Photoelectric conversion element, tandem solar cell, and window glass

Abstract

A photoelectric conversion element (1) according to the present disclosure comprises a first electrode layer (12) that is a transparent electrode, a second electrode layer (16), and a photoelectric conversion band (141) positioned between the first electrode layer (12) and the second electrode layer (16). The photoelectric conversion element (1) according to the present disclosure further comprises, between the photoelectric conversion band (141) and the first electrode layer (12), a reflection suppression band (142) containing inorganic nanoparticles that are an insulator and / or a semiconductor. With such a configuration, the photoelectric conversion element (1) according to the present disclosure can improve photoelectric conversion efficiency.

Description

Photoelectric conversion element, tandem solar cell, and window glass

[0001] This disclosure relates to a photoelectric conversion element, a tandem solar cell, and window glass.

[0002] Patent Document 1 describes a perovskite solar cell comprising a transparent conductive support, an electron blocking layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode, wherein both the electron blocking layer and the hole blocking layer contain inorganic materials.

[0003] Japanese Patent Publication No. 2017-547766

[0004] However, conventional solar cells have a problem in that sunlight is reflected at the interface of the photoelectric conversion layer, which reduces the amount of sunlight incident inside the photoelectric conversion layer, resulting in a decrease in photoelectric conversion efficiency.

[0005] In other words, conventional solar cells and photoelectric conversion elements used in solar cells have the problem of not being able to sufficiently improve photoelectric conversion efficiency. Patent Document 1 does not disclose any technology that can solve the above-mentioned problems.

[0006] This disclosure was made to solve these problems and aims to provide a photoelectric conversion element, a tandem solar cell, and window glass that can improve photoelectric conversion efficiency.

[0007] The photoelectric conversion element according to this disclosure comprises a first electrode layer which is a transparent electrode, a second electrode layer, and a photoelectric conversion band located between the first electrode layer and the second electrode layer. The photoelectric conversion element according to this disclosure further comprises a reflection suppression band between the photoelectric conversion band and the first electrode layer, which includes inorganic nanoparticles which are at least one of an insulator and a semiconductor.

[0008] With this configuration, the inorganic nanoparticles contained in the reflection suppression band scatter the light incident on the photoelectric conversion element, thereby suppressing the reflection of the incident light. As a result, the photoelectric conversion element according to this disclosure can improve the photoelectric conversion efficiency.

[0009] The photoelectric conversion element according to this disclosure may further include a carrier transport layer between the first electrode layer and the photoelectric conversion band. The reflection suppression band may be located between the photoelectric conversion band and the carrier transport layer. The configuration of the photoelectric conversion element according to this disclosure can also be applied to a photoelectric conversion element that includes a carrier transport layer.

[0010] In the photoelectric conversion element according to this disclosure, the average particle size of the inorganic nanoparticles may be greater than 15 nm. With such a configuration, the photoelectric conversion element according to this disclosure can further suppress the reflection of incident light.

[0011] In the photoelectric conversion element according to this disclosure, the average particle size of inorganic nanoparticles may be 45 nm or more. With such a configuration, the photoelectric conversion element according to this disclosure can further suppress the reflection of incident light.

[0012] In the photoelectric conversion element according to this disclosure, the average particle size of inorganic nanoparticles may be 122 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0013] In the photoelectric conversion element relating to this disclosure, the inorganic nanoparticles may be metal oxide insulators or dielectrics.

[0014] In the photoelectric conversion element according to this disclosure, the photoelectric conversion band may contain a perovskite compound as its main component. When applied to a perovskite-type photoelectric conversion element, the photoelectric conversion element according to this disclosure can be easily manufactured.

[0015] In the photoelectric conversion element according to this disclosure, the thickness of the reflection suppression band may be 200 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0016] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of an insulator, and the thickness of the reflection suppression band may be 110 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0017] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of silicon dioxide, and the thickness of the reflection suppression band may be 59 nm or more and 110 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0018] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of silicon dioxide, and the thickness of the reflection suppression band may be 61 nm or more and 87 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0019] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of semiconductors.

[0020] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of zirconium oxide, and the thickness of the reflection suppression band may be 19 nm or more and 86 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0021] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band mainly consist of zirconium oxide, and the thickness of the reflection suppression band may be 30 nm or more. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0022] In the photoelectric conversion element according to this disclosure, the inorganic nanoparticles included in the reflection suppression band may mainly consist of yttrium oxide, and the thickness of the reflection suppression band may be 102 nm or more and 182 nm or less. With such a configuration, the photoelectric conversion element according to this disclosure can further improve the photoelectric conversion efficiency.

[0023] In the photoelectric conversion element according to this disclosure, there may be regions in which the photoelectric conversion band and the carrier transport layer are in contact without the use of nanoparticles. With such a configuration, the photoelectric conversion element according to this disclosure can improve carrier transport efficiency.

[0024] The tandem solar cell according to this disclosure comprises, among a plurality of photoelectric conversion elements, the photoelectric conversion element located on the outermost surface when viewed from the light incident side comprises a first electrode which is a transparent electrode, a second electrode, and a photoelectric conversion band located between the first electrode and the second electrode, and further comprises a reflection suppression band between the photoelectric conversion band and the first electrode side, which includes inorganic nanoparticles that are at least one of an insulator and a semiconductor. By configuring the photoelectric conversion element located on the outermost surface when viewed from the light incident side as described above, the power generation amount of the photoelectric conversion element located deeper when viewed from the light incident side can also be improved in the tandem solar cell according to this disclosure.

[0025] The window glass according to this disclosure is a window glass equipped with a photoelectric conversion element. The photoelectric conversion element comprises a first electrode which is a transparent electrode, a second electrode, and a photoelectric conversion band located between the first electrode and the second electrode, and further comprises a reflection suppression band between the photoelectric conversion band and the first electrode layer, which includes inorganic nanoparticles that are at least one of an insulator and a semiconductor. With such a configuration, the window glass according to this disclosure can allow more light to enter the interior of the vehicle or building on which the window glass is installed.

[0026] This disclosure provides a photoelectric conversion element capable of improving photoelectric conversion efficiency, a tandem solar cell, and window glass.

[0027] This is a cross-sectional view showing the configuration of a photoelectric conversion element according to the first embodiment. This is a flowchart showing the manufacturing method of a photoelectric conversion element according to the first embodiment. This is a cross-sectional view for explaining the manufacturing method of a photoelectric conversion element according to the first embodiment. This is a cross-sectional view for explaining the manufacturing method of a photoelectric conversion element according to the first embodiment. This is a flowchart showing the configuration of a photoelectric conversion element according to the first embodiment. This is a cross-sectional view for explaining the manufacturing method of a photoelectric conversion element according to the first embodiment. This is a cross-sectional view for explaining the manufacturing method of a photoelectric conversion element according to the first embodiment. This is a graph showing the estimated short-circuit current density lost due to light reflection. This is a graph showing the estimated short-circuit current density lost due to light reflection. This is a graph showing the estimated short-circuit current density lost due to light reflection. This is a graph showing the estimated short-circuit current density lost due to light reflection.

[0028] <First Embodiment> (Configuration of Photoelectric Conversion Element) The first embodiment of the present disclosure will be described in detail below with reference to the drawings. First, the configuration of the photoelectric conversion element according to this embodiment will be described in detail.

[0029] Figure 1 is a cross-sectional view showing the configuration of a photoelectric conversion element according to the first embodiment. More specifically, it is a schematic cross-sectional view of the photoelectric conversion element according to the first embodiment when cut by a plane perpendicular to the main surface. Naturally, the right-handed xyz orthogonal coordinate system shown in Figure 1 and the other drawings is for convenience in explaining the positional relationships of the components and is common to all drawings. In this specification, for convenience, the positive z-axis side may be referred to as the upper side and the negative z-axis side as the lower side.

[0030] The photoelectric conversion element 1 according to this embodiment is an element that converts light incident from the positive or negative z-axis side into electric power. The photoelectric conversion element 1 is typically used as a solar cell. As shown in Figure 1, the photoelectric conversion element 1 comprises a substrate 11, a first electrode layer 12, a first carrier transport layer 13, a photoelectric conversion layer 14, a second carrier transport layer 15, and a second electrode layer 16.

[0031] Furthermore, the photoelectric conversion element 1 according to this embodiment may be used as the upper cell of a tandem solar cell. As will be described in detail later, the photoelectric conversion element 1 according to this embodiment can suppress the reflection of incident light. Therefore, by using the photoelectric conversion element 1 according to this embodiment as the photoelectric conversion element located on the outermost surface when viewed from the light incident side among a plurality of photoelectric conversion elements in a tandem solar cell, the power generation of the photoelectric conversion elements located deeper when viewed from the light incident side can also be improved. In other words, the photoelectric conversion element 1 according to this embodiment has a particular effect when used as the upper cell of a tandem solar cell.

[0032] Furthermore, the photoelectric conversion element 1 according to this embodiment may be used, for example, in a solar cell installed in the window glass of a vehicle or building. As described above, the photoelectric conversion element 1 according to this embodiment can suppress the reflection of incident light. Therefore, by using the photoelectric conversion element 1 according to this embodiment in a solar cell installed in the window glass of a vehicle or building, more light can be brought into the interior of the vehicle or building. In other words, the photoelectric conversion element 1 according to this embodiment has a particular effect when applied to a solar cell installed in window glass.

[0033] (Configuration of Substrate 11) The substrate 11 is a plate-shaped or film-shaped member and is in contact with the first electrode layer 12 on its main surface on the positive z-axis side. The substrate 11 may be made of any material that transmits light in the wavelength range absorbed by the photoelectric conversion element 1. Specific examples of materials for the substrate 11 include glass and resin.

[0034] From the viewpoint of manufacturing efficiency, the substrate 11 is preferably a film-like member made of a resin material, and from the viewpoint of durability, the substrate 11 is preferably a plate-like member made of a glass material. The configuration of the substrate 11 can be appropriately selected according to the intended use of the photoelectric conversion element 1.

[0035] (Configuration of the first electrode layer 12) The first electrode layer 12 is a conductive and light-transmitting layer. In other words, the first electrode layer 12 is realized as a transparent electrode layer. The first electrode layer 12 is in contact with the substrate 11 on its main surface on the negative z-axis side and in contact with the first carrier transport layer 13 on its main surface on the positive z-axis side. In other words, the first electrode layer 12 in this embodiment is located between the substrate 11 and the first carrier transport layer 13.

[0036] The first electrode layer 12 receives carriers generated in the photoelectric conversion layer 14 via the first carrier transport layer and outputs them to the outside. Here, "carrier" refers to holes or conduction electrons. If the first carrier transport layer 13, which will be described later, is a hole transport layer, the first electrode layer 12 receives holes generated in the photoelectric conversion layer 14 as carriers and outputs them to the outside. Also, if the first carrier transport layer 13 is an electron transport layer, the first electrode layer 12 receives conduction electrons generated in the photoelectric conversion layer 14 as carriers and outputs them to the outside.

[0037] Examples of materials for the first electrode layer 12 include tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), impurity-doped zinc oxide (ZnO), fluorine-doped tin dioxide (FTO), antimony-doped tin oxide (ATO), graphene, and metal nanowires.

[0038] (Configuration of the first carrier transport layer 13 and the second carrier transport layer 15) In the photoelectric conversion element 1 according to the present embodiment, the first carrier transport layer 13 is a hole transport layer (HTL, Hole transport layer), and the second carrier transport layer 15 is an electron transport layer (ETL, Electron transport layer). That is, the photoelectric conversion element 1 in the present embodiment is a photoelectric conversion element with an inverted structure. However, the photoelectric conversion element according to the present disclosure may have a normal structure. That is, the photoelectric conversion element according to the present disclosure may include an electron transport layer (ETL) as the first carrier transport layer and a hole transport layer (HTL) as the second carrier transport layer.

[0039] (Configuration of the first carrier transport layer 13) As described above, the first carrier transport layer 13 according to the present embodiment is a hole transport layer (HTL). The first carrier transport layer 13 abuts on the first electrode layer 12 on the main surface on the negative side of the z-axis and abuts on the photoelectric conversion layer 14 on the main surface on the positive side of the z-axis. That is, the first carrier transport layer 13 according to the present embodiment is located between the first electrode layer 12 and the photoelectric conversion layer 14.

[0040] The first carrier transport layer 13 transports the holes generated in the photoelectric conversion layer 14 to the first electrode layer 12. In other words, the holes generated in the photoelectric conversion layer 14 move to the first electrode layer 12 through the first carrier transport layer 13.

[0041] As the material of the first carrier transport layer 13, both inorganic hole transport materials and organic hole transport materials can be used. Examples of the inorganic hole transport materials include CuI, CuInSe ２ , CuS, CuSCN, GaP, NiO, FeO, Bi ２ O ３ , MoO , ３ , and Cr ２ O, etc. Examples of the organic hole transport materials include polythiophene derivatives, fluorene derivatives, carbazole derivatives, triphenylamine derivatives, diphenylamine derivatives, polysilane derivatives, and polyaniline derivatives, etc.

[0042] Specific examples of polythiophene derivatives include poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT). Specific examples of fluorene derivatives include 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD). Specific examples of carbazole derivatives include polyvinylcarbazole. Specific examples of triphenylamine derivatives include poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA).

[0043] The first carrier transport layer 13 in this embodiment may be configured as a monolayer. In this case, the first carrier transport layer 13 may be a monolayer formed by bonding a compound represented by the following formula (1) with the first electrode layer 12. Ar-(L-Z) ｎ ...Formula (1) where Ar is an n-valent aryl group which may contain a heteroaromatic ring, L is a single bond or a divalent functional group, Z is a monovalent functional group which has bonding properties, n is a natural number, and if n is 2 or more, (L-Z) may be different.

[0044] Ar is an n-valent aryl group which may contain a heteroaromatic ring, and from the viewpoint of improving hole transport properties, it is preferable that the heteroaromatic ring contains a nitrogen atom. When Ar contains a heteroaromatic ring, Ar may have a carbon atom with a bonding site, or a heteroatom with a bonding site, or both. Specific examples of Ar include, for example, a carbazole ring and a triazatrixene ring.

[0045] L is either a single bond or a divalent functional group. However, if L is a single bond, the compound represented by chemical formula (1) has a structure in which Ar and Z are directly bonded. Specific examples of L include, for example, divalent alkylene groups such as 1,1-methylene and 1,2-ethylene groups, and divalent alkoxy groups such as diethoxyethylene groups.

[0046] Z is a monovalent functional group with bonding properties, capable of bonding to and exchanging charge with the transparent electrode layer. Specific examples of Z include phosphonic acid groups, carboxyl groups, sulfo groups, boronic acid groups, trihalogenated silyl groups, and trialkoxysilyl groups.

[0047] n is a natural number, preferably a natural number between 1 and 4. When n is 2 or greater, the multiple (L-Z) may be the same or may be different. A specific example of the compound represented by formula (1) above is, for example, 3PATAT-C3 (Phosphonic acid functionalized triazatruxene).

[0048] (Configuration of the photoelectric conversion layer 14) The photoelectric conversion layer 14 excites electrons by absorbing sunlight incident from the negative z-axis side, generating holes and conduction electrons. The holes generated in the photoelectric conversion layer 14 are transported to the first electrode layer 12 via the first carrier transport layer 13, and the conduction electrons generated in the photoelectric conversion layer 14 are transported to the second electrode layer 16 via the second carrier transport layer 15.

[0049] The photoelectric conversion layer 14 according to this embodiment mainly contains a perovskite compound and may contain additives as appropriate. The term "perovskite compound" as used herein refers to a group of compounds that have a perovskite-type crystal structure.

[0050] Examples of compounds that can be used as the main component of the photoelectric conversion layer 14 include perovskite compounds represented by the compositional formula of the following formula (2): AMX ３ ...Equation (2) where A is a monovalent cation, M is a divalent cation, and X is a monovalent anion.

[0051] Specific examples of A include alkylamine compound ions such as methylammonium (MA) cation, ethylammonium (Ethylammonium) cation, and formamidinium (FA) cation, as well as alkali metal ions such as potassium cation, cesium cation, and rubidium cation. The perovskite compound according to this embodiment may contain multiple chemical species as A. From the viewpoint of photoelectric conversion efficiency and durability, it is preferable that the perovskite compound contains cesium cation, methylammonium cation, and formamidinium cation.

[0052] Specific examples of M include, for example, divalent metal ions such as lead, tin, antimony, indium, copper, bismuth, and germanium. The perovskite compound according to this embodiment may contain multiple chemical species as M. From the viewpoint of photoelectric conversion efficiency and durability, it is preferable that the perovskite compound contains at least one of lead cations and tin cations.

[0053] Specific examples of X include, for example, halide ions such as fluorine, chlorine, bromine, and iodine. The perovskite compound according to this embodiment may contain multiple chemical species as X. From the viewpoint of photoelectric conversion efficiency and durability, it is preferable that the perovskite compound contains at least one of bromine and iodine.

[0054] The chemical species used as A, M, and X, and their composition, can be appropriately adjusted according to the performance required of the photoelectric conversion element. In other words, the photoelectric conversion element 1 according to this embodiment can have its performance, such as durability and absorption wavelength, adjusted by adjusting the chemical species used as A, M, and X, and their composition.

[0055] Furthermore, the main component of the photoelectric conversion layer according to this disclosure is not limited to perovskite compounds. For example, the main component of the photoelectric conversion layer according to this disclosure may be silicon or cuprous oxide. In other words, the photoelectric conversion layer according to this disclosure may be composed of any material that can absorb incident light and generate carriers, i.e., a photoelectric conversion material. However, as will be described later, the photoelectric conversion layer according to this disclosure has inorganic nanoparticles NP distributed inside. Therefore, from the viewpoint of facilitating manufacturing, it is preferable to use a material that can be formed by a solution method for the photoelectric conversion layer according to this disclosure. In other words, the photoelectric conversion element according to this disclosure has the special effect of simplifying the manufacturing process when the material of the photoelectric conversion layer is a perovskite compound or the like.

[0056] As shown in Figure 1, the photoelectric conversion layer 14 according to this embodiment comprises a photoelectric conversion band 141 and a reflection suppression band 142. Here, the photoelectric conversion band 141 refers to a region in the photoelectric conversion layer 14 according to this embodiment in which inorganic nanoparticles NP are not distributed, and the reflection suppression band 142 refers to a region in the photoelectric conversion layer 14 according to this embodiment in which inorganic nanoparticles NP are distributed.

[0057] The photoelectric conversion band 141 is a dense layer composed of a photoelectric conversion material, and in this embodiment, it is a dense layer composed of a perovskite compound. As mentioned above, the photoelectric conversion band 141 is a region where nanoparticles NP are not present. The photoelectric conversion band 141 is in contact with the second carrier transport layer 15 on its main surface on the positive z-axis side, and is in contact with the first carrier transport layer 13 via the reflection suppression band 142 on its main surface on the negative z-axis side. The photoelectric conversion band 141 generates carriers by absorbing incident light.

[0058] It should be noted that the expression "no nanoparticles NP are present" here does not necessarily mean that nanoparticles NP are completely absent in a strict sense. In other words, the expression "does not contain nanoparticles NP" here allows for small amounts of nanoparticles NP to be unintentionally mixed into the photoelectric conversion band 141 during the manufacturing process, etc.

[0059] From the viewpoint of improving carrier transport efficiency, it is preferable that the photoelectric conversion band 141 and the first carrier transport layer 13 are not strictly separated by inorganic nanoparticles NP. In other words, at the interface between the photoelectric conversion layer 14 and the first carrier transport layer 13, it is preferable that there is a region where the photoelectric conversion band 141 and the first carrier transport layer 13 are in contact without the intervening nanoparticles NP. As shown in Figure 1, in this embodiment, the reflection suppression band 142 and the first carrier transport layer 13 are spatially and electrically connected via dense portions composed of photoelectric conversion material distributed to fill the gaps between inorganic nanoparticles NP. With this configuration, the photoelectric conversion element 1 according to this embodiment can improve carrier transport efficiency.

[0060] The reflection suppression band 142 is a layered region containing inorganic nanoparticles NP, which are at least one of an insulator and a semiconductor. In other words, the reflection suppression band 142 is a region in the photoelectric conversion layer 14 in which inorganic nanoparticles NP are distributed. As shown in Figure 1, the reflection suppression band 142 according to this embodiment is composed of layered inorganic nanoparticles NP and dense portions composed of a photoelectric conversion material distributed to fill the gaps between the inorganic nanoparticles NP.

[0061] As shown in Figure 1, the reflection suppression band 142 according to this embodiment is located between the photoelectric conversion band 141 and the first carrier transport layer 13 and includes inorganic nanoparticles NP that are insulators or semiconductors. In the reflection suppression band 142, light incident from the negative z-axis side is scattered by the distributed inorganic nanoparticles NP. As a result, the reflection suppression band 142 according to this embodiment can suppress the reflection of incident light. When the reflection suppression band 142 suppresses the reflection of incident light, the amount of light supplied to the photoelectric conversion band 141 increases. As a result, the photoelectric conversion element 1 according to this embodiment can improve the photoelectric conversion efficiency.

[0062] Inorganic nanoparticles NP are at least one of an insulator and a semiconductor, and may be, for example, a metal oxide. When inorganic nanoparticles NP are an insulator, examples of their main components include silicon dioxide and aluminum nitride. When inorganic nanoparticles NP are a semiconductor, examples of their main components include zirconium oxide, yttrium oxide, silicon carbide, and titania.

[0063] From the viewpoint of suppressing reflection of incident light, the average particle size of inorganic nanoparticles NP is preferably greater than 11 nm, more preferably 15 nm or larger, and particularly preferably 45 nm or larger. Furthermore, from the viewpoint of improving photoelectric conversion efficiency, the average particle size of inorganic nanoparticles NP is preferably 122 nm or smaller.

[0064] When the main component of the inorganic nanoparticles is an insulator, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 200 nm or less, more preferably 59 nm to 110 nm, and particularly preferably 61 nm to 87 nm. Furthermore, when the main component of the inorganic nanoparticles is a semiconductor, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 200 nm or less, more preferably 19 nm to 86 nm, and particularly preferably 30 nm to 86 nm.

[0065] From the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 0.26 times or less the thickness of the photoelectric conversion layer 14, more preferably 0.05 times or more and 0.20 times or less, and particularly preferably 0.08 times or more and 0.13 times or less. In other words, the thickness of the reflection suppression band 142 is preferably 0.26 times or less the sum of the thicknesses of the photoelectric conversion band and the reflection suppression band, more preferably 0.05 times or more and 0.20 times or less, and particularly preferably 0.08 times or more and 0.13 times or less.

[0066] More specifically, when the main component of the inorganic nanoparticles is an insulator, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 0.26 times or less the thickness of the photoelectric conversion layer 14, more preferably 0.08 times or more and 0.16 times or less, and particularly preferably 0.08 times or more and 0.12 times or less. In other words, when the main component of the inorganic nanoparticles is an insulator, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 0.26 times or less the sum of the thicknesses of the photoelectric conversion band 141 and the reflection suppression band 142, more preferably 0.08 times or more and 0.16 times or less, and particularly preferably 0.08 times or more and 0.12 times or less.

[0067] Furthermore, when the main component of the inorganic nanoparticles is a semiconductor, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 0.24 times or less the thickness of the photoelectric conversion layer 14, more preferably 0.05 times or more and 0.20 times or less, and particularly preferably 0.08 times or more and 0.13 times or less. In other words, when the main component of the inorganic nanoparticles is a semiconductor, from the viewpoint of improving photoelectric conversion efficiency, the thickness of the reflection suppression band 142 is preferably 0.24 times or less the sum of the thicknesses of the photoelectric conversion band 141 and the reflection suppression band 142, more preferably 0.05 times or more and 0.20 times or less, and particularly preferably 0.08 times or more and 0.13 times or less.

[0068] The thickness of the reflection suppression band as used herein may be defined as the distance from the upper end to the lower end of the reflection suppression band in a vertical cross-section of the photoelectric conversion element. The thickness of the reflection suppression band can be measured, for example, by observation using a scanning electron microscope (SEM). In this case, the thickness of the reflection suppression band may be measured as the distance from the upper end of the layer located below the reflection suppression band to the uppermost nanoparticle at the location where the most nanoparticles are deposited, in the cross-sectional SEM image. Alternatively, the thickness of the reflection suppression band may be calculated as the average value of multiple values ​​measured from cross-sectional SEM images taken in multiple fields of view, i.e., multiple cross-sectional SEM images taken from different cross-sections.

[0069] Furthermore, the thickness of the photoelectric conversion band as referred to here may be defined as the distance from the upper end to the lower end of the reflection suppression band in the vertical cross-section of the photoelectric conversion element. The thickness of the photoelectric conversion band can be measured, for example, by observation using a scanning electron microscope (SEM). In this case, the thickness of the photoelectric conversion band may be measured as the distance from the upper end of the layer located below the photoelectric conversion band to the uppermost nanoparticle at the location where the most nanoparticles are deposited, in the cross-sectional SEM image. Alternatively, the thickness of the photoelectric conversion band may be calculated as the average value of multiple values ​​measured from cross-sectional SEM images taken in multiple fields of view, that is, multiple cross-sectional SEM images taken from different cross-sections.

[0070] Furthermore, the thickness of the photoelectric conversion layer as referred to herein may be defined as the distance from the upper end of the reflection suppression band or photoelectric conversion band to the lower end of the reflection suppression band or photoelectric conversion band in the vertical cross-section of the photoelectric conversion element. The thickness of the photoelectric conversion layer can be measured, for example, by observation using a scanning electron microscope (SEM). In this case, the thickness of the photoelectric conversion band may be measured in a cross-sectional SEM as the distance from the uppermost end of the reflection suppression band or photoelectric conversion band to the lowermost end of the reflection suppression band or photoelectric conversion band. Alternatively, the thickness of the photoelectric conversion layer may be calculated as the average value of multiple values ​​measured from multiple cross-sectional SEM images taken in multiple fields of view, i.e., multiple cross-sectional SEM images taken from different cross-sections. Furthermore, the thickness of the photoelectric conversion band may be calculated as the sum of the measured results of the thickness of the reflection suppression band and the thickness of the photoelectric conversion band.

[0071] Although the reflection suppression band 142 in this disclosure is configured as part of the photoelectric conversion layer 14, the configuration of the reflection suppression band 142 in this disclosure is not limited thereto. For example, in the photoelectric conversion element according to this disclosure, inorganic nanoparticles may be distributed inside the first electrode layer. In this case, the photoelectric conversion layer is a uniform layer that does not contain inorganic nanoparticles. In this case, the entire photoelectric conversion layer may be called the photoelectric conversion band, and the region inside the first electrode layer where inorganic nanoparticles are distributed may be called the reflection suppression band. Furthermore, in the photoelectric conversion element according to this disclosure, the reflection suppression band may be distributed inside the photoelectric conversion band. In other words, there may be a photoelectric conversion band where inorganic nanoparticles are not present both above and below the region where inorganic nanoparticles are distributed. Moreover, in the photoelectric conversion element according to this disclosure, inorganic nanoparticles may be distributed inside a different layer located between the photoelectric conversion layer and the first electrode layer. In this case, the photoelectric conversion layer 14 in this disclosure is formed as a uniform layer that does not contain inorganic nanoparticles, and its entire area may be called the photoelectric conversion band. In this case, the region where inorganic nanoparticles are distributed may also be called the reflection suppression zone.

[0072] In other words, the reflection suppression band according to this disclosure is located between the photoelectric conversion band and the first electrode layer and may have any configuration as long as it contains inorganic nanoparticles. Furthermore, in this disclosure, the expression "the photoelectric conversion element comprises a reflection suppression layer between the photoelectric conversion band and the first electrode layer" may include cases where the photoelectric conversion element comprises a reflection suppression band inside the photoelectric conversion or the first electrode layer. In other words, in this disclosure, the expression "the photoelectric conversion element comprises a reflection suppression layer between the photoelectric conversion band and the first electrode layer" may mean that the photoelectric conversion element comprises one or more dense layers made of a transparent conductive material, one or more dense layers made of a photoelectric conversion material, and a reflection suppression layer is provided between these dense layers.

[0073] (Configuration of the Second Carrier Transport Layer 15) As described above, the second carrier transport layer 15 according to the present embodiment is an electron transport layer (ETL). The second carrier transport layer 15 abuts on the photoelectric conversion layer 14 on the main surface on the negative side of the z-axis and abuts on the second electrode layer 16 on the main surface on the positive side of the z-axis. That is, the second carrier transport layer 15 according to the present embodiment is located between the photoelectric conversion layer 14 and the second electrode layer 16.

[0074] The second carrier transport layer 15 transports the conduction electrons generated in the photoelectric conversion layer 14 to the second electrode layer 16. In other words, the conduction electrons generated in the photoelectric conversion layer 14 are transported to the second electrode layer 16 through the second carrier transport layer 15.

[0075] Examples of compounds that can be used as the main component of the second carrier transport layer 15 include elemental electron transport materials, oxide electron transport materials, sulfide electron transport materials, and organic electron transport materials.

[0076] Specific examples of the elemental electron transport material include, for example, silicon, germanium, etc. Specific examples of the oxide electron transport material include, for example, oxides of titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, and tantalum. Specific examples of the sulfide electron transport material include, for example, sulfides of cadmium, zinc, lead, silver, antimony, and bismuth. Specific examples of the organic electron transport material include, for example, fullerene C ６０ and phenyl C ６１ methyl ester of butyric acid (PCBM, [6,6]-Phenyl-C 61 -Butyric acid Methyl ester) and other fullerene derivatives.

[0077] (Configuration of the Second Electrode Layer 16) The second electrode layer 16 is a layer having conductivity. The second electrode layer 16 abuts on the second carrier transport layer 15 on the main surface on the negative side of the z-axis.

[0078] The second electrode layer 16 receives carriers generated in the photoelectric conversion layer 14 via the second carrier transport layer 15 and outputs them to the outside. If the second carrier transport layer 15 is an electron transport layer, the second electrode layer 16 receives conduction electrons generated in the photoelectric conversion layer 14 as carriers and outputs them to the outside. Also, if the second carrier transport layer 15 is a hole transport layer, the second electrode layer 16 receives holes generated in the photoelectric conversion layer 14 as carriers and outputs them to the outside.

[0079] The second electrode layer 16 may be a light-transmitting electrode layer or an electrode layer that does not transmit light. In other words, the second electrode layer 16 may be a transparent electrode layer or not. To put it another way, the photoelectric conversion element 1 according to this embodiment may be a transmissive photoelectric conversion element or an opaque photoelectric conversion element.

[0080] As mentioned above, the photoelectric conversion element 1 according to this embodiment is particularly effective when used as an upper cell in a tandem solar cell or as a photoelectric conversion element in a solar cell used as window glass. In such cases, the photoelectric conversion element 1 is transparent. In other words, in the above cases, the second electrode layer 16 is realized as a transparent electrode layer.

[0081] When the second electrode layer 16 is a transparent electrode layer, examples of materials for the second electrode layer 16 include tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), impurity-doped zinc oxide (ZnO), fluorine-doped tin dioxide (FTO), antimony-doped tin oxide (ATO), graphene, and metal nanowires. The first electrode layer 12 and the second electrode layer 16 may be made of the same material, or they may be made of different materials.

[0082] If the second electrode layer 16 is not a transparent electrode layer, examples of materials for the second electrode layer 16 include metals such as gold, silver, copper, aluminum, tungsten, titanium, chromium, nickel, and cobalt.

[0083] As described above, the photoelectric conversion element 1 according to this embodiment comprises a first electrode layer 12 which is a transparent electrode layer, a second electrode layer 16, and a photoelectric conversion band 141 located between the first electrode layer 12 and the second electrode layer 16. Furthermore, the photoelectric conversion element 1 according to this embodiment further comprises a reflection suppression band 142 between the photoelectric conversion band and the first electrode layer 12, which includes inorganic nanoparticles NP which are at least one of an insulator and a semiconductor. With this configuration, the inorganic nanoparticles NP contained in the reflection suppression band 142 scatter the light incident on the photoelectric conversion element 1, and the reflection of the incident light is suppressed. As a result, the photoelectric conversion element 1 according to this embodiment can improve the photoelectric conversion efficiency.

[0084] (Method for manufacturing a photoelectric conversion element) Next, the method for manufacturing a photoelectric conversion element according to this embodiment will be described in detail. Figure 2 is a flowchart showing the method for manufacturing a photoelectric conversion element according to the first embodiment.

[0085] In the method for manufacturing a photoelectric conversion element according to this embodiment, first, a substrate 11 on which a first electrode layer 12 is formed is prepared (step ST1). Step ST1 may be a step of forming the first electrode layer 12 on the substrate 11, or it may be a step of preparing a commercially available transparent electrode substrate.

[0086] Figure 3 is a schematic cross-sectional view illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 3 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element 1 after step ST1 is completed and before step ST2 is executed. As shown in Figure 3, in the photoelectric conversion element 1 after step ST1 is completed, a first electrode layer 12 is formed on the substrate 11.

[0087] In the method for manufacturing a photoelectric conversion element according to this embodiment, the first carrier transport layer 13 is then formed (step ST2). More specifically, in step ST2, the first carrier transport layer 13 is formed on the first electrode layer 12.

[0088] Methods for forming the first carrier transport layer 13 include applying a solution containing the material of the first carrier transport layer 13 and then volatilizing the solvent, or vacuum deposition of the material of the first carrier transport layer 13. The method for forming the first carrier transport layer 13 can be appropriately selected depending on the material of the first carrier transport layer 13. Examples of methods for applying the solution include inkjet printing, spray coating, die coating, and spin coating.

[0089] Figure 4 is a schematic cross-sectional view illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 4 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element 1 after step ST2 is completed and before step ST3 is executed. As shown in Figure 4, in the photoelectric conversion element 1 after step ST2 is completed, a first carrier transport layer 13 is formed on the first electrode layer 12.

[0090] In the method for manufacturing a photoelectric conversion element according to this embodiment, the next step is to form a photoelectric conversion layer 14 (step ST3). More specifically, in step ST3, the photoelectric conversion layer 14 is formed on the first carrier transport layer 13. As mentioned above, the photoelectric conversion layer 14 according to this embodiment includes a photoelectric conversion band 141 and a reflection suppression band 142.

[0091] Figure 5 is a flowchart illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 5 is a flowchart illustrating step ST3 in Figure 2 in more detail.

[0092] In step ST3, first, the nanoparticle dispersion solution is applied (step ST31). More specifically, in step ST31, the nanoparticle dispersion solution is applied to the first carrier transport layer 13. Examples of methods for applying the solution include inkjet printing, spray coating, die coating, and spin coating.

[0093] The concentration of the nanoparticle dispersion solution to be applied can be appropriately set according to the type of nanoparticles used. From the viewpoint of suppressing reflection of incident light, the concentration of the nanoparticle dispersion solution is preferably 4.0 wt% or less. More specifically, from the viewpoint of suppressing reflection of incident light, when the main component of the nanoparticles is an insulator, the concentration of the nanoparticle dispersion solution is preferably 4.0 wt% or less, more preferably 0.2 wt% to 3.0 wt%, and particularly preferably 1.0 wt% to 2.0 wt%. Furthermore, from the viewpoint of suppressing reflection of incident light, when the main component of the nanoparticles is a semiconductor, the concentration of the nanoparticle dispersion solution is preferably 4.0 wt% or less, more preferably 0.2 wt% to 4.0 wt%, and particularly preferably 2.0 wt% to 4.0 wt%.

[0094] In step ST3, the solvent in the nanoparticle dispersion solution is then evaporated (step ST32). By performing step ST32, the nanoparticles dispersed in the solution are deposited on the first carrier transport layer 13. As will be described in detail later, dense portions of the photoelectric conversion material are formed in the gaps between the deposited nanoparticles, thereby forming the reflection suppression band 142.

[0095] Figure 6 is a schematic cross-sectional view illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 6 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element 1 after step ST32 is completed and before step ST33 is executed. As shown in Figure 6, in the photoelectric conversion element 1 after step ST32 is completed, nanoparticles NP are deposited on the first carrier transport layer 13. In addition, in the photoelectric conversion element 1 after step ST32 is completed, inorganic nanoparticles can also be said to be uniformly distributed on the first carrier transport layer 13, or an inorganic nanoparticle layer can be said to have been formed.

[0096] In step ST3, the precursor solution for the photoelectric conversion band 141 is applied (step ST33). More specifically, in step ST33, the precursor solution for the photoelectric conversion band 141 is applied onto the first carrier transport layer 13 on which nanoparticles NP are deposited. The precursor solution for the photoelectric conversion band referred to here is a solution containing a photoelectric conversion material as a solute, and in this embodiment, it is a solution containing a perovskite compound as a solute. By performing step ST33, the precursor solution for the photoelectric conversion band 141 permeates into the gaps between the deposited nanoparticles NP. Furthermore, by performing step ST33, a liquid film of the precursor solution is formed on top of the deposited nanoparticles NP. Examples of methods for applying the solution include inkjet printing, spray coating, die coating, and spin coating.

[0097] In step ST3, the solvent in the precursor solution of the photoelectric conversion band 141 is finally evaporated (step ST34). The execution of step ST34 completes the deposition of the photoelectric conversion layer 14. As a result of step ST34, the photoelectric conversion material is deposited to fill the gaps between the deposited nanoparticles NP, forming the reflection suppression band 142. Furthermore, as a result of step ST34, the photoelectric conversion material is deposited on top of the reflection suppression band 142, forming the photoelectric conversion band 141.

[0098] Figure 7 is a schematic cross-sectional view illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 7 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element 1 after step ST34 is completed and before step ST4 is executed. As shown in Figure 7, in the photoelectric conversion element 1 after step ST34 is completed, a photoelectric conversion band 141 is formed on the reflection suppression band 142.

[0099] Returning to the explanation of Figure 2, in the method for manufacturing the photoelectric conversion element according to this embodiment, the second carrier transport layer 15 is then formed (step ST4). More specifically, in step ST4, the second carrier transport layer 15 is formed on the photoelectric conversion layer 14.

[0100] Methods for forming the second carrier transport layer 15 include applying a solution containing the material of the second carrier transport layer 15 and then evaporating the solvent, or vacuum deposition of the material of the second carrier transport layer 15. The method for forming the second carrier transport layer 15 can be appropriately selected depending on the material of the second carrier transport layer 15. Examples of methods for applying the solution include inkjet printing, spray coating, die coating, and spin coating.

[0101] Figure 8 is a schematic cross-sectional view illustrating a method for manufacturing a photoelectric conversion element according to the first embodiment. More specifically, Figure 8 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element 1 after step ST4 is completed and before step ST5 is executed. As shown in Figure 8, in the photoelectric conversion element 1 after step ST4 is completed, a second carrier transport layer 15 is formed on the photoelectric conversion layer 14.

[0102] In the method for manufacturing the photoelectric conversion element according to this embodiment, the photoelectric conversion element 1 is completed by finally forming a second electrode layer (step ST5). More specifically, in step ST5, a second electrode layer 16 is formed on the second carrier transport layer 15. After performing step ST5, the photoelectric conversion element according to this embodiment is in the state shown in Figure 1.

[0103] Methods for forming the second electrode layer 16 include applying a solution containing the material of the second electrode layer 16 and then volatilizing the solvent, or vacuum deposition of the material of the second electrode layer 16. The method for forming the second electrode layer 16 can be appropriately selected depending on the material of the second electrode layer 16. Examples of methods for applying the solution include inkjet printing, spray coating, die coating, and spin coating.

[0104] As described above, the method for manufacturing a photoelectric conversion element according to this embodiment comprises the steps of: applying a nanoparticle dispersion solution; volatilizing the solvent of the nanoparticle dispersion solution; applying a precursor solution for the photoelectric conversion band; and volatilizing the solvent of the precursor solution for the photoelectric conversion band. A photoelectric conversion element according to this disclosure can be manufactured by such a manufacturing method.

[0105] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following, "%" refers to "mass%" unless otherwise specified.

[0106] <Fabrication of Photoelectric Conversion Element> (Example 1) 3PATAT-C3 was dissolved in N,N-dimethylformamide (DMF) to prepare a solution. The prepared solution was applied to an ITO glass substrate by spin coating. Subsequently, the coated solution film was annealed to form a hole transport layer. These steps correspond to steps ST1 and ST2 in Figure 2.

[0107] Next, silicon dioxide nanoparticles with an average particle size of 65.8 nm were dispersed in isopropyl alcohol at various concentrations to prepare nanoparticle dispersion solutions. The prepared nanoparticle dispersion solutions were then coated onto the formed hole transport layer by spin coating. Subsequently, the coated nanoparticle dispersion solutions were annealed at 110 degrees Celsius. These steps correspond to steps ST31 and ST32 in Figure 5.

[0108] The average particle size of the nanoparticles was measured using a scanning electron microscope (SEM). For the nanoparticle size, 12 particles were randomly selected from images captured by the SEM, and the average and standard deviation were calculated. As mentioned above, the average was 65.8 nm, and the standard deviation was 3.87. The maximum measured nanoparticle size was 117.3 nm, and the minimum was 43.8 nm.

[0109] However, the example in which the concentration of the nanoparticle dispersion solution was 0.2 wt% is designated as Example 1-1, the example in which the concentration of the nanoparticle dispersion solution was 0.4 wt% is designated as Example 1-2, the example in which the concentration of the nanoparticle dispersion solution was 0.6 wt% is designated as Example 1-3, the example in which the concentration of the nanoparticle dispersion solution was 0.8 wt% is designated as Example 1-4, the example in which the concentration of the nanoparticle dispersion solution was 1.0 wt% is designated as Example 1-5, the example in which the concentration of the nanoparticle dispersion solution was 1.5 wt% is designated as Example 1-6, the example in which the concentration of the nanoparticle dispersion solution was 2.0 wt% is designated as Example 1-7, the example in which the concentration of the nanoparticle dispersion solution was 3.0 wt% is designated as Example 1-8, and the example in which the concentration of the nanoparticle dispersion solution was 4.0 wt% is designated as Example 1-9.

[0110] Next, cesium iodide (CsI), methylammonium bromide (MABr), formamidinium iodide (FAI), lead iodide (PbI) ２ ), and lead bromide (PbBr ２ A precursor solution for the photoelectric conversion band was prepared by dissolving the substance in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The prepared precursor solution for the photoelectric conversion band was applied to deposited nanoparticles by spin coating, and chlorobenzene was added dropwise to the applied precursor solution for the photoelectric conversion band. Subsequently, the coating of the precursor solution was annealed to form the photoelectric conversion band and the reflection suppression band. These steps correspond to steps ST33 and ST34 in Figure 5.

[0111] Next, [6,6]-phenyl C ６１A solution was prepared by dissolving methyl butyrate in 2-propanol. The prepared solution was applied by spin coating onto a substrate on which a perovskite layer had been deposited, and then the electron transport layer was formed by drying the solvent. These steps correspond to step ST4 in Figure 2.

[0112] Finally, a second electrode layer was fabricated by vacuum-depositing silver onto the fabricated electron transport layer, thereby creating the photoelectric conversion element according to Example 1-1. This step corresponds to step ST5 in Figure 2.

[0113] (Example 2) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that a solution of silicon dioxide nanoparticles with an average particle size of 115.5 nm dispersed in isopropyl alcohol at various concentrations was used as the nanoparticle dispersion solution.

[0114] As in Example 1, the average particle size of the nanoparticles was measured by observation using a scanning electron microscope (SEM). For the nanoparticle particle size, 12 particles were randomly selected from images captured by the scanning electron microscope, and the mean and standard deviation were calculated. As mentioned above, the mean was 115.5 nm, and the standard deviation was 6.35. The maximum measured nanoparticle size was 125.3 nm, and the minimum was 103.2 nm.

[0115] However, the example in which the concentration of the nanoparticle dispersion solution was 0.2 wt% is designated as Example 2-1, the example in which the concentration of the nanoparticle dispersion solution was 0.4 wt% is designated as Example 2-2, the example in which the concentration of the nanoparticle dispersion solution was 0.6 wt% is designated as Example 2-3, the example in which the concentration of the nanoparticle dispersion solution was 0.8 wt% is designated as Example 2-4, the example in which the concentration of the nanoparticle dispersion solution was 1.0 wt% is designated as Example 2-5, the example in which the concentration of the nanoparticle dispersion solution was 1.5 wt% is designated as Example 2-6, the example in which the concentration of the nanoparticle dispersion solution was 2.0 wt% is designated as Example 2-7, the example in which the concentration of the nanoparticle dispersion solution was 3.0 wt% is designated as Example 2-8, and the example in which the concentration of the nanoparticle dispersion solution was 4.0 wt% is designated as Example 2-9.

[0116] (Example 3) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that a solution of zirconium oxide nanoparticles with an average particle size of 13.4 nm dispersed in isopropyl alcohol at various concentrations was used as the nanoparticle dispersion solution.

[0117] As in Example 1, the average particle size of the nanoparticles was measured by observation using a scanning electron microscope (SEM). For the nanoparticle particle size, 12 particles were randomly selected from images captured by the scanning electron microscope, and the mean and standard deviation were calculated. As mentioned above, the mean was 13.4 nm, and the standard deviation was 2.16. The maximum measured nanoparticle size was 10.0 nm, and the minimum was 17.2 nm.

[0118] However, the example in which the concentration of the nanoparticle dispersion solution was 0.2 wt% is designated as Example 3-1, the example in which the concentration of the nanoparticle dispersion solution was 0.4 wt% is designated as Example 3-2, the example in which the concentration of the nanoparticle dispersion solution was 0.5 wt% is designated as Example 3-3, the example in which the concentration of the nanoparticle dispersion solution was 0.6 wt% is designated as Example 3-4, the example in which the concentration of the nanoparticle dispersion solution was 0.8 wt% is designated as Example 3-5, the example in which the concentration of the nanoparticle dispersion solution was 1.0 wt% is designated as Example 3-6, the example in which the concentration of the nanoparticle dispersion solution was 1.5 wt% is designated as Example 3-7, the example in which the concentration of the nanoparticle dispersion solution was 2.0 wt% is designated as Example 3-8, the example in which the concentration of the nanoparticle dispersion solution was 2.5 wt% is designated as Example 3-9, the example in which the concentration of the nanoparticle dispersion solution was 3.0 wt% is designated as Example 3-10, and the example in which the concentration of the nanoparticle dispersion solution was 4.0 wt% is designated as Example 3-11.

[0119] (Example 4) A photoelectric conversion element was fabricated in the same manner as in Example 1-1, except that a solution of yttrium(III) oxide nanoparticles dispersed in isopropyl alcohol at various concentrations was used as the nanoparticle dispersion solution.

[0120] However, the example in which the concentration of the nanoparticle dispersion solution was 0.2 wt% is designated as Example 4-1, the example in which the concentration of the nanoparticle dispersion solution was 0.4 wt% is designated as Example 4-2, the example in which the concentration of the nanoparticle dispersion solution was 0.6 wt% is designated as Example 4-3, the example in which the concentration of the nanoparticle dispersion solution was 0.8 wt% is designated as Example 4-4, the example in which the concentration of the nanoparticle dispersion solution was 1.0 wt% is designated as Example 4-5, the example in which the concentration of the nanoparticle dispersion solution was 1.5 wt% is designated as Example 4-6, the example in which the concentration of the nanoparticle dispersion solution was 2.0 wt% is designated as Example 4-7, the example in which the concentration of the nanoparticle dispersion solution was 2.5 wt% is designated as Example 4-8, the example in which the concentration of the nanoparticle dispersion solution was 3.0 wt% is designated as Example 4-9, the example in which the concentration of the nanoparticle dispersion solution was 3.0 wt% is designated as Example 4-10, and the example in which the concentration of the nanoparticle dispersion solution was 4.0 wt% is designated as Example 4-11.

[0121] (Comparative Example 1) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that a reflection suppression band was not formed.

[0122] (Comparative Example 2) A photoelectric conversion element was fabricated in the same manner as in Example 1, except that a solution of silicon dioxide nanoparticles with an average particle size of 19.3 nm dispersed in isopropyl alcohol at various concentrations was used as the nanoparticle dispersion solution.

[0123] As in Example 1, the average particle size of the nanoparticles was measured by observation using a scanning electron microscope (SEM). For the nanoparticle size, 12 particles were randomly selected from images captured by the scanning electron microscope, and the mean and standard deviation were calculated. As mentioned above, the mean was 19.3 nm, and the standard deviation was 3.87. The maximum measured nanoparticle size was 27.0 nm, and the minimum was 11.9 nm.

[0124] However, Comparative Example 2-1 is the one with a nanoparticle dispersion solution concentration of 0.2 wt%, Comparative Example 2-2 is the one with a nanoparticle dispersion solution concentration of 0.4 wt%, Comparative Example 2-3 is the one with a nanoparticle dispersion solution concentration of 0.6 wt%, Comparative Example 2-4 is the one with a nanoparticle dispersion solution concentration of 0.8 wt%, Comparative Example 2-5 is the one with a nanoparticle dispersion solution concentration of 1.0 wt%, Comparative Example 2-6 is the one with a nanoparticle dispersion solution concentration of 1.5 wt%, Comparative Example 2-7 is the one with a nanoparticle dispersion solution concentration of 2.0 wt%, Comparative Example 2-8 is the one with a nanoparticle dispersion solution concentration of 3.0 wt%, and Comparative Example 2-9 is the one with a nanoparticle dispersion solution concentration of 4.0 wt%.

[0125] <Estimation of the magnitude of short-circuit current density lost due to light reflection> Using a solar simulator with an AM (Air Mass) of 1.5G, light was shone onto the fabricated photoelectric conversion element, and the reflectivity of the light was measured. Based on the measured reflectivity of the light, the magnitude of the short-circuit current density lost due to light reflection was estimated. The estimation results are shown in Figures 9, 10, 11, and 12.

[0126] Figure 9 is a graph showing the estimated short-circuit current density lost due to light reflection. More specifically, Figure 9 is a graph plotting the estimated short-circuit current density lost in the photoelectric conversion element according to Example 1 and the estimated short-circuit current density lost in the photoelectric conversion element according to Comparative Example 2 against the dispersion solution concentration. Figure 10 is a graph showing the estimated short-circuit current density lost due to light reflection. More specifically, Figure 10 is a graph plotting the estimated short-circuit current density lost in the photoelectric conversion element according to Example 2 and the estimated short-circuit current density lost in the photoelectric conversion element according to Comparative Example 2 against the dispersion solution concentration. Figure 11 is a graph showing the estimated short-circuit current density lost due to light reflection. More specifically, Figure 11 is a graph plotting the estimated short-circuit current density lost in the photoelectric conversion element according to Example 3 and the estimated short-circuit current density lost in the photoelectric conversion element according to Comparative Example 2 against the dispersion solution concentration. Figure 12 is a graph showing the estimated short-circuit current density lost due to light reflection. More specifically, Figure 12 is a graph plotting the estimated short-circuit current density loss in the photoelectric conversion element according to Example 4 and the estimated short-circuit current density loss in the photoelectric conversion element according to Comparative Example 2 against the dispersion solution concentration.

[0127] The results shown in Figures 9 and 10 reveal that when the main component of inorganic nanoparticles is silicon dioxide, considering the standard deviation, if the average particle size of the inorganic nanoparticles is greater than 15 nm, the loss of short-circuit current density due to light reflection can be suppressed.

[0128] Furthermore, the results shown in Figures 9 and 10 reveal that when the main component of inorganic nanoparticles is silicon dioxide, the loss of short-circuit current density due to light reflection can be further suppressed if the average particle size of the inorganic nanoparticles is 122 nm or less, taking into account the standard deviation.

[0129] Furthermore, the results shown in Figures 9 and 10 revealed that when the main component of the inorganic nanoparticles is silicon dioxide, the concentration of the dispersion solution is preferably 0.2 wt% to 3.0 wt%, and particularly preferably 1.0 wt% to 2.0 wt%.

[0130] The results shown in Figure 11 reveal that when the main component of inorganic nanoparticles is zirconium oxide, considering the standard deviation, the loss of short-circuit current density due to light reflection can be suppressed if the average particle size of the inorganic nanoparticles is 11 nm or more. Furthermore, the results shown in Figure 11 reveal that when the main component of inorganic nanoparticles is zirconium oxide, the concentration of the dispersion solution is preferably 0.2 wt% to 4.0 wt%, and particularly preferably 2.0 wt% to 4.0 wt%.

[0131] As shown in Figure 12, when the main component of inorganic nanoparticles is yttrium oxide, the concentration of the dispersion solution is preferably 0.2 wt% to 4.0 wt%, and particularly preferably 2.0 wt% to 4.0 wt%.

[0132] <Measurement of the Thickness of the Reflection Suppression Band in Photoelectric Conversion Elements> For some examples, the cross-section of the fabricated photoelectric conversion elements was observed using a scanning electron microscope (SEM), and the thickness of the reflection suppression band and the photoelectric conversion layer was measured. The results are shown in Tables 1, 2, and 3. More specifically, cross-sectional SEM images were taken for three fields of view. The cross-sectional SEM images of the captured photoelectric conversion elements were observed, and the distance from the top of the layer located below the reflection suppression band to the top of the nanoparticles at the location where the most nanoparticles were deposited was measured. The average value of the distances measured in each field of view was then calculated as the thickness of the reflection suppression band. In addition, the cross-sectional SEM images of the captured photoelectric conversion elements were observed, and the distance from the top to the bottom of the photoelectric conversion layer was measured. The average value of the distances measured in each field of view was then calculated as the thickness of the photoelectric conversion layer. For each example and comparative example, 3 to 5 photoelectric conversion elements were fabricated, and their average values ​​were calculated.

[0133] <Evaluation of Battery Performance of Photoelectric Conversion Elements> For some of the embodiments, the fabricated photoelectric conversion elements were irradiated with light using a solar simulator with an AM (Air Mass) of 1.5G, and the open-circuit voltage and photoelectric conversion efficiency were measured. The results are shown in Tables 1, 2, and 3. For each embodiment and comparative example, 3 to 5 photoelectric conversion elements were fabricated, and the average value was calculated.

[0134]

[0135]

[0136]

[0137] From the results in Tables 1, 2, and 3, it became clear that the photoelectric conversion element according to this embodiment can have its photoelectric conversion efficiency improved by including a reflection suppression band.

[0138] (Discussion of Table 1) From a comparison of Examples 1-2, 1-3, 1-4, 1-5, 1-6, and 2-6 with Example 2-9, it became clear that when the main component of the inorganic nanoparticles is silicon dioxide, it is preferable that the thickness of the reflection suppression band be between 59 nm and 110 nm.

[0139] Furthermore, a comparison of Examples 1-3, 1-5, and 1-6 with Examples 1-2, 1-4, and 2-6 revealed that when the main component of the inorganic nanoparticles is silicon dioxide, it is particularly preferable that the thickness of the reflection suppression band be between 61 nm and 87 nm.

[0140] From a comparison of Examples 1-2, 1-3, 1-4, 1-5, 1-6, and 2-6 with Example 2-9, it became clear that when the main component of the inorganic nanoparticles is silicon dioxide, the thickness of the reflection suppression band is preferably 0.08 times or more and 0.26 times or less than the thickness of the photoelectric conversion layer, and more preferably 0.08 times or more and 0.16 times or less. Furthermore, from a comparison of Examples 1-2, 1-3, 1-4, 1-5, and 1-6 with Examples 2-6 and 2-9, it became clear that when the main component of the inorganic nanoparticles is silicon dioxide, the thickness of the reflection suppression band is particularly preferably 0.08 times or more and 0.12 times or less than the thickness of the photoelectric conversion layer.

[0141] (Discussion of Table 2) From the results of Examples 3-3, 3-6, 3-7, 3-8, 3-9, and 3-10, it became clear that when the main component of the inorganic nanoparticles is zirconium oxide, it is preferable that the thickness of the reflection suppression band be between 19 nm and 86 nm.

[0142] Furthermore, from a comparison of Examples 3-6, 3-7, 3-8, 3-9, and 3-10 with Example 3-3, it became clear that when the main component of the inorganic nanoparticles is zirconium oxide, it is particularly preferable that the thickness of the reflection suppression band be between 30 nm and 86 nm.

[0143] (Discussion of Table 3) From the results of Examples 4-5, 4-7, 4-8, 4-9, 4-10, and 4-11, it became clear that when the main component of the inorganic nanoparticles is yttrium oxide, it is preferable that the thickness of the reflection suppression band be between 102 nm and 182 nm.

[0144] (Discussion of Tables 2 and 3) From the results of Examples 3-3, 3-6, 3-7, 3-8, 3-9, 3-10, 4-5, 4-7, 4-8, 4-9, 4-10, and 4-11, it became clear that when the main component of inorganic nanoparticles is a semiconductor, the thickness of the reflection suppression band is preferably 0.03 times or more and 0.24 times or less the thickness of the photoelectric conversion layer.

[0145] Furthermore, from a comparison of Examples 3-6, 3-7, 3-8, 3-9, 3-10, 4-5, 4-7, 4-8, and 4-9 with Examples 3-3, 4-10, and 4-11, it became clear that when the main component of the inorganic nanoparticles is a semiconductor, it is even more preferable that the thickness of the reflection suppression band be 0.05 times or more and 0.20 times or less the thickness of the photoelectric conversion layer.

[0146] Furthermore, a comparison of Examples 3-7, 3-8, 3-9, and 3-10 with Examples 3-3, 3-6, 4-5, 4-7, 4-8, 4-9, 4-10, and 4-11 revealed that when the main component of the inorganic nanoparticles is a semiconductor, it is particularly preferable that the thickness of the reflection suppression band be 0.08 times or more and 0.13 times or less the thickness of the photoelectric conversion layer.

[0147] Although the present invention has been described above in reference to the embodiments described above, the present invention is not limited to the configuration of the embodiments described above, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application.

[0148] This application claims priority based on Japanese Patent Application No. 2025-027297, filed on 21 February 2025, and incorporates all of its disclosures herein.

[0149] 1 Photoelectric conversion element 11 Substrate 12 First electrode layer 13 First carrier transport layer 14 Photoelectric conversion layer 141 Photoelectric conversion band 142 Reflection suppression band 15 Second carrier transport layer 16 Second electrode layer NP Inorganic nanoparticles

Claims

1. A photoelectric conversion element comprising a first electrode layer which is a transparent electrode, a second electrode layer, and a photoelectric conversion band located between the first electrode layer and the second electrode layer, wherein the photoelectric conversion element further comprises a reflection suppression band between the photoelectric conversion band and the first electrode layer, the reflection suppression band containing inorganic nanoparticles which are at least one of an insulator and a semiconductor.

2. The photoelectric conversion element according to claim 1, further comprising a carrier transport layer between the first electrode layer and the photoelectric conversion band, wherein the reflection suppression band is located between the photoelectric conversion band and the carrier transport layer.

3. The photoelectric conversion element according to claim 1 or 2, wherein the average particle size of the inorganic nanoparticles is greater than 15 nm.

4. The photoelectric conversion element according to claim 3, wherein the average particle size of the inorganic nanoparticles is 45 nm or more.

5. The photoelectric conversion element according to claim 1 or 2, wherein the average particle size of the inorganic nanoparticles is 122 nm or less.

6. The photoelectric conversion element according to claim 1 or 2, wherein the inorganic nanoparticles are metal oxide insulators or semiconductors.

7. The photoelectric conversion element according to claim 1 or 2, wherein the photoelectric conversion band mainly comprises a perovskite compound.

8. The photoelectric conversion element according to either claim 1 or 2, wherein the thickness of the reflection suppression band is 200 nm or less.

9. The photoelectric conversion element according to claim 8, wherein the inorganic nanoparticles contained in the reflection suppression band mainly consist of an insulator, and the thickness of the reflection suppression band is 110 nm or less.

10. The photoelectric conversion element according to claim 9, wherein the inorganic nanoparticles contained in the reflection suppression band mainly consist of silicon dioxide, and the thickness of the reflection suppression band is 59 nm or more and 110 nm or less.

11. The photoelectric conversion element according to claim 10, wherein the thickness of the reflection suppression band is 61 nm or more and 87 nm or less.

12. The photoelectric conversion element according to claim 8, wherein the inorganic nanoparticles contained in the reflection suppression band mainly consist of a semiconductor.

13. The photoelectric conversion element according to claim 12, wherein the inorganic nanoparticles contained in the reflection suppression band mainly consist of zirconium oxide, and the thickness of the reflection suppression band is 19 nm or more and 86 nm or less.

14. The photoelectric conversion element according to claim 13, wherein the thickness of the reflection suppression band is 30 nm or more.

15. The photoelectric conversion element according to claim 12, wherein the inorganic nanoparticles contained in the reflection suppression band mainly consist of yttrium oxide, and the thickness of the reflection suppression band is 102 nm or more and 182 nm or less.

16. The photoelectric conversion element according to claim 2, wherein there is a region in which the photoelectric conversion band and the carrier transport layer are in contact without the inorganic nanoparticles.

17. A tandem solar cell comprising a plurality of photoelectric conversion elements, wherein the photoelectric conversion element located on the outermost surface when viewed from the light incident side comprises a first electrode layer which is a transparent electrode, a second electrode layer, and a photoelectric conversion band located between the first electrode layer and the second electrode layer, and further comprises a reflection suppression band between the photoelectric conversion band and the first electrode layer which includes inorganic nanoparticles which are at least one of an insulator and a semiconductor.

18. A window glass equipped with a photoelectric conversion element, wherein the photoelectric conversion element comprises a first electrode layer which is a transparent electrode, a second electrode layer, and a photoelectric conversion band located between the first electrode layer and the second electrode layer, and further comprises a reflection suppression band between the photoelectric conversion band and the first electrode layer which includes inorganic nanoparticles which are at least one of an insulator and a semiconductor.

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