WO2024111643A1 - Photoelectric conversion element, solar cell module, and method for manufacturing photoelectric conversion element - Google Patents

Abstract

A photoelectric conversion element (20) of the present disclosure is characterized in comprising: a transparent substrate (2), a transparent electroconductive film (3) provided on the transparent substrate (2), a hole-blocking layer (4) provided on the transparent electroconductive film (3), a photoelectric conversion layer (5) provided on the hole-blocking layer (4), an electron-blocking layer (9) provided on the photoelectric conversion layer (5), and a reverse-surface electrode (10) provided on the electron-blocking layer (9), the photoelectric conversion layer (5) including perovskite compound crystals (7) and filler particles (8), the photoelectric conversion layer (5) including a reflective region (6) in which the filler particles (8) are unevenly concentrated, the reflective region (6) being disposed adjacent to the electron-blocking layer (9).

Description

Photoelectric conversion element, solar cell module, and method for manufacturing photoelectric conversion element

This disclosure relates to a photoelectric conversion element, a solar cell module, and a method for manufacturing a photoelectric conversion element.

Photoelectric conversion elements are used, for example, in optical sensors, copiers, solar cell modules, etc. Among these, solar cell modules are becoming increasingly popular as a representative method of using renewable energy. The most widely used solar cell modules are those that use inorganic photoelectric conversion elements (for example, silicon-based solar cell modules, CIGS-based solar cell modules, and CdTe-based solar cell modules, etc.).

Meanwhile, solar cell modules using organic photoelectric conversion elements (for example, organic thin-film solar cell modules and dye-sensitized solar cell modules) are also being considered. Such solar cell modules using organic photoelectric conversion elements can be manufactured using a coating process without using a vacuum process, which has the potential to significantly reduce manufacturing costs. For this reason, solar cell modules using organic photoelectric conversion elements are expected to be the next generation of solar cell modules.

In recent years, organic photoelectric conversion elements that use compounds having a perovskite crystal structure (hereinafter sometimes referred to as perovskite compounds) in the light absorption layer have been studied (see, for example, Patent Document 1). Examples of perovskite compounds include lead complexes. Photoelectric conversion elements that use perovskite compounds in the light absorption layer have excellent photoelectric conversion efficiency.

JP 2019-67850 A

It is desirable to further improve the photoelectric conversion efficiency and durability of a photoelectric conversion element using a perovskite compound in a light absorption layer.
The present disclosure has been made in view of the above circumstances, and provides a photoelectric conversion element having excellent photoelectric conversion efficiency and excellent durability.

The present disclosure provides a photoelectric conversion element comprising a transparent substrate, a transparent conductive film provided on the transparent substrate, a hole blocking layer provided on the transparent conductive film, a photoelectric conversion layer provided on the hole blocking layer, an electron blocking layer provided on the photoelectric conversion layer, and a back electrode provided on the electron blocking layer, the photoelectric conversion layer including perovskite compound crystals and filler particles, the photoelectric conversion layer including a reflective region in which the filler particles are unevenly distributed, and the reflective region disposed adjacent to the electron blocking layer.

The photoelectric conversion layer includes the reflection region in which the filler particles are unevenly distributed, and this reflection region is disposed adjacent to the electron blocking layer, so that the photoelectric conversion layer can have two layers: a layer mainly composed of perovskite compound crystals, and a layer containing a large number of filler particles and having perovskite compound crystals between the particles. Therefore, the light that passes through the layer mainly composed of perovskite compound crystals and reaches the reflection region is diffusely reflected by the reflection region, so that the layer mainly composed of perovskite compound crystals can absorb reflected light or scattered light. In addition, since the perovskite compound crystals are present between the particles in the reflection region, the perovskite compound crystals can also absorb reflected light or scattered light. Therefore, the number of electrons and holes generated by photoexcitation in the perovskite compound crystals can be increased, and the photoelectric conversion efficiency of the photoelectric conversion element can be increased. In addition, the film thickness of the photoelectric conversion layer can be reduced, and the open circuit voltage and FF characteristics (recombination reduction) can be improved.
Since the photoelectric conversion layer contains filler particles, the solvent evaporation rate during the formation of the photoelectric conversion layer can be slowed down. Therefore, the crystal growth rate of the perovskite compound crystal can be slowed down, and defects at the crystal interface of the perovskite compound crystal can be reduced. Therefore, the intrusion of water molecules into the perovskite compound crystal can be suppressed, and the durability of the photoelectric conversion element can be improved.

1 is a schematic cross-sectional view of a photoelectric conversion element according to an embodiment of the present disclosure. FIG. 2 is a diagram showing a band structure of a photoelectric conversion element according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of a filler particle having a surface coating layer of an electron blocking material. 1A is a schematic diagram of a photoelectric conversion layer in which filler particles are unevenly distributed, and an enlarged view in which the filler particles are closely packed (face-centered cubic arrangement). FIG. 1 is a schematic diagram of a photoelectric conversion layer having a surface coating layer of an electron blocking material and in which filler particles are unevenly distributed, and an enlarged view of the filler particles in close packing (face-centered cubic arrangement). FIG. 1 is an explanatory diagram of a manufacturing method for forming a photoelectric conversion layer by applying and drying a perovskite compound solution containing filler particles. 1 is a schematic cross-sectional view of a solar cell module according to an embodiment of the present disclosure. 1 is a partial cross-sectional view of a solar cell module according to an embodiment of the present disclosure. 1 is an equivalent circuit of a solar cell module according to an embodiment of the present disclosure.

The photoelectric conversion element disclosed herein comprises a transparent substrate, a transparent conductive film provided on the transparent substrate, a hole blocking layer provided on the transparent conductive film, a photoelectric conversion layer provided on the hole blocking layer, an electron blocking layer provided on the photoelectric conversion layer, and a back electrode provided on the electron blocking layer, the photoelectric conversion layer including perovskite compound crystals and filler particles, the photoelectric conversion layer including a reflective region in which the filler particles are unevenly distributed, and the reflective region being disposed adjacent to the electron blocking layer.

The filler particles preferably contain inorganic material particles.
The thickness of the reflective region is preferably 0.04 to 0.3 times the thickness of the photoelectric conversion layer.
The thickness of the reflective region is preferably 40 nm or more and 150 nm or less.
The reflective region is preferably a region in which 50 wt % or more of the filler particles contained in the photoelectric conversion layer are unevenly distributed.
The average particle diameter D50 of the filler particles is preferably 10 nm or more and 50 nm or less. By arranging such filler particles in a close-packed structure in the reflective region, it is possible to improve the durability against the intrusion of water molecules into the perovskite compound crystal. In addition, by the perovskite compound crystal entering the arrangement structure of the close-packed filler particles, the effective refractive index on the back electrode side is lowered, and light is efficiently reflected to the photoelectric conversion layer, thereby reducing the light absorption loss by the back electrode and realizing a highly efficient solar cell. In addition, the reflective region can suppress local current leakage between the transparent conductive film and the back electrode.

The filler particles preferably include at least one of silica particles, alumina particles, titanium oxide particles, zirconia particles, nickel oxide particles, Cu ₂ O particles, CuO particles, and zinc oxide particles.
Preferably, the filler particles have a surface coating layer, and the material of the surface coating layer is an electron blocking material that blocks electrons generated in the perovskite compound crystal and transports holes generated in the perovskite compound crystal to the electron blocking layer. This makes it possible to block the propagation of electrons to the back electrode side, and efficiently propagate holes to the back electrode. As a result, high efficiency of the photoelectric conversion element can be achieved. In addition, when light is irradiated to the perovskite compound crystal, the contact area between the perovskite compound crystal and the electron blocking material is wide, so that photoexcited carriers can be efficiently extracted to the back electrode. This allows efficient separation of photoexcited carriers (conduction electrons and holes), and high efficiency, low cost, and high rigidity can be achieved.
The electron blocking material is preferably _Cu2O or NiO.

Preferably, the electron blocking layer is disposed adjacent to the reflective region, and the thickness of the electron blocking layer is preferably 50 nm or more and 100 nm or less. This makes it possible to block the propagation of electrons to the back electrode side, and to efficiently propagate holes to the back electrode. As a result, a high efficiency of the photoelectric conversion element can be achieved.
The material of the back electrode is preferably a metal having a work function of 5.0 eV or more. This makes it possible to block the propagation of electrons to the back electrode side and to efficiently propagate holes to the back electrode. As a result, a high efficiency of the photoelectric conversion element can be achieved.
The thickness of the photoelectric conversion layer is preferably 500 nm to 1 μm. Since the photoelectric conversion layer having a reflective region can efficiently absorb light, the thickness of the photoelectric conversion layer can be made thin, thereby improving the open circuit voltage and FF characteristics (recombination reduction).

The present disclosure also provides a solar cell module that includes a plurality of photoelectric conversion elements of the present disclosure, the plurality of photoelectric conversion elements being integrated together. The solar cell module that integrates the photoelectric conversion elements as solar cells can efficiently absorb light due to the light reflection structure described above, allowing the thickness of the photoelectric conversion layer to be thin, thereby improving the open circuit voltage and FF characteristics (recombination reduction).

The present disclosure also provides a method for manufacturing a photoelectric conversion element, comprising a coating step of coating a coating liquid containing a perovskite compound and filler particles on a hole blocking layer provided on a transparent substrate, and a drying step of drying the coating film formed by the coating step, characterized in that in the drying step, the transparent substrate is heated from the side opposite to the coated surface in the coating step. By coating and drying the perovskite compound solution containing filler particles, a reflective region in which the filler particles are unevenly distributed can be formed in the photoelectric conversion layer, and a good interface of the perovskite compound crystals can be formed. As a result, the FF characteristic (recombination reduction) can be improved.

Below, one embodiment of the present disclosure will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present disclosure is not limited to those shown in the drawings and the following description.

Photoelectric conversion element FIG. 1 is a schematic cross-sectional view of a photoelectric conversion element according to the present embodiment.
The photoelectric conversion element 20 of this embodiment includes a transparent substrate 2, a transparent conductive film 3 provided on the transparent substrate 2, a hole blocking layer 4 provided on the transparent conductive film 3, a photoelectric conversion layer 5 provided on the hole blocking layer 4, an electron blocking layer 9 provided on the photoelectric conversion layer 5, and a back electrode 10 provided on the electron blocking layer 9. The photoelectric conversion layer 5 includes perovskite compound crystals 7 and filler particles 8. The photoelectric conversion layer 5 includes a reflective region 6 in which the filler particles 8 are unevenly distributed, and the reflective region 6 is disposed adjacent to the electron blocking layer 9.
FIG. 2 is a diagram showing the band structure of the photoelectric conversion element 20 for explaining the flow of conduction electrons and holes generated by photoexcitation in the perovskite compound crystals 7 contained in the photoelectric conversion layer 5.

[Transparent substrate]
The transparent substrate 2 is a base of the photoelectric conversion element 20 and is made of a transparent material. The transparent substrate 2 is disposed on the light receiving surface side of the photoelectric conversion element 20. In addition, a hole blocking layer 4, a photoelectric conversion layer 5, etc. are laminated on the transparent substrate 2 in the manufacturing process of the photoelectric conversion element 20.
Examples of materials for the transparent substrate 2 include transparent glass (more specifically, soda-lime glass, non-alkali glass, etc.) and heat-resistant transparent resins.
When the material of the transparent substrate 2 is a transparent resin, the photoelectric conversion element 20 may have a barrier layer on the transparent substrate 2. This can prevent moisture and the like from penetrating into the photoelectric conversion layer 5.

[Transparent conductive film]
The transparent conductive film 3 corresponds to the cathode of the photoelectric conversion element 20. Examples of materials constituting the transparent conductive film 3 include transparent conductive materials (particularly, transparent conductive oxides (TCO)) and non-transparent conductive materials. Examples of transparent conductive materials include copper iodide (CuI), indium tin oxide (ITO), tin oxide (SnO ₂ ), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). In FIG. 2, the transparent conductive film 3 is shown as TCO, and conductive electrons generated by photoexcitation in the perovskite compound crystal 7 (Perovskite) move to the transparent conductive film 3 through the hole blocking layer 4 and are extracted to the outside of the photoelectric conversion element 20.

[Hole block layer]
As shown in FIG. 2, the hole blocking layer 4 is a layer that transports electrons generated by photoexcitation in the perovskite compound crystals 7 of the photoelectric conversion layer 5 to the transparent conductive film 3, while blocking holes generated by photoexcitation in the perovskite compound crystals 7. For this reason, the hole blocking layer 4 preferably contains a material that easily moves electrons generated in the perovskite compound crystals 7 to the transparent conductive film 3. In the photoelectric conversion element 20, the hole blocking layer 4 can contain titanium oxide. Specifically, the hole blocking layer 4 can include a dense titanium oxide layer having a relatively small porosity and a porous titanium oxide layer that is a porous layer having a higher porosity than the dense titanium oxide layer. The dense titanium oxide layer can be provided on the transparent conductive film 3, and the porous titanium oxide layer can be provided on the dense titanium oxide layer. The dense titanium oxide layer and the porous titanium oxide layer that constitute the hole blocking layer 4 will be described.

(Dense titanium oxide layer)
Since the dense titanium oxide layer has a low porosity, the perovskite compound-containing coating liquid used to form the photoelectric conversion layer 5 during the manufacture of the photoelectric conversion element 20 does not easily penetrate into the layer. Therefore, by providing the photoelectric conversion element 20 with a dense titanium oxide layer, contact between the perovskite compound crystals 7 and the transparent conductive film 3 is suppressed. Furthermore, by providing the photoelectric conversion element 20 with a dense titanium oxide layer, contact between the transparent conductive film 3 and the back electrode 10, which is a cause of a decrease in electromotive force, is suppressed. The film thickness of the dense titanium oxide layer is preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 100 nm or less. Furthermore, the filling rate in terms of mass is preferably 90% or more.

(Porous titanium oxide layer)
Since the porous titanium oxide layer has a high porosity, the perovskite compound-containing coating liquid used to form the photoelectric conversion layer 5 during the manufacture of the photoelectric conversion element 20 can easily penetrate into the pores in the layer. Therefore, by providing the photoelectric conversion element 20 with a porous titanium oxide layer, the contact area between the perovskite compound crystals 7 and the hole blocking layer 4 can be increased. This allows electrons generated by photoexcitation in the perovskite compound crystals 7 to be efficiently transferred to the hole blocking layer 4 and holes to be blocked.

[Photoelectric conversion layer]
The photoelectric conversion layer 5 is a layer that generates electrons and holes by photoexcitation, and includes perovskite compound crystals 7 and filler particles 8. The thickness of the photoelectric conversion layer 5 is preferably 500 nm or more and 1 μm or less, and more preferably 700 nm or more and 800 nm or less.
The photoelectric conversion layer 5 may have a structure in which a light absorbing region mainly composed of perovskite compound crystals 7 and a reflection region 6 containing perovskite compound crystals 7 and filler particles 8, in which the filler particles of the photoelectric conversion layer 5 are unevenly distributed, are laminated. The light absorbing region may be provided adjacent to the hole blocking layer 4. The light absorbing region may be a layered region. The light absorbing region may be a region in which the perovskite compound crystals 7 account for 95 wt % or more. The light absorbing region may also contain filler particles 8.
When electrons in the valence band of the perovskite compound crystal 7 are photoexcited to the conduction band, conduction electrons are generated in the conduction band and holes are generated in the valence band. These conduction electrons and holes move as shown in FIG.

The perovskite compound crystal 7 contained in the photoelectric conversion layer 5 is preferably a crystal of a compound (perovskite compound) represented by the general formula: _ABX3 (1). In the general formula (1), A is an organic molecule, B is a metal atom, and X is a halogen atom. In the general formula (1), the three Xs may be the same or different from each other.
Perovskite compounds are organic-inorganic hybrid compounds. Organic-inorganic hybrid compounds are compounds composed of inorganic materials and organic materials. Photoelectric conversion elements using perovskite compounds, which are organic-inorganic hybrid compounds, are also called organic-inorganic hybrid photoelectric conversion elements.

In the general formula (1), examples of the organic molecule represented by A include alkylamines, alkylammoniums, and nitrogen-containing heterocyclic compounds. In the perovskite compound (1), the organic molecule represented by A may be only one type of organic molecule, or may be two or more types of organic molecules.
Examples of alkylamines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, and ethylbutylamine.

The alkyl ammonium is _an ionized product of the above-mentioned alkyl amine. Examples of the alkyl ammonium include methyl ammonium ( _CH3NH3 ), ethyl ammonium, propyl ammonium, butyl ammonium, pentyl ammonium, hexyl ammonium, dimethyl ammonium, diethyl ammonium, dipropyl ammonium, dibutyl ammonium, dipentyl ammonium, dihexyl ammonium, trimethyl ammonium, triethyl ammonium, tripropyl ammonium, tributyl ammonium, tripentyl ammonium, trihexyl ammonium, ethyl methyl ammonium, methyl propyl ammonium, butyl methyl ammonium, methyl pentyl ammonium, hexyl methyl ammonium, ethyl propyl ammonium, and ethyl butyl ammonium.

Examples of the nitrogen-containing heterocyclic compound include imidazole, azole, pyrrole, aziridine, azirine, azetidine, azeto, azole, imidazoline, and carbazole. The nitrogen-containing heterocyclic compound may be an ionized compound. Phenethylammonium is a preferred example of the nitrogen-containing heterocyclic compound that is an ionized compound.

The organic molecule represented by A is preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, methylammonium, ethylammonium, propylammonium, butylammonium, pentylammonium, hexylammonium or phenethylammonium, more preferably methylamine, ethylamine, propylamine, methylammonium, ethylammonium or propylammonium, and even more preferably methylammonium.

In general formula (1), examples of the metal atom represented by B include lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. In the perovskite compound, the metal atom represented by B may be only one type of metal atom, or may be two or more types of metal atoms. From the viewpoint of improving the light absorption characteristics and charge generation characteristics of the perovskite compound crystal 7, the metal atom represented by B is preferably a lead atom.

In general formula (1), examples of halogen atoms represented by X include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. In the perovskite compound, the halogen atom represented by X may be one type of halogen atom, or may be two or more types of halogen atoms. From the viewpoint of narrowing the energy band gap of the perovskite compound, the halogen atom represented by X is preferably an iodine atom. In particular, of the three Xs, it is preferable that at least one X represents an iodine atom, and it is more preferable that three Xs represent iodine atoms.

As the perovskite compound, a compound represented by the general formula " _CH3NH3PbX3 (wherein X represents a _halogen atom)" is preferred, _{and CH3NH3PbI3} is more preferred. By using a compound represented by the general formula " _{CH3NH3PbX3 "} ( _{particularly CH3NH3PbI3 )} as the _perovskite compound, conduction electrons and holes can be generated more efficiently in the _perovskite compound crystal 7 _, and as a result, the photoelectric conversion efficiency of the photoelectric conversion element ₂₀ can be further improved.

The filler particles 8 are particles mixed in the perovskite compound crystals 7. The filler particles 8 are, for example, inorganic material particles. The filler particles 8 preferably include at least one of silica particles, alumina particles, titanium oxide particles, zirconia particles, nickel oxide particles, _Cu2O particles, CuO particles, and zinc oxide particles, and are more preferably silica particles, nickel oxide particles, or _Cu2O particles.
As shown in FIG. 3, the filler particle 8 may have a core particle 12 and a surface coating layer 11 that covers the surface of the core particle 12. The core particle 12 is, for example, an inorganic material particle, more specifically, for example, silica particles, alumina particles, titanium oxide particles, zirconia particles, nickel oxide particles, Cu ₂ O particles, CuO particles, zinc oxide particles, etc. The material of the surface coating layer 11 is an electron blocking material that blocks electrons generated in the perovskite compound crystal 7 and transports holes generated in the perovskite compound crystal 7 to the electron blocking layer 9. The material of the surface coating layer 11 is, for example, Cu ₂ O, NiO, etc. In addition, the film thickness of the surface coating layer 11 can be 5 nm or more and 20 nm or less. By using such a filler particle 8, it is possible to block the conductive electrons generated in the perovskite compound crystal 7 from moving to the back electrode, and to efficiently propagate the holes generated in the perovskite compound crystal 7 to the back electrode. This makes it possible to realize high photoelectric conversion efficiency of the photoelectric conversion element 20. In addition, the contact interface between the perovskite compound crystal 7 and the hole blocking material can be widened, and holes generated in the perovskite compound crystal 7 can be efficiently propagated to the back electrode. As a result, the conduction electrons and holes generated in the perovskite compound crystal 7 can be efficiently separated, and the photoelectric conversion efficiency of the photoelectric conversion element 20 can be improved.

The filler particles 8 and the core-shell type filler particles 8 can be produced by an RF thermal plasma method. For the core-shell structure, organic filler particles such as organic polystyrene, cellulose, polyacrylic acid, etc. can be produced by a suspension polymerization method, the pH of the solution in which the produced organic filler is dispersed can be adjusted, and the surface of the organic filler can be coated with inorganic nanoparticles to produce the core-shell type filler particles 8.

The average particle diameter D50 of the filler particles 8 contained in the photoelectric conversion layer 5 is preferably 10 nm or more and 50 nm or less, and more preferably 10 nm or more and 30 nm or less. This allows the filler particles 8 to be unevenly distributed on the surface when the perovskite compound is coated and dried, and allows the filler particles 8 to form a closely packed structure. This improves the durability of the perovskite compound crystals 7 against the intrusion of water molecules. The average particle diameter D50 of the filler particles 8 can be calculated from the measurement results, for example, by measuring the particle diameters of about 100 filler particles 8 from a photograph of the cross section of the photoelectric conversion layer 5.

The reflective region 6 is a region where the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed, and is disposed adjacent to the electron blocking layer 9 .
Since the photoelectric conversion layer 5 has the reflection region 6, the light that passes through the light absorption region and reaches the reflection region 6 is diffusely reflected by the reflection region 6, so that the light absorption region can absorb the reflected light or scattered light and generate conductive electrons and holes. In addition, since the perovskite compound crystals 7 exist between the particles in the reflection region 6, the perovskite compound crystals 7 can also absorb the reflected light or scattered light. Therefore, the number of conductive electrons and holes generated by photoexcitation in the perovskite compound crystals 7 can be increased, and the photoelectric conversion efficiency of the photoelectric conversion element 20 can be increased. In addition, the thickness of the photoelectric conversion layer 5 can be reduced, and the open circuit voltage and FF characteristics (recombination reduction) can be improved.

The reflection region 6 may be a layer in which the filler particles 8 occupy 20 wt % or more. In addition, the reflection region 6 is preferably a region in which 50 wt % or more of the filler particles 8 of all the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed, more preferably a region in which 70 wt % or more of the filler particles 8 of all the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed, and even more preferably a region in which 90 wt % or more of the filler particles 8 of all the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed. This allows a remarkable light reflection effect to be obtained. In addition, in the reflection region 6, perovskite compound crystals 7 are present between the particles of the filler particles 8.
The reflective region 6 may be a region in which the filler particles 8 are stacked. For example, the reflective region 6 may include a region in which the filler particles 8 are stacked in a close-packed structure.
By incorporating the perovskite compound crystals into the array structure of the close-packed filler particles 8, the effective refractive index on the back electrode side of the photoelectric conversion layer 5 can be lowered, and by efficiently reflecting light to the light absorption region, the light absorption loss by the back electrode 10 can be reduced, thereby realizing a highly efficient solar cell.
4 and 5 are schematic diagrams of a photoelectric conversion layer 5 in which filler particles are unevenly distributed, and enlarged views of filler particles 8 in close packing (face-centered cubic arrangement). The filler particles 8 contained in the photoelectric conversion layer 5 shown in Fig. 4 are inorganic material particles, and the filler particles 8 contained in the photoelectric conversion layer 5 shown in Fig. 5 are particles in which the surface of a core particle 12 is covered with a surface coating layer 11.
As shown in FIG. 5 , the reflective region 6 has a configuration in which filler particles 8 having a surface coating layer 11 are closely packed (in a face-centered cubic arrangement), so that electrons generated in the perovskite compound crystals 7 can be blocked from propagating to the rear surface electrode 10, and holes generated in the perovskite compound crystals 7 can be efficiently propagated to the rear surface electrode 10.

The reflective region 6 may be a layered region. The thickness of the reflective region 6 is preferably 0.04 to 0.3 times the thickness of the photoelectric conversion layer 5, and more preferably 0.04 to 0.15 times the thickness of the photoelectric conversion layer 5. The thickness of the reflective region 6 may be 40 nm to 150 nm. This can prevent the internal resistance of the photoelectric conversion element 20 from increasing. Furthermore, the light that passes through the light absorption region and reaches the reflective region 6 can be efficiently diffused and reflected by the reflective region 6.

FIG. 6 is a schematic diagram showing a manufacturing method for forming a photoelectric conversion layer 5 by applying and drying a perovskite compound solution containing filler particles 8.
The manufacturing method of the photoelectric conversion layer 5 includes a coating step of coating a coating liquid containing a perovskite compound and filler particles on the hole blocking layer 4 provided on the transparent substrate 2, and a drying step of drying the coating film formed by the coating step.
Specifically, a coating liquid in which the filler particles 8 are dispersed in the perovskite compound solution can be prepared by mixing/stirring/dispersing a solution (A) of the perovskite compound and a dispersion (B) of the filler particles 8 in a container (C). The coating liquid is preferably a dispersion containing 3 to 10 wt % of the filler particles 8 in the perovskite compound solution so that the film thickness of the reflective region 6 in which the filler particles 8 are closely packed (face-centered cubic arrangement) is ⅓ of the film thickness of the photoelectric conversion layer 5.

The weight ratio of the solids that will become the perovskite compound crystals in the perovskite compound solution before the filler particles 8 are dispersed to the solvent is preferably 20/80, and the solids concentration is 20% or less. The weight ratio of the filler particles 8 to the coating liquid can be 3 to 10 wt%. For example, when a coating film formed by coating a perovskite compound coating liquid in which 5 wt% of SiO ₂ filler particles are dispersed is dried, the thickness of the photoelectric conversion layer 5 is 540 nm and the thickness of the reflective region 6 is 90 nm. When a perovskite compound coating liquid in which 10 wt% of SiO ₂ filler particles 8 are dispersed is dried, the thickness of the photoelectric conversion layer 5 is 580 nm and the thickness of the reflective region 6 is 180 nm.

The coating liquid is applied onto the hole blocking layer 4 to form a coating film. The coating method is not particularly limited, but can be slit die coating. It is preferable that the coating environment is maintained in a low humidity environment, and the coating environment may be sealed with an inert gas such as nitrogen gas. The transparent substrate 2, the transparent conductive film 3, and the hole blocking layer 4 may be arranged such that the transparent substrate 2 is located on the top side and the hole blocking layer 4 is located on the ground side, and the coating liquid may be applied onto the hole blocking layer 4 from the ground side of the laminate. This can prevent dripping from the slit die. In addition, by including the filler particles 8 in the coating liquid, the movement of the coating liquid in the coating film can be suppressed, a coating film having a uniform thickness can be formed, and the occurrence of pinholes can be suppressed. In addition, the occurrence of the coffee ring effect can be suppressed in the drying step. In addition, in the drying step, when the transparent substrate 2 is heated from the opposite side to the coating surface, the occurrence of convection in the coating film can be suppressed, and a reflective region 6 in which the filler particles 8 are unevenly distributed can be formed.

In the drying step, the solvent contained in the coating film evaporates. As a result, the concentration of the perovskite compound in the coating film increases, and the crystallization of the perovskite compound advances from the hole blocking layer 4 side. At this time, most of the filler particles 8 remain in the liquid phase, and a light absorbing region (a region mainly composed of the perovskite compound crystals 7) adjacent to the hole blocking layer 4 is formed. After the light absorbing region is formed, the crystallization of the perovskite compound advances on the coating film surface containing many filler particles 8, and a reflection region 6 in which the filler particles 8 are unevenly distributed is formed. It is preferable that 50 wt% or more of the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed in the reflection region 6, more preferably 70 wt% or more of the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed, and even more preferably 90 wt% or more of the filler particles 8 contained in the photoelectric conversion layer 5 are unevenly distributed. This provides a remarkable light reflection effect.
In addition, since the coating liquid contains the filler particles 8, the solvent evaporation rate in the drying step can be slowed down. This makes it possible to slow down the crystal growth rate of the perovskite compound crystals 7 and reduce defects at the crystal interface of the perovskite compound crystals 7. This makes it possible to suppress the intrusion of water molecules into the perovskite compound crystals 7, thereby improving the durability of the photoelectric conversion element 20.

The specific gravity of the filler particles 8 (e.g., 2.5 to 3.5 g/cm ³ ) is preferably lower than the specific gravity of the perovskite compound (e.g., 4.16 g/cm ³ ). This makes it possible to form the reflective region 6 in which the filler particles 8 are unevenly distributed on the surface of the photoelectric conversion layer 5.
In the drying step, it is preferable to heat the transparent substrate 2 from the side opposite to the coated surface in the coating step. The coating liquid surface at the bottom of the laminate is subjected to negative pressure, causing the solvent in the coating liquid to evaporate, and the coating liquid surface is cooled by the heat of evaporation, which diffuses the latent heat generated during crystallization of the perovskite compound crystals from the coating liquid side, thereby making the local temperature gradient uniform and realizing uniform crystallization.
In addition, since the coating film is not directly heated, the occurrence of a large temperature distribution in the coating film can be suppressed.

[Electron Blocking Layer]
The electron blocking layer 9 is a layer that captures holes generated in the photoelectric conversion layer 5, transports them to the back electrode 10 which is an anode, and blocks electrons generated in the perovskite compound crystal 7. The material constituting the electron blocking layer 9 is a material having an energy level (Eebc) of the conduction electron band that satisfies Eebc≧Eopc+0.5 eV compared to the energy level (Eopc) of the conduction electron band of the perovskite compound crystal 7. Specific examples of the material for the electron blocking layer 9 include inorganic compounds such as _Cu2O , NiO, and ZnS. This makes it possible to efficiently block electrons generated by photoexcitation in the perovskite compound crystal 7, thereby realizing a highly efficient photoelectric conversion element 20.
For example, as shown in the band structure of FIG. 2, the electron blocking layer 9 blocks electrons and allows holes to propagate to the rear electrode 10 (Ni).
Moreover, the electron blocking layer 9 is preferably disposed adjacent to the reflective region 6. The thickness of the electron blocking layer 9 is preferably 50 nm or more and 100 nm or less, and more preferably 70 nm or more and 80 nm or less. This makes it possible to block the propagation of electrons toward the rear electrode side, and to efficiently propagate holes to the rear electrode 10. As a result, high efficiency of the photoelectric conversion element 20 can be achieved.

[Back electrode]
The back electrode 10 corresponds to the anode of the photoelectric conversion element 20. Examples of materials constituting the back electrode 10 include metals, transparent conductive inorganic materials, conductive fine particles, and conductive polymers (particularly, transparent conductive polymers). Examples of metals include nickel, gold, silver, and platinum. Examples of transparent conductive inorganic materials include copper iodide (CuI), indium tin oxide (ITO), tin oxide (SnO ₂ ), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), and gallium-doped zinc oxide (GZO). Examples of conductive fine particles include silver nanowires and carbon nanofibers. Examples of transparent conductive polymers include polymers containing poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT/PSS).

In order to efficiently apply a built-in potential to the photoelectric conversion layer 5, it is desirable to use a metal with a work function Φ≧5.0 eV as the material for the back electrode 10. This results in a structure in which electrons are extracted from the transparent conductive film 3 on the transparent substrate 2 side, and holes are extracted from the back electrode 10 side, allowing a smooth flow of holes at the interface between the electron blocking layer 9 on the hole extraction side and the back electrode 10, resulting in a highly efficient photoelectric conversion element.

7 and 8 show schematic cross-sectional views of a solar cell module 50 (series-connected solar cells) according to this embodiment.
A photoelectric conversion element 20 (20a to 20e) of this embodiment includes a transparent substrate 2, a transparent conductive film 3 (3a to 3e) provided on the transparent substrate 2, a hole blocking layer 4 (4a to 4e) provided on the transparent conductive film 3, a photoelectric conversion layer 5 (5a to 5e) provided on the hole blocking layer 4, an electron blocking layer 9 (9a to 9e) provided on the photoelectric conversion layer 5, a back electrode 10 (10a to 10e) provided on the electron blocking layer 9, and a second barrier layer 22 provided to cover a side portion of the photoelectric conversion layer 5, the second barrier layer 22 being a dense inorganic material layer.

The solar cell module 50 of this embodiment includes a plurality of photoelectric conversion elements 20 (20a to 20e), a first terminal 37, and a second terminal 38. The plurality of photoelectric conversion elements 20 are connected in series, with the photoelectric conversion element 20a at one end of the plurality of photoelectric conversion elements 20 connected in series being connected to the first terminal 37, and the photoelectric conversion element 20e at the other end being connected to the second terminal 38. There is no particular limit to the number of photoelectric conversion elements 20 connected in series, as long as there is more than one.

The transparent substrate 2 is a substrate of the solar cell module 50. The transparent substrate 2 may be a glass substrate or a transparent organic film. This allows light to enter the inside of the photoelectric conversion element 20. When the transparent substrate 2 is a flexible organic film, the solar cell module 50 becomes a flexible solar cell module.
Specific examples of materials for the organic film that will become the transparent substrate 2 include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyamideimide (PAI), polyethylene naphthalate (PEN), etc., but other resins can also be used as long as they satisfy the requirements. The thickness of the organic film that will become the transparent substrate 2 is preferably 50 to 100 μm.

When the transparent substrate 2 is a transparent organic film, the first barrier layer 21 may be provided on one of the main surfaces of the transparent substrate 2. The first barrier layer 21 is a layer of a material with high gas barrier properties. This can prevent deterioration inside the photoelectric conversion element 20 (20a to 20e) due to moisture and oxygen in the air. The first barrier layer 21 is also a layer of an insulating material. This can suppress leakage current from flowing. The film thickness of the first barrier layer 21 can be several tens to 100 nm. This allows the first barrier layer 21 to have light transmissibility. In addition, the photoelectric conversion element 20 can have flexibility. Specific examples of materials for the first barrier layer 21 include silicon oxide and aluminum oxide. As long as the first barrier layer 21 has gas barrier properties, insulating properties, and light transmissivity, other oxide substances and insulators can also be used as the material for the first barrier layer 21. Main methods for forming the first barrier layer 21 include sputtering film formation and vacuum deposition.

The transparent conductive film 3 (3a to 3e) is provided on the transparent substrate 2 (or on the first barrier layer 21) and is an electrode for extracting a current generated by the photovoltaic power of the photoelectric conversion element 20 (20a to 20e). The transparent conductive film 3 is made of a conductive transparent material such as aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), gallium-doped zinc oxide (GZO), fluorine-doped tin oxide (FTO), indium tin oxide (ITO), or the like.
The transparent conductive film 3 preferably has a sheet resistance of 10 Ω/sq or less, and a light transmittance of 30% or more. Examples of a method for forming the transparent conductive film 3 include a sputtering method and a vacuum deposition method.

When multiple photoelectric conversion elements 20 are provided on the transparent substrate 2, the transparent conductive film 3 formed on the transparent substrate 2 is divided for each photoelectric conversion element 20. For example, the solar cell module 50 shown in FIG. 7 includes five photoelectric conversion elements 20a to 20e, so the transparent conductive film 3 is divided to form five transparent conductive films 3a to 3e. The grooves that divide two adjacent transparent conductive films 3 may be filled with a photoelectric conversion layer 5 or the like.

The first terminal 37 of the solar cell module 50 is formed on the organic film that is the transparent substrate 2, and a part of the first terminal 37 penetrates the organic film (transparent substrate 2) and the first barrier layer 21, and is in contact with or electrically connected to the transparent conductive film 3a of the end photoelectric conversion element 20a of the serially connected photoelectric conversion elements 20a to 20e. This first terminal 37 can be used to extract the current generated by the photovoltaic power of the solar cell module 50. An example of the material for the first terminal 37 is a SnZn-based solder paste. Other conductive pastes and electrode materials can also be used as long as they meet the requirements.

The hole blocking layer 4 is a layer that transports electrons generated by photoexcitation in the photoelectric conversion layer 5 to the transparent conductive film 3. Therefore, the hole blocking layer 4 is made of a material that allows electrons generated in the photoelectric conversion layer 5 to easily move to the hole blocking layer 4 and allows electrons in the hole blocking layer 4 to easily move to the transparent conductive film 3. The hole blocking layer 4 may also be a seed layer for oriented growth of the perovskite compound crystals 7 inside the photoelectric conversion layer 5. This can improve the quality of the perovskite compound crystals 7 contained in the photoelectric conversion layer 5. The hole blocking layer 4 is, for example, a titanium oxide (TiO ₂ ) layer. A TiN layer or a TiO _2-x N _x layer may be formed on the surface of the titanium oxide contained in the titanium oxide layer.

For example, a TiN (NaCl structure) layer having a thickness of 5 to 30 nm may be formed on the surface of the TiO ₂ of the porous titanium oxide layer on the transparent conductive film 3 as a seed layer to be the hole blocking layer 4 by subjecting the surface of the TiO ₂ to a surface modification treatment using nitrogen plasma.
The lattice constants of _TiO2 (rutile structure) and TiN (NaCl structure) are relatively well matched, and a good interface with few defects is formed between the _TiO2 layer made of _TiO2 and the TiN layer made of TiN. The mixed crystal material TiO2 _{-xNx is} formed near the interface, which changes the lattice constant continuously and suppresses the occurrence of interface defects. When the TiN layer is exposed to the atmosphere after surface modification treatment with nitrogen plasma, a reoxidation layer is formed on the surface to a thickness of several nm, but since the formed _TiO2 layer is thin, structural relaxation of the lattice constant does not occur, and the lattice constant of the underlying TiN layer is maintained.

After the transparent conductive film 3 is formed on the organic film (transparent substrate 2) covered with the first barrier layer 21, in order to separate and form the photoelectric conversion elements 20a to 20e on the organic film (transparent substrate 2), a cut (L1) is made in the transparent conductive film by laser scribing. The wavelength of the laser used is preferably in the infrared region. The cut (L1) is made in the transparent conductive film, and the transparent conductive films 3a to 3e are formed. No cut is made in the first barrier layer 21.
For example, the photoelectric conversion layer 5 can be formed by forming the perovskite compound crystal 7 on the transparent substrate 2 having a notch (L1) made thereon by laser scribing.

Perovskite compounds have a basic tetragonal unit cell, which has an organic group (organic molecule) A at each vertex, a metal atom B at the body center, and a halogen atom X at each face center, and is represented by the general formula A-B- _X3 .
Examples of organic solvents (contained in the coating solution) used in the coating method for forming the photoelectric conversion layer 5 include aromatic hydrocarbons such as toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, and dichlorobenzene; halogenated hydrocarbons such as dichloromethane, dichloroethane, and tetrachloropropane; ethers such as tetrahydrofuran (THF), dioxane, dibenzyl ether, dimethoxymethyl ether, and 1,2-dimethoxyethane; ketones such as methyl ethyl ketone, cyclohexanone, acetophenone, and isophorone; esters such as methyl benzoate, ethyl acetate, and butyl acetate; sulfur-containing solvents such as diphenyl sulfide; fluorine-based solvents such as hexafluoroisopropanol; aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and dimethylsulfoxide; alcohols such as methanol, ethanol, and isopropanol; and glyme-based solvents such as ethylene glycol and diethylene glycol monomethyl ether. These solvents may be mixed with water. Among these solvents, non-halogenated organic solvents are preferably used in consideration of the global environment.
In addition to this, the coating liquid may contain additives such as an antioxidant, a viscoelasticity modifier, a preservative, and a curing catalyst.
The coating method is not particularly limited, but for example, a dip coating method, a spray coating method, a slide hopper coating method, etc. are preferable.

After the photoelectric conversion layer 5 is formed, a cut (L2) is made in part of the photoelectric conversion layer 5 by laser scribing in order to connect the transparent conductive film 3 of one of two adjacent photoelectric conversion elements 20 (20a to 20e) to the electron block layer 9 and back electrode 10 of the other photoelectric conversion element 20. The wavelength of the laser used is preferably in the visible light region. For example, the cut (L2) is made in the photoelectric conversion layer 5, and the photoelectric conversion layers 5a to 5e are formed. With this laser scribing, the photoelectric conversion layer 5 is removed, but the transparent conductive film 3 and the first barrier layer 21 are not removed.

The back electrode 10 (10a to 10e) is provided on the photoelectric conversion layer 5 and is an electrode for extracting a current generated by the photovoltaic power of the photoelectric conversion layer 5 of the photoelectric conversion element 20 (20a to 20e). The back electrode 10 is, for example, a metal film with a work function of 5 eV or more. By making the back electrode 10 out of a metal with a deep work function (5 eV or more), a bending of the band structure occurs at the interface between the photoelectric conversion layer 5 and the back electrode 10, which makes the flow of holes smooth. Examples of materials for the back electrode 10 include metals such as Ni, Pt, and Pd. The film thickness of the back electrode 10 is preferably 50 nm to 150 nm. The photoelectric conversion layer 5 or the back electrode 10 can be formed by a sputtering deposition method, a vacuum deposition method, or the like.

After the back electrode 10 is formed, a cut (L3) is made in a part of the electron blocking layer 9 and the back electrode 10 by laser scribing in order to form a series connection circuit of adjacent photoelectric conversion elements 20a to 20e on the transparent substrate 2. In addition, in order to make the second barrier layer 22 described later function as a varistor 31, a cut (L4) is made in the hole blocking layer 4, the photoelectric conversion layer 5, the electron blocking layer 9, and the back electrode 10. The wavelength of the laser used is preferably in the ultraviolet region. For example, the cut (L3) is made in the electron blocking layer 9 and the back electrode 10 to form the electron blocking layers 9a to 9e and the back electrodes 10a to 10e. In addition, a cut (L4) for forming the varistor 31 can be made. Note that if the part with the cut (L3) functions as the varistor 31, the cut (L4) can be omitted.

The second barrier layer 22 is a dense inorganic material layer and is provided so as to cover the side of the photoelectric conversion layer 5 (5a to 5e). The second barrier layer 22 can be provided so as to cover the entire periphery of the photoelectric conversion layer 5. The second barrier layer 22 can be provided so as to cover the upper surface of the back electrode 10. This second barrier layer 22 can prevent moisture (such as water vapor) from entering the photoelectric conversion layer 5, and can prevent the photoelectric conversion element 20 from deteriorating. In addition, because the second barrier layer 22 is a dense inorganic material layer, it is possible to prevent the barrier function of the second barrier layer 22 from being reduced by ultraviolet rays, temperature changes, etc. In addition, by completely coating the photoelectric conversion layer 5 with the second barrier layer 22, the transparent conductive film 3, the transparent substrate 2, etc., the barrier properties against water vapor can be improved.

The second barrier layer 22 may be made of a material that exhibits varistor characteristics. The second barrier layer 22 can be provided so as to be connected to the transparent conductive film 3 and the back electrode 10 so that the second barrier layer 22 and the photoelectric conversion layer 5 are connected in parallel. The varistor characteristics are voltage-current characteristics (current nonlinearity) in which a current suddenly starts to flow at a certain constant voltage. There are no particular limitations on the material that exhibits the varistor characteristics as long as it is a material that can be used in a varistor element.
The thickness of the second barrier layer 22 can be, for example, not less than 30 nm and not more than 100 nm.
The second barrier layer 22 is formed on the back electrode 10 after laser scribing. The second barrier layer 22 can be formed so as to fill the notch (L3). This allows the periphery and upper surface of the photoelectric conversion layer 5 to be covered with the second barrier layer 22. The second barrier layer 22 can be formed so as to fill the notch (L4). This allows the second barrier layer 22 to be connected to the transparent conductive film 3 and the back electrode 10 such that the second barrier layer 22 and the photoelectric conversion layer 5 are connected in parallel.

A part of the second barrier layer 22 is connected in parallel to the photoelectric conversion layer 5 as a varistor element structure, thereby realizing a photoelectric conversion element 20 integrally provided with a bypass diode (varistor of the second barrier layer 22). This makes it possible to prevent a decrease in power generation efficiency due to shadowing on the module at low cost.
The second barrier layer 22 may contain, for example, zinc oxide (ZnO) as a main material, and may contain, as additive materials, silicon oxide, aluminum oxide, titanium oxide, etc. The varistor characteristics (I=KVα, K: element-specific constant, α: voltage nonlinearity coefficient) of the second barrier layer 22 between the transparent conductive film 3 and the rear electrode 10 are preferably α=20 to 60, with a bending point voltage of 2 V or more.

The rear substrate 24 is a substrate disposed on the upper part of the second barrier layer 22, and the photoelectric conversion layer 5 is located between the transparent substrate 2 and the rear substrate 24. The rear substrate 24 may be a substrate of the solar cell module 50. The rear substrate 24 may be a glass substrate, a transparent organic film, or an opaque organic film.
When the rear substrate 24 is an organic film, a third barrier layer 23 may be provided on one of the main surfaces of the rear substrate 24. The third barrier layer 23 is a layer of a material with high gas barrier properties. This can prevent deterioration inside the photoelectric conversion element 20 (20a to 20e) due to moisture or oxygen in the air. The third barrier layer 23 is also a layer of an insulating material. This can suppress the flow of leakage current. The film thickness of the third barrier layer 23 can be several tens to 100 nm. Specific examples of materials for the third barrier layer 23 include silicon oxide and aluminum oxide.

The second terminal 38 of the solar cell module 50 is formed on the organic film that is the rear substrate 24, and a part of the second terminal 38 penetrates the organic film (rear substrate 24) and the third barrier layer 23, and is in contact with the rear electrode 10e of the end photoelectric conversion element 20e of the photoelectric conversion elements 20a to 20e connected in series or is connected via the second barrier layer 22. The first terminal 37 and the second terminal 38 can be used to extract the current generated by the photovoltaic power of the solar cell module 50. The second terminal 38 can be made of a SnZn-based solder paste. Other conductive pastes and electrode materials can also be used as long as they meet the requirements.

After forming the second barrier layer 22 on the back electrode 10, etc., an organic film (back substrate 24) on which the second terminal 38 is formed is attached to the second barrier layer 22 via a laminate sheet 35, and then heat-laminated to complete a solar cell module 50 in which a plurality of photoelectric conversion elements 20a to 20e are connected in series. Note that a hole is drilled at the location of the second terminal 38 of the laminate sheet 35 sandwiched between the second barrier layer 22 and the back substrate 24. Therefore, the second terminal 38 and the second barrier layer 22 are well connected during lamination. As a result, a varistor is formed between the back electrode 10e and the second terminal 38. Since a high voltage is applied between the back electrode 10e and the second terminal 38 during power generation, the varistor characteristics do not impede current extraction. In addition, the back electrode 10e and the second terminal 38 may come into contact with each other.
The laminate sheet 35 may be a general laminate material, and is preferably a resin film that has a high waterproof property and can be laminated at a temperature of 130° C. or less.
FIG. 8 is a diagram in which a schematic cross-sectional view of one photoelectric conversion element 20 included in a solar cell module 50 and an equivalent circuit of the photoelectric conversion element 20 are superimposed, and FIG. 9 is an equivalent circuit of the solar cell module 50.
8, the hole blocking layer 4, the photoelectric conversion layer 5 and the electron blocking layer 9 can be represented by a current source 32 and a diode 33. The second barrier layer 22 in the notch of L4 is represented by a varistor 31, which is connected to the transparent conductive film 3 and the back electrode 10 so as to be connected in parallel with the photoelectric conversion layer 5.

Manufacture of Photoelectric Conversion Devices Photoelectric conversion devices 1 to 34 as shown in FIG. 1 were manufactured.
Methylamine iodide (1.14 M), lead iodide (1.2 M), 5-aminovaleric acid hydroiodide (0.06 M), silica particles (filler particles), and γ-butyrolactone (solvent) were mixed and stirred to prepare a perovskite compound precursor solution containing filler particles.
Furthermore, perovskite compound precursor solutions 1 to 7 were prepared using silica particles having an average particle size of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or 70 nm, and the dispersibility of the silica particles in the perovskite compound precursor solutions was evaluated. The evaluation results are shown in Table 1. From these results, it was found that by preparing a perovskite compound precursor solution using silica particles having an average particle size of 50 nm or less, the silica particles can be uniformly dispersed in the precursor solution. Furthermore, in the production of photoelectric conversion elements 1 to 34, silica particles having an average particle size of 10 nm were used.

A glass substrate having a fluorine-doped tin oxide film was used for the transparent substrate 2 and the transparent conductive film 3. First, a titanium oxide dense layer (hole blocking layer 4) was formed on the fluorine-doped tin oxide film using a spray pyrolysis method. Next, a titanium oxide paste was applied onto the titanium oxide dense layer and dried to form a titanium oxide porous layer (hole blocking layer 4).

Next, the prepared perovskite compound precursor solution was applied onto the titanium oxide porous layer using a coating device such as that shown in Figure 6, and the coating film was dried to form the photoelectric conversion layer 5. When the coating film dries, the filler particles become unevenly distributed as shown in Figure 1, forming the reflective region 6.

A dispersion liquid in which _Cu2O powder (electron blocking material) was dispersed in isopropyl alcohol was applied onto the photoelectric conversion layer 5 by spin coating, and the applied film was dried to form the electron blocking layer 9. In the photoelectric conversion elements 21 to 26, the thickness of the electron blocking layer 9 was 30 nm, 50 nm, 70 nm, 80 nm, 90 nm, or 110 nm. In the other photoelectric conversion elements, the thickness of the electron blocking layer 9 was 70 nm.
Next, a Ni vapor deposition film (rear electrode 10) was formed on the electron blocking layer 9 by vacuum deposition.
In this manner, a plurality of photoelectric conversion elements were fabricated.

Measurement of current-voltage characteristics The current-voltage characteristics of the produced photoelectric conversion elements were measured, and the short-circuit current Jsc and the open-circuit voltage Voc were calculated.
Table 2 shows the evaluation of the short-circuit current Jsc of photoelectric conversion elements 1 to 7 in which the ratio (A/B) of the thickness A of the reflective region to the thickness B of the photoelectric conversion layer was changed. In photoelectric conversion elements 1 to 7, A/B was changed by adjusting the amount of silica particles mixed in the preparation of the perovskite compound precursor solution. The thickness of the photoelectric conversion layer was 800 nm.
In Table 2, photoelectric conversion elements having a short-circuit current of 22 mA/ ^cm2 or more are evaluated with "◎", photoelectric conversion elements having a short-circuit current of less than 22 mA/ ^cm2 and 21 mA/ ^cm2 or more are evaluated with "◯", and photoelectric conversion elements having a short-circuit current of less than 21 mA/ ^cm2 and 20 mA/ ^cm2 or more are evaluated with "△". The same is true for Tables 3, 4, and 5.
From the results shown in Table 2, it was found that the short-circuit current of the photoelectric conversion element can be increased by setting the thickness of the reflective region to be 0.04 to 0.3 times the thickness of the photoelectric conversion layer.

Table 3 shows an evaluation of the short-circuit current Jsc of photoelectric conversion elements 8 to 14 with different thicknesses of the reflective region. In photoelectric conversion elements 8 to 14, the thickness of the reflective region was changed by adjusting the amount of silica particles mixed in the preparation of the perovskite compound precursor solution. The thickness of the photoelectric conversion layer was also set to 800 nm. From the results shown in Table 3, it was found that the short-circuit current of the photoelectric conversion element can be increased by setting the thickness of the reflective region to 40 nm or more and 150 nm or less.

Table 4 shows the evaluation of the short-circuit current Jsc of photoelectric conversion elements 15 to 20 in which the ratio (uneven distribution ratio) of filler particles unevenly distributed in the reflective region among all the filler particles contained in the photoelectric conversion layer was changed. In photoelectric conversion elements 15 to 20, the uneven distribution ratio was changed by controlling the particle size and drying (crystallization) speed of the filler particles. The thickness of the photoelectric conversion layer was set to 800 nm.
From the results shown in Table 4, it was found that the short-circuit current of the photoelectric conversion element can be increased by setting the ratio of the filler particles unevenly distributed in the reflective region to 50 wt % or more.

Table 5 shows an evaluation of the short-circuit current Jsc of photoelectric conversion elements 21 to 26 with different thicknesses of the electron blocking layer. The results shown in Table 5 show that the short-circuit current of the photoelectric conversion element can be increased by setting the thickness of the electron blocking layer to 50 nm or more and 100 nm or less.

Table 6 shows the evaluation of the open circuit voltage Voc of photoelectric conversion elements 27 to 34 in which the thickness of the photoelectric conversion layer was changed. The thickness of the photoelectric conversion layer was adjusted by changing the coating amount of the perovskite compound precursor solution. In Table 6, photoelectric conversion elements in which the open circuit voltage was 1.3 V or more were evaluated with "◎", photoelectric conversion elements in which the open circuit voltage was less than 1.3 V and 1.2 V or more were evaluated with "◯", and photoelectric conversion elements in which the open circuit voltage was less than 1.2 V and 1.1 V or more were evaluated with "△".
From the results shown in Table 6, it was found that the open circuit voltage of the photoelectric conversion element can be increased by setting the thickness of the photoelectric conversion layer to be 500 nm or more and 1 μm or less.

The photoelectric conversion element and solar cell module according to the embodiments of the present disclosure can be used in solar power generation systems such as mega solar systems, solar cells, and power sources for small portable devices.

2: Transparent substrate 3, 3a-3e: Transparent conductive film 4, 4a-4e: Hole blocking layer 5, 5a-5e: Photoelectric conversion layer 6: Reflection area 7: Perovskite compound crystal 8: Filler particles 9, 9a-9e: Electron blocking layer 10, 10a-10e: Back electrode 11: Surface coating layer 12: Core particles 20, 20a-20e: Photoelectric conversion element 21: First barrier layer 22: Second barrier layer 23: Third barrier layer 24: Back substrate 31: Varistor 32: Current source 33: Diode 35: Laminate sheet 37: First terminal 38: Second terminal 50: Solar cell module

Claims (14)

a transparent substrate, a transparent conductive film provided on the transparent substrate, a hole blocking layer provided on the transparent conductive film, a photoelectric conversion layer provided on the hole blocking layer, an electron blocking layer provided on the photoelectric conversion layer, and a back electrode provided on the electron blocking layer;
The photoelectric conversion layer includes a perovskite compound crystal and a filler particle,
the photoelectric conversion layer includes a reflective region in which the filler particles are unevenly distributed,
The photoelectric conversion element, wherein the reflective region is disposed adjacent to the electron blocking layer. The photoelectric conversion element according to claim 1, wherein the filler particles include inorganic material particles. The photoelectric conversion element according to claim 1, wherein the thickness of the reflective region is 0.04 to 0.3 times the thickness of the photoelectric conversion layer. The photoelectric conversion element according to claim 1, wherein the thickness of the reflective region is 40 nm or more and 150 nm or less. The photoelectric conversion element according to claim 1, wherein the reflective region is a region in which 50 wt% or more of the filler particles contained in the photoelectric conversion layer are unevenly distributed. The photoelectric conversion element according to claim 1, wherein the average particle diameter D50 of the filler particles is 10 nm or more and 50 nm or less. 2. The photoelectric conversion element according to claim 1, wherein the filler particles include at least one of silica particles, alumina particles, titanium oxide particles, zirconia particles, nickel oxide particles, _Cu2O particles, CuO particles, and zinc oxide particles. The filler particles have a surface coating layer,
2. The photoelectric conversion element according to claim 1, wherein the material of the surface coating layer is an electron blocking material that blocks electrons generated in the perovskite compound crystal and transports holes generated in the perovskite compound crystal to the electron blocking layer. 9. The photoelectric conversion element according to claim 8, wherein the electron blocking material is _Cu2O or NiO. the electron blocking layer is disposed adjacent the reflective region;
2. The photoelectric conversion element according to claim 1, wherein the electron blocking layer has a thickness of 50 nm to 100 nm. The photoelectric conversion element according to claim 1, wherein the material of the back electrode is a metal having a work function of 5.0 eV or more. The photoelectric conversion element according to claim 1, wherein the thickness of the photoelectric conversion layer is 500 nm or more and 1 μm or less. A photoelectric conversion element according to any one of claims 1 to 12,
A solar cell module in which multiple photoelectric conversion elements are integrated. a coating step of coating a coating liquid containing a perovskite compound and filler particles on a hole blocking layer provided on a transparent substrate;
A drying step of drying the coating film formed by the coating step,
A method for producing a photoelectric conversion element, comprising: heating the transparent substrate from a side opposite to the coated surface in the coating step in the drying step.