semiconductor perfluoro compounds (perfluoropentacene, perfluorophthalocyanine, etc.), naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic diimide, perylenetetracarboxylic acid Examples thereof include polymer compounds containing an anhydride, an aromatic carboxylic acid anhydride such as perylenetetracarboxylic acid diimide, or an imidized product thereof as a skeleton.

  Among these, fullerene-containing polymer compounds are preferable. Fullerene-containing polymer compounds include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), etc. Examples thereof include a polymer compound having a skeleton. As the fullerene-containing polymer compound, a polymer compound (derivative) having fullerene C60 as a skeleton is preferable.

  The fullerene-containing polymers are roughly classified into polymers in which fullerene is pendant from a polymer main chain and polymers in which fullerene is contained in the polymer main chain. Fullerene is contained in the polymer main chain. Are preferred. This is not because fullerene is contained in the main chain because the polymer does not have a branched structure, so that it can be packed with high density when solidified, resulting in high mobility. It is estimated that.

  As a method for forming a bulk heterojunction layer in which an electron acceptor and an electron donor are mixed, a coating method is particularly preferable.

  Then, the bulk heterojunction layer of the photoelectric conversion part is annealed at a predetermined temperature during the manufacturing process in order to improve the photoelectric conversion rate, and is partially crystallized microscopically.

  In organic thin-film solar cells, light incident from the anode through the substrate is absorbed by the electron acceptor or electron donor in the bulk heterojunction structure of the photoelectric conversion layer, and electrons move from the electron donor to the electron acceptor. A hole-electron pair (charge separation state) is formed. The generated electric charge differs depending on the internal electric field, for example, when the work functions of the anode and the cathode are different, the electrons pass between the electron acceptors and the holes pass between the electron donors due to the potential difference between the anode and the cathode. It is carried to the electrode and the photocurrent is detected. For example, when the work function of the anode is greater than that of the cathode, electrons are transported to the anode and holes are transported to the cathode. If the magnitude of the work function is reversed, electrons and holes are transported in the opposite direction. In addition, the transport direction of electrons and holes can be controlled by applying a potential between the anode and the cathode.

  The photoelectric conversion unit may be composed of a single layer in which an electron acceptor and an electron donor are uniformly mixed, or may be composed of a plurality of layers in which the mixing ratio of the electron acceptor and the electron donor is changed. Good.

  As a method of forming a bulk heterojunction layer in which an electron acceptor and an electron donor are mixed, in order to increase the area of the interface where the hole and electron are separated, the device having high photoelectric conversion efficiency is manufactured. A coating method is preferred. After application, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and chemical reaction of the semiconductor material as described above.

[Middle layer]
Further, the above-described bulk heterojunction type organic thin film solar cell is composed of an anode sequentially stacked on a substrate, a photoelectric conversion part of a bulk heterojunction layer, and a cathode, but is not limited thereto. Bulk heterojunction type organic thin-film solar cells are constructed with other layers such as hole transport layer, electron transport layer, hole block layer, electron block layer, or smoothing layer between the photoelectric conversion part. May be. Among these, a hole transport layer or an electron blocking layer is intermediate between the bulk heterojunction layer and the anode (usually the anode side), and an electron transport layer or hole blocking layer is intermediate between the cathode (usually the cathode side). Since it becomes possible to take out the electric charges generated in the bulk heterojunction layer more efficiently, it is preferable to have these layers.

(Hole transport layer)
Examples of the material preferably used as the hole transport layer (electron block layer) include PEDOT such as trade name BaytronP, polyaniline and its doped material, triarylamine described in JP-A-5-271166, etc. Further, cyanide compounds described in WO 2006/019270 pamphlet and the like, metal oxides such as molybdenum oxide, nickel oxide, and tungsten oxide can be used. A layer made of a single p-type semiconductor material used for the bulk heterojunction layer can also be used. The means for forming these layers is preferably formed by a solution coating method.

[Tandem configuration]
It is good also as a tandem-type structure which laminated | stacked the organic thin film type solar cell for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency). In the case of the tandem type configuration, the anode, the first photoelectric conversion unit are sequentially stacked on the substrate, the charge recombination layer is stacked, the second photoelectric conversion unit, and then the cathode are stacked to form a tandem type. It can be set as this structure. The second photoelectric conversion unit may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion unit, or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. The material of the charge recombination layer is preferably a layer using a compound having both transparency and conductivity, such as transparent metal oxides such as ITO, AZO, FTO, and titanium oxide, Ag, Al, Au, etc. A very thin metal layer, a conductive polymer material such as PEDOT: PSS, polyaniline, and the like are preferable.

[Sealing]
Moreover, it is preferable to seal by the well-known method so that the produced organic thin-film solar cell does not deteriorate with oxygen, moisture, etc. in the environment. For example, a method of sealing a cap made of aluminum or glass by bonding with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide or aluminum oxide is formed and an organic thin film solar cell with an adhesive. A method of bonding, a method of spin-coating an organic polymer material with high gas barrier properties (polyvinyl alcohol, etc.), a method of directly depositing an inorganic thin film with high gas barrier properties (silicon oxide, aluminum oxide, etc.), and a combination of these The method of laminating can be mentioned.

  Furthermore, the structure which seals with the form which packed the getter with respect to the water | moisture content which permeate | transmitted the barrier layer can also be used preferably in this invention.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the aspect of this invention is not limited to these.

Example << Preparation of Organic Thin Film Solar Cell SC-101 >>
[Formation of anode]
On a polyethylene naphthalate (PEN) film with a barrier (the barrier layer is formed on the CHC-PEN by a CVD method), a 140 nm thick ITO (indium tin oxide) film is formed by a sputtering method under vacuum environment conditions ( Sheet resistance 12Ω / □), normal photolithography technology and hydrochloric acid etching were used to form 5 rows of anodes having a size of 10 mm × 100 mm at regular intervals.

  The patterned anode was cleaned in the order of ultrasonic cleaning with a surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, followed by drying with a nitrogen flow, and finally ultraviolet ozone cleaning.

(Formation of hole transport layer)
A hole transporting layer obtained by diluting polyethylenedioxythiophene / polystyrenesulfonate (PEDOT / PSS, CLEVIUS P AI 4083, manufactured by HC Starck Co., Ltd.) with 40% by mass of pure water 30% by mass and isopropanol 30% by mass. As a forming coating solution, it was applied on the PEN substrate including the anode. Coating is performed by using a slit coater to form a film so that the liquid thickness is about 30 μm and the thickness after drying is 50 to 70 nm, and patterning is performed by bringing the wiping member into contact with the anode so as to have the same shape as the anode. Subsequently, the hole transport layer was formed by drying and heat treatment in the atmosphere at 150 ° C. for 30 minutes.

[Formation of photoelectric conversion layer]
The substrate was moved to a nitrogen atmosphere with a moisture concentration of 1 ppm, and P3HT (Plextronics: regioregular poly-3-hexylthiophene) and PCBM (Frontier Carbon: 6,6) were added to chlorobenzene on the hole transport layer. 6-phenyl _{-C 61} - the butyric acid methyl ester) 1: mixed solution was prepared in 0.8, using a slit coater, a liquid thickness of about 30 [mu] m, the film thickness after drying becomes 180~200nm Application was performed as described above, and the film was allowed to stand at room temperature and dried to form a photoelectric conversion layer.

(Formation of electron transport layer)
Next, the substrate is moved to the atmosphere, a solution in which Ti-isopropoxide is dissolved in dehydrated methanol so as to be 0.02 mol / L is prepared, and the film is applied to a thickness of 10 nm. The electron transport layer was formed by allowing to stand.

  Patterning was performed by wiping the photoelectric conversion layer and the electron transport layer applied on the anode in contact with a wiping member to form a photoelectric conversion layer and an electron transport layer.

[Formation of cathode]
The prepared sample was transported to a vacuum deposition chamber, and under a vacuum condition where the pressure was reduced to 5 × 10 ⁻⁴ Pa, a mask pattern was passed by a vacuum deposition method to form a cathode made of aluminum having a thickness of 100 nm. The mask pattern was formed such that five rows of elements were connected in series (5 series) on the long side (100 mm side).

[Pasting of sealing member]
Next, the manufactured element was moved to a nitrogen environment having a moisture concentration of 1 ppm or less, and the leftmost first electrode connected in series in five rows (region where the organic layer was removed by patterning), the rightmost first Except for the lead part connected to the electrode of 2, a thermosetting liquid adhesive (epoxy resin) is dropped from a plurality of nozzles onto the inner area and coated with a thickness of 30 μm, and an aluminum foil with a thickness of 100 μm Were laminated by a roll laminating method (pressing about 0.1 MPa) and heat-treated at 150 ° C. for 30 minutes to cure and seal the adhesive.

  An organic thin film solar cell SC-101 was produced by the series of production methods described above.

<< Preparation of Organic Thin Film Solar Cell SC-102 >>
In the production of the organic thin film type solar cell SC-101, an organic thin film type solar cell SC-102 was produced in the same manner except that the cathode was produced as follows.

[Formation of cathode]
Using a slit coater coated in a strip shape on the sample formed up to the electron transport layer in the same manner as the organic thin film solar cell SC-101, a polyethylenedioxythiophene / polystyrenesulfonate aqueous dispersion (PEDOT / PSS, H C. CLEVIOS PH510 manufactured by C. Starck Co., Ltd. was applied to a solution in which 10% by mass of isopropanol and 7% by mass of DMSO were mixed with 83% by mass so as to have the same shape as the above-described cathode pattern. Then, a heat treatment was performed for 15 minutes to form a cathode made of a conductive polymer having a dry film thickness of about 280 to 300 nm. Subsequently, the substrate was moved under a nitrogen atmosphere having a moisture concentration of 1 ppm or less and dried at 150 ° C. for 20 minutes.

<< Preparation of Organic Thin Film Type Solar Cell SC-103 >>
In the production of the organic thin film type solar cell SC-102, an organic thin film type solar cell SC-103 was produced in the same manner except that the electron transport layer and the cathode were produced as follows.

(Formation of electron transport layer)
Following the photoelectric conversion layer, in a nitrogen atmosphere with a moisture concentration of 1 ppm or less, 1.0 mass of ET-A was added to a liquid in which 70 mass% of dehydrated tetrafluoropropanol (TFPO) and 30 mass% of n-butanol were mixed. %, And an electron transport layer having a dry film thickness of 20 nm was formed by applying a slit coater.

  The photoelectric conversion layer and the electron transport layer were patterned by wiping the photoelectric conversion layer and the electron transport layer in contact with the wiping member in the same manner as in the organic thin film solar cell SC-101, thereby forming the photoelectric conversion layer and the electron transport layer.

[Formation of cathode]
In 200 ml of ultrapure water (18 MΩ · cm), 0.6 g of silver nitrate was dissolved, 0.3 g of hydroxymethylcellulose was added, and the liquid temperature was kept at 10 ° C. After adding 10 ml of 0.2M sodium hydroxide aqueous solution at a high speed with vigorous stirring, the stirring speed is lowered, the liquid temperature is increased to 40 ° C. over 10 minutes, and the mixture is stirred as it is for 20 minutes to give a silver oxide suspension. Got.

  The prepared suspension was concentrated to 50 ml using an ultrafiltration device, and then diluted by adding 150 ml of a methanol: water = 1: 1 solution. The above concentration-dilution was repeated 3 times to wash the solution, and then concentrated to 75 ml. Subsequently, 3 g of ethylene glycol was added as a reducing agent to prepare a silver compound paste.

  The above prepared paste was applied in the air using a 250 mesh-tetron plate (emulsion thickness 10 μm) in the same shape as the cathode pattern described above by screen printing, and heat-treated at 150 ° C. for 30 minutes, A cathode made of coated silver having a thickness of about 2 μm was formed. Subsequently, the substrate was moved under a nitrogen atmosphere having a moisture concentration of 1 ppm or less and dried at 150 ° C. for 20 minutes.

<< Production of Organic Thin Film Solar Cell SC-104 >>
In the production of the organic thin film type solar cell SC-103, an organic thin film type solar cell SC-104 was produced in the same manner except that the electron transport layer was produced as follows.

(Formation of electron transport layer)
Following the photoelectric conversion layer, in a nitrogen atmosphere with a moisture concentration of 1 ppm or less, 1.0 mass of ET-A was added to a liquid in which 70 mass% of dehydrated tetrafluoropropanol (TFPO) and 30 mass% of n-butanol were mixed. %, CH ₃ COOCs as an organic alkali metal salt was dissolved so as to be 0.1% by mass, and an electron transport layer having a dry film thickness of 20 nm was formed by applying a slit coater.

  The photoelectric conversion layer and the electron transport layer were patterned by wiping the photoelectric conversion layer and the electron transport layer in contact with the wiping member in the same manner as in the organic thin film solar cell SC-101, thereby forming the photoelectric conversion layer and the electron transport layer.

<< Preparation of Organic Thin Film Type Solar Cell SC-105 >>
In the production of the organic thin film type solar cell SC-104, an organic thin film type solar cell SC-105 was produced in the same manner except that the cathode was produced as follows.

[Formation of second electrode (cathode)]
In 200 ml of ultrapure water (18 MΩ · cm), 0.6 g of silver nitrate was dissolved, 0.3 g of hydroxymethylcellulose was added, and the liquid temperature was kept at 10 ° C. After adding 10 ml of 0.2M sodium hydroxide aqueous solution at a high speed with vigorous stirring, the stirring speed is lowered, the liquid temperature is increased to 40 ° C. over 10 minutes, and the mixture is stirred as it is for 20 minutes to give a silver oxide suspension. Got. The prepared suspension was concentrated to 50 ml using an ultrafiltration apparatus, and then diluted by adding 150 ml of a methanol: water = 1: 1 solution. The above concentration-dilution was repeated 3 times to wash the solution.

  In a separately prepared container, a solution obtained by dissolving 4.2 g of terephthalic acid in 50 ml of methanol was vigorously stirred, and an aqueous solution obtained by dissolving 1.0 g of sodium hydroxide in 50 ml of ultrapure water was slowly added. Subsequently, an aqueous solution in which 5.0 g of silver nitrate was dissolved in 50 ml of ultrapure water was added, and the mixture was stirred for 20 minutes to obtain a suspension composed of organic silver. This suspension was concentrated to 50 ml using an ultrafiltration apparatus, and then diluted by adding 150 ml of a methanol: water = 1: 1 solution. The above concentration-dilution was repeated 3 times to wash the solution, followed by filtration to obtain silver terephthalate.

  After adding 2.5 g of silver terephthalate to the silver oxide dispersion prepared above, it was concentrated to 75 ml using an ultrafiltration device.

  Subsequently, 3 g of ethanolamine and 3 g of ethylene glycol were added to prepare a silver compound paste containing organic silver and silver oxide.

  The prepared paste was applied using a 250 mesh-tetron plate (emulsion thickness 10 μm) so as to have the same shape as the cathode pattern described above by screen printing, and heat-treated at 150 ° C. for 60 minutes to obtain a thickness of about A second electrode (cathode) made of 2 μm coated silver was formed. Subsequently, the substrate was moved under a nitrogen atmosphere having a moisture concentration of 1 ppm or less and dried at 150 ° C. for 20 minutes.

<< Preparation of Organic Thin Film Type Solar Cell SC-106 >>
In the production of the organic thin film type solar cell SC-105, an organic thin film type solar cell SC-106 was produced in the same manner except that the electron transport layer was produced as follows.

(Formation of electron transport layer)
Following the photoelectric conversion layer, in a nitrogen atmosphere with a moisture concentration of 1 ppm or less, 1.0 mass of ET-A was added to a liquid in which 70 mass% of dehydrated tetrafluoropropanol (TFPO) and 30 mass% of n-butanol were mixed. %, HCOOCs as an organic alkali metal salt were dissolved so as to be 0.13% by mass, and an electron transport layer having a dry film thickness of 20 nm was formed by applying a slit coater.

  The photoelectric conversion layer and the electron transport layer were patterned by wiping the photoelectric conversion layer and the electron transport layer in contact with the wiping member in the same manner as in the organic thin film solar cell SC-101 to form the photoelectric conversion layer and the electron transport layer.

<< Preparation of Organic Thin Film Type Solar Cell SC-107 >>
In the production of the organic thin film type solar cell SC-105, an organic thin film type solar cell SC-107 was produced in the same manner except that the electron transport layer had a two-layer laminated structure and was produced as follows.

(Formation of electron transport layer)
Following the photoelectric conversion layer, in a nitrogen atmosphere having a moisture concentration of 1 ppm or less, 1.0% of the material of Chemical 2 is added to a liquid in which 70% by mass of dehydrated tetrafluoropropanol (TFPO) and 30% by mass of n-butanol are mixed. The electron transport layer 1 having a dry film thickness of 20 nm was formed by dissolving CH ₃ COOCs as an organic alkali metal salt in an amount of 0.05% by mass and applying a slit coater.

Subsequently, 1.0% by mass of ET-A and 0.15% by mass of CH ₃ COOCs as an organic alkali metal salt are dissolved in dehydrated tetrafluoropropanol (TFPO), and dried by applying a slit coater. An electron transport layer 2 having a thickness of 20 nm was formed.

  Using an X-ray photoelectron spectrometer (XPS), the Cs atom distribution in the stacked film of the electron transport layer 1 and the electron transport layer 2 separately prepared in the same manner as described above was confirmed. As a result, it was a stacked structure with different Cs concentrations. .

<< Production of Organic Thin Film Solar Cell SC-108 >>
In the production of the organic thin film type solar cell SC-107, an organic thin film type solar cell SC-108 was produced in the same manner except that the electron transport layer was produced as follows.

(Formation of electron transport layer)
Following the photoelectric conversion layer, in a nitrogen atmosphere having a moisture concentration of 1 ppm or less, 1.0% of the material of Chemical 2 is added to a liquid in which 70% by mass of dehydrated tetrafluoropropanol (TFPO) and 30% by mass of n-butanol are mixed. It melt | dissolved so that it might become mass%, and the electron carrying layer 1 with a dry film thickness of 20 nm was formed into a film by apply | coating a slit coater.

Subsequently, by dissolving ET-A in dehydrated tetrafluoropropanol (TFPO) at 1.0 mass% and CH ₃ COOCs as an organic alkali metal salt at 0.15 mass%, and applying a slit coater, An electron transport layer 2 having a dry film thickness of 20 nm was formed.

  Using an X-ray photoelectron spectrometer (XPS), the Cs atom distribution of the stacked film of the electron transport layer 1 and the electron transport layer 2 separately prepared in the same manner as described above was confirmed. There was a region in which Cs atoms could not be confirmed (a Cs atom diffusion region was observed about 10 nm from the interface between the electron transport layer 1 and the electron transport layer 2 to the electron transport layer 1 side).

<< Evaluation of organic thin film solar cells >>
[Energy conversion efficiency]
About the produced organic thin film type solar cell, using a solar simulator, irradiating light with an intensity of AM 1.5G filter and 100 mW / cm ² , evaluating the IV characteristic, and as a characteristic value, a short-circuit current density Jsc (mA / Cm ² ), open circuit voltage Voc (V), and fill factor ff, energy conversion efficiency η (%) was obtained using Equation 1. The energy conversion efficiency is expressed as a relative value where the energy conversion efficiency of the organic thin film solar cell SC-101 is 100. In addition, the short circuit current density was normalized and calculated with the area equivalent to the effective power generation part of an organic solar cell panel.

Formula 1 η (%) = Jsc (mA / cm ² ) × Voc (V) × ff
[Light and heat durability]
The organic thin-film solar cell produced above was irradiated with light from a metal halogen lamp light source for 1000 hours in an environment of 65 ° C. so that the radiation intensity was 150 mW / cm ^2. Evaluation was performed in the same manner, and a retention rate (%) serving as an index of durability was calculated according to Equation 2.

Formula 2 Retention rate (%) = (energy conversion efficiency after light irradiation) / (energy conversion efficiency before light irradiation) × 100
The evaluation results are shown in Table 1.

  From Table 1, the organic thin-film solar cell of the present invention is superior in energy conversion efficiency while being produced by a process that can be formed on a flexible substrate, with respect to SC-101 having a cathode formed by a conventional vapor deposition method. It is clear that it is excellent in durability against light irradiation.

  In particular, in the organic thin film type solar cell SC-104, the organic electron transport layer is doped with Cs acetate, and the cathode is made of a silver oxide paste. Obviously, it is excellent in energy conversion efficiency and durability against light irradiation. Further, by using the cathode second electrode in combination of silver oxide and organic silver, higher durability is obtained as seen in the organic thin film solar cell SC-105.

  In the organic thin film type solar cell SC-107, the energy conversion efficiency and the durability against light irradiation are greatly improved by adopting a laminated structure of electron transport layers having different amounts of doped Cs acetate, and particularly adjacent to the photoelectric conversion layer. It turned out that the high effect of this invention is acquired by setting it as the structure in which an electron carrying layer does not contain acetic acid Cs, as seen in organic thin-film solar cell SC-108.

11 Substrate 12 Anode (Anode)
13 Photoelectric conversion layer 14 Cathode (cathode)
21 Substrate 22 Anode (Anode)
23 hole transport layer 24 photoelectric conversion layer 25 electron transport layer 26 cathode (cathode)

Claims (8)

  An organic thin film solar cell having at least an anode, a photoelectric conversion layer, an electron transport layer and a cathode on a substrate, wherein the cathode is formed from a coating solution containing at least a silver compound and a reducing agent, and the electron transport layer At least one layer is a layer adjacent to the cathode, and contains an organic alkali metal salt.   2. The organic thin film solar cell according to claim 1, wherein the silver compound is a paste containing silver oxide fine particles.   The organic thin-film solar cell according to claim 2, wherein the silver compound is a paste further containing an organic silver compound.   The organic thin film solar cell according to any one of claims 1 to 3, wherein the organic alkali metal salt is an alkali metal salt of an aliphatic carboxylic acid.   The electron transport layer comprises a plurality of layers, and the electron transport layer on the cathode side has a higher concentration of the organic alkali metal salt than the electron transport layer on the photoelectric conversion layer side. 2. The organic thin film type solar cell according to item 1.   6. The organic thin film solar cell according to claim 5, wherein the electron transport layer closest to the photoelectric conversion layer does not contain an organic alkali metal salt.   A method for producing an organic thin film solar cell in which at least an anode, a photoelectric conversion layer, an electron transport layer, and a cathode are laminated on a substrate, wherein the cathode is reduced to at least one or more of silver oxide and organic silver. And a solution containing a charge transport material doped with an organic alkali metal salt, wherein the electron transport layer is at least between the photoelectric conversion layer and the cathode. A method for producing an organic thin-film solar cell, characterized by being formed by applying   8. The organic thin film solar cell according to claim 7, wherein a layer not doped with an organic alkali metal salt is formed on the photoelectric conversion layer, a doped layer is formed, and then a cathode is formed. Manufacturing method.

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