JP2015026716A - Method of manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a photoelectric conversion element for forming ideal morphology of an organic photoelectric conversion layer for exhibiting excellent photoelectric conversion efficiency in a simple step.SOLUTION: A method of manufacturing a photoelectric conversion element includes a step (A) in which π electron conjugated polymer and electron accepting organic semiconductor are dissolved in organic solvent to provide an organic semiconductor solution, a step (B) in which at least two kinds of poor solvent of π electron conjugated polymer whose SP value is 18.1-26.5 are added to the organic semiconductor solution, and a step (C) in which the organic semiconductor solution obtained in the step (B) is film-formed by a coating method, so that a photoelectric conversion layer is formed.

Description

  The present invention relates to a method for producing a photoelectric conversion element capable of forming a good phase separation structure (morphology) in an organic photoelectric conversion layer.

  Solar cells are attracting attention as a powerful energy source that is friendly to the environment. At present, inorganic materials such as silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and compound semiconductor materials such as GaAs, CIGS, and CdTe are used as photoelectric conversion elements for solar cells. These photoelectric conversion elements have a relatively high photoelectric conversion efficiency, but are expensive compared to other power supply costs. The cause of the high cost is the process in which the semiconductor thin film must be manufactured under high vacuum and high temperature. Therefore, organic semiconductor cells using organic semiconductors and organic dyes such as π-electron conjugated polymers and organic crystals are being studied as semiconductor materials that are expected to simplify the manufacturing process. Since these organic semiconductor materials can be formed into a film by a coating method or a printing method, they are attracting attention because the manufacturing process is simplified, mass production is possible, and inexpensive organic solar cells can be obtained.

An organic solar cell has a structure in which an organic photoelectric conversion layer is provided between two different electrodes. Generally, the organic photoelectric conversion layer is formed from a mixture of an electron donating organic semiconductor and an electron accepting organic semiconductor. As typical examples, poly (3-hexylthiophene) which is a π-electron conjugated polymer as an electron-donating organic semiconductor, and [6,6] -phenyl C ₆₁ butyric acid methyl ester which is a fullerene derivative as an electron-accepting organic semiconductor ( PC ₆₁ BM).

  The problem of the organic solar cell is to increase the photoelectric conversion efficiency, and in particular, reports have been made on improving the photoelectric conversion efficiency by changing the morphology of the organic photoelectric conversion layer. The ideal organic photoelectric conversion layer morphology is characterized in that the electron-donating organic semiconductor and the electron-accepting organic semiconductor are phase-separated and each has a domain size of about 100 nm. When any of the p / n phase separation domains has a domain size in this range, there is a high probability that excitons generated inside by light absorption reach the p / n interface before deactivation, and a high current is obtained. . At the same time, the continuity of the phase separation domain that affects carrier transport resistance is easily obtained, and carriers generated at the p / n interface can be efficiently taken out to the electrode, resulting in high conversion efficiency. Expected.

  From this point of view, as a method of changing the morphology of the organic photoelectric conversion layer, a method of treating with heat or solvent vapor, a method of devising a solvent that dissolves a π-electron conjugated polymer or a fullerene derivative, or reducing the volatilization rate of the solvent Methods and methods for controlling the structure of π-electron conjugated polymers have been studied. For example, Patent Document 1 describes a method for controlling the morphology of an organic photoelectric conversion layer using a π-electron conjugated block copolymer. Patent Document 2 describes a method of controlling morphology by using two or more conjugated polymers having a solubility difference. However, in order to improve the photoelectric conversion efficiency of the organic solar cell, it is necessary to form a finer and better morphology, and a solution is required.

WO2013 / 005614 brochure WO2013 / 018853 brochure

  The present invention has been made in order to solve the above-described problems, and is a method for producing a photoelectric conversion element that can form an ideal organic photoelectric conversion layer morphology in a simple process and that exhibits excellent photoelectric conversion efficiency. The purpose is to provide.

  The inventors of the present invention have intensively studied to achieve the above object. As a result, in the step of forming a photoelectric conversion layer containing a π-electron conjugated polymer and an electron-accepting organic semiconductor, it has been found that the above problem can be solved by adding at least two poor solvents for the π-electron conjugated polymer, The present invention has been reached.

  That is, the manufacturing method of the photoelectric conversion element according to claim 1, which has been made in order to achieve the above-described object, includes a method in which at least one of the positive electrode and the negative electrode having light transmissivity is π A method for producing a photoelectric conversion element having a photoelectric conversion layer comprising an electron conjugated polymer and an electron-accepting organic semiconductor, wherein the π-electron conjugated polymer includes a condensed ring containing at least one thiophene ring as a part of a chemical structure. a monomer unit having at least one heterocyclic skeleton selected from a π-conjugated skeleton, a carbazole skeleton, a dibenzosilole skeleton, a dibenzogermole skeleton, and a diketopyrrolopyrrole skeleton, and the π-electron conjugated polymer and the electron acceptor Step (A) of dissolving an organic semiconductor in an organic solvent to obtain an organic semiconductor solution, wherein the organic semiconductor solution has the SP value in the range of 18.1 to 26.5. A step (B) of adding at least two poor solvents for the conjugated polymer, and a step of forming the organic semiconductor solution obtained in the step (B) between the positive electrode and the negative electrode by a coating method; A step (C) of forming a conversion layer.

  Similarly, the method for producing a photoelectric conversion element according to claim 2 is the method according to claim 1, wherein the poor solvent used in the step (B) has a solubility of the π-electron conjugated polymer of 1. It is 0 mg / mL or less.

  The method for producing a photoelectric conversion device according to claim 3 is the method according to claim 1 or 2, wherein at least one of the poor solvents used in the step (B) is 1,8-diiodine. It is any one selected from octane, anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N, N-dimethylformamide and N, N-dimethylacetamide.

  The method for producing a photoelectric conversion device according to claim 4 is the method according to claim 3, wherein at least one of the poor solvents used in the step (B) is 1,8-diiodooctane. , At least one other is any one selected from anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N, N-dimethylformamide and N, N-dimethylacetamide .

  The manufacturing method of the photoelectric conversion element of Claim 5 is described in any one of Claims 1-4, Comprising: The sum total of the addition amount of the at least 2 sort (s) of poor solvent used by the said process (B). Is in the range of 0.1 vol% to 50.0 vol% of the organic semiconductor solution.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the photoelectric conversion element which can form the morphology of an ideal organic photoelectric converting layer can be provided with a simple process. In the photoelectric conversion element obtained by the production method of the present invention, the electron-donating organic semiconductor and the electron-accepting organic semiconductor in the photoelectric conversion layer can form a fine morphology, so that the deactivation of excitons generated by light absorption is reduced. Less, a high current can be obtained, and excellent photoelectric conversion efficiency can be exhibited.

3 is a morphology image of a cross section of the photoelectric conversion element obtained in Example 2. 6 is an image obtained by binarizing the morphology image of the cross section of the photoelectric conversion element obtained in Example 2. FIG. 6 is an image obtained by binarizing the morphology image of the cross section of the photoelectric conversion element obtained in Comparative Example 2. FIG. It is an image obtained by binarizing the morphology image of the cross section of the photoelectric conversion element obtained in Comparative Example 5.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, the scope of the present invention is not limited to these forms.

  The present invention relates to a method for producing a photoelectric conversion element having a photoelectric conversion layer containing a π-electron conjugated polymer and an electron-accepting organic semiconductor between a positive electrode and a negative electrode, at least one of which is light transmissive.

  The π-electron conjugated polymer is any one selected from a condensed π-conjugated skeleton, a carbazole skeleton, a dibenzosilole skeleton, a dibenzogermole skeleton, and a diketopyrrolopyrrole skeleton containing at least one thiophene ring as part of the chemical structure. It is a polymer containing a monomer unit having at least one heterocyclic skeleton. Among these, a preferable π-electron conjugated polymer includes a monomer unit containing a condensed π-conjugated skeleton containing at least one thiophene ring as a part of the chemical structure. Thiophene diyl group, dithienopyrrole diyl group, dithienosilole diyl group, dithienogermol diyl group, benzodithiophene diyl group, naphthodithiophene diyl group, thienothiophene diyl group, thienopyrrole dione diyl group, diketopyrrolopyrrole It is a polymer containing a monomer unit containing a heterocyclic skeleton such as a diyl group. Two or more kinds of these heterocyclic skeletons (heterocyclic groups) may be contained in the monomer unit.

  The π-electron conjugated polymer having a heterocyclic skeleton in a monomer unit is preferably a narrow band gap polymer. A narrow band gap polymer is a polymer with a small energy difference (band gap) between the highest occupied orbital (HOMO) level and the lowest unoccupied orbital (LUMO) level. It is a polymer having both a high organic group and a high acceptor organic group. For example, the cyclopentadithiophenediyl group and the benzodithiophenediyl group exemplified above are heterocyclic groups having a relatively high donor property, and the thienothiophenediyl group is a heterocyclic group having a relatively high acceptor property. May be combined into one monomer unit. The narrow band gap polymer can absorb light in a wide wavelength region from the ultraviolet region to a long wavelength region of 600 nm or more in the sunlight spectrum. Therefore, by including a narrow band gap polymer in the photoelectric conversion layer, it is possible to produce an organic solar cell excellent in light utilization efficiency.

  The π-electron conjugated polymer has at least one side chain selected from an optionally substituted alkyl group, alkoxy group, aryl group, heteroaryl group, alkylcarbonyl group, and alkyloxycarbonyl group in the polymer main chain. It is preferable. The side chain refers to a substituent having carbon branched from the main chain constituting the π-electron conjugated polymer. By having a side chain, the solubility of the π-electron conjugated polymer in an organic solvent is improved, which is advantageous for forming a photoelectric conversion layer. In particular, those having an alkyl group having 3 to 20 carbon atoms, an alkoxy group or an alkylcarbonyl group are preferred. These side chains may be further substituted with a halogen atom, a hydroxyl group, an amino group, a thiol group, a silyl group, an alkoxy group, an ester group, an aryl group or a heteroaryl group.

  The alkyl group may be linear or branched, and specific examples thereof include n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n -Nonyl group, n-decyl group, n-dodecyl group, n-hexadecyl group, isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, 2 -Ethylhexyl group, 3-heptyl group, 3,7-dimethyloctyl group, 2-butyloctyl group, etc. are mentioned.

  The alkoxy group may be linear or branched, and specific examples thereof include n-propyloxy group, n-butyloxy group, n-pentyloxy group, n-hexyloxy group, n-heptyloxy group, n- Octyloxy group, n-nonyloxy group, n-decyloxy group, n-dodecyloxy group, n-hexadecyloxy group, isopropyloxy group, isobutyloxy group, sec-butyloxy group, tert-butyloxy group, isopentyloxy group, Neopentyloxy group, tert-pentyloxy group, isohexyloxy group, 2-ethylhexyloxy group, 3-heptyloxy group, 3,7-dimethyloctyloxy group, 2-butyloctyloxy group and the like can be mentioned.

  Specific examples of the alkylcarbonyl group include those in which a carbonyl group is bonded to the alkyl group.

  The number-average molecular weight of the π-electron conjugated polymer is not particularly limited, but is preferably 600 to 1,000,000 g / mol and 5,000 to 500,000 g / mol from the viewpoint of hole mobility and mechanical properties. More preferred is 10,000 to 200,000 g / mol. Here, the number average molecular weight means a molecular weight in terms of polystyrene by gel permeation chromatography.

  The π-electron conjugated polymer may be a polymer having any structure of a random copolymer, a block copolymer, a star polymer, and a graft copolymer. Among these, a random copolymer and a block copolymer are more preferable from the viewpoint of morphology control, and a block copolymer is particularly preferable. The connection structure of the block copolymer is not particularly limited. In the case of containing two kinds of conjugated polymer blocks, for example, an AB type diblock copolymer, an AB type triblock copolymer, an AB type AB block tetrablock copolymer And A-B-A-B-A type pentablock copolymer. In the case of containing three types of conjugated polymer blocks, examples include an ABC type triblock copolymer and an ABAC type tetrablock copolymer.

  In the case of a block copolymer, the bonding mode of the conjugated block copolymer is not particularly limited. As the bonding mode, a linear conjugated block copolymer in which the ends of the conjugated polymer block are bonded to each other, or a T-type conjugated block copolymer in which the end of the conjugated polymer block is bonded to other than the end of the conjugated polymer block. It may be. The binding sites may be linked by π conjugation or may be bound by a non-conjugated structure.

  As a first method for producing a block copolymer, at least two kinds of conjugated polymer blocks constituting each block, for example, conjugated polymer block A and conjugated polymer block B are synthesized separately, There is a method of connection (hereinafter sometimes referred to as “connection method”). As a second method, there is a method in which the conjugated polymer block A and the conjugated polymer block B are sequentially polymerized by pseudo-living polymerization (hereinafter sometimes referred to as “sequential polymerization method”). As a third method, there is a method of polymerizing the conjugated block B in the presence of the conjugated polymer block A (hereinafter sometimes referred to as “macroinitiator method”). As the linking method, sequential polymerization, and macroinitiator method, an optimum method can be used depending on the π-electron conjugated polymer to be synthesized.

As the electron-accepting organic semiconductor, fullerene or a fullerene derivative is preferable. Suitable fullerene derivatives include unsubstituted ones such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ and [6,6] -phenyl C _61. butyric acid methyl ester _{([6,6] -C 61 -PCBM)} , [5,6] - phenyl _{C 61} butyric acid methyl ester, [6,6] - phenyl _{C 61} butyric acid n- butyl ester, [6,6] -phenyl C ₆₁ butyric acid i-butyl ester, [6,6] -phenyl C ₆₁ butyric acid hexyl ester, [6,6] -phenyl C ₆₁ butyric acid dodecyl ester, [6 6] - diphenyl _{C 62} bis (butyric acid methyl _{ester) ([6,6] -C 62 -bis} -PCBM), [6,6 - and substituted derivatives including phenyl _{C 71} butyric acid methyl ester _([6,6] -C 71 -PCBM) and the like.

The fullerene derivatives can be used alone or as a mixture thereof, but [6,6] -C ₆₁ -PCBM, [6,6] -C ₆₂ -bis-PCBM) from the viewpoint of solubility in organic solvents. [6,6] -C ₇₁ -PCBM is preferably used.

  In the method for producing a photoelectric conversion element of the present invention, the π-electron conjugated polymer and the electron-accepting organic semiconductor are dissolved in an organic solvent to obtain an organic semiconductor solution (A), and the organic semiconductor solution has an SP value. The step (B) of adding at least two poor solvents for the π-electron conjugated polymer within the range of 18.1 to 26.5, and the step (B) between the positive electrode and the negative electrode. A step (C) of forming the photoelectric conversion layer by forming the organic semiconductor solution into a film by a coating method. Hereinafter, each process will be described.

  The organic solvent used in the step (A) is not particularly limited as long as it is a solvent in which most of the π-electron conjugated polymer and the electron-accepting organic semiconductor are dissolved. Specific examples of the solvent include ethers such as diethyl ether, tetrahydrofuran, diisopropyl ether, dioxane, dimethoxyethane, and dibutyl ether; halogen solvents such as methylene chloride and chloroform; benzene, toluene, orthoxylene, metaxylene, chlorobenzene, and bromo. Aromatic solvents such as benzene, iodobenzene, orthodichlorobenzene, pyridine and the like can be mentioned. These solvents may be used singly or in combination of two or more, but ortho-dichlorobenzene, chlorobenzene, bromobenzene, iodo having high solubility of both the π-electron conjugated polymer and the electron-accepting organic semiconductor. Benzene, chloroform, ortho-xylene, and mixtures thereof are preferred. Particularly preferred are orthodichlorobenzene, chlorobenzene, chloroform and mixtures thereof.

  The π-electron conjugated polymer and the electron-accepting organic semiconductor are dissolved in the organic solvent and then mixed to obtain an organic semiconductor solution. The mixing method is not particularly limited. For example, after adding to a solvent in a desired ratio, a method of heating, stirring, ultrasonic irradiation or the like is used in one or a combination of a plurality of methods to dissolve and mix in the solvent. Is mentioned.

  The content ratio of the π electron conjugated polymer and the electron accepting organic semiconductor in the organic semiconductor solution is preferably 10 to 1000 parts by mass of the electron accepting organic semiconductor with respect to 100 parts by mass of the π electron conjugated polymer. More preferably, it is 50-500 mass parts. Moreover, it is preferable that the sum (solution mass) of content of the π-electron conjugated polymer and the electron-accepting organic semiconductor is 0.1 to 50 parts by mass with respect to 100 parts by mass of the organic solvent. The amount is more preferably 1 to 30 parts by mass, and further preferably 0.5 to 20 parts by mass.

The poor solvent used in the step (B) is a solvent having an SP value in the range of 18.1 to 26.5. In the present invention, the SP value refers to a solubility parameter and is a value unique to a substance. In the present invention, the SP value is a numerical value described in “Polymer Hand Book (4th) Edition, (1999), Wiley-Interscience”. The SP value can be measured experimentally or estimated using empirical approximation based on the molecular structure. Examples of the experimental measurement method include a method of estimating from the evaporation heat, a method of estimating from the surface tension, and a method of estimating from the refractive index. In addition, as a method of estimating using empirical approximation based on the molecular structure, for example, Bicerano method, Hildebrand method, Small method, Fedors method, Van Krevelen method, Hansen method, Hoy method, Ascadskii method, Okitsu method, etc. Is mentioned. When the SP value of the poor solvent is not described in “Polymer Hand Book (4th) Edition, (1999), Wiley-Interscience”, it may be calculated using any of these methods, but it is simple and useful. From the viewpoint of being proven, it is preferable to calculate using the Fedors method. In that case, the unit of SP value is MPa ^1/2 .

  The poor solvent used in the step (B) of the present invention is preferably one in which the solubility of the π-electron conjugated polymer at 25 ° C. is 1.0 mg / mL or less. Moreover, it is more preferable that it is a thing whose boiling point is higher than the organic solvent used at a process (A). Examples of such poor solvents include 1,8-diiodooctane, anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N, N-dimethylformamide, N, N-dimethylacetamide and the like. Can be mentioned. Among these, at least one poor solvent is preferably 1,8-diiodooctane. More preferably, at least the other one is anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N, N-dimethylformamide or N, N-dimethylacetamide, methyl benzoate, More preferred is N, N-dimethylformamide or N, N-dimethylacetamide.

  The SP value of each of the poor solvents exemplified above is as follows: 1,8-diiodooctane (20.4), anisole (19.4), methyl benzoate (21.5), aniline (21. 1), 1,2-dibromoethane (21.3), morpholine (22.1), N, N-dimethylformamide (24.9), N, N-dimethylacetamide (22.1).

  One of the functions required for the π-electron conjugated polymer used in the organic photoelectric conversion layer is high hole mobility. The holes are conducted through a π-π stack structure formed by overlapping π electron conjugated polymers on the π plane. In general, a strongly interacting π-π stack structure facilitates movement of holes, and the interaction increases as the overlap integral of the lowest occupied orbitals (HOMO) of overlapping π-electron conjugated polymers increases. That is, as one means for improving the hole mobility of the π-electron conjugated polymer, it is effective to change the molecular structure in the direction of improving crystallinity or cohesion. However, a π-electron conjugated polymer having high crystallinity or aggregation is generally difficult to be compatible with an electron-accepting organic semiconductor such as a fullerene derivative. The reason is that in the π-electron conjugated polymer, a long-chain alkyl group or a substituent that lowers the SP value, such as fluorine, is introduced in order to improve the crystallinity and cohesion. These all change the chemical structure of the π-electron conjugated polymer in the direction of decreasing the SP value, but generally the fullerene derivative (SP value: about 21) has a higher SP value than the π-electron conjugated polymer. By applying such chemical modification, the difference in SP value between the two becomes larger, and as a result, the π-electron conjugated polymer and the fullerene derivative are hardly compatible. As a result, the π-electron conjugated polymer obtained based on the design aiming at high crystallinity or high cohesiveness has an enlarged p / n phase separation domain and forms a p / n phase separation structure of 100 nm or more. It is considered that high conversion efficiency cannot be obtained due to a decrease in current.

  In the production method of the present invention, when the π-electron conjugated polymer and the electron-accepting organic semiconductor are mixed, the poor solvent for the π-electron conjugated polymer having an SP value in the range of 18.1 to 26.5. The above problem can be solved by adding at least two kinds. That is, by adding two or more poor solvents having a specific SP value, even in a combination of a π-electron conjugated polymer and an electron-accepting organic semiconductor, in which the SP value difference is large and the p / n phase separation domain is likely to be enlarged, These are compulsorily compatibilized, and the morphology of the obtained photoelectric conversion layer can be refined. With this function, the photoelectric conversion element obtained by the production method of the present invention can achieve high conversion efficiency. The production method of the present invention is particularly effective in the production of a photoelectric conversion element having a photoelectric conversion layer containing a narrow band gap polymer. In the production method of the present invention, when a fullerene derivative is used as the electron-accepting organic semiconductor, the SP value of the π-electron conjugated polymer is not particularly limited, but is preferably 16.0 to 21.5, More preferably, it is 16.3 to 21.4.

  In the production method of the present invention, the two or more poor solvents used preferably have a difference in SP value of 0.1 or more. When there is little or no difference in SP value, the above morphological refinement effect may not be sufficiently obtained. Preferred antisolvent combinations are not particularly limited, and examples thereof include 1,8-diiodooctane and anisole, 1,8-diiodooctane and methyl benzoate, 1,8-diiodooctane and aniline, 1,8-diiodooctane and 1,2-dibromoethane, 1,8-diiodooctane and morpholine, 1,8-diiodooctane and N, N-dimethylformamide, 1,8-diiodooctane and N, N-dimethylacetamide etc. are mentioned.

  The total addition amount of the poor solvent is difficult to determine in general, but is preferably in the range of 0.1 vol% to 50.0 vol% of the organic semiconductor solution. More preferably, it is 0.1 vol%-40.0 vol%, More preferably, it is 0.1 vol%-30.0 vol%, Most preferably, it is 0.5 vol%-30.0 vol%. When the total amount of addition is more than 50.0 vol%, the π-electron conjugated polymer is not sufficiently dissolved, resulting in poor film formation of the photoelectric conversion active layer, or between the π-electron conjugated polymer and the electron-accepting organic semiconductor. Macro phase separation may occur. The addition amount of each of the two or more poor solvents is not particularly limited, but the lower limit of the content of each component is 5 vol% or more when the total amount of the poor solvent is 100 vol%. Is preferred. For example, when two poor solvents are used, the volume ratio of each poor solvent is preferably 5:95 to 95: 5, and more preferably 20:80 to 80:20.

  After the poor solvent is added to the organic semiconductor solution, the organic semiconductor solution may be diffused by performing stirring, ultrasonic irradiation, or the like. Moreover, you may perform a process (A) and a process (B) simultaneously. For example, an organic semiconductor solution may be prepared by adding and dissolving a π-electron conjugated polymer and an electron-accepting organic semiconductor in an organic solvent to which at least two kinds of poor solvents have been added in advance.

  The organic semiconductor solution obtained in the step (A) and the step (B) may contain other additive components such as a surfactant, a binder resin, and a filler as long as the effects of the present invention are not impaired. . The content of these third components is preferably 30% by mass or less with respect to the total mass of the π-electron conjugated polymer and the electron-accepting organic semiconductor from the viewpoint of the performance of the photoelectric conversion element, and is 10% by mass or less. Is more preferable.

  In the step (C), examples of the method for forming the organic semiconductor solution obtained in the step (B) by coating include spin coating, casting, micro gravure coating, gravure coating, and slot die coating. Well-known methods such as a bar coating method, a roll coating method, a dip coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, an ink jet printing method, a nozzle coating method, and a capillary coating method can be used. . A photoelectric conversion layer can be formed by drying after film formation by a coating method.

  When forming the photoelectric conversion layer, heat or solvent annealing may be performed as necessary. By performing the annealing treatment, the crystallinity of the material of the photoelectric conversion layer and the phase separation structure between the π-electron conjugated polymer and the electron-accepting organic semiconductor can be changed, and an element having excellent photoelectric conversion characteristics can be obtained.

  The thermal annealing is performed by holding the substrate on which the photoelectric conversion layer is formed at a desired temperature. Thermal annealing may be performed under reduced pressure or in an inert gas atmosphere, and a preferable temperature is 40 ° C to 150 ° C, more preferably 70 ° C to 150 ° C. If the temperature is low, a sufficient effect cannot be obtained, and if the temperature is too high, the photoelectric conversion layer is oxidized and / or decomposed, and sufficient photoelectric conversion characteristics cannot be obtained.

  The solvent annealing is performed by holding the substrate on which the photoelectric conversion layer is formed in a solvent atmosphere for a desired time. The annealing solvent at this time is not particularly limited, but is preferably a good solvent for the photoelectric conversion layer. The solvent annealing may be performed in a state where the organic semiconductor composition constituting the photoelectric conversion layer is applied onto the substrate and the solvent remains in the composition.

  Although it is difficult to determine the film thickness of the photoelectric conversion layer according to the intended application, it is usually 1 nm to 1000 nm, preferably 2 nm to 1000 nm, more preferably 5 nm to 500 nm, and still more preferably. Is 20 nm to 300 nm. If the film thickness is too thin, the light is not sufficiently absorbed. Conversely, if the film thickness is too thick, it becomes difficult for the carriers to reach the electrode, and high conversion efficiency cannot be obtained.

  As the electrode material used in the step (C), it is preferable to use a conductive material having a high work function for one electrode and a conductive material having a low work function for the other electrode. An electrode using a conductive material having a large work function is a positive electrode. Conductive materials with a large work function include metals such as gold, platinum, chromium and nickel, transparent metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium Zinc oxide (IZO), fluorine-doped tin oxide (FTO), etc.) are preferably used. Here, the conductive material used for the positive electrode is preferably an ohmic junction with the photoelectric conversion layer.

  An electrode using a conductive material having a low work function serves as a negative electrode. As the conductive material having a low work function, alkali metal or alkaline earth metal, specifically, lithium, magnesium, or calcium is used. Tin, silver, and aluminum are also preferably used. Furthermore, an electrode made of an alloy made of the above metal or a laminate of the above metal is also preferably used. Further, it is possible to improve the extraction current by introducing a metal fluoride such as lithium fluoride or cesium fluoride at the interface between the negative electrode and the electron transport layer described later. Here, the conductive material used for the negative electrode is preferably an ohmic junction with the photoelectric conversion layer. Furthermore, when the electron transport layer is used, it is preferable that the conductive material used for the negative electrode is in ohmic contact with the electron transport layer. In the present invention, the electrode layer means an electrode or an electrode provided with a hole transport layer, an electron transport layer, or an inorganic layer described below.

  The electrode of the photoelectric conversion element has light transmittance in either the positive electrode or the negative electrode. The light transmittance of the electrode is not particularly limited as long as incident light reaches the photoelectric conversion layer and electromotive force is generated. The thickness of an electrode should just be the range which has a light transmittance and electroconductivity, and although it changes with electrode materials, 20 nm-300 nm are preferable. Note that in the case where one electrode has light transparency, the light transmission property is not necessarily required as long as the other electrode has conductivity. Furthermore, the thickness of this electrode is not particularly limited.

  The photoelectric conversion element obtained by the production method of the present invention is preferably produced on a substrate. This substrate may be any substrate that does not change when an electrode is formed and a photoelectric conversion layer is formed. Examples of substrate materials include inorganic materials such as non-alkali glass and quartz glass, metal films such as aluminum, polyester, polycarbonate, polyolefin, polyamide, polyimide, polyphenylene sulfide, polyparaxylene, epoxy resin, fluorine resin, and the like. A film or plate produced from any organic material by any method can be used. If an opaque substrate is used, the opposite electrode, i.e. the electrode far from the substrate, must be transparent or translucent. Although the film thickness of a board | substrate is not specifically limited, Usually, it is the range of 1 micrometer-10 mm.

  In order to improve the wettability of the electrode layer on the substrate, and to improve the interfacial adhesion between the photoelectric conversion layer, the hole transport layer and the electron transport layer and the electrode on the substrate, ultraviolet ozone treatment, corona discharge treatment, It is preferable to clean or modify the surface of the electrode layer by physical means such as plasma treatment. A method of chemically modifying the surface of the solid substrate such as a silane coupling agent, a titanate coupling agent, or a self-assembled monolayer is also effective.

The manufacturing method of the photoelectric conversion element of this invention may include the process of providing a positive hole transport layer between a positive electrode and a photoelectric converting layer as needed. Examples of the material for forming the hole transport layer include conductive polymers such as polythiophene-based π-electron conjugated polymers, poly-p-phenylene vinylene-based π-electron conjugated polymers, polyfluorene-based π-electron conjugated polymers, phthalocyanine ( Pc) derivatives (H ₂ Pc, CuPc, ZnPc, etc.), low molecular organic compounds exhibiting p-type semiconductor properties such as porphyrin derivatives are preferably used. In particular, polyethylenedioxythiophene (PEDOT), which is a polythiophene-based π-electron conjugated polymer, or PEDOT in which polystyrene sulfonate (PSS) is added is preferably used. In the case of using a hole transport layer, the conductive material used for the positive electrode described above is preferably an ohmic junction with the hole transport layer. The hole transport layer preferably has a thickness of 5 nm to 600 nm, more preferably 20 nm to 300 nm.

  Moreover, the manufacturing method of the photoelectric conversion element of this invention may include the process of providing an electron carrying layer between a negative electrode and a photoelectric converting layer as needed. The material for forming the electron transport layer includes electron-accepting organic semiconductor materials such as phenanthrene compounds such as bathocuproine, naphthalenetetracarboxylic acid anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, and perylenetetracarboxylic acid diimide , And n-type inorganic oxides such as titanium oxide, zinc oxide, and gallium oxide, and alkali metal compounds such as lithium fluoride, sodium fluoride, and cesium fluoride can be used. Moreover, the layer which consists of an electron-accepting organic-semiconductor material single-piece | unit used for the photoelectric converting layer can also be used.

  When preparing a hole transport layer between the positive electrode and the photoelectric conversion layer, for example, in the case of a conductive polymer soluble in a solvent, a dip coating method, a spray coating method, an inkjet method, an aerosol jet method, a spin coating method Can be applied by bead coating method, wire bar coating method, blade coating method, roller coating method, curtain coating method, slit die coater method, gravure coater method, slit reverse coater method, micro gravure method, comma coater method, etc. . When using a low molecular weight organic material such as a phthalocyanine derivative or a porphyrin derivative, it is preferable to apply a vapor deposition method using a vacuum vapor deposition machine. The electron transport layer can be similarly produced.

  Moreover, the manufacturing method of the photoelectric conversion element of this invention may include the process of providing an inorganic layer further. Examples of the material contained in the inorganic layer include titanium oxide, tin oxide, zinc oxide, iron oxide, tungsten oxide, zirconium oxide, hafnium oxide, strontium oxide, indium oxide, cerium oxide, yttrium oxide, lanthanum oxide, and vanadium oxide. , Metal oxides such as niobium oxide, tantalum oxide, gallium oxide, nickel oxide, strontium titanate, barium titanate, potassium niobate, sodium tantalate; silver iodide, silver bromide, copper iodide, copper bromide, Metal halides such as lithium fluoride; metals such as zinc sulfide, titanium sulfide, indium sulfide, bismuth sulfide, cadmium sulfide, zirconium sulfide, tantalum sulfide, molybdenum sulfide, silver sulfide, copper sulfide, tin sulfide, tungsten sulfide, and antimony sulfide Sulfide; Cadmium selenide Metal selenides such as zirconium selenide, zinc selenide, titanium selenide, indium selenide, tungsten selenide, molybdenum selenide, bismuth selenide, lead selenide; cadmium telluride, tungsten telluride, molybdenum telluride, tellurium Metal tellurides such as zinc phosphide and bismuth telluride; metal phosphides such as zinc phosphide, gallium phosphide, indium phosphide and cadmium phosphide; gallium arsenide, copper-indium selenide, copper-indium sulfide, Examples thereof include silicon and germanium, and a mixture of two or more of these may be used. Examples of the mixture include a mixture of zinc oxide and tin oxide, a mixture of tin oxide and titanium oxide, and the like. Although the place including these inorganic layers is not particularly limited, it is preferable that the inorganic layer is included in any place of the thin film sandwiched between the positive electrode and the negative electrode. Although the method for forming these inorganic layers is not particularly limited, it is preferable to apply a vapor deposition method using a vacuum vapor deposition machine from the viewpoint of controlling an arbitrary film thickness.

  The photoelectric conversion element obtained by the production method of the present invention can be applied to various photoelectric conversion devices using a photoelectric conversion function, an optical rectification function (photo diode), and the like. For example, it is useful for optical recording materials such as photovoltaic cells such as organic solar cells, optical elements such as optical sensors, optical switches, and phototransistors, and optical memories. Therefore, the manufacturing method of the photoelectric conversion element of this invention can be utilized universally as manufacturing methods, such as an organic solar cell containing an organic thin film, and various optical sensors.

  Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples.

  The description regarding the synthesis | combination of the (pi) electron conjugated polymer used for the Example of this invention and the comparative example, and the conjugated block copolymer is described in the polymerization examples 1-3. The detail which produced the photoelectric conversion element using the manufacturing method within the application of this invention is shown in Examples 1-4. Comparative examples 1 to 10 show that the present invention is not applicable.

<Purification of polymer>
The polymer was purified using a preparative GPC column. As the apparatus used, Recycling Preparative HPLC LC-908 manufactured by Nippon Analytical Industrial Co., Ltd. was used. In addition, the kind of column connects the two styrene-type polymer columns 2H-40 and 2.5H-40 by Nippon Analysis Industry Co., Ltd. in series. Further, chloroform was used as an elution solvent.

<SP value of solvent>
In the following examples and comparative examples, the SP values of the solvents used were those described in “Polymer Hand Book (4th) Edition, (1999), Wiley-Interscience”.

(Polymerization example 1)
The π-electron conjugated polymer A1 was synthesized according to the following reaction formula (1). In the following reaction formulas, the 3-heptyl group as a substituent is abbreviated as 3-Hep or Hep-3. In the following reaction formulas, a methyl group as a substituent is abbreviated as Me.

  As a monomer constituting the π-electron conjugated polymer A1 in a 100 mL three-necked flask under a nitrogen atmosphere, 2,6-bis (trimethyltin) -4,8-didodecylbenzo [1,2-b: 4,5- b ′] dithiophene (0.74 g, 0.87 mmol), 1- (4,6-dibromothieno [3,4-b] thiophen-2-yl) -2-ethylhexane-1-one (0.32 g, 0 .75 mmol), DMF (1.1 mL), toluene (4.3 mL), tetrakis (triphenylphosphine) palladium (0) (9.2 mg, 7.8 μmol) were added, and the mixture was heated at 115 ° C. for 1 hour 30 minutes. Next, 2,5-dibromothiophene (1.84 g, 7.6 mmol) was added as a terminal treating agent and heated at 115 ° C. for 8 hours. After completion of the reaction, the reaction solution was poured into methanol (500 mL), the precipitated solid was collected by filtration, and the obtained solid was dried under reduced pressure to obtain a crude product. The crude product was washed with acetone (200 mL) and hexane (200 mL) using a Soxhlet extractor and then extracted with chloroform (200 mL). The organic layer was concentrated to dryness, and the resulting black purple solid was dissolved in chloroform (30 mL) and reprecipitated with methanol (300 mL). The obtained solid was collected by filtration and dried under reduced pressure to obtain π-electron conjugated polymer A1 (0.51 g, 86%) as a black purple solid.

As for the weight average molecular weight (Mw) and the number average molecular weight (Mn), both GPC / V2000 manufactured by Waters is used as a GPC device, and two Shodex AT-G806MS manufactured by Showa Denko KK are connected in series as a column. I used it. The column and injector were 145 ° C., and o-dichlorobenzene was used as an elution solvent. The obtained π-electron conjugated polymer A1 had a weight average molecular weight of 45,000, a number average molecular weight of 18,000, and a polydispersity of 2.5.
¹ H-NMR (270 MHz, CDCl ₃ ): δ = 7.60-7.30 (br, 3H), 3.30-3.00 (br, 5H), 2.00-1.10 (br, 52H ), 1.00-0.70 (br, 12H).
This physicochemical analysis result supports the chemical structure shown in the reaction formula (1).

(Polymerization example 2)
A π-electron conjugated polymer A2 was synthesized according to the following reaction formula.

To an eggplant flask A thoroughly dried and purged with argon, 25 mL of tetrahydrofuran (THF) subjected to dehydration and peroxide removal treatment, 1.865 g (5 mmol) of 2-bromo-5-iodo-3-hexylthiophene, Then, 2.5 mL of a 2.0M solution of i-propylmagnesium chloride was added and stirred at 0 ° C. for 30 minutes to synthesize an organomagnesium compound solution represented by the chemical formula (a1) in the above reaction formula.
To the dried argon-substituted eggplant flask B, 25 mL of THF and 27 mg (0.05 mmol) of dehydrated and peroxide-removed treatment and 27 mg (0.05 mmol) of NiCl ₂ (dppp) were added and heated to 35 ° C. Then, the organic magnesium compound solution (a1 ) Was added. After stirring with heating at 35 ° C. for 1.5 hours, 50 mL of 5M hydrochloric acid was added and stirred at room temperature for 1 hour. This reaction solution was extracted with 450 mL of chloroform, and the organic layer was washed with 100 mL of sodium bicarbonate water and 100 mL of distilled water in this order. The organic layer was dried over anhydrous sodium sulfate and concentrated to dryness. The obtained black-purple solid was dissolved in 30 mL of chloroform, reprecipitated into 300 mL of methanol, and sufficiently dried, and purified using a preparative GPC column to obtain a π-electron conjugated polymer A2. (690 mg) was obtained. In addition, THF as a solvent was purified by distillation of dehydrated tetrahydrofuran (without stabilizer) manufactured by Wako Pure Chemical Industries, Ltd. in the presence of metallic sodium, and then on molecular sieves 5A manufactured by Wako Pure Chemical Industries, Ltd. for one day or more. What was refine | purified by making it contact was used.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) are both determined in terms of polystyrene based on measurement by gel permeation chromatography (GPC). The measurement was performed using an HLC-8020 (product number) manufactured by Tosoh Corporation as the GPC apparatus, and a TSKgel Multipore HZ manufactured by Tosoh Corporation connected in series as the column. The measurement temperature in the column and the injector was 40 ° C., and chloroform was used as the solvent. The obtained π-electron conjugated polymer A2 had a weight average molecular weight of 24,150 g / mol, a number average molecular weight of 21,000 g / mol, and a polydispersity of 1.15.
¹ H-NMR: δ = 6.97 (s, 1H), 2.80 (t, J = 8.0 Hz, 2H), 1.89-1.27 (m, 10H), 0.91 (t, J = 6.8 Hz, 3H).
This physicochemical analysis result supports the chemical structure shown in the reaction formula (2).

(Polymerization Example 3)
The π-electron conjugated block copolymer B1 was synthesized according to the following reaction formula. In the following reaction formulas, EtHex represents a 2-ethylhexyl group.

  In a 50 mL flask under nitrogen atmosphere, π-electron conjugated polymer A1 (160.0 mg, 0.12 mol) and 2,6-bis (trimethyltin) -4,8 as two types of monomers constituting polymer block B -Bis (2-ethylhexyloxy) benzo [1,2-b: 4,5-b '] dithiophene (113.0 mg, 0.16 mmol), 2,6-bis (trimethyltin) -4,8-di Propylbenzo [1,2-b: 4,5-b ′] dithiophene (40.9 mg, 0.07 mmol) and 1- (4,6-dibromothieno [3,4-b] thiophen-2-yl) -2 -Ethylhexane-1-one (86.0 mg, 0.20 mmol), DMF (3.0 mL), toluene (12 mL), tetrakis (triphenylphosphine) palladium (0) (30 mg, 26 μmo) ) Was added and the vessel was bubbled 20 minutes with argon gas, and heated at 110 ° C. 10 hours. After completion of the reaction, the reaction solution was poured into methanol (300 mL), the precipitated solid was collected by filtration, and the obtained solid was dried under reduced pressure to obtain a crude product. The crude product was washed with acetone (200 mL) and hexane (200 mL) using a Soxhlet extractor and then extracted with chloroform (200 mL). The obtained solution was concentrated, poured into methanol (300 mL), and the precipitated solid was collected by filtration and dried under reduced pressure to obtain a π-electron conjugated block copolymer B1 as a black purple solid (221.0 mg, 75 .4%).

Using the same method as in Polymerization Example 1, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined. The resulting conjugated block copolymer B1 had a weight average molecular weight of 86,400, a number average molecular weight of 28,800, and a polydispersity of 2.99.
¹ H-NMR (270 MHz, CDCl ₃ ): δ = 7.60-7.30 (br, 3H), 4.40-4.00 (br, 4H), 3.30-3.00 (br, 4H) ), 2.00-0.60 (br, 51H).
This physicochemical analysis result supports the chemical structure shown in the reaction formula (3).

(Measurement of solubility of π-electron conjugated polymer in added solvent)
The polymers obtained in Polymerization Examples 1 to 3 were dissolved in chlorobenzene to prepare a dilute solution of 1.0 × 10 ⁻⁵ mol / L. The prepared diluted solution is filtered through a PTFE syringe filter having a pore diameter of 0.45 μm, and the obtained filtrate is put into a quartz cell having an optical path length of 1 cm. -3700), an absorption spectrum of 300 to 1000 nm was measured. From the obtained absorption spectrum, the molar extinction coefficient of the π-electron conjugated polymer was calculated using the absorbance at the maximum absorption wavelength in the range of 500 to 700 nm. Next, 10 mg of the π-electron conjugated polymer obtained in Polymerization Examples 1 to 3 was added to 1 mL of the additive solvent used in Examples and Comparative Examples, and stirred at 80 ° C. for 3 hours, and then stirred at 25 ° C. for 3 hours. Dispersed or dissolved. The adjusted solution was filtered with a PTFE syringe filter having a pore diameter of 0.45 μm, and the obtained filtrate was put into a quartz cell with an optical path length of 20 μm, and an absorption spectrum was measured using chlorobenzene as a reference solution. Using the absorbance at the wavelength at which the molar extinction coefficient was calculated and the molar extinction coefficient obtained with the dilute solution, the solubility of the π-electron conjugated polymer in each solvent was measured.

Example 1
A glass substrate provided with an ITO film (resistance value 10Ω / □) with a thickness of 150 nm by a sputtering method was subjected to surface treatment by UV ozone cleaning for 15 minutes in an oxygen atmosphere. A PEDOT: PSS aqueous solution (manufactured by HC Starck: CLEVIOS PH500) to be a hole transport layer is formed on a substrate to a thickness of 40 nm by spin coating, and is heated and dried at 140 ° C. for 20 minutes by a hot plate. went. Next, in 1 ml of chlorobenzene (manufactured by Wako Pure Chemical Industries, Ltd .: special grade), the π-electron conjugated polymer A1 obtained in Polymerization Example 1 as an electron-donating organic semiconductor material, and a fullerene derivative PC as an electron-accepting organic semiconductor material 30 mg of a powder obtained by mixing ₇₁ BM (manufactured by Frontier Carbon Co., Ltd .: E110) at a mass fraction of 1: 1.5 was added, and 1,8-diiodooctane was used as a poor solvent for the π-electron conjugated polymer. , N, N-dimethylformamide were added at 2.5 vol% and 8.0 vol%, respectively, and dissolved at 100 ° C., and then an organic semiconductor solution containing a π electron conjugated polymer and PC ₇₁ BM was prepared. The adjusted organic semiconductor solution was applied onto a substrate coated with a PEDOT: PSS aqueous solution by a spin coating method to obtain a photoelectric conversion layer (film thickness of about 100 nm) of an organic solar cell. After vacuum drying this for 3 hours, lithium fluoride was vapor-deposited with a film thickness of 1 nm by a vacuum vapor deposition machine, and then aluminum was vapor-deposited with a film thickness of 100 nm. The degree of vacuum at the time of vapor deposition was 2 × 10 ⁻⁴ Pa or less. As a result, an organic solar cell made of a π-electron conjugated polymer was obtained. The shape of the organic solar cell was a regular square of 5 × 5 mm.

(Example 2)
An organic solar cell was produced in the same manner as in Example 1 except that 1,8-diiodooctane and methyl benzoate were added in an amount of 2.5 vol% and 5.0 vol%, respectively, as a poor solvent for the π-electron conjugated polymer.

Example 3
An organic solar cell was produced in the same manner as in Example 1 except that the conjugated block copolymer B1 obtained in Polymerization Example 3 was used as the π-electron conjugated polymer.

Example 4
An organic solar cell was produced in the same manner as in Example 2 except that the conjugated block copolymer B1 obtained in Polymerization Example 3 was used as the π-electron conjugated polymer.

(Comparative Example 1)
An organic solar cell was produced in the same manner as in Example 1 except that the poor solvent for the π-electron conjugated polymer was not added.

(Comparative Example 2)
An organic solar cell was produced in the same manner as in Example 1 except that 2.5 vol% of 1,8-diiodooctane alone was added as a poor solvent for the π-electron conjugated polymer.

(Comparative Example 3)
An organic solar cell was produced in the same manner as in Example 1 except that only 5.0 vol% of methyl benzoate was added as a poor solvent for the π-electron conjugated polymer.

(Comparative Example 4)
An organic solar cell was produced in the same manner as in Example 1 except that only 5.0 vol% of N, N-dimethyl sulfoxide was added as a poor solvent for the π-electron conjugated polymer.

(Comparative Example 5)
An organic solar cell was prepared in the same manner as in Example 1 except that 1,8-diiodooctane and N, N-dimethyl sulfoxide were added as poor solvents for the π-electron conjugated polymer, 2.5 vol% and 5.0 vol%, respectively. Produced.

(Comparative Example 6)
An organic solar cell was produced in the same manner as in Example 1 except that 1,8-diiodooctane and chloroform were added at 2.5 vol% and 5.0 vol%, respectively, as a poor solvent for the π-electron conjugated polymer.

(Comparative Example 7)
An organic solar cell was produced in the same manner as in Example 1 except that the conjugated block copolymer B1 obtained in Polymerization Example 3 was used as the π-electron conjugated polymer and the poor solvent for the π-electron conjugated polymer was not added.

(Comparative Example 8)
An organic solar cell was prepared in the same manner as in Comparative Example 7 except that 1,8-diiodooctane and N, N-dimethyl sulfoxide were added as poor solvents for the π-electron conjugated polymer, 2.5 vol% and 5.0 vol%, respectively. Produced.

(Comparative Example 9)
The π-electron conjugated polymer A2 obtained in Polymerization Example 2 as the π-electron conjugated polymer, and the fullerene derivative PC ₆₁ BM (manufactured by Frontier Carbon Co., Ltd .: E100H) as the electron-accepting organic semiconductor material, An organic solar cell was produced in the same manner as in Example 1 except that the photoelectric conversion layer was formed by mixing at a mass fraction, dissolving in chlorobenzene, and no poor solvent for the π-electron conjugated polymer was added.

(Comparative Example 10)
An organic solar cell was produced in the same manner as in Comparative Example 9, except that 2.5 vol% and 5.0 vol% of 1,8-diiodooctane and methyl benzoate were added as poor solvents for the π-electron conjugated polymer.

(Evaluation of photoelectric conversion characteristics)
The photoelectric conversion efficiencies of the organic solar cells obtained in the examples and comparative examples were measured with a 300 W solar simulator (Peccell Technology, trade name: PEC L11: AM1.5G filter, irradiance: 100 mW / cm ² ). . The measurement results are shown in Tables 1 and 2.

  From the comparison between Comparative Example 1 and Examples 1 and 2 and the comparison between Comparative Example 7 and Examples 3 and 4, by adding two poor solvents of π electron conjugated polymer within the scope of the present invention, the poor solvent It can be seen that higher conversion efficiency can be obtained than an organic solar cell prepared without adding. From the comparison between Comparative Examples 2 to 4 and Examples 1 and 2, it can be seen that the present invention provides higher conversion efficiency than when only one poor solvent is added. From the comparison between Comparative Example 5 and Examples 1 and 2 and the comparison between Comparative Example 8 and Examples 3 and 4, the present invention is a poor solvent of a π electron conjugated polymer and the SP value is outside the range of the present invention. It can be seen that the conversion efficiency is higher than that of the organic solar cell produced by adding one kind of poor solvent. From the comparison between Comparative Example 6 and Examples 1 and 2, when one kind of poor solvent of π electron conjugated polymer and chloroform which is a good solvent of π electron conjugated polymer are added, the conversion efficiency is improved. I understand that there is not. From Comparative Examples 9 and 10, it can be seen that when the π-electron conjugated polymer is outside the scope of the present invention, conversion efficiency cannot be improved even when the production method of the present invention is applied.

(Evaluation of morphology image of cross section of photoelectric conversion layer)
The morphology of the cross section of the photoelectric conversion layer of the photoelectric conversion elements obtained in Example 2 and Comparative Examples 2 and 5 was observed and analyzed by the following method. A thin film slice in the cross-sectional direction of the photoelectric conversion element having the photoelectric conversion layer was produced at an acceleration voltage of 30 kV using a focused ion beam apparatus (SMI3200F manufactured by SII Nanotechnology). The ion current during rough processing of the thin film slice was 6500 pA, and the ion current during finishing was 80 pA. The prepared thin film slice had a thickness of 50 to 100 nm.

  A morphological image of the cross section was obtained from the prepared thin film slice using the STEM method (manufactured by Hitachi High-Technologies; S-5500). The acquisition of the morphology image by the STEM method was performed at an acceleration voltage of 30 kV. The obtained image had a resolution of 2 pixels / nm or higher, and after conversion to grayscale, the contrast and brightness were adjusted so that the morphology contrast was easy to understand.

  A morphology image of a cross section of the photoelectric conversion element obtained in Example 2 is shown in FIG. From the morphology image of this cross section, a hole transport layer composed of a PEDOT / PSS film is formed on the ITO electrode film on the glass substrate to form an electrode layer, a photoelectric conversion layer is formed thereon, and further thereon It can be confirmed that an electrode layer which is an aluminum electrode deposited on the lithium fluoride film is formed. FIG. 2 shows a morphology image obtained by performing binarization processing on this FIG. 1 using PhotoShop CS5 (manufactured by Adobe Systems) and trimming a region corresponding to the photoelectric conversion layer. In this observation, the dark part is a phase containing a lot of π-electron conjugated polymers which are electron-donating organic semiconductors, and the bright part is a phase containing a lot of fullerene derivatives which are electron-accepting organic semiconductors.

  In the same manner as described above, a morphology image of the cross section of the photoelectric conversion element obtained in Comparative Examples 2 and 5 was obtained. 3 and 4 show image morphology images obtained by binarizing the obtained image and trimming the region corresponding to the photoelectric conversion active layer, respectively.

  From the comparison of FIGS. 2 and 3, it is clear that the present invention can obtain a finer morphology than the production method in which only 1,8-diiodooctane is added as a poor solvent, and by adding two kinds of poor solvents. It can be seen that the morphology of the photoelectric conversion layer can be controlled. From the comparison of FIGS. 2 and 4, when the SP value of the two poor solvents to be added is in the range of 18.1 to 26.5, the poor solvent whose SP value is outside the range is added. In comparison, it can be seen that the morphological refinement effect is excellent.

Claims (5)

A method for producing a photoelectric conversion element having a photoelectric conversion layer containing a π-electron conjugated polymer and an electron-accepting organic semiconductor between a positive electrode and a negative electrode, at least one of which is light transmissive,
The π-electron conjugated polymer is a heterocyclic skeleton selected from a condensed π-conjugated skeleton, a carbazole skeleton, a dibenzosilole skeleton, a dibenzogermol skeleton, and a diketopyrrolopyrrole skeleton containing at least one thiophene ring as part of the chemical structure. A monomer unit having at least one of
Dissolving the π-electron conjugated polymer and the electron-accepting organic semiconductor in an organic solvent to obtain an organic semiconductor solution (A),
A step (B) of adding at least two poor solvents of the π-electron conjugated polymer having an SP value in the range of 18.1 to 26.5 to the organic semiconductor solution; and between the positive electrode and the negative electrode A process (C) of forming the photoelectric conversion layer by forming the organic semiconductor solution obtained in the process (B) by a coating method.   The method for producing a photoelectric conversion element according to claim 1, wherein the poor solvent used in the step (B) has a solubility of the π-electron conjugated polymer of 1.0 mg / mL or less.   At least one poor solvent used in the step (B) is 1,8-diiodooctane, anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N, N-dimethylformamide and N, The method for producing a photoelectric conversion element according to claim 1, which is any one selected from N-dimethylacetamide.   At least one poor solvent used in the step (B) is 1,8-diiodooctane, and at least one other is anisole, methyl benzoate, aniline, 1,2-dibromoethane, morpholine, N The method for producing a photoelectric conversion element according to claim 3, which is any one selected from N, N-dimethylformamide and N, N-dimethylacetamide.   5. The total amount of at least two kinds of poor solvents used in the step (B) is in the range of 0.1 vol% to 50.0 vol% of the organic semiconductor solution. Manufacturing method of the photoelectric conversion element.

Images