JP2010050159A - Organic power generation element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic power generation element having high conversion efficiency from light to electricity. <P>SOLUTION: An organic power generation element includes a power generation layer 4 formed by mixing an electron-donative semiconductor and a hole-donative semiconductor, between electrodes 2 and 6 at least one of which is transparent to external light. The surface of the power generation layer 4 has a mean square roughness of 2 nm or less, and the variation in film thickness of the whole power generation layer 4 is within ±10%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic power generation element (organic solar battery) that generates electricity upon receiving light.

  With the development of industry, the amount of energy used has increased dramatically. Under these circumstances, development of economical and high-performance new clean energy production technology that does not burden the global environment is required. Solar cells are attracting attention as a new energy source because they use sunlight, which can be said to be infinite.

  Most of the solar cells currently in practical use are inorganic solar cells using single crystal silicon, polycrystalline silicon, or amorphous silicon. However, these inorganic silicon solar cells have the disadvantages that their manufacturing process is complicated and expensive, so they have not been widely used in general households. In order to eliminate such drawbacks, research on organic solar cells (organic power generation elements) using organic materials, which can reduce costs and increase the area by a simple process, has been actively conducted.

  Among the types of organic solar cells (organic power generation elements), in recent years, Professor Gratzel of Lausanne University of Technology, Switzerland, proposed dye sensitization based on photochemical reaction using porous titanium oxide, ruthenium dye, iodine and iodine ion. It has been announced that type solar cells have a high conversion efficiency of 10% (B. O 'Regan, M. Gratzel, Nature, 353, 737 (1991)).

  On the other hand, organic thin-film solar cells, which are classified as other types of organic solar cells, are low-evaporation materials formed by vacuum deposition using low-molecular-weight electron-donating materials (donors) and electron-accepting materials (acceptors). It has been reported that a conversion efficiency of 3.6% was obtained for molecular organic thin-film solar cells (P. Peumans and SR Forrest, Appl. Phys. Lett. 79, 126 (2001)).

  Studies are also underway on the use of polymer materials as materials for the power generation layer formed in organic power generation elements. This can be expected to further reduce the cost because it does not use a costly vacuum deposition method for forming the power generation layer.

  In recent years, it has been reported that a conversion efficiency of 5.5% is obtained in an organic solar battery of a type in which a power generation layer is formed of a mixed film of a conjugated polymer and a fullerene derivative (Non-patent Document 1). Various research institutes have been devised and studied to obtain highly efficient organic power generation elements.

In other words, in order to further increase the efficiency, for example, after forming an organic solar cell, it is heated moderately to realize a rearrangement of the conjugated polymer and an appropriate mixed state of the hole transport material and the electron transport material. , A method for improving charge separation (Non-Patent Document 2), a method for improving efficiency by performing low-speed drying called solvent annealing when forming a power generation layer, and utilizing the microphase separation phenomenon of the power generation material ( Non-Patent Document 3) In forming a power generation layer by dissolving a power generation material in a solvent and applying it, the solubility of the power generation material is improved using a mixed solvent in which two types of solvents are mixed in equal amounts. A method (Non-Patent Document 4) for improving the efficiency is proposed.
J. Peet et al., Nature Mater. 6, 497 (2007). WL Ma et al., Adv. Funct. Mater., 15, 1617 (2005). G. Li et al., Adv. Funct. Mater., 17,1636 (2007). SH Jin et al., Sol. Energy Mater. Sol. Cells, 91, 1187 (2007).

  As described above, when forming a power generation layer by dissolving a power generation material in a solvent and applying it, it has been studied to increase the efficiency of the organic power generation element by changing the solvent. However, a power generation layer made using a single solvent with a high boiling point or a power generation layer formed using a mixed solvent in which two types of solvents are mixed in equal amounts have large surface irregularities and form a power generation layer. Since the wettability with the lower layer (for example, hole transport layer) is poor, the film surface of the power generation layer becomes non-uniform and the film thickness tends to vary greatly, and has a large power generation area. In the case of obtaining an organic power generation element, there are problems such as reduced efficiency and variations in characteristics.

  The present invention has been made in view of the above points, and aims to provide an organic power generation element with high conversion efficiency. Further, the power generation layer can be formed flat and with a uniform thickness. An object of the present invention is to provide an organic power generation element.

  An organic power generation element according to the present invention includes a power generation layer formed by mixing an electron donating semiconductor and a hole donating semiconductor, at least one of which is between electrodes that are transparent to external light. The surface average square roughness of the surface of the power generation layer is 2 nm or less, and the variation in the film thickness of the power generation layer is within ± 10% for the entire power generation layer.

  Thus, the surface mean square roughness of the surface of the power generation layer is 2 nm or less, the surface flatness of the power generation layer is high, and the variation in the film thickness of the power generation layer is within ± 10%. The film thickness is highly uniform and the conversion efficiency can be increased.

  In the present invention, the power generation layer is formed by applying a mixed solvent in which an electron-donating semiconductor and a hole-donating semiconductor are dissolved, and the mixed solvent is composed of a main solvent and the main solvent. It consists of an additive solvent whose vapor pressure is two orders of magnitude higher, and the volume ratio of the main solvent and the additive solvent is in the relationship of main solvent> added solvent.

  By using such a mixed solvent composed of the main solvent and the additive solvent, wettability can be improved, and a power generation layer with high surface flatness and high film thickness uniformity can be formed as described above. Is.

  ADVANTAGE OF THE INVENTION According to this invention, an electric power generation layer can be formed in flat and uniform thickness, and an organic electric power generation element with high conversion efficiency can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described.

  An example of the layer structure of the organic power generation element (organic solar cell) according to the present invention is shown in FIG. On the substrate 1, a positive electrode 2, a hole transport layer 3, a power generation layer 4, an electron transport layer 5, and a negative electrode 6 are laminated in this order, and a positive electrode layer 2, a hole transport layer 3, a power generation layer 4, The surfaces of the electron transport layer 5 and the negative electrode layer 6 are covered with the surface protective layer 7 so that they are not exposed to the outside. At least one of the pair of electrodes 2 and 6 sandwiching the power generation layer 4 is formed as a transparent electrode so that extraneous light is introduced into the power generation layer 4. In the embodiment of FIG. 1, the substrate 1 is formed of a transparent plate and the positive electrode 2 is formed of a transparent electrode so that extraneous light is introduced into the power generation layer 4 through the substrate 1 and the positive electrode 2.

  In the present invention, the power generation layer 4 is formed such that the surface mean square roughness of the surface of the power generation layer 4 is 2 nm or less and the variation in the film thickness of the power generation layer 4 is within ± 10%. It is. In this way, by forming the surface of the power generation layer 4 on a flat surface and forming the film thickness of the power generation layer 4 uniformly, the contact with the adjacent hole transport layer 3 and electron transport layer 5 becomes uniform. A highly efficient organic power generation element can be realized. If the surface mean square roughness of the surface of the power generation layer 4 exceeds 2 nm, and if the variation in the film thickness of the power generation layer exceeds the range of ± 10%, the efficiency may decrease and the variation in characteristics may increase. . The smaller the variation of the surface mean square roughness and the film thickness, the better. Therefore, the lower limit is not particularly set.

  Here, in the present invention, the surface mean square roughness is a value that determines the roughness of the surface by averaging the square of the deviation from the average value of the in-plane film thickness to the measured film thickness and taking the square root. Rms. The variation in film thickness of ± 10% means 10% above and below the average value of the in-plane film thickness.

  In the organic compound used for the power generation layer 4 that contributes to this power generation, the electron-donating semiconductor includes phthalocyanine pigments, indigo, thioindigo pigments, quinacridone pigments, merocyanine compounds, cyanine compounds, squalium compounds, polycyclic aromatic compounds, Examples of the charge transfer agent used in the organic electrophotographic photosensitive member, an electrically conductive organic charge transfer complex, and a conductive polymer may also be used. is not.

  As the phthalocyanine pigments, halogen atoms such as divalent pigments such as Cu, Zn, Co, Ni, Pb, Pt, Fe, Mg, metal-free phthalocyanine, aluminum chlorophthalocyanine, indium chlorophthalocyanine, gallium chlorophthalocyanine, etc. Although there are phthalocyanines coordinated with oxygen, such as trivalent metal phthalocyanine coordinated with, and other baanadyl phthalocyanine, titanyl phthalocyanine, etc., it is not particularly limited thereto.

  Examples of the polycyclic aromatic compound include anthracene, tetracene, pentacene, and derivatives thereof, but are not particularly limited thereto.

  Examples of the charge transfer agent include hydrazone compounds, pyrazoline compounds, triphenylmethane compounds, and triphenylamine compounds, but are not particularly limited thereto.

  Examples of the electroconductive organic charge transfer complex include tetrathiofulvalene and tetraphenyltetrathioflavalene, but are not particularly limited thereto.

  Examples of the conductive polymer that donates electrons include those that are soluble in organic solvents such as poly (3-alkylthiophene), polyparaphenylene vinylene derivatives, polyfluorene derivatives, thiophene polymers, and conductive polymer oligomers. However, the present invention is not limited to this.

In addition, as a hole-donating semiconductor that is a material that transmits and receives electrons, a compound semiconductor can be given, and in particular, a compound semiconductor nanocrystal can be used. Here, the nanocrystal means one having a size of 1 to 100 nm. The shape of the nanocrystal includes a rod shape, a spherical shape, and a tetrapod shape. Specific materials include III-V compound semiconductor crystals such as InP, InAs, GaP, and GaAs, II-VI compound semiconductor crystals such as CdSe, CdS, CdTe, and ZnS, ZnO, SiO ₂ , TiO ₂ , and Al _2. Examples thereof include oxide semiconductor crystals such as O ₃ , CuInSe ₂ , and CuInS, but are not particularly limited thereto. The compound semiconductor may be formed in a comb shape in contact with the electron transport layer 5. In this case, it is preferable that the diameter is 1 to 100 nm and the distance is 200 nm at maximum. As long as you can receive and transport, it is not limited to this size. Moreover, as long as it is a material which transports electrons, not only these compound semiconductors but also low molecular materials, conductive polymers, carbon nanotubes, and the like made of fullerene derivatives containing high-order fullerenes such as C60, C70, and C84 are used. You can also.

  Regardless of whether each of the above materials is a high molecular material or a low molecular material, any material can be used as long as it can form the power generation layer 4 by being dissolved in a solvent and applied. .

  The power generation layer 4 can be formed by dissolving these materials in a mixed solvent and coating the solution on the hole transport layer 3 (or the electron transport layer 5). In the present invention, the mixed solvent is composed of a main solvent and an additive solvent whose vapor pressure is two orders of magnitude or more higher than the main solvent, and the volume ratio of the main solvent in the mixed solvent is higher than the volume ratio of the additive solvent. Those having a high relationship (main solvent> added solvent) are used.

  Here, the additive solvent whose vapor pressure is two orders of magnitude higher than that of the main solvent means that the vapor pressure of the additive solvent is 100 times or more the vapor pressure of the main solvent, and in particular, 100 times to 999 times. The degree is particularly preferred. Moreover, if the volume ratio of the main solvent in a mixed solvent is higher than the volume ratio of an addition solvent, it will not specifically limit, but a main solvent and an addition solvent are 5.5: 4.5-9.5: 0. It is preferable to use a mixture in a volume ratio range of 5.

  By using such a mixed solvent, when applying a solution in which the material for forming the power generation layer 4 is dissolved, the added solvent has an effect of lowering the surface tension of the main solvent. The wettability with the hole transport layer 3 can be improved, and the surface of the power generation layer 4 can be formed flat and with a uniform film thickness as described above. Further, since the added solvent has a high vapor pressure, it volatilizes immediately when the power generation layer 4 is formed, and does not remain in the power generation layer 4. For this reason, it can reduce that the carrier (hole or electron) which generate | occur | produced in the electric power generation layer 4 receiving light receives a charge trap by a residual impurity, and the electric power generation efficiency of an organic electric power generation element, especially the short circuit current value converted from light It will improve.

  The solvent used as the main solvent or additive solvent in the present invention is not particularly limited, but 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, chlorobenzene, chloroform, xylene, toluene, 1-chloro Organic solvents such as naphthalene, acetone, isopropyl alcohol, ethanol, methanol, cyclohexane and the like can be mentioned. From the vapor pressure, they can be used in combination as a main solvent and an additional solvent as appropriate. For example, a combination of 1,2-dichlorobenzene (vapor pressure: 160 Pa (20 ° C.)) as the main solvent and chloroform (vapor pressure: 21.2 kPa (20 ° C.)) as the added solvent can be cited. There is a difference of two or more digits, and the volume ratio of the mixture only needs to be in the relationship of main solvent> added solvent, and the combination of the solvents is not limited to this. Even if a plurality of solvents are used as the main solvent or a plurality of solvents are used as the additive solvent, there is no particular limitation as long as the relationship between the vapor pressure and the volume ratio of mixing is as described above.

  In addition, when dissolving the above-mentioned materials forming the power generation layer in the mixed solvent, for example, the procedure of adding the added solvent after dissolving in the main solvent, or conversely, adding the main solvent after dissolving in the added solvent There is a procedure, such as mixing the main solvent and the added solvent and then dissolving them, but it is sufficient if the material that forms the power generation layer is finally dissolved in the mixed solvent of the main solvent and the added solvent. Is not limited to this.

  A method for forming the power generation layer 4 by applying a solution in which a material for forming the power generation layer is dissolved in a mixed solvent is not particularly limited, but includes a spin coating method, a dip coating method, a die coating method, a gravure printing method, and the like. There are a method of forming a film by directly contacting the solution with a substrate, a method of forming a film by spraying a solution in a gas phase, such as an ink jet method and a spray coating method. The film thickness of the power generation layer 4 is not particularly limited, but is generally preferably in the range of 80 to 240 nm.

  Next, other members constituting the organic power generation element will be described.

  When the substrate 1 is provided on the light incident surface side, the substrate 1 has light transparency, and may be slightly colored or ground glass in addition to being colorless and transparent. For example, a transparent glass plate such as soda lime glass or non-alkali glass, a plastic film or a plastic plate produced by an arbitrary method from a resin such as polyester, polyolefin, polyamide, or epoxy, or a fluorine resin can be used. . Moreover, what has a light-diffusion effect by containing the particle | grains, powder, foam, etc. with a different refractive index from a base material in the board | substrate 1 can also be used. When the substrate 1 is not provided on the light incident surface side, the material and the like are not particularly defined, and any material can be used as long as it can support the solar cell portion.

The positive electrode 2 is an electrode for efficiently collecting holes generated in the power generation layer 4, and an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function is used. It is preferable to use a material having a work function of 4 eV or more. Examples of the material of the positive electrode 2 include metals such as gold, CuI, ITO (indium-tin oxide), SnO ₂ , ZnO, IZO (indium-zinc oxide), and conductive materials such as PEDOT and polyaniline. Examples thereof include a conductive polymer doped with a conductive polymer and an optional acceptor, and a conductive light-transmitting material such as a carbon nanotube. The positive electrode 2 can be produced, for example, by forming these electrode materials on the surface of the substrate 1 into a thin film by a method such as vacuum vapor deposition, sputtering, or coating. In order to allow extraneous light to pass through the positive electrode 2 and enter the power generation layer 4, the light transmittance of the positive electrode 2 is preferably set to 70% or more. Further, the sheet resistance of the positive electrode 2 is preferably several hundred Ω / □ or less, particularly preferably 100 Ω / □ or less. Here, the film thickness of the positive electrode 2 varies depending on the material in order to control the characteristics such as light transmittance and sheet resistance of the positive electrode 2 as described above, but is 500 nm or less, preferably in the range of 10 to 200 nm. It is good to set.

The negative electrode 6 is an electrode for efficiently collecting electrons generated in the power generation layer 4, and an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a small work function is used. The work function is preferably 5 eV or less. Examples of the electrode material of the negative electrode 6 include alkali metals, alkali metal halides, alkali metal oxides, alkaline earth metals, rare earths, and alloys of these with other metals such as sodium, sodium- Examples include potassium alloys, lithium, magnesium, magnesium-silver mixtures, magnesium-indium mixtures, aluminum-lithium alloys, and Al / LiF mixtures. Aluminum, Al / Al ₂ O ₃ mixture, etc. can also be used. In addition, an alkali metal oxide, an alkali metal halide, or a metal oxide is used as a base of the negative electrode 6, and one or more layers of materials (or alloys containing them) having a work function of 5 eV or less are used. You may use it, laminating | stacking. For example, an alkali metal / Al laminate, an alkali metal halide / alkaline earth metal / Al laminate, an Al ₂ O ₃ / Al laminate, and the like can be given as examples. The negative electrode 6 can be produced, for example, by forming these electrode materials into a thin film by a method such as vacuum deposition or sputtering.

  In addition, the hole transport material constituting the hole transport layer 3 has the ability to transport holes, has a hole transfer effect from the power generation layer 4, and has an excellent positive electrode with respect to the positive electrode 2. Examples thereof include a compound having a hole moving effect, a property of blocking electrons, and an excellent thin film forming ability. Specifically, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD), 4,4 ′ -Aromatic diamine compounds such as bis [N- (naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, poly Arylalkane, butadiene, 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), and polyvinylcarbazole, polysilane, aminopyridine derivative, polyethylenediol Derivation of side thiophene (PEDOT) Examples include, but are not limited to, high molecular materials such as photosensitive polymers, inorganic oxides such as molybdenum trioxide, vanadium pentoxide, tungsten trioxide, and rhenium oxide having hole transport properties and p. Inorganic oxides such as nickel oxide and copper oxide, which are type semiconductors, can be used, and even inorganic materials can be used without being limited thereto as long as they have hole transportability.

Examples of the material used for the electron transport layer 5 include bathocuproin, bathophenanthroline, and derivatives thereof, TPBi, silole compound, triazole compound, tris (8-hydroxyquinolinato) aluminum complex, bis (4- Methyl-8-quinolinato) aluminum complex, oxadiazole compound, distyrylarylene derivative, silole compound, TPBI (2,2 ′, 2 ″-(1,3,5-benzenetolyl) tris- [1-phenyl- 1H-benzimidazole]), etc., but may be any material as long as it is an electron transporting material, and is not particularly limited thereto, and is a compound semiconductor that is a material for transferring and transporting electrons used in the power generation layer 4. And fullerene derivatives containing higher order fullerenes such as C60, C70 and C84 A low molecular weight material, a conductive polymer, a carbon nanotube, etc. can be used, and any electron transporting material can be used without particular limitation. The material to be obtained is preferably a material having an electron mobility of 10 ⁻⁶ cm ² / Vs or higher, more preferably 10 ⁻⁵ cm ² / Vs or higher.

  Further, the surface protective layer 7 is formed of a material having a gas barrier property. For example, a metal such as Al is laminated by sputtering, a fluorine compound, a fluorine polymer, another organic molecule, Molecules can be formed as a thin film by vapor deposition, sputtering, CVD, plasma polymerization, etc. Also, they can be applied and UV-cured, heat-cured, or formed as a thin film by other methods. Is also possible. Further, it is possible to form the surface protective layer 7 with a film-like or plate-like structure that is light transmissive and has gas barrier properties. Such a light-transmitting surface protective layer 7 can be provided on the light incident surface side. At this time, in order to allow light to reach the organic power generation layer 4, the light transmittance of the surface protective layer 7 is set to 70. % Or more is preferable.

  In the embodiment of FIG. 1 described above, an organic power generation element having a layer configuration of positive electrode / hole transport layer / power generation layer / electron transport layer / negative electrode is shown. The power generation layer / negative electrode is fundamental, and other layer configurations such as positive electrode / hole transport layer / power generation layer / negative electrode, positive electrode / power generation layer / electron transport layer / negative electrode, and the like may be used.

  Next, the present invention will be specifically described with reference to examples.

Example 1
A glass substrate 1 with ITO provided with an ITO film as a positive electrode 2 (manufactured by Kuramoto Seisakusho), acetone, isopropyl alcohol (both manufactured by Kanto Chemical Co., Ltd.), semi-clean (manufactured by Furuuchi Kagaku), After ultrasonic cleaning with pure water for 10 minutes each, it was cleaned with isopropyl alcohol vapor and dried. Further, the surface treatment of the substrate 1 with ITO was performed for 3 minutes by an atmospheric pressure plasma surface treatment apparatus (Matsushita Electric Works Co., Ltd.).

  On the positive electrode 2 made of ITO, polyethylenedioxythiophene: polystyrene sulfonate (PEDOT: PSS) (manufactured by Starck) was formed as a hole transport layer 3 with a film thickness of 40 nm.

  On the other hand, poly (3-hexylthiophene) (abbreviated as P3HT; manufactured by Merck, regioregular type) is used as an electron-donating semiconductor, and [6,6] -phenyl C61-butylic acid methyl is a fullerene derivative as a hole-donating semiconductor. Esters (abbreviated as PCBM; manufactured by Solenne) were used. In addition, 1,2-dichlorobenzene (vapor pressure; 160 Pa (20 ° C.)) was used as the main solvent, chloroform (vapor pressure; 21.2 kPa (20 ° C.)) was used as the additive solvent, and chloroform was added to 1,2-dichlorobenzene. A material obtained by mixing P3HT and PCBM at a mass ratio of 1: 0.7 in a mixed solvent mixed at a volume ratio of 6: 4 was dissolved so that the solid content concentration was 51 mg / ml.

  Then, the substrate 1 on which the hole transport layer 3 is formed is transferred to a glove box in a dry nitrogen atmosphere having a dew point of −76 ° C. or less and oxygen of 1 ppm or less, and P3HT and PCBM are used as a mixed solvent on the hole transport layer 3. The dissolved solution was spin-coated to form a power generation layer 4 having a thickness of 200 nm.

  Next, this substrate 1 is set in a vacuum deposition apparatus (manufactured by ULVAC), and LiF is deposited to a thickness of 0.5 nm and Al is deposited thereon to a thickness of 100 nm using a vacuum deposition method. An electrode 6 was formed.

  Next, the substrate 1 formed by laminating these layers was transported to a glove box in a dry nitrogen atmosphere having a dew point of −76 ° C. or less without being exposed to the air. On the other hand, a getter kneaded with calcium oxide as a water-absorbing material is attached to a glass sealing plate with an adhesive, and a sealing agent made of an ultraviolet curable resin is applied in advance to the outer periphery of the sealing plate. Then, a sealing plate was bonded to the substrate 1 with a sealing agent in the glove box, and the sealing agent was cured with UV to obtain an organic power generation element coated with the surface protective layer 7.

(Example 2)
1,2-dichlorobenzene (vapor pressure; 160 Pa (20 ° C.)) and 1,2,4-trichlorobenzene (vapor pressure; 40 Pa (25 ° C.)) were used as the main solvent, and chloroform (vapor pressure; 21) was used as the additive solvent. .2 kPa (20 ° C.)), and a solution in which P3HT and PCBM were dissolved in a mixed solvent obtained by mixing these at a volume ratio of 5: 1: 4 was prepared in the same manner as in Example 1. This solution was spin-coated to form a power generation layer 4 having a thickness of 200 nm. Other than that, an organic power generation element was obtained in the same manner as in Example 1.

(Comparative Example 1)
1,2-dichlorobenzene (vapor pressure; 160 Pa (20 ° C.)) is used as the main solvent, and chloroform (vapor pressure; 21.2 kPa (20 ° C.)) is used as the additive solvent, and this is mixed at a volume ratio of 4: 6. A solution in which P3HT and PCBM were dissolved in the mixed solvent was prepared in the same manner as in Example 1. This solution was spin-coated to form a power generation layer 4 having a thickness of 200 nm. Other than that, an organic power generation element was obtained in the same manner as Example 1.

(Comparative Example 2)
Using a single solvent of 1,2-dichlorobenzene (vapor pressure: 160 Pa (20 ° C.)) as a solvent, a solution in which P3HT and PCBM were dissolved was prepared in the same manner as in Example 1. This solution was spin-coated to form a power generation layer 4 having a thickness of 200 nm. Other than that, an organic power generation element was obtained in the same manner as in Example 1.

(Comparative Example 3)
1,2-dichlorobenzene (vapor pressure: 160 Pa (20 ° C.)) is used as the main solvent, and chlorobenzene (vapor pressure: 1.17 kPa (20 ° C.)) is used as the additive solvent, which is mixed at a volume ratio of 6: 4. A solution in which P3HT and PCBM were dissolved in the mixed solvent was prepared in the same manner as in Example 1. This solution was spin-coated to form a power generation layer 4 having a thickness of 200 nm. Other than that, an organic power generation element was obtained in the same manner as Example 1.

  About the organic power generation element obtained in Examples 1-2 and Comparative Examples 1-3 as described above, the surface unevenness of the power generation layer 4 was measured with an atomic force microscope (AFM), and the surface of the surface of the power generation layer 4 was measured. The mean square roughness was determined. Moreover, the film thickness of the electric power generation layer 4 was measured with the surface shape measuring apparatus (Dektak8), and the dispersion | variation in the thickness with respect to 200 nm was calculated. And the conversion efficiency of the organic power generation element was calculated | required by irradiating simulated sunlight (AM1.5, 1sun) with the solar simulator (made by Yamashita Denso Co., Ltd.). The results are shown in Table 1.

  As can be seen from Table 1, in the organic power generation elements of Examples 1 and 2, the surface average square roughness of the power generation layer 4 is 2 nm or less, and the variation in the thickness of the power generation layer 4 is ± 10% or less. It was confirmed that high luminous efficiency can be obtained.

It is a schematic sectional drawing which shows an example of the laminated constitution of an organic solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Positive electrode 3 Hole transport layer 4 Power generation layer 5 Electron transport layer 6 Negative electrode

Claims (2)

  In an organic power generation device comprising a power generation layer formed by mixing an electron-donating semiconductor and a hole-donating semiconductor, at least one of which is transparent to extraneous light, the surface average of the surface of the power generation layer An organic power generation element having a square roughness of 2 nm or less and a variation in film thickness of the power generation layer within ± 10% of the entire power generation layer.   The power generation layer is formed by applying a mixed solvent in which an electron-donating semiconductor and a hole-donating semiconductor are dissolved. The mixed solvent has a main solvent and a vapor pressure of two digits relative to the main solvent. 2. The organic power generation element according to claim 1, wherein the organic power generation element is composed of a high additive solvent, and the volume ratio of the main solvent and the additive solvent is in a relation of main solvent> addition solvent.

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