JP6943591B2 - Solar cell - Google Patents

Description

The present invention relates to a solar cell having high photoelectric conversion efficiency, less likely to cause peeling between the hole transport layer and the anode, and excellent durability.

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 electrons through an N-type semiconductor and holes moving through 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, inorganic solar cells are expensive to manufacture, difficult to increase in size, and have a limited range of use. Therefore, organic solar cells manufactured using organic semiconductors instead of inorganic semiconductors and organic semiconductors are used. Organic-inorganic solar cells combined with inorganic semiconductors are attracting attention.

Among them, a perovskite solar cell having a photoelectric conversion layer containing an organic-inorganic perovskite compound can be expected to have high photoelectric conversion efficiency and can be manufactured by a printing method, so that the manufacturing cost can be significantly reduced (for example, Patent Documents). 1. Non-patent document 1).

Japanese Unexamined Patent Publication No. 2014-72227

M. M. Lee, et al, Science, 2012, 338, 643

In perovskite solar cells, an organic semiconductor film is often provided as a hole transport layer between the photoelectric conversion layer and the anode. Such an organic semiconductor film plays a role of improving the photoelectric conversion efficiency of a solar cell by allowing electrons and holes generated by photoexcitation to move efficiently without rejoining. However, in a perovskite solar cell containing such an organic semiconductor film, due to problems of linear expansion and adhesion of the organic semiconductor, peeling occurs between the organic semiconductor film and the anode in a harsh environment such as a high temperature atmosphere. In addition, there is a problem that the durability is inferior due to cracks in the anode.
An object of the present invention is to provide a solar cell having high photoelectric conversion efficiency, less likely to cause peeling between the hole transport layer and the anode, and excellent durability.

The present invention is a solar cell having a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order, wherein the photoelectric conversion layer is a general formula RMX ₃ (where R is an organic molecule and M is a metal. The atom and X contain an organic-inorganic perovskite compound represented by a halogen atom or a chalcogen atom), and the hole transport layer contains an organic semiconductor and an insulating polymer compound having a glass transition point of 100 ° C. or higher. It is a solar cell.
Hereinafter, the present invention will be described in detail.

The present inventors have investigated a solar cell having a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order, and the photoelectric conversion layer contains a specific organic-inorganic perovskite compound. In the hole transport layer of such a solar cell, the present inventors add an insulating polymer compound having a glass transition point of 100 ° C. or higher in addition to the organic semiconductor as the main component to form the hole transport layer and the anode. We have found that the durability of the solar cell can be improved by suppressing the peeling between the two, and have completed 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.

The material of the cathode is not particularly limited, and conventionally known materials can be used.
As the cathode material, for example, FTO (fluorine-doped tin oxide), sodium, sodium - potassium alloy, lithium, magnesium, aluminum, magnesium - silver mixture, a magnesium - indium mixture, an aluminum - lithium alloy, Al / _Al 2 _{O 3} mixture, Al / LiF mixture, gold, silver, titanium, molybdenum, tantalum, tungsten, carbon, nickel, chromium and the like can be mentioned. These materials may be used alone or in combination of two or more.

The photoelectric conversion layer contains an organic-inorganic perovskite compound represented by the general formula R-MX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). A solar cell in which the photoelectric conversion layer contains the organic-inorganic perovskite compound is also called an organic-inorganic hybrid 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 R is an organic molecule, and is preferably represented by C _l N _m H _n (all l, m, and n are positive integers).
Specifically, the R is, for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropyl. Amine, tributylamine, trypentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, formamidine, acetamidine, guanidine, imidazole, Examples thereof include azole, pyrrole, aziridine, azirin, azetidine, azeto, azole, imidazoline, carbazole, ions thereof (for example, methylammonium (CH ₃ NH ₃ ), etc.), phenethylammonium and the like. Among them, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, formamidine, acetamidine and their ions and phenethylammine are preferable, and methylamine, ethylamine, propylamine, formamidine and these ions are more preferable. preferable.

The above M is a metal atom, for example, lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, Europium and the like can be mentioned. These metal atoms may be used alone or in combination of two or more.

The X is a halogen atom or a chalcogen atom, and examples thereof include chlorine, bromine, iodine, oxygen, sulfur, and selenium. When the X is a halogen atom or a chalcogen atom, the absorption wavelength of the organic-inorganic perovskite compound is widened, and high photoelectric conversion efficiency can be achieved. These halogen atoms or chalcogen atoms may be used alone or in combination of two or more. Among them, a halogen atom is preferable because the inclusion of halogen in the structure makes the organic-inorganic perovskite compound soluble in an organic solvent and can be applied to an inexpensive printing method or the like. Further, iodine is more preferable 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 body center, an organic molecule R is arranged at each apex, and a halogen atom or a chalcogen atom X is arranged at the face center.
FIG. 1 shows an example of the crystal structure of an organic-inorganic perovskite compound, which is a cubic structure in which a metal atom M is arranged at the body center, an organic molecule R is arranged at each apex, and a halogen atom or a chalcogen atom X is arranged at the face center. It is a schematic diagram. 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. The crystallinity is determined by separating the scattering peak derived from the crystalline substance and the halo derived from the amorphous part detected by the X-ray scattering intensity distribution measurement by fitting, and obtaining the intensity integration of each to obtain the crystal part of the whole. 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 is 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.

When the photoelectric conversion layer contains the organic-inorganic perovskite compound, 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. It may be included. 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 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.

Examples of the inorganic semiconductor include 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 , and so on. Examples thereof include MoS _{2 , MoSe 2} , and Cu ₂ S.

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 inorganic semiconductor moiety and a thin-film organic-inorganic perovskite compound moiety are laminated. 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 occurrence of a region where charge separation is not possible, which leads to an 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. A more preferable lower limit of the thickness is 40 nm, a more preferable upper limit is 2000 nm, a further preferable lower limit is 50 nm, and a 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 deposition method, a sputtering method, a vapor phase reaction method (CVD), an electrochemical deposition method, and a printing method. In particular, 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 and a casting method, and examples of the method using the printing method include a roll-to-roll method.

The hole transport layer contains an organic semiconductor and an insulating polymer compound having a glass transition point of 100 ° C. or higher (also simply referred to as “insulating polymer compound” in the present specification).
In the hole transport layer, by adding an insulating polymer compound having a glass transition point of 100 ° C. or higher in addition to the organic semiconductor as the main component, peeling between the hole transport layer and the anode is suppressed. Therefore, the durability of the solar cell can be improved. The reason for this is that by adding an insulating polymer compound having a glass transition point of 100 ° C. or higher, the movement of the molecules of the organic semiconductor in a harsh environment such as a high temperature atmosphere is suppressed, and the hole transport layer is used. It is thought that this is because it is possible to prevent the deformation of.

The organic semiconductor is not particularly limited, and an organic semiconductor generally used for the hole transport layer can be used. Examples of the organic semiconductor include P-type conductive polymers, P-type low-molecular-weight organic semiconductors, surfactants, and the like. Specifically, for example, compounds having a thiophene skeleton such as poly (3-alkylthiophene) and the like. Can be mentioned. Further, for example, a conductive polymer having a triarylamine skeleton, a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton and the like can 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 the like can be mentioned. These organic semiconductors may be used alone or in combination of two or more. Among them, a compound having a spirobifluorene skeleton and a triarylamine skeleton is preferable from the viewpoint of compatibility with the insulating polymer compound.

The lower limit of the glass transition point (Tg) of the insulating polymer compound is 100 ° C. When the glass transition point (Tg) is 100 ° C. or higher, peeling between the hole transport layer and the anode is less likely to occur, and the durability of the solar cell is improved. The preferable lower limit of the glass transition point (Tg) is 110 ° C, and the more preferable lower limit is 120 ° C.
The upper limit of the glass transition point (Tg) is not particularly limited, but a preferable upper limit is 200 ° C. When the glass transition point (Tg) is 200 ° C. or lower, the film can be maintained without cracking the hole transport layer even when a flexible base material is used. A more preferable upper limit of the glass transition point (Tg) is 180 ° C.
The glass transition point (Tg) can be determined by differential scanning calorimetry at a heating rate of 10 ° C./min.

The preferable lower limit of the weight average molecular weight of the insulating polymer compound is 10000, and the preferable upper limit is 1,000,000. When the weight average molecular weight is 10,000 or more, peeling between the hole transport layer and the anode is less likely to occur, and the durability of the solar cell is improved. When the weight average molecular weight is 1,000,000 or less, the organic semiconductor and the insulating polymer compound are easily compatible with each other, and sufficient film forming accuracy can be obtained. The more preferable lower limit of the weight average molecular weight is 50,000, and the more preferable upper limit is 500,000.
The weight average molecular weight can be determined by measuring by gel permeation chromatography and converting from a standard polymer of polystyrene, polymethylmethacrylate and polyethylene oxide.

Since the insulating polymer compound is insulating, electrons and holes are not exchanged between the organic semiconductor and the insulating polymer compound, and the insulating polymer compound is used for carrier transport between the organic semiconductors. It does not become an obstacle. Therefore, by adding the insulating polymer compound, the durability can be improved without lowering the photoelectric conversion efficiency of the solar cell.
As an index of insulating property, the resistivity of the insulating polymer compound can be evaluated. Resistivity of the insulating polymer is a preferred lower limit is 10 ⁵ Ω · cm. If the resistivity is 10 ⁵ Ω · cm or more, the insulating polymer is not easily become an obstacle when the hole-transporting be added to the hole transport layer. A more preferred lower limit is 10 ⁸ Ω · cm, still more preferred lower limit ^{10 14 Ω} · cm, even more preferred lower limit to the resistivity is ^{10 16 Ω} · cm.
The resistivity can be determined by the double ring electrode method using, for example, High Restor-UX MCP-HT800 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

The preferable lower limit of the transmittance of the insulating polymer compound is 80%. When the transmittance is 80% or more, the performance of the solar cell can be maintained without lowering the transmittance of the hole transport layer. The more preferable lower limit of the transmittance is 90%.
The transmittance can be determined by measuring the transmittance of a sample having a thickness of 1 mm at a wavelength of 500 nm using, for example, a spectrophotometer U-4100 (manufactured by Hitachi High-Technologies Corporation).

Specific examples of the insulating polymer compound include resins having an alicyclic skeleton, acrylic resins, polystyrenes, epoxy resins, urethane resins, polycarbonates, polyamides, PET resins, polyesters, phenol resins, melamine resins and the like. Be done. These insulating polymer compounds may be used alone or in combination of two or more. Of these, polystyrene, which has an alicyclic skeleton, is preferable because it has good compatibility with the organic semiconductor.

The resin having the alicyclic skeleton is not particularly limited as long as it has a glass transition point of 100 ° C. or higher and has an alicyclic skeleton, and may be a thermoplastic resin or thermosetting. It may be a resin or a photocurable resin. These resins having an alicyclic skeleton may be used alone or in combination of two or more.
The alicyclic skeleton is not particularly limited, and examples thereof include skeletons such as norbornene, isobornene, adamantane, cyclohexane, dicyclopentadiene, dicyclohexane, and cyclopentane. These skeletons may be used alone or in combination of two or more.
Examples of the resin having an alicyclic skeleton include a polymer of norbornene resin (TOPAS9014, manufactured by Polyplastics Co., Ltd.) and adamantane acrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.).

The content of the insulating polymer compound is not particularly limited, but the preferable lower limit of the content in the hole transport layer is 0.01% by weight, and the preferable upper limit is 50% by weight. When the content is 0.01% by weight or more, peeling between the hole transport layer and the anode is less likely to occur, and the durability of the solar cell is improved. When the content is 50% by weight or less, even if the insulating polymer compound is added to the hole transport layer, it is unlikely to be an obstacle during hole transport. The more preferable lower limit of the content is 1% by weight, and the more preferable upper limit is 20% by weight.

The combination of the organic semiconductor and the insulating polymer compound is not particularly limited, but from the viewpoint of compatibility with these, it has an organic semiconductor having a spirobifluorene skeleton, a resin having an alicyclic skeleton, and a spirobifluorene skeleton. A combination of an organic semiconductor and polystyrene, an organic semiconductor having a triarylamine skeleton and a resin having an alicyclic skeleton, and an organic semiconductor having a triarylamine skeleton and polystyrene is preferable.

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 as 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, it is unlikely to become a resistance during hole transportation, and the photoelectric conversion efficiency becomes 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 method for forming the hole transport layer is not particularly limited, and examples thereof include a method in which the organic semiconductor and the insulating polymer compound are dissolved in chlorobenzene and a film is formed by a spin coating method.

The material of the anode is not particularly limited, and conventionally known materials can be used. The anode is often a patterned electrode.
Examples of the anode material include metals such as gold, and conductivity such as CuI, ITO (indium tin oxide), SnO ₂ , AZO (aluminum zinc oxide), IZO (indium zinc oxide), and GZO (gallium zinc oxide). Examples include sex transparent materials. These materials may be used alone or in combination of two or more.

The thickness of the anode is not particularly limited, but a preferable lower limit is 100 nm, a preferable upper limit is 1000 nm, a more preferable lower limit is 200 nm, and a more preferable upper limit is 500 nm.

In the solar cell of the present invention, an electron transport layer may be arranged between the cathode and the photoelectric conversion layer.
The material of the electron transport layer is not particularly limited, and examples thereof include n-type metal oxides, N-type conductive polymers, N-type low-molecular-weight organic semiconductors, alkali metal halides, alkali metals, and surfactants. Specifically, for example, titanium oxide, tin oxide, cyano group-containing polyphenylene vinylene, boron-containing polymer, vasocuproin, vasofenantrene, hydroxyquinolinatoaluminum, oxadiazole compound, benzoimidazole compound, naphthalenetetracarboxylic acid compound, perylene derivative, Examples thereof include phosphine oxide compounds, phosphine sulfide compounds, and fluorogroup-containing phthalocyanine.

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 photoelectric conversion can be obtained. Since the efficiency is high, it is preferable that the composite film is formed on the porous electron transport layer.

The preferred lower limit of the thickness of the electron transport layer is 1 nm, and the preferred upper limit is 2000 nm. When the thickness is 1 nm or more, 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 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, a plastic substrate, and a metal substrate.

In the solar cell of the present invention, the laminate having the above-mentioned cathode, the above-mentioned photoelectric conversion layer, the above-mentioned hole transport layer, and the above-mentioned anode in this order may be sealed with a barrier layer.
The material of the barrier layer is not particularly limited as long as it has a barrier property, and examples thereof include a thermosetting resin, a thermoplastic resin, and an inorganic material.
Examples of the thermosetting resin or thermoplastic resin include epoxy resin, acrylic resin, silicone resin, phenol resin, melamine resin, urea resin, butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, and poly. Examples thereof include vinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene and the like.

When the material of the barrier layer is a thermosetting resin or a thermoplastic resin, the thickness of the barrier layer (resin layer) has a preferable lower limit of 100 nm and a preferable upper limit of 100,000 nm. A more preferable lower limit of the thickness is 500 nm, a more preferable upper limit is 50,000 nm, a further preferable lower limit is 1000 nm, and a further preferable upper limit is 20000 nm.

Examples of the inorganic material include oxides, nitrides or oxynitrides of Si, Al, Zn, Sn, In, Ti, Mg, Zr, Ni, Ta, W, Cu or alloys containing two or more of them. .. Of these, oxides, nitrides or oxynitrides of metal elements containing both Zn and Sn metal elements are preferable in order to impart water vapor barrier properties and flexibility to the barrier layer.

When the material of the barrier layer is an inorganic material, the thickness of the barrier layer (inorganic layer) has a preferable lower limit of 30 nm and a preferable upper limit of 3000 nm. When the thickness is 30 nm or more, the inorganic layer can have a sufficient water vapor barrier property, and the durability of the solar cell is improved. When the thickness is 3000 nm or less, even when the thickness of the inorganic layer is increased, the stress generated is small, so that peeling between the inorganic layer and the laminated body can be suppressed. The more preferable lower limit of the thickness is 50 nm, the more preferable upper limit is 1000 nm, the further preferable lower limit is 100 nm, and the further preferable upper limit is 500 nm.
The thickness of the inorganic layer can be measured using an optical interferometry film thickness measuring device (for example, FE-3000 manufactured by Otsuka Electronics Co., Ltd.).

Among the materials of the barrier layer, the method of sealing the laminate with the thermosetting resin or the thermoplastic resin is not particularly limited, and for example, the material of the sheet-shaped barrier layer is used to seal the laminate. Method, a method of applying a solution of a barrier layer material dissolved in an organic solvent to the laminate, a method of applying a liquid monomer to be a barrier layer to the laminate, and then cross-linking or polymerizing the liquid monomer with heat or UV or the like. Examples thereof include a method, a method in which the material of the barrier layer is heated to melt it, and then cooled.

Among the materials for the barrier layer, a vacuum vapor deposition method, a sputtering method, a vapor phase reaction method (CVD), and an ion plating method are preferable as a method for sealing the laminate with the inorganic material. Among them, the sputtering method is preferable for forming a dense layer, and the DC magnetron sputtering method is more preferable among the sputtering methods.
In the sputtering method, an inorganic layer made of an inorganic material can be formed by using a metal target and oxygen gas or nitrogen gas as raw materials and depositing the raw materials on the laminate to form a film.
The material of the barrier layer may be a combination of the thermosetting resin or the thermoplastic resin and the inorganic material.

In the solar cell of the present invention, the barrier layer may be further covered with another material such as a resin film or a resin film coated with an inorganic material. That is, the solar cell of the present invention may have a configuration in which the laminate and the other material are sealed, filled or adhered by the barrier layer. As a result, even if there is a pinhole in the barrier layer, water vapor can be sufficiently blocked, and the durability of the solar cell can be further improved.

FIG. 2 is a cross-sectional view schematically showing an example of the solar cell of the present invention.
The solar cell 1 shown in FIG. 2 has an electron transport layer 3 (thin-film electron transport layer 31 and a porous electron transport layer 32), a photoelectric conversion layer 4, a hole transport layer 5, and an anode 6 on the cathode 2. Have in order. The photoelectric conversion layer 4 contains an organic-inorganic perovskite compound as described above. The hole transport layer 5 contains an organic semiconductor and an insulating polymer compound having a glass transition point of 100 ° C. or higher. By having such a hole transport layer 5, the solar cell 1 is less likely to be separated from the hole transport layer 5 and the anode 6, and the durability is improved. In the solar cell 1 shown in FIG. 2, the anode 6 is a patterned electrode.

The method for producing the solar cell of the present invention is not particularly limited, and for example, a method of forming the cathode, the electron transport layer, the photoelectric conversion layer, the hole transport layer, and the anode on the substrate in this order may be used. Can be mentioned.

According to the present invention, it is possible to provide a solar cell having high photoelectric conversion efficiency, less likely to cause peeling between the hole transport layer and the anode, and excellent durability.

It is a schematic diagram which shows an example of the crystal structure of an organic-inorganic perovskite compound. It is sectional drawing which shows typically an example of the solar cell of this invention.

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

( Reference example 1 )
An aluminum film having a thickness of 200 nm and a titanium film having a thickness of 50 nm were continuously formed on a glass substrate by an electron beam vapor deposition method, and this was used as a cathode.
Next, titanium oxide was sputtered on the surface of the cathode using a sputtering device (manufactured by ULVAC, Inc.) to form a thin-film electron transport layer having a thickness of 30 nm. Further, an ethanol dispersion of titanium oxide nanoparticles (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, and then fired at 200 ° C. for 10 minutes to form a porous body having a thickness of 150 nm. A pledged electron transport layer was formed.

Next, as a solution for forming an organic-inorganic perovskite compound, CH ₃ NH ₃ I and Pb I ₂ were dissolved in a molar ratio of 1: 1 _{using N, N-dimethylformamide (DMF) as a solvent, and the sum of CH 3} NH ₃ I and PbI ₂ was added. The weight concentration was adjusted to 20%. This solution was laminated on the electron transport layer by a spin coating method and then fired at 100 ° C. for 10 minutes to form a photoelectric conversion layer.

Next, on the photoelectric conversion layer, 79.91 mg of Spiro-OMeTAD (organic semiconductor having a spirobifluorene skeleton), 34 μL of t-butylpyridine, and bis (trifluoromethylsulfonyl) imide / silver salt were added to 1 mL of chlorobenzene as an organic semiconductor. A solution prepared by dissolving 10 mg of norbornene resin (TOPAS6017, manufactured by Polyplastics Co., Ltd., glass transition point 170 ° C.) as an insulating polymer compound (10 mg) was applied by a spin coating method to form a hole transport layer having a thickness of 150 nm. Formed.

An ITO film having a thickness of 200 nm is formed as an anode on the obtained hole transport layer by sputtering using a sputtering device (manufactured by ULVAC, Inc.), and the cathode / electron transport layer / photoelectric conversion layer / hole transport layer / anode is formed. A laminated solar cell was obtained.

(Examples 2 to 3)
A solar cell was obtained in the same manner as in Reference Example 1 except that the content of the insulating polymer compound in the hole transport layer was changed as shown in Table 1.

( Reference Example 2, Examples 5 to 6)
The insulating polymer compound in the hole transport layer was changed to norbornene resin (TOPAS6013, manufactured by Polyplastics, glass transition point 130 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Example 7)
The insulating polymer compound in the hole transport layer was changed to a dicyclopentadiene resin (ARTONF4540, manufactured by JSR Corporation, glass transition point 130 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Example 8)
The insulating polymer compound in the hole transport layer was changed to a dicyclopentadiene resin (ARTONF4520, manufactured by JSR Corporation, glass transition point 150 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Example 9)
The insulating polymer compound in the hole transport layer was changed to polymethylmethacrylate (PMMA, manufactured by Sigma-Aldrich, glass transition point 100 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Example 10)
Same as Reference Example 1 except that the insulating polymer compound in the hole transport layer was changed to polystyrene (PS, glass transition point 100 ° C.) and the content of the insulating polymer compound was changed as shown in Table 1. And got a solar cell.

(Examples 11 to 14)
The organic semiconductor in the hole transport layer was changed to PTAA (organic semiconductor having a triarylamine skeleton), the insulating polymer compound was changed as shown in Table 1, and the content of the insulating polymer compound is shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except that it was changed as shown.

(Comparative Example 1)
A solar cell was obtained in the same manner as in Reference Example 1 except that an insulating polymer compound was not added to the hole transport layer.

(Comparative Example 2)
The insulating polymer compound in the hole transport layer was changed to norbornene resin (TOPAS8007, manufactured by Polyplastics, glass transition point 80 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Comparative Example 3)
The insulating polymer compound in the hole transport layer was changed to polybutyl methacrylate (PBMA, manufactured by Sigma-Aldrich, glass transition point 15 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Comparative Example 4)
Except that the insulating polymer compound in the hole transport layer was changed to polypropylene (PP, manufactured by Sigma-Aldrich, glass transition point 0 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. Obtained a solar cell in the same manner as in Reference Example 1.

(Comparative Example 5)
The insulating polymer compound in the hole transport layer was changed to polymethylmethacrylate (PMMA, manufactured by Sigma-Aldrich, glass transition point 70 ° C.), and the content of the insulating polymer compound was changed as shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except for the above.

(Comparative Examples 6-9)
The organic semiconductor in the hole transport layer was changed to PTAA (organic semiconductor having a triarylamine skeleton), the insulating polymer compound was changed as shown in Table 1, and the content of the insulating polymer compound is shown in Table 1. A solar cell was obtained in the same manner as in Reference Example 1 except that it was changed as shown.

<Evaluation>
The solar cells obtained in Examples, Reference Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.

(1) Measurement of photoelectric conversion efficiency Connect a power supply (236 model manufactured by KEITHLEY) between the electrodes of the solar cell, and draw a current-voltage curve using a solar simulation (manufactured by Yamashita Denso Co., Ltd.) ^{with an intensity of 100 mW / cm 2.} Then, the photoelectric conversion efficiency was calculated. This was used as the initial conversion efficiency.
In Reference Examples 1, 2, Examples 1 , 3, 5 to 10, and Comparative Examples 2 to 5, the obtained initial conversion efficiency is 95% or more of the initial conversion efficiency obtained in Comparative Example 1. 〇, the case of less than 95% was evaluated as x.
In Examples 11 to 14 and Comparative Examples 7 to 9, the case where the initial conversion efficiency obtained is 95% or more as compared with the initial conversion efficiency obtained in Comparative Example 6 is 〇, and the case where it is less than 95% is ×. bottom.

(2) Evaluation of Durability A durability test was conducted by placing the solar cell in an environment with a humidity of 85% and a temperature of 85 ° C. for 1000 hours. A power supply (KEITHLEY 236 model) is connected between the electrodes of the solar cell after the durability test, and a current-voltage curve is drawn using a solar simulation (Yamashita Denso Co., Ltd.) ^{with a strength of 100 mW / cm 2 and photoelectric.} The conversion efficiency was calculated, and the value of the photoelectric conversion efficiency after the durability test / the initial conversion efficiency obtained above was obtained. Photoelectric conversion efficiency after durability test / When the value of the initial conversion efficiency obtained above is 0.9 or more, it is ⊚, when it is less than 0.9 and 0.8 or more, it is 〇, and when it is less than 0.8, it is ×. bottom.

According to the present invention, it is possible to provide a solar cell having high photoelectric conversion efficiency, less likely to cause peeling between the hole transport layer and the anode, and excellent durability.

1 Solar cell 2 Cathode 3 Electron transport layer 31 Thin-film electron transport layer 32 Porous electron transport layer 4 Photoelectric conversion layer 5 Hole transport layer 6 Anode (patterned electrode)

Claims (1)

A solar cell having a cathode, a photoelectric conversion layer, a hole transport layer, and an anode in this order.
The photoelectric conversion layer contains an organic-inorganic perovskite compound represented by the general formula R-MX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom).
The hole transport layer contains an organic semiconductor and an insulating polymer compound having a glass transition point of 100 ° C. or higher.
A solar cell characterized in that the content of the insulating polymer compound is 1% by weight or more and 20% by weight or less.

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