JP2021174940A - Photoelectric conversion element and power generation device - Google Patents

Abstract

To improve the power generation efficiency in a low-illuminance region, in a photoelectric conversion element that uses an organic-inorganic hybrid semiconductor material.SOLUTION: A photoelectric conversion element 100 has: a pair of electrodes configured by an upper electrode 105 and a lower electrode 101; an active layer 103 located between the pair of electrodes and that contains an organic-inorganic hybrid semiconductor compound; and a hole transport layer 102 located between the active layer 103 and at least one of the pair of electrodes and that contains an organic semiconductor compound. In the photoelectric conversion element 100, an ionization potential of the active layer 103 is equal to or more than -6.0 eV and equal to or less than -5.7 eV, and a bandgap of the active layer 103 is equal to or more than 1.6 eV and equal to or less than 2.3 eV. An ionization potential of the organic semiconductor compound is equal to or more than -5.8 eV and equal to or less than -5.4 eV.SELECTED DRAWING: Figure 1

Description

The present invention relates to photoelectric conversion elements and power generation devices.

As a photoelectric conversion element, one in which an active layer, a buffer layer and the like are arranged between a pair of electrodes is known. For the purpose of improving the photoelectric conversion efficiency, the use of an organic-inorganic hybrid semiconductor material as an active layer has been studied, and in particular, a compound having a perovskite structure has attracted attention.

Further, an organic semiconductor compound or the like is used as the hole transport layer of such a photoelectric conversion element, and in Patent Document 1, in order to improve the durability of the photoelectric conversion element, a phthalocyanine-based organic semiconductor compound is positively used. It is described as being applied to the hole transport layer.

JP-A-2017-066096

However, when such an organic semiconductor compound is used for the hole transport layer, it is particularly important in energy harvesting applications, in a low illuminance environment such as a room where visible light from a fluorescent lamp or LED is used as a light source. Power generation efficiency may decrease.

An object of the present invention is to improve the power generation efficiency in low illuminance in a photoelectric conversion element using an organic-inorganic hybrid semiconductor material as an active layer.

By adopting a hole transport layer having a specific range of ionization potential together with an active layer having a specific range of ionization potential and bandgap, the present inventors have excellent power generation even in a low illuminance environment by visible light. We have found that we can provide a photoelectric conversion element with efficiency, and completed the present invention.

That is, the gist of the present invention lies below.
[1] A pair of electrodes composed of an upper electrode and a lower electrode, an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and at least one of the active layer and the pair of electrodes. A photoelectric conversion element having a hole transport layer containing an organic semiconductor compound, which is located between the two.
The ionization potential of the active layer is -6.0 eV or more and -5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the ionization potential of the hole transport layer is , -5.8 eV or more and -5.4 eV or less, photoelectric conversion element.
[2] The photoelectric conversion element according to [1], wherein the organic semiconductor compound is a semiconductor compound having a polytriarylamine structure.
[3] The photoelectric conversion element according to [1] or [2], wherein the hole transport layer further contains a dopant.
[4] The photoelectric conversion element according to [3], wherein the dopant is an organic compound containing trivalent iodine.
[5] The photoelectric conversion element according to [3] or [4], wherein the dopant is a diaryliodonium salt.
[6] The photoelectric conversion element according to any one of [1] to [5], wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure.
[7] The photoelectric conversion element according to any one of [1] to [6], wherein the photoelectric conversion efficiency at 200 lux is 25% or more.
[8] A power generation device having the photoelectric conversion element according to any one of [1] to [7].

INDUSTRIAL APPLICABILITY According to the present invention, in a photoelectric conversion element using an organic-inorganic hybrid semiconductor material, it is possible to improve the power generation efficiency particularly in a low illuminance environment using an indoor light source.

It is sectional drawing which shows typically the photoelectric conversion element as one Embodiment. It is sectional drawing which shows typically the solar cell as one Embodiment. It is sectional drawing which shows typically the solar cell module as one Embodiment.

The photoelectric conversion element according to one embodiment of the present invention includes a pair of electrodes composed of an upper electrode and a lower electrode, an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and the above-mentioned active layer. It is a photoelectric conversion element located between the active layer and at least one of the pair of electrodes and having a hole transport layer containing an organic semiconductor compound. The ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the hole transport layer is ionized. The potential is -5.8 eV or more and -5.4 eV or less. The photoelectric conversion element having such a configuration is excellent in power generation efficiency in a low illuminance environment.
In the present specification, the low illuminance region means 10 to 5000 lux, and is typically around 200 lux.

Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents as long as the gist thereof is not exceeded.

[1. Photoelectric conversion element according to one embodiment]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a photoelectric conversion element according to the present invention. The photoelectric conversion element shown in FIG. 1 is a photoelectric conversion element used in a general thin-film solar cell, but the photoelectric conversion element according to the present invention is not limited to the one shown in FIG.
In the photoelectric conversion element 100 shown in FIG. 1, the lower electrode 101, the active layer 103, and the upper electrode 105 are arranged in this order. Further, in the photoelectric conversion element 100, the buffer layer 102 existing between the lower electrode 101 and the active layer 103 can be a hole transport layer containing an organic semiconductor compound. In this case, the dopant can be further contained together with the organic semiconductor compound. However, the photoelectric conversion element 100 may have a buffer layer 104 between the upper electrode 105 and the active layer 103, and in this case, the buffer layer 104 can be used as the hole transport layer described above. Further, as shown in FIG. 1, the photoelectric conversion element 100 may have a base material 106, or may have an insulator layer and other layers such as a work function tuning layer.

[2. Active layer]
The active layer contains an organic-inorganic hybrid semiconductor material, its ionization potential range is -6.0 eV or more and -5.7 eV or less, and its band gap is 1.6 e.
V or more and 2.3 eV or less.

Fluorescence, which is a visible light source widely used indoors and indoors, by setting the ionization potential of the active layer to -6.0 eV or more and -5.7 eV or less and the band gap to 1.6 eV or more and 2.3 eV or less. It is possible to improve the power generation efficiency for lights and LED lights.
This is because if the ionization potential of the active layer is less than −6.0 eV, the absorbable region in the long wavelength region is insufficient for the light source in the visible light region that gives white light. It is preferably −5.95 eV or higher, and more preferably −5.9 eV or higher.
Further, when the ionization potential of the active layer exceeds −5.7 eV, the loss of the obtained voltage becomes large with respect to the light source in the visible light region. It is preferably −5.75 eV or less, and more preferably −5.8 eV or less.
Further, if the bandgap of the active layer is less than 1.6 eV, the energy required to separate excitons generated in the semiconductor into positive and negative charges by receiving an indoor light source is insufficient. It is preferably 1.65 eV or more, more preferably 1.7 eV or more, and further preferably 1.75 eV or more.
Further, when the band gap of the active layer exceeds 2.3 eV, excess energy is generated for excitons generated by an indoor light source, resulting in inferior power generation efficiency. It is preferably 2.25 eV or less, more preferably 2.2 eV or less, and even more preferably 2.15 eV or less.

In the embodiment of FIG. 1, the active layer 103 is a layer on which photoelectric conversion is performed. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103 to generate carriers, and the generated carriers are taken out from the lower electrode 101 and the upper electrode 105.

In the present embodiment, the active layer 103 contains an organic-inorganic hybrid semiconductor material. The organic-inorganic hybrid semiconductor material refers to a material in which an organic component and an inorganic component are combined at the molecular level or the nano level and exhibits semiconductor characteristics.

In the present embodiment, the organic-inorganic hybrid semiconductor material is preferably a compound having a perovskite structure (hereinafter, may be referred to as a perovskite semiconductor compound). The perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. The perovskite semiconductor compound is not particularly limited, but for example, Galasso et al. You can choose from those listed in Structure and Properties of Organic Solids, Chapter 7-Perovskite type and directed structures. For example, examples of the perovskite semiconductor compound include _{those of AMX 3} type represented by the _{general formula AMX 3 and those of A 2} MX ₄ type represented by the general formula A ₂ MX _4. Here, M refers to a divalent cation, A refers to a monovalent cation, and X refers to a monovalent anion.

The monovalent cation A is not particularly limited, but the one described in the above-mentioned Galasso's book can be used. More specific examples include cations containing Group 1 and Group 13 to Group 16 elements of the Periodic Table. Among these, cesium ion, rubidium ion, potassium ion, ammonium ion which may have a substituent or phosphonium ion which may have a substituent are preferable. Examples of ammonium ions that may have a substituent include primary ammonium ions or secondary ammonium ions. There are no particular restrictions on the substituents. Specific examples of ammonium ions that may have a substituent include alkylammonium ions or arylammonium ions. In particular, monoalkylammonium ions having a three-dimensional crystal structure are preferable in order to avoid steric hindrance, and from the viewpoint of improving stability, alkylammonium ions substituted with one or more fluorine groups are preferably used. Further, a combination of two or more kinds of cations can be used as the cation A.

Specific examples of the monovalent cation A include methylammonium ion, monofluoromethylammonium ion, difluoride methylammonium ion, trifluoride methylammonium ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, and isobutylammonium ion. , N-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidium ion, formamidinium ion, acetamidinium ion or imidazolium Ions and the like can be mentioned.

The divalent cation M is also not particularly limited, but is preferably a divalent metal cation or a metalloid cation. Specific examples include cations of Group 14 elements of the periodic table, and more specific examples include lead cations (Pb ²⁺ ), ^{tin cations (Sn 2+} ), and germanium cations (Ge ²⁺ ). Further, a combination of two or more kinds of cations can be used as the cation M. From the viewpoint of obtaining a stable photoelectric conversion element, it is particularly preferable to use a lead cation or two or more kinds of cations containing a lead cation.

Examples of monovalent anion X include halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, and titanoic acid. Examples thereof include an ion, a zirconate ion, a 2,4-pentandionato ion, a siliceous fluorine ion and the like. In order to adjust the bandgap, X may be one kind of anion or a combination of two or more kinds of anions. In one embodiment, X includes a halide ion, or a combination of a halide ion and another anion. Examples of the halide ion X include chloride ion, bromide ion, iodide ion and the like. From the viewpoint of not widening the band gap of the semiconductor too much, it is preferable to mainly use iodide ions or bromide ions, but iodide ions and bromide ions may be combined in an appropriate ratio.

Preferred examples of the perovskite semiconductor compound include an organic-inorganic perovskite semiconductor compound, and in particular, a halide-based organic-inorganic perovskite semiconductor compound. Specific examples of perovskite semiconductor _{compound, CH 3 NH 3 PbI 3,} CH 3 NH 3 PbBr 3, CH 3 NH 3 PbCl 3, CH 3 NH 3 SnI 3, CH 3 NH 3 SnBr 3, CH 3 NH 3 SnCl 3 , CH ₃ NH ₃ PbI _(3-x) Cl _x , CH ₃ NH ₃ PbI _(3-x) Br _x , CH ₃ NH ₃ PbBr _(3-x) Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Br ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Cl ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y I _{(3) −x)} Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Br _x , and CH ₃ NH ₃ Pb _(1-y) Sn _y Br _(3-x) Cl _x , and , CFH ₂ NH ₃ , CF ₂ HNH ₃ , or CF ₃ NH ₃ is used _{instead of CH 3} NH ₃ in the above compounds. Note that x indicates an arbitrary value of 0 or more and 3 or less, and y indicates an arbitrary value of 0 or more and 1 or less.

The active layer 103 may contain two or more kinds of perovskite semiconductor compounds. For example, the active layer 103 may contain two or more types of perovskite semiconductor compounds in which at least one of A, B, and X is different. Further, the active layer 103 may have a laminated structure formed of a plurality of layers containing different materials or having different components.

The amount of the perovskite semiconductor compound contained in the active layer 103 is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more so that good semiconductor properties can be obtained. be. There is no particular upper limit. Further, the active layer 103 may contain an additive in addition to the perovskite semiconductor compound. Examples of additives include inorganic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts, or organic compounds.

There is no particular limitation on the thickness of the active layer 103. The thickness of the active layer 103 is 10 nm or more in one embodiment, 50 nm or more in another embodiment, 100 nm or more in yet another embodiment, and 120 nm or more in yet another embodiment in that more light can be absorbed. Is. On the other hand, the thickness of the active layer 103 is 1500 nm or less in one embodiment, 1200 nm or less in another embodiment, and 800 nm or less in another embodiment in terms of lowering the series resistance or increasing the charge extraction efficiency. Is.

The method for forming the active layer 103 is not particularly limited, and any method can be used. Specific examples include a coating method and a vapor deposition method (or a co-evaporation method). The coating method can be used in that the active layer 103 can be easily formed. For example, a method of forming the active layer 103 by applying a coating liquid containing a perovskite semiconductor compound or a precursor thereof and heating and drying it as necessary can be mentioned. Further, after applying such a coating solution, the perovskite semiconductor compound can be precipitated by further applying a solvent having low solubility of the perovskite semiconductor compound.

The precursor of a perovskite semiconductor compound refers to a material that can be converted into a perovskite semiconductor compound after the coating liquid is applied. As a specific example, a perovskite semiconductor compound precursor that can be converted into a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general formula MX ₂ , and a solvent, and heating and stirring the mixture. By applying this coating liquid and performing heat drying, an active layer 103 containing a perovskite semiconductor compound represented _{by the general formula AMX 3 can be produced.} The solvent is not particularly limited as long as the perovskite semiconductor compound and the additive are dissolved, and examples thereof include organic solvents such as N, N-dimethylformamide.

Any method can be used as the coating method, and for example, a spin coating method, an inkjet method, a doctor blade method, a drop casting method, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, etc. Examples thereof include a spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation / coating method, and a curtain coating method.

As a method for setting the ionization potential of the active layer within the desired range, for example, the cation component in the perovskite semiconductor compound may be appropriately changed.
Further, as a method for setting the band gap of the active layer within the desired range, for example, the composition ratio of the halogen element in the perovskite semiconductor compound may be appropriately changed.

[3. electrode]
The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 103. The photoelectric conversion element 100 according to the embodiment of the present invention has a pair of electrodes, one of the pair of electrodes is referred to as an upper electrode, and the other is referred to as a lower electrode. When the photoelectric conversion element 100 has a base material or is provided on the base material, an electrode closer to the base material can be called a lower electrode, and an electrode farther from the base material can be called an upper electrode. Further, the transparent electrode may be referred to as a lower electrode, and the electrode having a lower transparency than the lower electrode may be referred to as an upper electrode. The photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105.

As the pair of electrodes, an anode suitable for collecting holes and a cathode suitable for collecting electrons can be used. In this case, the photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 105 is the cathode, or the lower electrode 101 is the cathode and the upper electrode 105 is the anode. It may have a mold configuration.

One of the pair of electrodes may be translucent, and both may be translucent. Translucent means that sunlight is transmitted by 40% or more. Further, it is preferable that the solar ray transmittance of the transparent electrode is 70% or more because more light passes through the transparent electrode and reaches the active layer 103. The light transmittance can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Tech).

There are no particular restrictions on the lower electrode 101 and the upper electrode 105, the components of the anode and the cathode, and the method for manufacturing the same, and a well-known technique can be used. For example, the members described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194, and methods for producing the same can be used.

[4. Buffer layer]
The buffer layer is a layer located between the active layer 103 and at least one of the pair of electrodes 101 and 105. The buffer layer can be used, for example, to improve the carrier transfer efficiency from the active layer 103 to the lower electrode 101 or the upper electrode 105.

(Hole transport layer)
In the present invention, the buffer layer has at least a hole transport layer containing an organic semiconductor compound, and the ionization potential of this hole transport layer is −5.8 eV or more and −5.4 eV or less.
This is because if the ionization potential of the hole transport layer is less than -5.8 eV, a mismatch will occur with the holes generated in the active layer, leading to energy loss. It is preferably −5.75 eV or higher, and more preferably −5.70 eV or higher.
Further, when the ionization potential of the hole transport layer exceeds −5.4 eV, a mismatch is made with the holes generated in the active layer, leading to voltage loss. It is preferably −5.45 eV or less, and more preferably −5.5 eV or less.

Further, by incorporating the dopant in the hole transport layer together with the organic semiconductor compound, it is possible to control the characteristics such as the conductivity and the hole transport capacity.
In this case, the content of the dopant can be, for example, in the range of 0.001 to 5% by mass with respect to the total amount of the organic semiconductor compound and the dopant.
By setting the content of the dopant to 0.001% by mass or more, the conductivity and hole transporting ability of the buffer layer tend to be further improved with respect to the active layer. It is more preferably 0.01% by mass or more, further preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more.
Further, by setting the content of the dopant to 5% by mass or less, the generation of the leakage current of the photoelectric conversion element is suppressed, and the power generation efficiency tends to be further improved particularly in the low illuminance region. More preferably, it is 4.5% by mass or less, and further preferably 4% by mass or less.
Examples of the method for setting the ionization potential of the hole transport layer within the above desired range include introducing an electron-withdrawing functional group into the organic semiconductor compound constituting the hole transport layer, and conjugating the organic semiconductor compound. By expanding the site component, electrons can be delocalized and stability can be improved.

(Organic semiconductor compound)
A semiconductor compound refers to a compound that can be used as a semiconductor material exhibiting semiconductor properties. In addition, in this specification, "semiconductor" is defined by the magnitude of carrier mobility in a solid state. As is well known, carrier mobility is an index showing how quickly (or many) charges (electrons or holes) can be transferred. Specifically, the “semiconductor” in the present specification preferably has a carrier mobility at room temperature of 1.0 × 10 ^-6 cm ² / V · s or more, more preferably 1.0 × 10 ^-5 cm ² / s. It is V · s or more, more preferably 5.0 × 10 ^-5 cm ² / V · s or more, and particularly preferably 1.0 × 10 ^-4 cm ² / V · s or more. The carrier mobility can be measured, for example, by measuring the IV characteristics of the field effect transistor, the time-of-flight method, or the like.

In the present invention, an organic semiconductor compound is used as the semiconductor compound, but the type thereof is not particularly limited, and for example, conventionally known compounds can be used. Low molecular weight compounds and high molecular weight compounds are known as organic semiconductor compounds. Examples of low-molecular-weight organic semiconductor compounds include polycyclic aromatic compounds, and specific examples thereof include acenese compounds such as tetracene and pentacene, oligothiophene compounds, phthalocyanine compounds, perylene compounds, rubrene compounds, and tria. Aromatic compounds such as reelamine compounds, and the like can be mentioned. Examples of the high molecular weight organic semiconductor compound include a polythiophene polymer, a polyacetylene polymer, a polyaniline polymer, a polyphenylene polymer, a polyphenylene vinylene polymer, a polyfluorene polymer, a conjugated polymer such as a polypyrrole polymer, or a triaryl. Arylamine polymers such as amine polymers can be mentioned.

The organic semiconductor compound is preferably an arylamine-based compound, and more preferably a triarylamine-based compound. The arylamine-based compound is a compound having an arylamine structure (bonding of an aryl group and a nitrogen atom), and includes an arylamine-based polymer. The arylamine-based polymer is a polymer whose repeating unit contains an arylamine structure, and is also referred to as a polyarylamine-based compound. The triarylamine-based compound is a compound having a triarylamine structure (bonding of three aryl groups to the same nitrogen atom), and includes a triarylamine-based polymer. The triarylamine polymer is a polymer whose repeating unit contains a triarylamine structure, and is also referred to as a polytriarylamine-based compound. Such arylamine-based compounds or triarylamine-based compounds are preferable in that they can be stably oxidized by a dopant and exhibit good semiconductor properties, and among them, triarylamine-based compounds are more preferable.

Here, the aryl group (or aromatic group) refers to an aromatic hydrocarbon group or an aromatic heterocyclic group, and a monocyclic group, a fused ring group, and a monocyclic ring or a fused ring group are linked. Including things. The aromatic group is not particularly limited, but preferably has 30 or less carbon atoms, and more preferably 12 or less carbon atoms. Specific examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group and the like. Specific examples of the aromatic heterocyclic group include a thienyl group, a frill group, a pyrrolyl group, a pyridyl group, an imidazolyl group and the like.

The aromatic group may have additional substituents. The substituent that the aromatic group may have is not particularly limited, but is limited to a halogen atom, a hydroxyl group, a cyano group, an amino group, a carboxyl group, an ester group, an alkylcarbonyl group, an acetyl group, a sulfonyl group, a silyl group, and the like. Examples thereof include a boryl group, a nitrile group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a thio group, a seleno group, an aromatic hydrocarbon group and an aromatic heterocyclic group. Preferred examples of the substituent contained in the aryl group include an amino group and an alkyl group having 1 to 6 carbon atoms. Here, the amino group is preferably a dialkylamino group having 2 to 12 carbon atoms, an alkylarylamino group having 7 to 20 carbon atoms, or a diarylamino group having 12 to 30 carbon atoms.

As the organic semiconductor compound used in the present invention, a triarylamine compound is preferable as described above, but it has high electrochemical stability and high hole transporting ability, and is suitable for a wet film forming method. From the viewpoint of being a compound, a polytriarylamine-based compound having a repeating unit represented by the following formula (I) is particularly preferable.

In formula (I), R ¹ and R ² each independently have a hydrogen atom, an aromatic hydrocarbon group which may have a substituent, an aromatic heterocyclic group which may have a substituent, or an aromatic heterocyclic group. Representing an alkyl group which may have a substituent, R ¹ and R ² may be bonded to each other to form a ring.
n represents an integer from 0 to 3
Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a direct bond and a substituent, or an aromatic heterocyclic group which may have a substituent.
Ar ^{3 to} Ar ⁵ each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent.

The fluorene ring in the main chain of the above formula (I) has HOMO (highest expanded molecular orbital) and LUMO (lowest) in this portion.
By spreading unoccuped molecular orbital), it is strongly involved in charge transport.

Examples of the aromatic hydrocarbon group having a substituent in Ar ^{1 to} Ar ⁵ include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, and a benzpyrene ring. Examples thereof include groups derived from a 6-membered monocyclic ring or a 2-5 fused ring such as a chrysen ring, a triphenylene ring, an acenaphthene ring, a fluorantene ring, and a fluorene ring.

Examples of the aromatic heterocyclic group having a substituent in Ar ^{1 to} Ar ⁵ include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, and an oxa. Diazol ring, indole ring, carbazole ring, pyroloymidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, flopirol ring, flofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring. Ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridin ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. Can be mentioned as a group derived from a 5- or 6-membered monocyclic ring or a 2-4 fused ring.

From the viewpoint of solubility in organic solvents and heat resistance, Ar ^{1 to} Ar ⁵ independently have a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a thiophene ring, a pyridine ring, and a fluorene ring. Ring-derived groups selected from the group consisting of are preferred.
Further, as Ar ^{1 to} Ar ⁵ , a divalent group in which one or more rings selected from the above group are directly bonded or linked by a −CH = CH− group is also preferable, and a biphenylene group and a terphenylene group are also preferable. , Are more preferred.
The ^{substituents that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar 1 to} Ar ⁵ may have are not particularly limited, but are, for example, one selected from the following [substituent group Z] or one. Two or more types can be listed.

[Substituent group Z]
An alkyl group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms such as a methyl group and an ethyl group; an alkenyl group having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms such as a vinyl group. ;
An alkynyl group having preferably 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as an ethynyl group;
An alkoxy group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methoxy group and an ethoxy group;
An aryloxy group having preferably 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms such as a phenoxy group, a naphthoxy group and a pyridyloxy group; preferably 2 to 24 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group. Preferably, an alkoxycarbonyl group having 2 to 12 carbon atoms;
A dialkylamino group having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a dimethylamino group and a diethylamino group;
A diarylamino group having preferably 10 to 36 carbon atoms, more preferably 12 to 24 carbon atoms, such as a diphenylamino group, a ditrilamino group, and an N-carbazolyl group;
An arylalkylamino group having preferably 6 to 36 carbon atoms, more preferably 7 to 24 carbon atoms, such as a phenylmethylamino group;

An acetyl group, a benzoyl group, etc., preferably having 2 to 24 carbon atoms, preferably 2 to 1 carbon atoms.
Acyl group of 2;
Halogen atoms such as fluorine atoms and chlorine atoms;
A haloalkyl group having 1 to 2 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group;
An alkylthio group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methylthio group and an ethylthio group;
An arylthio group having preferably 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms, such as a phenylthio group, a naphthylthio group, and a pyridylthio group;
A silyl group having preferably 2-336 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsilyl group and a triphenylsilyl group;
A syroxy group having preferably 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsiloxy group and a triphenylsiloxy group;
Cyano group;
An aromatic hydrocarbon group having preferably 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms, such as a phenyl group and a naphthyl group;
An aromatic heterocyclic group having preferably 3 to 36 carbon atoms, more preferably 4 to 24 carbon atoms, such as a thienyl group and a pyridyl group;
Each of the above-mentioned substituents may further have a substituent, and examples thereof include the groups exemplified in the above-mentioned Substituent Group Z.

The molecular weight of the substituents that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ^{1 to} Ar ⁵ may have is preferably 500 or less, more preferably 250 or less, including the further substituted group.
In terms of improving the solubility in an organic solvent, the substituents that the aromatic hydrocarbon group and the aromatic heterocyclic group in ^{Ar 1 to} Ar ^{5 may have are each independently having 1 to 12 carbon atoms.} An alkyl group and an alkoxy group having 1 to 12 carbon atoms are preferable.

When n is 2 or more, the repeating unit represented by the formula (I) has two or more Ar ⁴ and Ar ⁵ . In that case, Ar ⁴ and Ar ⁵ may be the same or different from each other. Further, Ar ⁴ and Ar ⁵ may be bonded to each other directly or via a linking group to form a cyclic structure.

The method for synthesizing the above-mentioned polytriarylamine compound is not particularly limited, but for example, it can be synthesized by a method as described in JP-A-2009-263665, and oxidative polymerization or transition of the triarylamine monomer can be used. It can be synthesized by a coupling reaction using a metal catalyst.
The number average molecular weight of this polytriarylamine compound can be adjusted by adjusting the reaction temperature, reaction time, catalyst, etc., but is preferably 8,500 or more.

By setting the number average molecular weight of this polytriarylamine compound to 8,500 or more, the durability of the photoelectric conversion element (maintenance rate of photoelectric conversion efficiency) tends to be improved. It is more preferably 9,000 or more, further preferably 10,000 or more, particularly preferably 15,000 or more, and most preferably 20,000 or more.
On the other hand, the upper limit of the number average molecular weight is not particularly limited, but for example, 500,000 or less is preferable in terms of cost of the polytriarylamine compound and in terms of ensuring solubility in a solvent. It is more preferably 300,000 or less, and even more preferably 200,000 or less.

Further, the weight average molecular weight of the polytriarylamine compound is preferably 15,000 or more, more preferably 20,000 or more, further preferably 30,000 or more, and 35,000. The above is particularly preferable, and 40,000 or more is the most preferable. By setting this lower limit, the durability of the photoelectric conversion element tends to be improved. On the other hand, the upper limit of the weight average molecular weight is not particularly limited, but is preferably 500,000 or less, more preferably 300,000 or less, and particularly preferably 200,000 or less. By setting this upper limit, the cost can be reduced and the solubility in the solvent can be guaranteed. When the polytriarylamine compound satisfies the range of the number average molecular weight and the weight average molecular weight at the same time, the maintenance rate of the photoelectric conversion efficiency may be further improved.

(Dopant)
The dopant is an additive to the above-mentioned organic semiconductor compound, and is a substance for optimizing the conductivity and hole transporting ability of the hole transporting layer in the present invention with respect to the active layer.
Substances that can be used as dopants include boron compounds such as tetrakis (pentafluorophenyl) borate and molybdenum compounds such as tris [1- (methoxycarbonyl) -2- (trifluoromethyl) -ethane-1,2-dithiolene] molybdenum. , 2,3,4,6-tetrafluoro-7,7,8,8-Tetracyanoquinodimethane and the like, which include organic compounds having a tetracyanoquinodimethane skeleton. The dopant preferably causes a charge transfer reaction with at least one organic semiconductor compound before or after the hole transport layer is formed. As the dopant, a hypervalent iodine compound is preferable because it has excellent solubility and produces an electron-accepting active site that functions as an oxidizing agent by heating or the like.

It is known that this hypervalent iodine compound acts as a dopant for an organic semiconductor compound and exhibits electron acceptability (that is, acts as an oxidizing agent). In addition, the electron-accepting dopant can improve the conductivity or hole transporting ability of the semiconductor compound by depriving the semiconductor compound of electrons. As described above, the hypervalent iodine compound can improve the charge transport property of the semiconductor compound.

The hypervalent iodine compound is a compound containing hypervalent iodine, and is defined as a compound containing iodine having an oxidation number of +3 or more. For example, the dopant can be an iodine (III) compound or an iodine (V) compound. The iodine (V) compound containing pentavalent iodine can be, for example, a peryodinane compound such as Dess-Martin peryodinan. Examples of the iodine (III) compound containing trivalent iodine include a compound having a structure in which iodobenzene is oxidized, such as (diacetoxyiode) benzene, or a diallyl iodonium salt. The dopant is preferably an organic compound containing trivalent iodine, and more preferably a diallyl iodonium salt, because it exhibits good electron acceptability and the reverse reaction is unlikely to occur when the molecule is destroyed in the oxidation process. ..

The diallyl iodonium salt is a salt having a [Ar-I ⁺ -Ar] X ^- structure. Here, each of the two Ars represents an aryl group. The aryl group (aromatic group) is not particularly limited, and may be, for example, those already mentioned with respect to an organic semiconductor compound. X ⁻ represents any anion. X ⁻ may be, for example, a halide ion, a trifluoroacetate ion, a tetrafluoroborate ion, a tetrakis (pentafluorophenyl) borate ion, or the like. X- is preferably an anion having a fluorine atom because it has high solubility and the formation reaction of the coating liquid can proceed smoothly.

Preferred examples of the dopant include those represented by the general formula (II). In formula (II), X ⁻ represents an arbitrary anion, and specific examples are as described above.
[R ¹¹ −I ⁺ −R ¹² ] X ⁻ (II)

In formula (II), R ¹¹ and R ¹² are independently monovalent organic groups. Examples of monovalent organic groups include aliphatic groups or aromatic groups. Examples of the aliphatic group include an aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aliphatic heterocyclic group having 4 to 20 carbon atoms. For example, examples of the aliphatic group include an alkyl group containing a cycloalkyl group, an alkenyl group, an alkynyl group and the like, and specific examples thereof include a methyl group, an ethyl group, a butyl group, a cyclohexyl group, a tetrahydrofuryl group and the like. Be done.

Examples of the aromatic group include an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms. For example, examples of the aromatic group include a phenyl group, a naphthyl group, a biphenyl group, a thienyl group, a pyridyl group and the like.

The above aliphatic group and aromatic group may have a substituent. The substituent which may have is not particularly limited, but is a halogen atom, a hydroxyl group, a cyano group, an amino group, a carboxyl group, an ester group, an alkylcarbonyl group, an acetyl group, a sulfonyl group, a silyl group and a boryl group. , Nitrile group, alkyl group, alkenyl group, alkynyl group, alkoxy group, thio group, seleno group, aromatic hydrocarbon group, aromatic heterocyclic group and the like.

R ¹¹ and R ¹² are preferably aromatic hydrocarbon groups having 6 to 20 carbon atoms, and more preferably phenyl groups. Here, the aromatic hydrocarbon group preferably has no substituent or has an alkyl group having 1 to 6 carbon atoms. R ¹¹ and R ¹² are particularly preferably phenyl groups having an alkyl group at the para position.

As described above, the photoelectric conversion element 100 can have a buffer layer 102 between the lower electrode 101 and the active layer 103, or has a buffer layer 104 between the upper electrode 105 and the active layer 103. Can be done. Further, the photoelectric conversion element 100 may have both a buffer layer 102 and a buffer layer 104. Here, the buffer layer 102 provided between the lower electrode 101 and the active layer 103 and the buffer layer 104 provided between the upper electrode 105 and the active layer 103 may be made of different materials. That is, one buffer layer may be a hole transport layer containing an organic semiconductor compound, while the other buffer layer may be an electron transport layer or the like composed of a different substance. As described above, the hole transport layer containing the organic semiconductor compound may be located between the lower electrode 101 and the active layer 103, or may be located between the active layer 103 and the upper electrode 105. May be. However, when the hole transport layer containing the organic semiconductor compound is formed by the coating method, the coating solvent may immerse the active layer 103 and affect the active layer 103, so that the hole transport is performed. The layer is preferably located between the lower electrode 101 and the active layer 103.

The buffer layer provided between the anode and the active layer is sometimes called a hole transport layer, and the buffer layer provided between the cathode and the active layer is sometimes called an electron transport layer. In the present invention, the buffer layer containing the organic semiconductor compound is used as the hole transport layer because the amount of transport charge tends to be easily controlled in the n-ip laminated photoelectric conversion element.

In the present invention, the buffer layer containing the above-mentioned organic semiconductor compound and its dopant can be preferably used as the hole transport layer, but the material of the buffer layer is not particularly limited. For example, for the hole transport layer, any material that can improve the efficiency of removing holes from the active layer to the anode can be used. Specifically, the inorganic compound, the organic compound, or the organic-inorganic perovskite compound according to the present invention described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230 or JP2012-191194A. Can be mentioned. For example, examples of the inorganic compound include metal oxides such as copper oxide, nickel oxide, manganese oxide, iron oxide, molybdenum oxide, vanadium oxide and tungsten oxide. Examples of the organic compound include a conductive polymer in which a dopant is doped in polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline, etc., a polythiophene derivative having a sulfonyl group as a substituent, a conductive organic compound such as arylamine, nafion, or Examples include lithium-doped spiro-OMeTAD.

Similarly, for the electron transport layer, any material capable of improving the efficiency of electron extraction from the active layer to the cathode can be used. Specifically, the inorganic compound, the organic compound, or the organic-inorganic perovskite compound according to the present invention described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230 or JP2012-191194A. Can be mentioned. For example, examples of the inorganic compound include salts of alkali metals such as lithium, sodium, potassium and cesium, and metal oxides such as zinc oxide, titanium oxide, aluminum oxide and indium oxide. Examples of the organic compound include vasocuproin (BCP), vasophenanthrene (Bphen), (8-hydroxyquinolinato) aluminum (Alq3), boron compound, oxadiazole compound, benzoimidazole compound, naphthalenetetracarboxylic acid anhydride (NTCDA), and the like. Examples thereof include phosphine compounds having a double bond with a Group 16 element of the periodic table such as perylene tetracarboxylic acid anhydride (PTCDA), fullerene compound, or phosphine oxide compound or phosphine sulfide compound.

The film thickness of the buffer layer is not particularly limited including the hole transport layer in the present invention, but is 0.5 nm or more in one embodiment, 1 nm or more in another embodiment, and 5 nm or more in another embodiment. On the other hand, it is 1 μm or less in one embodiment, 500 nm or less in another embodiment, 200 nm or less in yet another embodiment, and 150 nm or less in yet another embodiment. When the film thickness of the buffer layer is within the above range, the carrier movement efficiency can be easily improved, and the photoelectric conversion efficiency can be improved.

Further, the method for forming the buffer layer including the hole transport layer in the present invention is not limited, and the forming method can be selected according to the characteristics of the material. For example, a buffer layer can be formed by preparing a coating liquid containing the above-mentioned organic semiconductor compound, dopant, and solvent and using a wet film forming method such as a spin coating method or an inkjet method. Further, the buffer layer can be formed by a dry film forming method such as a vacuum vapor deposition method.

[5. Base material]
The photoelectric conversion element 100 usually has a base material 106 that serves as a support. However, the photoelectric conversion element according to the present invention does not have to have the base material 106. The material of the base material 106 is not particularly limited as long as the effects of the present invention are not significantly impaired. The materials described in 1 can be used.

[6. Manufacturing method of photoelectric conversion element]
The photoelectric conversion element 100 can be manufactured by forming each layer constituting the photoelectric conversion element 100 according to the above method. There is no particular limitation on the method of forming each layer constituting the photoelectric conversion element 100, and the layers can be formed by a sheet-to-sheet (many-leaf) method or a roll-to-roll method.

The roll-to-roll method is a method in which a flexible base material wound in a roll shape is unwound and processed intermittently or continuously while being wound by a winding roll. be. According to the roll-to-roll method, long substrates on the order of km can be collectively processed, so that the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method. On the other hand, when each layer is to be formed by the roll-to-roll method, the film may be scratched or partially peeled off due to the contact between the film-forming surface and the roll due to its structure.

The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by the roll-to-roll method manufacturing apparatus, but the upper limit of the outer diameter is preferably 5 m or less, more preferably 3 m or less, and more preferably. It is 1 m or less. On the other hand, the lower limit is preferably 10 cm or more, more preferably 20 cm or more, and more preferably 30 cm or more. The upper limit of the outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and more preferably 0.5 m or less. On the other hand, the lower limit is preferably 1 cm or more, more preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, and particularly preferably 20 cm or more. It is preferable that these diameters are not more than the above upper limit because the roll is easy to handle, and more than the lower limit is preferable because the layer formed in each step is less likely to be broken by bending stress. .. The lower limit of the width of the roll is preferably 5 cm or more, more preferably 10 cm or more, and more preferably 20 cm or more. On the other hand, the upper limit is preferably 5 m or less, more preferably 3 m or less, and more preferably 2 m or less. It is preferable that the width is not more than the upper limit from the viewpoint of high roll handleability, and it is preferable that the width is not more than the lower limit because the degree of freedom in the size of the photoelectric conversion element 100 is increased.

Further, after stacking the upper electrodes 105, the photoelectric conversion element 100 is 50 in one embodiment.
It can be heated in a temperature range of ° C. or higher, 80 ° C. or higher in another embodiment, while 300 ° C. or lower in one embodiment, 280 ° C. or lower in another embodiment, and 250 ° C. or lower in yet another embodiment. (This process may be referred to as an annealing process). Performing the annealing treatment step at a temperature of 50 ° C. or higher improves the adhesion between the layers of the photoelectric conversion element 100, for example, the adhesion between the buffer layer 102 and the lower electrode 101, and the buffer layer 102 and the active layer 103. The effect is obtained. By improving the adhesion between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. When the temperature of the annealing treatment step is set to 300 ° C. or lower, the possibility that the organic compound contained in the photoelectric conversion element 100 is thermally decomposed is reduced. In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time is 1 minute or more in one embodiment and 3 minutes or more in another embodiment, while 180 minutes or less in one embodiment, in order to improve adhesion while suppressing thermal decomposition. It is less than 60 minutes. The annealing process can be completed when the open circuit voltage, short circuit current and fill factor, which are the parameters of the solar cell performance, reach constant values. Further, the annealing treatment step can be carried out under normal pressure and in an atmosphere of an inert gas in order to prevent thermal oxidation of the constituent materials. As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. Further, the heating may be performed by a batch method or a continuous method.

[7. Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element 100 can be obtained as follows. The photoelectric conversion element 100 is irradiated with light having an appropriate spectrum at a certain irradiation intensity, and the current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained. As an example, by irradiating the photoelectric conversion element 100 with white LED light having a color temperature of 5000 K at an appropriate irradiation intensity (illuminance), the current-voltage characteristics at each illuminance can be measured.

The photoelectric conversion element of the present invention is excellent in power generation efficiency in a low illuminance region (10 to 5000 lux), and the photoelectric conversion efficiency can be set to 20% or more particularly when a light source such as white LED light is used. Further, the photoelectric conversion efficiency at 200 lux can be set to 25% or more. There is no particular limit to the upper limit of this efficiency, the higher it is, the better.
The photoelectric conversion efficiency (PCE) is the total energy amount (for example, for example) of the irradiation light having the output (maximum output) at the optimum operating point of the current-voltage curve of the photoelectric conversion element, which is measured by the predetermined irradiation light. In the case of sunlight with an intensity of AM1.5G, it is a value (%) divided by ^{100 mW / cm 2).}

[8. Power generation device]
In one embodiment, the photoelectric conversion element 100 according to the present invention is suitably used as a power generation device, particularly an indoor solar cell. FIG. 2 is a cross-sectional view schematically showing the configuration of a solar cell according to an embodiment of the present invention, and FIG. 2 shows a solar cell which is a solar cell according to an embodiment of the present invention. As shown in FIG. 2, the thin-film solar cell 14 according to the present embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter film 4, a sealing material 5, and a solar cell. The element 6, the sealing material 7, the getter material film 8, the gas barrier film 9, and the back sheet 10 are provided in this order. The thin-film solar cell 14 according to the present embodiment has the photoelectric conversion element according to the present invention as the solar cell element 6. Then, light is irradiated from the side where the protective film 1 is formed (lower part in FIG. 2), and the solar cell element 6 generates electricity. The thin-film solar cell 14 does not have to have all of these constituent members, and the necessary constituent members can be arbitrarily selected.

There are no particular restrictions on these constituent members constituting the photoelectric conversion element and the manufacturing method thereof, and well-known techniques can be used. For example, the techniques described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194 can be used.

The application of the solar cell according to the present embodiment, particularly the thin-film solar cell 14 described above, is not limited, and can be used for any application. For example, the solar cells according to the embodiment include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, solar cells for airplanes, solar cells for spacecraft, and solar cells for home appliances. It can be used as a battery, a solar cell for a mobile phone, or a solar cell for a toy. As described above, since it has excellent change efficiency in a low-light environment, it can be suitably applied to energy harvesting applications in particular.

The solar cell according to the present embodiment, particularly the thin-film solar cell 14 described above, may be used as it is, or may be used as a component of the solar cell module. For example, as shown in FIG. 3, a solar cell module 13 having the solar cell according to the present embodiment, particularly the above-mentioned solar cell 14 on the base material 12, is manufactured, and the solar cell module 13 is installed at a place of use. Can be used.

Hereinafter, embodiments of the present invention will be described with reference to examples. However, the present invention is not limited to the following examples.

[Measurement of ionization potential]
A semiconductor compound to be evaluated was formed on a glass substrate on which a thin film ITO was formed, and the number of photoelectrons generated by exposing the semiconductor compound to light was measured with an open counter that requires oxygen. In this open counter, ionized oxygen molecules are measured by capturing photoelectrons by oxygen molecules in the atmosphere. A threshold value at which photoelectrons start to be emitted is observed as the energy of the irradiated light is increased, and this threshold value, that is, the minimum energy (eV) required for the irradiation energy to eject photoelectrons, corresponds to the ionization potential (eV). It becomes the value to be. The ionization potential measurement by the photoelectron coefficient method was performed with a series of AC-2, AC-3, etc. of RIKEN KEIKI Co., Ltd.

[Calculation of band gap]
The band gap of the semiconductor compound was calculated from the absorption edge wavelength and the absorbance of the compound. A semiconductor compound thin film is formed on an appropriate sample such as a transparent glass substrate, the transmission spectrum thereof is measured, the horizontal axis wavelength is converted to eV, and the vertical axis transmittance is converted to √ (ahν), and the rise of this absorption is measured. It was fitted as a straight line, and the eV value intersecting the baseline was calculated as a band gap. This transmission spectrum was measured using, for example, a spectrophotometer such as Hitachi High-Tech U-4100.

[Measurement of photoelectric conversion efficiency of photoelectric conversion element]
The photoelectric conversion element was irradiated with white LED light having a color temperature of 5000 K whose irradiation intensity was adjusted to 200 lux using an illuminometer. In this environment, the current-voltage curve (IV curve) was measured using a source meter, and the maximum output value thereof was obtained. This value was divided by the total amount of energy possessed by the above irradiation light to obtain the photoelectric conversion efficiency (%) of the photoelectric conversion element.

[Example 1]
(Preparation of coating liquid for electron transport layer)
A 7.5% by mass aqueous tin oxide dispersion was prepared by adding ultrapure water to a 15% by mass aqueous dispersion of tin (IV) oxide (manufactured by Alfa Aesar).

(Preparation of coating liquid for active layer)
Lead (II) iodide was weighed into a vial and introduced into the glove box. N, N-dimethylformamide was added as a solvent so that the concentration of lead (II) iodide was 1.3 mol / L, and then the coating liquid 1 for the active layer was prepared by heating and stirring at 100 ° C. for 1 hour. ..

Next, in another vial, formaldehyde hydrobromide (FABr), methylamine hydrobromide (MABr), and methylamine hydrobromide (MACl) 7.25: 1: 1.5. Weighed so as to have a mass ratio of, and introduced into a glove box. By adding isopropyl alcohol as a solvent there, a coating liquid 2 for an active layer having a total concentration of FABr, MABr, and MACl of 0.49 mol / L was prepared.

(Synthesis of Polytriarylamine Compound A)
The polytriarylamine compound A represented by the following formula (A) was synthesized by the same method as that described in International Publication No. 2015/133437 and Japanese Patent Application Laid-Open No. 2016-0843370.

(Preparation of coating liquid for hole transport layer)
64 mg of polytriarylamine compound A and 2.6 mg of 4-isopropyl-4'-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate (TPFB, manufactured by TCI) were weighed into a vial and introduced into a glove box. bottom. 1.6 mL of ortodichlorobenzene was added thereto as a solvent. Next, the obtained mixed liquid was heated and stirred at 150 ° C. for 1 hour to prepare a coating liquid for a hole transport layer.

(Manufacturing of photoelectric conversion element)
A glass substrate (manufactured by Geomatec Co., Ltd.) provided with a patterned indium tin oxide (ITO) transparent conductive film was subjected to ultrasonic cleaning using ultrapure water, drying by nitrogen blowing, and UV-ozone treatment.

Next, the coating liquid for the electron transporting layer prepared as described above was spin-coated on the above-mentioned substrate at room temperature at a speed of 2000 rpm to form an electron transporting layer having a thickness of about 35 nm. Then, the substrate was heated on a hot plate at 150 ° C. for 10 minutes.

Further, the substrate was introduced into the glove box, 150 μL of the coating liquid 1 for the active layer heated to 100 ° C. was dropped onto the electron transport layer, and spin coating was performed at a speed of 2000 rpm. Next, the lead iodide layer was formed by heating and annealing the substrate on a hot plate at 100 ° C. for 10 minutes. Next, after the substrate has returned to room temperature, the active layer coating liquid 2 (120 μL) is spin-coated on the lead iodide layer at a speed of 2000 rpm and heated at 150 ° C. for 20 minutes to obtain an active layer of organic-inorganic perovskite. (Thickness 650 nm) was formed.

Next, after the substrate has returned to room temperature, the hole transport layer coating solution (120 μL) is spin-coated on the active layer at a speed of 2000 rpm, and further heated on a hot plate at 90 ° C. for 5 minutes to obtain holes. A transport layer (100 nm) was formed.

_{Next, MoO 3 having} a thickness of about 10 nm, then IZO having a thickness of about 30 nm and silver having a thickness of about 100 nm were deposited on the hole transport layer by a resistance heating type vacuum deposition method to form an upper electrode.
As described above, the photoelectric conversion element was manufactured.
Table 1 shows the measurement results of the ionization potential of the active layer, the band gap of the active layer, the ionization potential of the hole transport material, and the photoelectric conversion efficiency under the irradiation condition of 200 lux of white LED light in this photoelectric conversion element.

[Example 2]
Instead of the polytriarylamine compound A, the polytriarylamine compound B represented by the following formula (B) was synthesized in the same manner as described in International Publication No. 2015/133437 and JP-A-2016-08437. A photoelectric conversion element was produced in the same manner as in Example 1 except that the above was used.

Table 1 shows the measurement results of the ionization potential of the active layer, the band gap of the active layer, the ionization potential of the hole transport material, and the photoelectric conversion efficiency under the irradiation condition of 200 lux of white LED light in this photoelectric conversion element.

[Comparative Example 1]
The same as in Example 1 except that poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] was used instead of polytriarylamine compound A as the hole transport layer coating liquid. To produce a photoelectric conversion element. Table 1 shows the measurement results of the ionization potential of the active layer, the band gap of the active layer, the ionization potential of the hole transport material, and the photoelectric conversion efficiency under the irradiation condition of 200 lux of white LED light in this photoelectric conversion element.

As shown in Table 1, the ionization potential of the active layer is -6.0 eV or more and -5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the hole transport material. In Examples 1 and 2, the ionization potential of the photoelectric conversion element is -5.8 eV or more and -5.4 eV or less, and the photoelectric conversion efficiencies of the photoelectric conversion element at 200 lux of white LED light are 27.0% and 26.8, respectively. It was%, showing high conversion efficiency.
On the other hand, although the ionization potential of the active layer is -5.8 eV and the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, the ionization potential of the hole transport material is -5.3 eV. In a certain Comparative Example 1, the photoelectric conversion efficiency of the photoelectric conversion element at 200 lux of white LED light was 23.5%, which was an insufficient value.

1 Weatherproof protective film 2 UV cut film 3, 9 Gas barrier film 4, 8 Getter film 5, 7 Encapsulant 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell 100 Photoelectric conversion element 101 Lower part Electrode 102 Buffer layer 103 Active layer 104 Buffer layer 105 Upper electrode 106 Base material

Claims (8)

A pair of electrodes composed of an upper electrode and a lower electrode, an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and at least one of the active layer and the pair of electrodes. A photoelectric conversion element having a hole transport layer containing an organic semiconductor compound located between the electrodes.
The ionization potential of the active layer is -6.0 eV or more and -5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the ionization potential of the hole transport layer is A photoelectric conversion element having a value of −5.8 eV or more and −5.4 eV or less. The photoelectric conversion element according to claim 1, wherein the organic semiconductor compound is a semiconductor compound having a polytriarylamine structure. The photoelectric conversion element according to claim 1 or 2, wherein the hole transport layer further contains a dopant. The photoelectric conversion element according to claim 3, wherein the dopant is an organic compound containing trivalent iodine. The photoelectric conversion element according to claim 3 or 4, wherein the dopant is a diaryliodonium salt. The photoelectric conversion element according to any one of claims 1 to 5, wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure. The photoelectric conversion element according to any one of claims 1 to 6, wherein the photoelectric conversion efficiency at 200 lux is 25% or more. A power generation device having the photoelectric conversion element according to any one of claims 1 to 7.

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