WO2022004882A1

WO2022004882A1 - Solar cell

Info

Publication number: WO2022004882A1
Application number: PCT/JP2021/025165
Authority: WO
Inventors: 明伸早川; 哲也榑林; 允子岡本; 祥平花ノ木
Original assignee: 積水化学工業株式会社
Priority date: 2020-07-02
Filing date: 2021-07-02
Publication date: 2022-01-06
Also published as: JPWO2022004882A1

Abstract

The purpose of the present invention is to provide a solar cell capable of exhibiting high photoelectric conversion efficiency even after having passed through a heating step. The present invention is a solar cell having, in the stated order, a negative electrode, a photoelectric conversion layer, a hole transport layer, and a positive electrode. The photoelectric conversion layer contains an organic-inorganic perovskite compound represented by AMX (where A is an organic base compound and/or alkaline metal, M is a lead or tin atom, and X is a halogen atom). The hole transport layer contains a halogenated quaternary amine salt.

Description

Solar cell

The present invention relates to a solar cell capable of exhibiting high photoelectric conversion efficiency even after undergoing a heating step.

Conventionally, a solar cell having a laminate (photoelectric conversion layer) in which an N-type semiconductor layer and a P-type semiconductor layer are arranged between facing electrodes has been developed. In such a solar cell, an optical carrier (electron-hole pair) is generated by photoexcitation, and an electric field is generated by moving an electron in an N-type semiconductor and a hole in a P-type semiconductor.

Most of the solar cells currently in practical use are inorganic solar cells manufactured by using an inorganic semiconductor such as silicon. However, since inorganic solar cells are costly to manufacture, difficult to increase in size, and have a limited range of use, organic solar cells manufactured using organic semiconductors instead of inorganic semiconductors (for example, patent documents). Attention is being paid to 1, 2) and organic-inorganic solar cells that combine organic semiconductors and inorganic semiconductors.

In most organic solar cells and organic inorganic solar cells, fullerenes are used. Fullerenes are known to mainly act as N-type semiconductors. For example, Patent Document 1 describes a semiconductor heterojunction film formed by using an organic compound as a P-type semiconductor and fullerenes. However, in organic solar cells and organic-inorganic solar cells manufactured using fullerenes, it is known that the cause of deterioration is fullerenes (see, for example, Non-Patent Document 1), and a material that replaces fullerenes is required. ing.

Therefore, in recent years, a photoelectric conversion material having a perovskite structure using lead, tin, etc. as a central metal, which is called an organic-inorganic hybrid semiconductor, has been discovered and shown to have high photoelectric conversion efficiency (for example, Non-Patent Document 2). ..

Japanese Unexamined Patent Publication No. 2006-344794 Japanese Patent No. 4120362

In a solar cell using a photoelectric conversion material having such a perovskite structure, a hole transport layer is often provided between the photoelectric conversion layer and the anode, and the hole transport layer is tert-in order to improve the photoelectric conversion efficiency. -A pyridine derivative such as butyl pyridine is added. However, when the pyridine derivative is added to the hole transport layer, the photoelectric conversion efficiency may decrease after the heating step.

An object of the present invention is to provide a solar cell capable of exhibiting high photoelectric conversion efficiency even after undergoing a heating step.

The present invention has a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order, and the photoelectric conversion layer is AMX (where A is an organic base compound and / or an alkali metal, M is a lead or tin atom, and X is. Is a halogen atom.) Is an organic-inorganic perovskite compound, and the whole transport layer is a solar cell containing a halogenated quaternary amine salt.
The present invention will be described in detail below.

As a result of investigating the cause of the decrease in photoelectric conversion efficiency in a solar cell in which a pyridine derivative is added to a hole transport layer through a heating step, the present inventors have found that the cause is the volatilization of the pyridine derivative by heating. When the pyridine derivative volatilizes in the heating step, the amount of the pyridine derivative in the hole transport layer decreases. Further, if the pyridine derivative invades the photoelectric conversion layer in the heating step, the photoelectric conversion layer is deteriorated, so that the photoelectric conversion efficiency is lowered. As a result of further studies based on this finding, the present inventors have found that by changing the additive from a pyridine derivative to a halogenated quaternary amine salt, high photoelectric conversion efficiency can be exhibited even after a heating step. The finding has led to the completion of the present invention.

The solar cell of the present invention has a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order.
In the present specification, the layer means not only a layer having a clear boundary but also a layer having a concentration gradient in which the contained elements gradually change. The elemental analysis of the layer can be performed, for example, by performing FE-TEM / EDS line analysis measurement of the cross section of the solar cell and confirming the elemental distribution of the specific element. Further, in the present specification, the layer means not only a flat thin film-like layer but also a layer capable of forming a complicated and intricate structure together with other layers.

Examples of the cathode material include FTO (fluorine-doped tin oxide), ITO (tin-doped indium oxide), sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, and aluminum-lithium alloy. Examples thereof include an Al / Al ₂ O ₃ mixture and an Al / LiF mixture. These materials may be used alone or in combination of two or more.

The thickness of the cathode is not particularly limited, but the preferred lower limit is 10 nm and the preferred upper limit is 1000 nm. When the thickness is 10 nm or more, the cathode can function as an electrode and the resistance can be suppressed. When the thickness is 1000 nm or less, the light transmittance can be further improved. A more preferable lower limit of the thickness of the cathode is 50 nm, and a more preferable upper limit is 500 nm.

The photoelectric conversion layer contains an organic-inorganic perovskite compound represented by the general formula AMX (where A is an organic base compound and / or an alkali metal, M is a lead or tin atom, and X is a halogen atom). A solar cell in which the photoelectric conversion layer contains the organic-inorganic perovskite compound is also referred to as an organic-inorganic hybrid type solar cell.
By using the organic-inorganic perovskite compound in the photoelectric conversion layer, the photoelectric conversion efficiency of the solar cell can be improved.

The above A is an organic base compound and / or an alkali metal.
Specific examples of the organic basic compound include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, and triethylamine. Tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, formamidine, acetoamidine, guanidine, Examples thereof include imidazole, azole, pyrrole, aziridine, azirin, azetidine, azeto, azole, imidazoline, carbazole and ions thereof (for example, methylammonium (CH ₃ NH ₃ ) and the like), phenethylammonium and the like. Among them, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, formamidine, acetoamidine and their ions and phenethylammon are preferable, and methylamine, ethylamine, propylamine, formamidine and these ions are more preferable. preferable.
Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium and the like.

The above M is a metal atom and is a lead or tin atom. These metal atoms may be used alone or in combination of two or more.

The X is a halogen atom, and examples of the halogen atom include chlorine, bromine, iodine, sulfur, and selenium. These halogen atoms may be used alone or in combination of two or more. By containing a halogen in the structure, the organic-inorganic perovskite compound becomes soluble in an organic solvent, and can be applied to an inexpensive printing method or the like. Among them, X is preferably iodine because the energy band gap of the organic-inorganic perovskite compound is narrowed.

The organic-inorganic perovskite compound preferably has a cubic structure in which a metal atom M is arranged at the center of the body, an organic base compound or an alkali metal A is arranged at each apex, and a halogen atom X is arranged at the center of the body.
FIG. 1 is an example of a crystal structure of an organic-inorganic perovskite compound, which is a cubic structure in which a metal atom M is arranged at the center of the body, an organic base compound or an alkali metal A is arranged at each apex, and a halogen atom X is arranged at the face center. It is a schematic diagram which shows. Although the details are not clear, the orientation of the octahedron in the crystal lattice can be easily changed by having the above structure, so that the mobility of electrons in the organic-inorganic perovskite compound is high, and the photoelectric of the solar cell is high. It is estimated that the conversion efficiency will improve.

The organic-inorganic perovskite compound is preferably a crystalline semiconductor. The crystalline semiconductor means a semiconductor capable of measuring the X-ray scattering intensity distribution and detecting the scattering peak. Since the organic-inorganic perovskite compound is a crystalline semiconductor, the mobility of electrons in the organic-inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the solar cell is improved.

It is also possible to evaluate the degree of crystallization as an index of crystallization. For the crystallinity, the scattering peak derived from the crystalline substance detected by the X-ray scattering intensity distribution measurement and the halo derived from the amorphous part are separated by fitting, and the intensity integration of each is obtained, and the crystal part of the whole is obtained. It can be obtained by calculating the ratio of.
The preferable lower limit of the crystallinity of the organic-inorganic perovskite compound is 30%. When the crystallinity is 30% or more, the mobility of electrons in the organic-inorganic perovskite compound becomes high, and the photoelectric conversion efficiency of the solar cell is improved. A more preferable lower limit of crystallinity is 50%, and a more preferable lower limit is 70%.
Further, as a method for increasing the crystallinity of the organic-inorganic perovskite compound, for example, thermal annealing, irradiation with strong light such as a laser, plasma irradiation and the like can be mentioned.

The photoelectric conversion layer may further contain an organic semiconductor or an inorganic semiconductor in addition to the organic-inorganic perovskite compound as long as the effect of the present invention is not impaired. The organic semiconductor or the inorganic semiconductor referred to here may play a role as a hole transport layer or an electron transport layer.
Examples of the organic semiconductor include compounds having a thiophene skeleton such as poly (3-alkylthiophene). Further, for example, a conductive polymer having a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton and the like can also be mentioned. Further, for example, a compound having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, and carbon-containing materials such as carbon nanotubes, graphene, and fullerene which may be surface-modified. Can also be mentioned.

As the inorganic semiconductor, e.g., titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc _{_{sulfide, CuSCN, Cu 2 O, CuI}} , MoO 3, V 2 O 5, WO 3, Examples thereof include MoS ₂ _{, MoSe 2} , Cu ₂ S and the like.

When the organic-inorganic perovskite compound and the organic semiconductor or the inorganic semiconductor are contained, the photoelectric conversion layer is a laminate in which a thin-film organic semiconductor or an inorganic semiconductor moiety and a thin-film organic-inorganic perovskite compound moiety are laminated. Alternatively, it may be a composite film in which an organic semiconductor or an inorganic semiconductor moiety and an organic-inorganic perovskite compound moiety are composited. A laminated body is preferable in terms of simple manufacturing method, and a composite film is preferable in that the charge separation efficiency in the organic semiconductor or the inorganic semiconductor can be improved.

The thickness of the thin-film organic-inorganic perovskite compound moiety has a preferable lower limit of 5 nm and a preferable upper limit of 5000 nm. When the thickness is 5 nm or more, light can be sufficiently absorbed and the photoelectric conversion efficiency becomes high. When the thickness is 5000 nm or less, it is possible to suppress the generation of a region where charge separation is not possible, which leads to improvement in photoelectric conversion efficiency. The more preferable lower limit of the thickness is 10 nm, the more preferable upper limit is 1000 nm, the further preferable lower limit is 20 nm, and the further preferable upper limit is 500 nm.

When the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor moiety and an organic-inorganic perovskite compound moiety are composited, the preferable lower limit of the thickness of the composite film is 30 nm, and the preferable upper limit is 3000 nm. When the thickness is 30 nm or more, light can be sufficiently absorbed and the photoelectric conversion efficiency becomes high. When the thickness is 3000 nm or less, the electric charge easily reaches the electrode, so that the photoelectric conversion efficiency is high. The more preferable lower limit of the thickness is 40 nm, the more preferable upper limit is 2000 nm, the further preferable lower limit is 50 nm, and the further preferable upper limit is 1000 nm.

The method for forming the photoelectric conversion layer is not particularly limited, and examples thereof include a vacuum vapor deposition method, a sputtering method, a vapor phase reaction method (CVD), an electrochemical deposition method, and a printing method. Above all, by adopting the printing method, it is possible to easily form a solar cell capable of exhibiting high photoelectric conversion efficiency in a large area. Examples of the printing method include a spin coating method, a casting method, and the like, and examples of the method using the printing method include a roll-to-roll method.

The solar cell of the present invention may have an electron transport layer between the cathode and the photoelectric conversion layer.
The material of the electron transport layer is not particularly limited, and for example, N-type conductive polymer, N-type low molecular weight organic semiconductor, N-type metal oxide, N-type metal sulfide, halogenated alkali metal, alkali metal, and surface activity. Examples thereof include cyano group-containing polyphenylene vinylene, boron-containing polymer, vasocuproin, vasophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compound, benzoimidazole compound, naphthalenetetracarboxylic acid compound, perylene derivative, and the like. Examples thereof include phosphine oxide compounds, phosphine sulfide compounds, fluorogroup-containing phthalocyanine, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

The electron transport layer may be composed of only a thin-film electron transport layer, but preferably includes a porous electron transport layer. In particular, when the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor moiety and an organic-inorganic perovskite compound moiety are composited, a more complicated composite film (more complicated structure) can be obtained, and the photoelectric conversion efficiency can be obtained. Therefore, it is preferable that the composite film is formed on the porous electron transport layer.

The thickness of the electron transport layer has a preferable lower limit of 1 nm and a preferred upper limit of 2000 nm. If the thickness is 1 nm or more, the holes can be sufficiently blocked. When the thickness is 2000 nm or less, it is unlikely to become a resistance during electron transport, and the photoelectric conversion efficiency becomes high. The more preferable lower limit of the thickness of the electron transport layer is 3 nm, the more preferable upper limit is 1000 nm, the further preferable lower limit is 5 nm, and the further preferable upper limit is 500 nm.

The material of the hole transport layer is not particularly limited, and the hole transport layer may be made of an organic material. Examples of the material of the hole transport layer include a P-type conductive polymer, a P-type low molecular weight organic semiconductor, a P-type metal oxide, a P-type metal sulfide, a surfactant, and the like. Examples thereof include compounds having a thiophene skeleton such as poly (3-alkylthiophene). Further, for example, a conductive polymer having a triphenylamine skeleton, a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton and the like can be mentioned. Further, for example, compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentasen skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide and the like, fluorogroup-containing phosphonic acid, Examples thereof include carbonyl group-containing phosphonic acid, copper compounds such as CuSCN and CuI.

The hole transport layer contains a halogenated quaternary amine salt.
Since the hole transport layer contains a halogenated quaternary amine salt, the photoelectric conversion efficiency can be improved. Conventional solar cells contain a pyridine derivative as an additive, but the pyridine derivative volatilizes at a high temperature, and if the pyridine derivative invades the photoelectric conversion layer during heating, the photoelectric conversion layer is deteriorated. Therefore, it has been a factor of lowering the photoelectric conversion efficiency. In the present invention, by using a halogenated quaternary amine salt which has the effect of improving the photoelectric conversion efficiency but does not volatilize, it is possible to exhibit higher photoelectric conversion efficiency than the conventional solar cell. The halogenated quaternary amine salt may be used alone or in combination of two or more.

Examples of the quaternary amine constituting the halogenated quaternary amine salt include tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, tetraoctylammonium, tetradodecylammonium, and benzyltriethylammonium. Examples thereof include 5-azoniaspiro [4.4] nonane, dimethyldioctadecylammonium, trimethyl [2-[(trimethylsilyl) methyl] benzyl] ammonium, (ferrocenylmethyl) trimethylammonium and the like. Among them, since the photoelectric conversion efficiency can be further improved, it is preferable to use a quaternary amine in which an alkyl group having 4 or more carbon atoms is bonded to a nitrogen atom, and an alkyl group having 4 or more carbon atoms and 12 or less carbon atoms is a nitrogen atom. It is more preferable that it is a quaternary amine bonded to.

The halogen constituting the halogenated quaternary amine salt is not particularly limited, and examples thereof include chlorine, bromine, and iodine. Of these, bromine and iodine are preferable, and iodine is more preferable, because the photoelectric conversion efficiency can be further improved.

The content of the halogenated quaternary amine salt in the hole transport layer is preferably 0.05% or more and 30% or less.
When the content of the halogenated quaternary amine salt in the hole transport layer is within the above range, the photoelectric conversion efficiency can be further improved. The amount of the halogenated quaternary amine salt added in the hole transport layer is more preferably 0.5% or more, further preferably 1.0% or more, still more preferably 20% or less. It is more preferably 10% or less.
The content of the halogenated quaternary amine salt in the hole transport layer can be quantified by extracting the hole transport layer into a soluble solvent and analyzing it with GC-MS or the like.

Further, it is preferable that the halogenated quaternary amine salt segregates more on the photoelectric conversion layer side than on the anode side during hole transportation. During hole transportation, the halogenated quaternary amine salt segregates a large amount toward the photoelectric conversion layer side, so that charge transfer can be promoted and the photoelectric conversion efficiency can be improved. The amount of the halogenated quaternary amine salt at the photoelectric conversion layer side interface is preferably 2 times or more, more preferably 3 times or more, with respect to the amount of the halogenated quaternary amine salt at the electrode side interface in the hole transport layer. It is preferable, and more preferably 5 times or more. As a method for segregating the halogenated quaternary amine salt more on the photoelectric conversion layer side than on the anode side, for example, a method of forming a film using a specific organic solvent, a method of segregating by thermal annealing, and the like are used. Can be mentioned.
Whether or not the halogenated quaternary amine salt is segregated in the hole transport layer is determined by performing time-of-flight secondary ion mass spectrometry (TOF-SIMS) on the surface of the hole transport layer by sputtering for a predetermined time. ) Can be confirmed by repeating the analysis.

In the time-of-flight type secondary ion mass spectrometry (TOF-SIMS: Time-of-Fright Second Ion Mass Spectrometry), a solid sample is irradiated with an ion beam (primary ion), and ions (secondary ion) emitted from the surface are emitted. Is a method of mass separation using the flight time difference (the flight time is proportional to the square root of the weight). With TOF-SIMS, information on elements and molecular species existing in a region of 1 nm in the thickness direction from the sample surface can be obtained with high detection sensitivity. Examples of the analyzer used for TOF-SIMS include "TOF-SIMS5" manufactured by ION-TOF. Further, the ion intensity ratio can be obtained, for example, by using a Bi ₃ ⁺ ion gun as a primary ion source for measurement and measuring under the condition of 25 keV.

In sputtering, an inert gas such as argon is introduced in a vacuum, a negative voltage is applied to the target to generate a glow discharge, the inert gas atom is ionized, and the gas ion collides with the surface of the target at high speed. The surface of the target can be ground to a depth of nanometer to micrometer order.
Specifically, for _example, by performing sputtering using _O ^{2 +,} can go digging the surface of the hole transport layer by 0.01 nm ~ 10 nm / dose depth.

A part of the hole transport layer may be immersed in the photoelectric conversion layer, or may be arranged in a thin film on the photoelectric conversion layer. When the hole transport layer is present in the form of a thin film, the preferable lower limit is 1 nm and the preferable upper limit is 2000 nm. When the thickness is 1 nm or more, electrons can be sufficiently blocked. When the thickness is 2000 nm or less, resistance during hole transportation is unlikely to occur, and the photoelectric conversion efficiency is high. The more preferable lower limit of the thickness is 3 nm, the more preferable upper limit is 1000 nm, the further preferable lower limit is 5 nm, and the further preferable upper limit is 500 nm.

The material of the anode is not particularly limited, and conventionally known materials can be used. Examples of the anode material include metals such as gold, copper, aluminum, antimony, and molybdenum, CuI, ITO (indium tin oxide), SnO ₂ , AZO (aluminum zinc oxide), IZO (indium zinc oxide), and GZO (. Examples thereof include a conductive transparent material such as gallium-zinc oxide) or a conductive transparent polymer. Above all, it is preferable that the anode contains molybdenum because the resistance (light resistance) to the decrease in photoelectric conversion efficiency when exposed to light for a long time is improved. The cause of this is not clear, but it is thought that the interaction between the halogenated quaternary amine salt and molybdenum significantly improves the light resistance.

The thickness of the anode is not particularly limited, but the preferred lower limit is 10 nm and the preferred upper limit is 1000 nm. When the thickness is 10 nm or more, the anode can function as an electrode and the resistance can be suppressed. When the thickness is 1000 nm or less, the light transmittance can be further improved. The more preferable lower limit of the thickness of the anode is 20 nm, and the more preferable upper limit is 100 nm.

The solar cell of the present invention is selected from at least a group consisting _{of carbon, vanadium oxide (VO x} ), molybdenum oxide (MoO _x ) and nickel oxide (NiO _x ) between the hole transport layer and the anode. It is preferable to have an intermediate layer containing one type.
By providing the intermediate layer, the photoelectric conversion efficiency can be further improved. The cause of this is not clear, but it is thought that the photoelectric conversion efficiency is significantly improved by the interaction with the quaternary amine. Since the photoelectric conversion efficiency can be further improved, the thickness of the intermediate layer is preferably 1 nm or more, more preferably 5 nm or more, preferably 100 nm or less, and more preferably 50 nm or less.

The solar cell of the present invention may further have a substrate or the like. The substrate is not particularly limited, and examples thereof include a transparent glass substrate such as soda lime glass and non-alkali glass, a ceramic substrate, and a transparent plastic substrate.

The method for manufacturing the solar cell of the present invention is not particularly limited, and for example, the cathode, the electron transport layer, the photoelectric conversion layer, the hole transport layer, the intermediate layer, and the anode are formed on the substrate in this order. How to do it, etc.

According to the present invention, it is possible to provide a solar cell capable of exhibiting high photoelectric conversion efficiency even after undergoing a heating step.

It is a schematic diagram which shows an example of the crystal structure of an organic-inorganic perovskite compound. Normalized with the maximum value of each of Pb ion, Spiro-OMETAD ion, and tetrabutylammonium ion set to 1 on the horizontal axis with the cumulative sputtering time N when TOF-SIMS measurement was performed on the hole transport layer of Example 1. It is a graph in which the calculated values are plotted on the vertical axis. Normalized with the maximum value of each of Pb ion, Spiro-OMETAD ion, and tetrabutylammonium ion set to 1 on the horizontal axis when the cumulative sputtering time N is measured for the hole transport layer of Comparative Example 2. It is a graph in which the calculated values are plotted on the vertical axis.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1)
An ITO film having a thickness of 200 nm was formed on a glass substrate as a cathode, and was ultrasonically cleaned with pure water, acetone, and methanol in this order for 10 minutes each, and then dried.
A thin-film electron transport layer having a thickness of 20 nm was formed on the surface of the ITO film by sputtering. Further, a titanium oxide paste containing titanium oxide (a mixture of an average particle diameter of 10 nm and 30 nm) is applied onto the thin-film electron transport layer by a spin coating method to form a porous electron transport layer having a thickness of 100 nm. Formed.

Next, lead iodide as a metal halide compound was dissolved in a mixed solvent of N, N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) to prepare a 1 M solution, which was then spun onto the porous electron transport layer. A film was formed by the coating method. Further, methylammonium iodide as an amine compound was dissolved in 2-propanol to prepare an 8 wt% solution. This solution was spin-coated on the lead iodide and annealed at 150 ° C. for 10 minutes to form a layer containing _{CH 3} NH ₃ PbI _{3 which is an organic-inorganic perovskite compound.}

Next, on the photoelectric conversion layer, Spiro-OMETAD (manufactured by Merck) 2% by weight as a main agent and tetrabutylammonium iodide as an additive 0. A hole transport layer having a thickness of 50 nm was formed by spin-coating a chlorobenzene solution containing 1% by weight.

Next, an intermediate layer made _{of molybdenum oxide (MoO x} ) having a thickness of 10 nm was formed on the hole transport layer by an electron beam vapor deposition method.

A gold film having a thickness of 100 nm was formed as an anode on the obtained intermediate layer by resistance heating and vapor deposition to obtain a solar cell in which a cathode / electron transport layer / photoelectric conversion layer / hole transport layer / intermediate layer / anode was laminated. ..

On the other hand, a measurement sample laminated up to the hole transport layer was prepared by the above method. The surface of the obtained measurement sample on the hole transport layer side was sputtered under the following conditions using an Ar cluster, and the operation of performing analysis by TOF-SIMS under the following conditions was repeated 10 times to obtain the hole transport layer. The abundance ratios of Pb, spiro-OMeTAD and tetrabutylammonium in the thickness direction were measured.
<Sputtering conditions>
Sputter ion: Ar gas cluster ion Acceleration voltage: 5 kV
Acceleration current: 5nA
Irradiation range: 800 μm x 800 μm
Irradiation time: 60 seconds <TOF-SIMS measurement conditions>
Primary ion: Bi ₃ ⁺⁺
Ion voltage: 30kV
Ion current: 0.5 μA
Mass range: 1 to 1850 mass
Analysis area: 200 μm × 200 μm (imaging)
Charge prevention: Electron irradiation neutralization

FIG. 2 shows a graph in which the normalized values are plotted on the vertical axis with the cumulative sputtering time N as the horizontal axis and the maximum values of each of Pb ion, Spiro-OMETAD ion, and tetrabutylammonium ion as 1. In FIG. 2, the portion where N is approximately 100 seconds to 300 seconds corresponds to the boundary between the hole transport layer and the photoelectric conversion layer. As shown in FIG. 2, since the abundance of tetrabutylammonium ions is small at the interface with the outside of the hole transport layer and increases toward the interface with the photoelectric conversion layer, the tetrabutylammonium ions are on the photoelectric conversion layer side. It can be seen that the surface is segregated.

(Examples 2 to 56, Comparative Examples 1 to 16)
The same as in Example 1 except that the type of the main agent, the type and content of the additive, the thickness of the hole transport layer, the type of the intermediate layer, the type of the anode and the composition of the photoelectric conversion layer are as shown in Tables 1 to 3. I got a solar cell. In Tables 1 to 3, those with no segregation indicate that there was no segregation as a result of sputtering and TOF-SIMS measurement, and those with segregation of "-" indicate sputtering and TOF-SIMS measurement. It means that you haven't done it.
As for Comparative Example 2, the results of sputtering and TOF-SIMS measurement in the same manner as in Example 1 are shown in FIG. Also in FIG. 3, the portion where N is approximately 100 to 300 seconds corresponds to the boundary between the hole transport layer and the photoelectric conversion layer. As shown in FIG. 3, no segregation was observed with tert-butyl pyridine.

<Evaluation>
The solar cells obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 1 to 3.

(1) Evaluation of photoelectric conversion efficiency Immediately after the manufacture of the solar cell, a power supply (236 model manufactured by KEITHLEY) is connected between the electrodes of the solar cell, and a solar simulation (manufactured by Yamashita Denso Co., Ltd.) ^{with a strength of 100 mW / cm 2 is used.} The photoelectric conversion efficiency was measured, and the obtained photoelectric conversion efficiency was used as the initial conversion efficiency. It was standardized based on the initial conversion efficiency of the solar cell obtained from Comparative Example 1.
10: Normalized initial conversion efficiency value is 1.30 or more 9: Normalized initial conversion efficiency value is 1.25 or more and less than 1.30 8: Normalized initial conversion efficiency value is 1.20 or more 1 Less than .25 7: Normalized initial conversion efficiency value is 1.15 or more and less than 1.20 6: Normalized initial conversion efficiency value is 1.10 or more and less than 1.15 5: Normalized initial conversion efficiency Value is 1.05 or more and less than 1.10 4: Normalized initial conversion efficiency value is 1.00 or more and less than 1.05 3: Normalized initial conversion efficiency value is 0.95 or more and less than 1.00 2: Normalized initial conversion efficiency value is 0.90 or more and less than 0.95 1: Normalized initial conversion efficiency value is less than 0.90

(2) Evaluation of heat resistance The solar cell was heated to 90 ° C. under nitrogen for 100 hours to perform a heat resistance test. Before and after the heat resistance test, the photoelectric conversion efficiency was measured by the same method as above.
The obtained photoelectric conversion efficiency was evaluated according to the following criteria.
10: The photoelectric conversion efficiency after the heat resistance test is 98% or more with respect to the initial conversion efficiency 9: The photoelectric conversion efficiency after the heat resistance test is 95% or more and less than 98% with respect to the initial conversion efficiency 8: photoelectric after the heat resistance test The conversion efficiency is 90% or more and less than 95% with respect to the initial conversion efficiency 7: The photoelectric conversion efficiency after the heat resistance test is 80% or more and less than 90% with respect to the initial conversion efficiency 6: The photoelectric conversion efficiency after the heat resistance test is 70% or more and less than 80% of the initial conversion efficiency 5: The photoelectric conversion efficiency after the heat resistance test is 60% or more and less than 70% of the initial conversion efficiency 4: The photoelectric conversion efficiency after the heat resistance test becomes the initial conversion efficiency On the other hand, 50% or more and less than 60% 3: The photoelectric conversion efficiency after the heat resistance test is 40% or more and less than 50% with respect to the initial conversion efficiency 2: The photoelectric conversion efficiency after the heat resistance test is 30% with respect to the initial conversion efficiency. More than 40% 1: The photoelectric conversion efficiency after the heat resistance test is less than 30% of the initial conversion efficiency.

(3) Evaluation of durability (light resistance) when a voltage is applied for a long period of time A power supply (236 model manufactured by KEITHLEY) is connected between the electrodes of the solar cell, and ^{a solar simulation with a strength of 100 mW / cm 2} (manufactured by Yamashita Denso Co., Ltd.) ) Was applied at 25 ° C., and the photoelectric conversion efficiency was measured after 24 hours had passed. The obtained photoelectric conversion efficiency was evaluated according to the following criteria.
10: Photoelectric conversion efficiency after voltage application is 98% or more with respect to initial conversion efficiency 9: Photoelectric conversion efficiency after voltage application is 95% or more and less than 98% with respect to initial conversion efficiency 8: Photoelectric after voltage application The conversion efficiency is 90% or more and less than 95% with respect to the initial conversion efficiency 7: The photoelectric conversion efficiency after voltage application is 80% or more and less than 90% with respect to the initial conversion efficiency 6: The photoelectric conversion efficiency after voltage application is 70% or more and less than 80% of the initial conversion efficiency 5: The photoelectric conversion efficiency after voltage application is 60% or more and less than 70% of the initial conversion efficiency 4: The photoelectric conversion efficiency after voltage application is the initial conversion efficiency On the other hand, 50% or more and less than 60% 3: The photoelectric conversion efficiency after voltage application is 40% or more and less than 50% with respect to the initial conversion efficiency 2: The photoelectric conversion efficiency after voltage application is 30% with respect to the initial conversion efficiency. More than 40% 1: The photoelectric conversion efficiency after voltage application is less than 30% of the initial conversion efficiency.

Claims

The photoelectric conversion layer has a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order, and the photoelectric conversion layer is AMX (where A is an organic base compound and / or an alkali metal, M is a lead or tin atom, and X is a halogen atom. A solar cell containing an organic-inorganic perovskite compound represented by (1), wherein the whole transport layer contains a halogenated quaternary amine salt.
The solar cell according to claim 1, wherein the halogenated quaternary amine salt is segregated more on the photoelectric conversion layer side than on the anode side in the hole transport layer.
The solar cell according to claim 1 or 2, wherein the quaternary amine constituting the halogenated quaternary amine salt has an alkyl group having 4 or more carbon atoms bonded to a nitrogen atom.
The solar cell according to claim 1, 2 or 3, wherein the anode contains molybdenum.
An intermediate layer between the hole transport layer and the anode containing at least one selected from the group consisting of carbon, vanadium oxide (VO x ), molybdenum oxide (MoO x ) and nickel oxide (NiO x). The solar cell according to claim 1, 2, 3 or 4, wherein the solar cell has.