Hole transport material, photoelectric conversion element using the same, and organic solar cell

Abstract

The present invention provides a hole transport material that exhibits excellent resistance to high temperatures and humidity, and has excellent photoelectric conversion properties even under weak light conditions such as indoor lighting, as well as a photoelectric conversion element and an organic solar cell using the same. [Solution] A hole transport material represented by the following general formula (1). In formula (1), R1 to R 10 This represents a hydrogen atom, or an alkyl group or alkoxy group having 8 or fewer carbon atoms. [Formula 1] JPEG2026066831000014.jpg49139

Description

Technical Field

[0001] The present invention relates to a hole transport material used as a material for a hole transport layer, a photoelectric conversion device using the same, and an organic solar cell.

Background Art

[0002] In recent years, the driving power in electronic circuits has become very small, and various electronic components such as sensors can be driven even with weak power. Furthermore, when utilizing sensors, applications to self-powered power sources (environmental power generation devices) that can generate and consume power on-site are expected. Among them, solar cells have attracted attention as devices that can generate power anywhere as long as there is light.

[0003] As solar cells, inorganic solar cells and organic solar cells are known. However, inorganic solar cells have a problem that their range of use is limited from the viewpoints of high manufacturing cost and difficulty in downsizing because inorganic semiconductor materials such as silicon are used as p-type semiconductors and n-type semiconductors. Therefore, currently, the development of organic solar cells manufactured using organic semiconductors instead of inorganic semiconductors is underway. Organic solar cells are classified into, for example, dye-sensitized solar cells, organic thin-film solar cells, organic-inorganic hybrid solar cells, and the like.

[0004] An organic solar cell contains a p-type semiconductor and an n-type semiconductor, and a hole transport layer (hole transport layer) is often provided between a photoelectric conversion layer that absorbs light and generates positive and negative charges and an anode. The hole transport layer plays a role of improving the photoelectric conversion efficiency of the solar cell by enabling the positive charges (holes) generated by photoexcitation and the negative charges (electrons) to move efficiently without recombination.

[0005] Among organic solar cells, solar cells equipped with a photoelectric conversion layer containing a perovskite compound, as described in Patent Document 1, Non-Patent Documents 1 and 2 (hereinafter also referred to as perovskite solar cells), have been reported to exhibit higher photoelectric conversion efficiency than amorphous silicon solar cells in weak indoor light environments, and reports on further improvements in photoelectric conversion efficiency have been successively published. The basic structure of a perovskite solar cell is generally a laminate in which a transparent electrode (cathode), electron transport layer, photoelectric conversion layer (perovskite layer), hole transport layer, and metal electrode (anode) are stacked in this order. In some cases, a mesoporous titania layer is included between the electron transport layer and the perovskite layer, and the photoelectric conversion layer is composed of the perovskite layer and the mesoporous titania layer. Of these layers, the hole transport layer is generally composed of a material containing an organic semiconductor.

[0006] Among the organic semiconductors included in hole transport layer materials reported to date, one example is 2,2′,7,7′-tetrakis-(N,N-di-methoxyphenylamine)-9,9′-spirobifluorene (hereinafter also referred to as Spiro-OMeTAD), which was developed as a hole transport layer material for dye-sensitized solar cells and is described in Non-Patent Document 3. It is also commonly used in the aforementioned perovskite solar cells. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 2016-539914 [Non-patent literature]

[0008] [Non-Patent Document 1] Michael M. Lee et al., "Efficient Hybrid Solar Cells Based on Meso-Super structured Organometal Halide Perovskites", Science (2012) 338, P643-647 [Non-Patent Document 2] Nam Joong Jeon et al., "Solvent engineering for high-performance inorganic-organic hybrid perovskite solar cells", Nature Materials (2014) 13, P897-903 [Non-Patent Document 3] Nature volume (1998) 395, P583-585 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, when Spiro-OMeTAD is used as the material for the hole transport layer, it cannot be said that sufficiently good photoelectric conversion performance is achieved. Therefore, when using this material, it is generally necessary to add a large amount of dopant such as lithium bis(trifluoromethanesulfonyl)imide (hereinafter also called LiTFSI salt) to improve photoelectric conversion performance, and the doping of large amounts of LiTFSI salt has the problem that solar cells have poor durability in high temperature and high humidity.

[0010] In view of the above problems, the present invention aims to provide a hole transport material that has excellent high temperature and high humidity durability and excellent photoelectric conversion properties even in weak light such as indoor light, as well as a photoelectric conversion element and an organic solar cell using the same. [Means for solving the problem]

[0011] To achieve the above objective, the first configuration of the present invention is a hole transport material represented by the following general formula (1). [ka] In formula (1), R1~R 10 This represents a hydrogen atom, or an alkyl group or alkoxy group having 8 or fewer carbon atoms. [Effects of the Invention]

[0012] According to the first configuration of the present invention, by using the compound represented by the above formula (1) as a material for the hole transport layer of the photoelectric conversion element and the solar cell, the high-temperature and high-humidity durability and the mobility of charges (holes) can be improved, and the energy conversion efficiency of the photoelectric conversion element and the solar cell is improved.

Brief Description of Drawings

[0013] [Figure 1] It is a partial cross-sectional view of an organic solar cell 100 according to an embodiment of the present invention, showing an example in which the first electrode 2 is an electron injection electrode and the second electrode 6 is a hole injection electrode. [Figure 2] It is a partial cross-sectional view of an organic solar cell 100 according to an embodiment of the present invention, showing an example in which the first electrode 2 is a hole injection electrode and the second electrode 6 is an electron injection electrode.

Embodiments for Carrying Out the Invention

[0014] [1. Structure of Organic Solar Cell] First, a solar cell using the hole transport material of the present invention will be described. FIG. 1 is a partial cross-sectional view of an organic solar cell 100 according to an embodiment of the present invention. The organic solar cell 100 (hereinafter simply referred to as the solar cell 100) includes a substrate 1, a first electrode 2, an electron transport layer 3, a photoelectric conversion layer 4, a hole transport layer 5, and a second electrode 6. The first electrode 2 is provided on the substrate 1. The photoelectric conversion layer 4 is laminated on the first electrode 2 via the electron transport layer 3. The second electrode 6 is laminated on the photoelectric conversion layer 4 via the hole transport layer 5. Note that the electron transport layer may not be provided, and the photoelectric conversion layer 4 may be directly laminated on the first electrode 2. In this case, the electron transport layer 3 shown in FIG. 1 is omitted. When the solar cell 100 is in use, for example, light L (for example, sunlight or indoor light) is irradiated onto the surface of the solar cell 100 on the side of the substrate 1. Note that when the solar cell 100 is in use, light L may be irradiated onto the surface of the solar cell 100 on the side of the second electrode 6.

[0015] <Substrate> The substrate 1 is not particularly limited as long as it can be used for the solar cell 100. The substrate 1 may be transparent or opaque. However, when the surface of the substrate 1 side of the solar cell 100 serves as the light-receiving surface, the substrate 1 is preferably transparent. Examples of the transparent substrate include glass such as quartz glass, transparent rigid substrates such as synthetic quartz plates, and transparent flexible substrates such as transparent resin films and optical resin plates. The transparent flexible substrate has advantages such as ease of processing, reduction of manufacturing cost, weight reduction, difficulty in cracking, and applicability to curved surfaces.

[0016] <First electrode> The first electrode 2 is, for example, an electron injection electrode. The first electrode 2 is not limited to a material having conductivity. Examples of the material having a high work function used as the first electrode 2 include gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), carbon (C), indium tin oxide (ITO), tin oxide (SnO2), fluorine-doped tin oxide (FTO), and zinc oxide (ZnO).

[0017] In addition, the material of the first electrode 2 is appropriately selected in consideration of whether the light-receiving surface of the solar cell 100 is the surface on the substrate 1 side or the surface on the second electrode 6 side. When the light-receiving surface is the surface on the substrate 1 side, the first electrode 2 is preferably a transparent electrode. Examples of the material used when the first electrode 2 is a transparent electrode include indium zinc oxide (IZO), ITO, FTO, ZnO-Al, and Zn-Sn-O.

[0018] The total light transmittance of the first electrode 2 is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more. When the total light transmittance of the first electrode 2 is 85% or more, when the light-receiving surface of the solar cell 100 is the surface on the substrate 1 side, light can sufficiently pass through the first electrode 2 on the substrate 1, and the photoelectric conversion layer 4 can efficiently absorb the light.

[0019] The sheet resistance of the first electrode 2 is preferably 20 [Ω / sq] or less, and more preferably 15 [Ω / sq] or less. When the sheet resistance of the first electrode 2 is 20 [Ω / sq] or less, the charge generated in the photoelectric conversion layer 4 is sufficiently transmitted to the external circuit. The sheet resistance can be measured, for example, using a resistivity meter (Loresta AXMCP-T370, manufactured by Nitto Seiko Analytech Co., Ltd., 4-probe type) in accordance with JIS (Japanese Industrial Standards) R1637 (Test method for resistivity of fine ceramic thin films - Measurement method by 4-probe method).

[0020] The film thickness of the first electrode 2 is preferably 0.1 nm or more and 500 nm or less, and more preferably 1 nm or more and 300 nm or less. When the film thickness of the first electrode 2 is 0.1 nm or more, the sheet resistance of the first electrode 2 does not become too large, and the charge (holes) generated in the photoelectric conversion layer 4 can be sufficiently transmitted to the external circuit. On the other hand, when the film thickness of the first electrode 2 is 500 nm or less, the total light transmittance of the first electrode 2 is high.

[0021] The first electrode 2 may be a single layer. Alternatively, the first electrode 2 may be composed of multiple layers having different work functions. When the first electrode 2 consists of multiple layers, the film thickness of the first electrode 2 described above refers to the total film thickness of the multiple layers.

[0022] The first electrode 2 may be formed in a sheet shape over the entire surface of the substrate 1, or it may be formed in a pattern shape on the substrate 1. The shape of the first electrode 2 may be flat or uneven. Examples of uneven shapes include a textured structure, a pyramidal structure, a wave-shaped structure, a comb-shaped structure, and a nanopillow structure. When the first electrode 2 is uneven, the incident light is scattered by the unevenness of the first electrode 2, so that more light is taken up by the photoelectric conversion layer 4, and the energy conversion efficiency of the solar cell 100 is improved.

[0023] <Electron transport layer> The electron transport layer 3 is laminated between the first electrode 2 and the photoelectric conversion layer 4. The electron transport layer 3 is provided to facilitate the injection (movement) of electrons from the photoelectric conversion layer 4 to the first electrode 2 (electron injection electrode). By laminating the electron transport layer 3, the electron injection efficiency from the photoelectric conversion layer 4 to the first electrode 2 is increased, and the energy conversion efficiency of the solar cell 100 is improved.

[0024] The material contained in the electron transport layer 3 (electron transport layer material) is not particularly limited as long as it is a material that can stably inject electrons from the photoelectric conversion layer 4 to the second electrode 6. Examples of electron transport layer materials include conductive organic compounds, charge transfer complexes, alkali metals, alkaline earth metals, and organic compounds and metal oxides doped with alkali metals or alkaline earth metals.

[0025] Examples of alkali metals that can be used as electron transport layer materials include lithium, sodium, potassium, rubidium, and cesium. Examples of alkaline earth metals that can be used as electron transport layer materials include beryllium, magnesium, calcium, strontium, and barium. Examples of alkali metal or alkaline earth metal-doped organic compounds that can be used as electron transport layer materials include alkali metal or alkaline earth metal-doped bathocuproine (BCP) and batphenanthroline (Bphen). Preferred alkali metals and alkaline earth metals used for doping are lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, or barium, with lithium, cesium, barium, or strontium being more preferred. Examples of metal oxides that can be used as electron transport materials include titanium oxide, zinc oxide, and tin oxide.

[0026] When the electron transport layer material is a conductive organic compound, a charge transfer complex, or a metal oxide, the film thickness of the electron transport layer 3 is preferably 10 nm to 200 nm. When the electron transport layer material is an alkali metal, an alkaline earth metal, or an organic compound doped with an alkali metal or alkaline earth metal, the film thickness of the electron transport layer 3 is preferably 0.1 nm to 50 nm.

[0027] <Photoelectric conversion layer> The photoelectric conversion layer 4 may be a bulk heterojunction type photoelectric conversion layer containing a donor (electron donor) and an acceptor (electron acceptor), or it may be a photoelectric conversion layer having a perovskite layer, which is a so-called perovskite.

[0028] In the case of a bulk heterojunction type photoelectric conversion layer, the donor is not particularly limited as long as it functions as a donor, but it is preferably an electron-donating conductive polymer (electron-donating organic material). An electron-donating organic material refers to the organic compound with the lower electron affinity when two organic compounds are brought into contact. In other words, any organic compound that is electron-donating can be used as a donor. The donor is preferably a compound that can be formed into a thin film using a solution in which the donor is dissolved in an organic solvent (for example, a coating method such as casting or spin coating). The photoelectric conversion layer 4 may contain only the donor and acceptor, or it may contain other compounds.

[0029] Examples of electron-donating conductive polymers that can be used as donors include polyphenylene, polyphenylene vinylene, polysilane, polythiophene, polybenzodithiophene, polycarbazole, polyvinylcarbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinylpyrene, polyvinylanthracene, and derivatives thereof. The donor may be a copolymer obtained by copolymerizing at least two of these electron-donating conductive polymers. Other examples of electron-donating conductive polymers include phthalocyanine-containing polymers, carbazole-containing polymers, and organometallic polymers.

[0030] As an electron-donating conductive polymer that can be used as a donor, a polymer having at least one of the following structures—thiophene, benzothiophene, and benzodithiophene (polythiophene polymer)—is preferred. The polythiophene polymer is preferably capable of absorbing visible light. Furthermore, the polythiophene polymer is preferably of the donor-acceptor (DA) type.

[0031] The acceptor is not particularly limited as long as it functions as an acceptor, but it is preferably a conductive polymer (electron-accepting organic material) that has electron-accepting properties. Electron-accepting organic materials are mainly represented by electron-transporting organic compounds and refer to organic compounds that have a property of readily accepting electrons. More specifically, it refers to the organic compound with the greater electron affinity when two organic compounds are used in contact. In other words, any organic compound that has electron-accepting properties can be used as an acceptor.

[0032] Examples of electron-accepting organic materials include fullerenes and their derivatives (such as PCBM), carbon nanotubes and their derivatives, perylenes and their derivatives (such as PTCDA and PTCDI), naphthalene derivatives (such as NTCDA and NTCDI), oligomers and polymers having pyridine and its derivatives as a backbone, fluorinated metal-free phthalocyanines, fluorinated metal phthalocyanines and their derivatives, tris(8-hydroxyquinolinate)aluminum complexes, bis(4-methyl-8-quinolinate)aluminum complexes, distylyl arylene derivatives, and silole compounds. Fullerene derivatives (such as PCBM) are particularly preferred, but the material is not limited thereto.

[0033] In the photoelectric conversion layer 4, the ratio of the acceptor mass (MA) to the donor mass (MD) (MA / MD) is preferably 0.1 or more and 2.0 or less, and more preferably 1.0 or more and 2.0 or less. When the ratio (MA / MD) is within this range, the balance between the acceptor and donor of the solar cell 100 is good, and the energy conversion efficiency of the solar cell 100 is improved.

[0034] The photoelectric conversion layer having a perovskite layer uses a compound represented by the general formula (ABX3). This compound may be a perovskite crystal or a perovskite complex. Examples of A include monovalent cations formed from organic amino compounds such as methylamine, ethylamine, n-butylamine, di-n-butylamine, trimethylamine, triethylamine, methyl-n-hexylamine, methyldiethylamine, tri-n-hexylamine, imidazole, pyrrole, aziridine, formamidine, guanidine, pyridine, 4-t-butylpyridine, phenethylamine, and 5-aminovaleric acid, as well as cesium, potassium, rubidium, etc., and these may be used alone or as a mixture of two or more. Examples of B include divalent cations such as lead and tin, and these may be used alone or in mixtures. In addition, small amounts of trivalent cations such as indium and antimony may be mixed in. X can be a halogen atom or anion source such as chlorine, bromine, or iodine, and may be used alone or in a mixture of two or more.

[0035] The film thickness of the photoelectric conversion layer 4 is not particularly limited, as long as the desired energy conversion efficiency can be obtained, whether it is a bulk heterojunction photoelectric conversion layer or a perovskite-type photoelectric conversion layer. The film thickness of the photoelectric conversion layer 4 is preferably 0.2 nm or more and 3000 nm or less, and more preferably 10 nm or more and 600 nm or less. When the film thickness of the photoelectric conversion layer 4 is 3000 nm or less, the sheet resistance of the photoelectric conversion layer 4 is more likely to be the desired value. On the other hand, when the film thickness of the photoelectric conversion layer 4 is 0.2 nm or more, a short circuit between the first electrode 2 and the second electrode 6 is less likely to occur.

[0036] <Hole transport layer> The hole transport layer 5 is laminated between the photoelectric conversion layer 4 and the second electrode 6. The hole transport layer 5 is provided to facilitate the injection (movement) of holes from the photoelectric conversion layer 4 to the second electrode 6 (hole injection electrode). By laminating the hole transport layer 5, the hole injection efficiency from the photoelectric conversion layer 4 to the second electrode 6 is increased, improving the energy conversion efficiency of the solar cell 100. The hole transport layer 3 contains a 2,7-bis[(4-diphenylamino)phenyl]-9,9'-spirobi[fluorene] derivative represented by the following general formula (1). The hole transport layer 3 may contain only the 2,7-bis[(4-diphenylamino)phenyl]-9,9'-spirobi[fluorene] derivative represented by the general formula (1), or it may further contain additives. Conventional known additives such as interface treatment agents can be used as additives.

[0037] [ka]

[0038] In formula (1), R1~R 10 This represents a hydrogen atom, or an alkyl group or alkoxy group having 8 or fewer carbon atoms.

[0039] Specific examples of 2,7-bis[(4-diphenylamino)phenyl]-9,9'-spirobi[fluorene] derivatives represented by general formula (1) include compounds HTM-1 to HTM-3, which are represented by the following chemical formulas.

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] By using the compound represented by formula (1) above as the hole transport material constituting the hole transport layer 5, the mobility of charge (holes) can be improved, thereby increasing the energy conversion efficiency of the solar cell 100.

[0044] <Second electrode> The second electrode 6 is, for example, a hole injection electrode. The second electrode 6 is provided opposite the first electrode 2. The second electrode 6 is not particularly limited as long as it is conductive. The material of the second electrode 6 is appropriately selected, for example, taking into consideration the work function of the hole transport layer 5. If the material of the hole transport layer 5 is a material with a high work function, it is preferable that the material of the second electrode 6 is a material with a low work function.

[0045] Examples of materials that can be used as the material for the second electrode 6 include gold (Au), silver (Ag), cobalt (Co), nickel (Ni), platinum (Pt), carbon (C), indium tin oxide (ITO), tin oxide (SnO2), fluorine-doped tin oxide (FTO), and zinc oxide (ZnO).

[0046] Furthermore, the material of the second electrode 6 is appropriately selected, for example, by considering whether the light-receiving surface of the solar cell 100 is the surface on the substrate 1 side or the surface on the second electrode 6 side. If the light-receiving surface is the surface on the substrate 1 side, the first electrode 2 is preferably a transparent electrode, but the second electrode 6 does not have to be a transparent electrode.

[0047] The film thickness of the second electrode 6 is preferably 0.1 nm or more and 500 nm or less, and more preferably 1 nm or more and 300 nm or less. When the film thickness of the second electrode 6 is 0.1 nm or more, the sheet resistance of the second electrode 6 does not become too large, and the charge generated in the photoelectric conversion layer 4 can be sufficiently transmitted to the external circuit.

[0048] The second electrode 6 may be a single layer. Alternatively, the second electrode 6 may be composed of multiple layers having different work functions. If the second electrode 6 consists of multiple layers, the film thickness of the second electrode 6 as described above refers to the total film thickness of the multiple layers.

[0049] The second electrode 6 may be formed in a sheet shape over the entire surface of the hole transport layer 5, or it may be formed in a pattern shape on the hole transport layer 5.

[0050] <Other components> The solar cell 100 may further include other components in addition to the substrate 1, first electrode 2, electron transport layer 3, photoelectric conversion layer 4, hole transport layer 5, and second electrode 6 described above, as needed. Examples of other components include a protective sheet layer, filler layer, barrier layer, protective hard coat layer, strength support layer, anti-fouling layer, high light reflectivity layer, light containment layer, ultraviolet blocking layer, infrared blocking layer, and sealing layer. Furthermore, adhesive layers may be laminated between each layer of the solar cell 100, as needed.

[0051] Furthermore, the solar cell 100 is not limited to the structure shown in Figure 1; for example, the first electrode 2 may be a hole injection electrode and the second electrode 6 may be an electron injection electrode. In that case, the stacking order of the hole transport layer 5 and the electron transport layer 3 will be reversed from that in Figure 1. Specifically, as shown in Figure 2, the hole transport layer 5 is stacked between the first electrode 2 and the photoelectric conversion element 4, and the electron transport layer 3 is stacked between the photoelectric conversion element 4 and the second electrode 6.

[0052] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, an example was given in which the hole transport material of the present invention was used in the hole transport layer 5 of a solar cell 100, but it is not limited to the solar cell 100, and can also be used, for example, as a hole transport layer of a photoelectric conversion element.

[0053] As an example of a photoelectric conversion element, for instance, a semiconductor electrode (first electrode) is fabricated by laminating a hole-blocking layer and a porous electron transport layer on a glass substrate, and further supporting a photosensitizing material. A hole transport layer is formed on this semiconductor electrode (first electrode) by spin coating using a solution of the hole transport material of the present invention dissolved in an organic solvent, and a second electrode is formed by laminating silver on the formed hole transport layer using a vacuum deposition method. The effects of the present invention will be further explained in detail below with reference to examples. [Examples]

[0054] [Example of synthesis of 2,7-bis[(4-diphenylamino)phenyl]-9,9'-spirobi[fluorene] derivative (HMT-1)] A stirring bar was placed in a 500 mL two-necked flask equipped with a reflux condenser, and 17.91 g (0.03156 mol) of 2,7-bis(4-chlorophenyl)-9,9'-spirobio[fluorene] represented by chemical formula (A), 14.51 g (0.0633 mol) of bis(4-methoxyphenyl)amine represented by chemical formula (B), 0.610 g (0.00128 mol) of 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, and 9.11 g (0.09494 mol) of sodium-tert-butoxide were charged. The system was then purged with nitrogen. Subsequently, 150 g of xylene was added, and the oil bath was heated to 140°C (flask contents 130°C) while stirring with a magnetic stirrer, and the reaction was allowed to proceed for 3 hours. After the reaction, the oil bath was cooled to 60°C, and the disappearance of the starting material, 2,7-bis(4-chlorophenyl)-9,9'-spirobio[fluorene], was confirmed by TLC (thin-layer chromatography).

[0055] After the reaction, as a clay adsorption treatment, 19 g of activated clay was added to the reaction solution, stirred at over 80°C for 10 minutes, and the filtrate was collected by hot filtration. This clay adsorption treatment was performed a total of three times. The filtrate after the clay adsorption treatment was concentrated to 100 g under reduced pressure using an evaporator. While stirring the concentrated solution, 50 g of isohexane and 50 g of methanol were added in small amounts to precipitate a solid. The precipitated solid was filtered and vacuum-dried (100°C, 5 hours) to obtain a primary solid. This primary solid was purified by column chromatography (eluent: toluene / isohexane), and the solution containing the target product was concentrated and crystallized with isohexane and methanol. The filtered solid was vacuum-dried (100°C, 5 hours) to obtain a pale yellow final solid (12.9 g, yield 42.9%). The synthesis scheme is shown below.

[0056] [ka] [Examples]

[0057] [Manufacturing of perovskite-type organic solar cells] A 1.6 mm thick conductive glass substrate (FTN1.6, manufactured by Nippon Sheet Glass Co., Ltd., hereinafter referred to as FTO substrate) with a fluorine-doped tin oxide layer (first electrode) formed on it was used as the substrate. The FTO substrate was cut into 20 mm x 20 mm squares.

[0058] The FTO substrate was protected with masking tape except for the edges (5 mm), and the FTO portion was etched and removed using a cotton swab soaked in 6N hydrochloric acid and zinc powder. After removal, it was washed with deionized water, and the masking tape was removed. Then, the FTO substrate was ultrasonically cleaned for 15 minutes each in the following order: 10% neutral detergent solution (Clean Ace S, manufactured by AS ONE), deionized water, isopropyl alcohol, and acetone. After cleaning, the surface of the FTO substrate was treated with UV-ozone for 30 minutes.

[0059] Next, 200 μL of a 4% aqueous solution of tin(IV) nanoparticles (a mixture of Thermo Fisher's SnO2 aqueous dispersion (15% concentration) and deionized water in a 4:11 ratio) was dropped onto the FTO substrate, and spin coating was performed with acceleration for 3 seconds, rotation for 20 seconds (4000 rpm), and deceleration for 3 seconds until stopping. After that, the substrate was annealed (heat treated) on a hot plate at 150°C for 30 minutes to form an electron transport layer on the FTO substrate.

[0060] After the FTO substrate with this electron transport layer was subjected to UV-ozone treatment again for 15 minutes, it was placed in a glove box under conditions of 23°C ± 1°C and a dew point of -20 ± 5°C.

[0061] Separately, under the glove box, 0.692 g (1.5 mmol) of lead iodide (L0279, manufactured by Tokyo Chemical Industry Co., Ltd.), 0.059 g (0.225 mmol) of cesium iodide (C2205, manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.219 g (1.275 mmol) of formamidine hydroiodide (F0974, manufactured by Tokyo Chemical Industry Co., Ltd.) were weighed with 1.25 mL of a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (volume ratio 4:6), and the mixture was stirred at 70°C for 1 hour to dissolve.

[0062] After the dissolved coating solution was cooled to room temperature, 150 μL of the coating solution was dropped onto the electron transport layer and the coated substrate. After 30 seconds, spin coating was performed with acceleration for 0.8 seconds, rotation for 50 seconds (3000 rpm), further acceleration for 0.8 seconds, rotation for 30 seconds (6000 rpm), and deceleration for 1 second until stopping. Additionally, 200 μL of ethyl acetate was dropped 4 seconds after reaching 6000 rpm. After stopping the rotation, the substrate was annealed (heat treated) on a hot plate at 135°C for 15 minutes to form a perovskite power generation layer (photoelectric conversion layer) on the electron transport layer.

[0063] Next, 75 mg of the compound HTM-1 synthesized in Example 1, along with 9.1 mg of lithium bis(trifluoromethanesulfonyl)imide and 26.5 mg of 4-tert-butylpyridine as additives, were dissolved in 1 mL of chlorobenzene and 0.017 mL of acetonitrile to prepare a hole transport layer forming composition. Using the prepared hole transport layer forming composition solution, a 100 nm hole transport layer was formed on a substrate by spin coating at a rotation speed of 4000 rpm for 30 seconds. The prepared device was left in an environment with 5% humidity for 12 hours. Subsequently, a gold electrode (second electrode) was formed on the hole transport layer by vacuum deposition to a depth of 80 nm, thereby producing the perovskite-type organic solar cell of the present invention 1.

[0064] The perovskite-type organic solar cells of the present invention 2 and 3 were manufactured by the same method as described above, except that compounds HTM-2 and HTM-3 were used instead of compound HTM-1.

[0065] Perovskite-type organic solar cells of Comparative Examples 1 and 2 were manufactured in the same manner as described above, except that compounds HTM-4 and HTM-5, represented by the following chemical formulas, were used instead of compound HTM-1.

[0066] [ka]

[0067] [ka] [Examples]

[0068] [Evaluation of the photoelectric conversion characteristics of perovskite-type organic solar cells] The photoelectric conversion efficiency of organic solar cells of Invention 1-3 and Comparative Examples 1 and 2, manufactured in Example 2, was evaluated. A solar simulator (HAL-320, manufactured by Asahi Spectrometer Co., Ltd.) was used as the measurement device, and the light intensity of the measurement light source was adjusted to 100 mW / cm2 using a reference solar cell. In the actual measurement, the measurement area was 0.1 cm². 2 The JV curve characteristics were measured using a source meter (Model 6242, manufactured by ADC) while irradiating a masked solar cell element with light. The measurement was performed once each under Forward (forward scan, scanning in the direction of voltage increase) and Reverse (reverse scan, scanning in the direction of voltage decrease) conditions (total of 2 measurements), and the conversion efficiency was determined.

[0069] From the measurement results, the short-circuit current (Jsc[mA / cm²]) for both forward and reverse was determined. 2 ]), open-circuit voltage (Voc[V]), curve factor (FF[mW / cm 2 The following formula was derived: Furthermore, the photoelectric conversion efficiency (PCE[%]) was calculated using the following formula. PCE = (Jsc × Voc × FF / 100) × 100 Table 1 shows the PCE of the organic solar cells of Inventions 1-3 and Comparative Examples 1 and 2, along with Jsc, Voc, and FF. Table 1 shows the results for the solar cell with the highest conversion efficiency.

[0070] [Table 1]

[0071] As shown in Table 1, the organic solar cells of Invention 1 to 3, which used compounds HTM-1 to HTM-3 as hole transport materials, all had a PCE of 14.5% or higher, and their photoelectric conversion efficiency was higher than that of the organic solar cell of Comparative Example 4, which used compound HTM-4 as the hole transport material. Furthermore, they showed comparable or better photoelectric conversion efficiency compared to the organic solar cell of Comparative Example 5, which used compound HTM-5 as the hole transport material.

[0072] In particular, the organic solar cells of the present invention 1 and 3, which use HTM-1 and HTM-3 as hole transport materials, showed extremely high photoelectric conversion efficiency, with PCE exceeding 15% under both forward and reverse conditions.

[0073] Based on these results, it was confirmed that using compounds HTM-1 to HTM-3 as hole transport materials can effectively improve the photoelectric conversion efficiency of solar cells. [Industrial applicability]

[0074] The present invention relates to a hole transport material used as a material for a hole transport layer, and can be used in photoelectric conversion elements and organic solar cells using the same. By utilizing the present invention, it is possible to provide a hole transport material that has excellent high temperature and high humidity durability and excellent photoelectric conversion performance even in weak light such as indoor light, as well as a photoelectric conversion element and organic solar cell using the same. [Explanation of Symbols]

[0075] 1 circuit board 2 1st electrode 3 Electron transport layer 4. Photoelectric conversion layer 5. Hole transport layer 6 Second electrode 100 solar cells

Claims

1. A hole transport material represented by the following general formula (1). 【Chemistry 1】 (In formula (1), R 1 ~R 10 (This represents a hydrogen atom, or an alkyl group or alkoxy group having 8 or fewer carbon atoms.)

2. The hole transport material according to claim 1, characterized in that the general formula (1) is any of the following chemical formulas (HTM-1), (HTM-2), or (HTM-3). 【Chemistry 2】 【Transformation 3】 【Chemistry 4】

3. circuit board and A first electrode, which is an electron injection electrode, is stacked on the aforementioned substrate, An electron transport layer stacked on the first electrode, A photoelectric conversion layer stacked on the electron transport layer, A hole transport layer is laminated on the aforementioned photoelectric conversion layer, A second electrode, which is a hole injection electrode, is stacked on the hole transport layer, Equipped with, The hole transport layer comprises the hole transport material described in claim 1 or claim 2, wherein the hole transport layer is an organic solar cell.

4. circuit board and A first electrode, which is a hole injection electrode, is stacked on the substrate, A hole transport layer is stacked on the first electrode, A photoelectric conversion layer stacked on the electron transport layer, An electron transport layer stacked on the aforementioned photoelectric conversion layer, A second electrode, which is an electron injection electrode, is stacked on the hole transport layer, Equipped with, The hole transport layer comprises the hole transport material described in claim 1 or claim 2, wherein the hole transport layer is an organic solar cell.

5. circuit board and A hole-blocking layer and a porous electron transport layer are laminated on the aforementioned substrate, and a first electrode supporting a photosensitizing material is provided. A hole transport layer is stacked on the first electrode, A second electrode stacked on the hole transport layer, Equipped with, The hole transport layer comprises the hole transport material described in claim 1 or claim 2, wherein the photoelectric element is a photoelectric element.

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