Photoelectric conversion element, coating liquid, and method for producing photoelectric conversion element

Abstract

Provided is a photoelectric conversion element (1) comprising a first electrode (7), a second electrode (3), and a photoelectric conversion layer (5) which is disposed between the first electrode (7) and the second electrode (3) and which includes a crystal with a perovskite structure, said photoelectric conversion element (1) being characterized by having a first charge transport layer (6) between the photoelectric conversion layer (5) and the first electrode (7) and having a second charge transport layer (4) between the photoelectric conversion layer (5) and the second electrode (3), wherein the photoelectric conversion element (1) has crystals A(5A) which contact the second charge transport layer (4) and a crystal B(5B) which covers a gap between adjacent crystals A(5A), which contacts the first charge transport layer (6), and which does not contact the second charge transport layer (4).

Description

Photoelectric conversion element, coating solution, and method for manufacturing a photoelectric conversion element

[0001] This disclosure relates to a photoelectric conversion element, a coating solution, and a method for manufacturing a photoelectric conversion element.

[0002] In order to address the depletion of fossil fuels and the environmental problems caused by their use, research into renewable and clean alternative energy sources such as solar, wind, and hydroelectric power is actively being conducted. Among these, there is growing interest in solar cells, which directly convert sunlight into electrical energy. Here, a solar cell refers to a battery that absorbs light energy from sunlight and generates current and voltage using the photovoltaic effect, which generates electrons and holes.

[0003] Currently, n-p diode type silicon (Si) single-crystal based solar cells with a light energy conversion efficiency exceeding 20% ​​are widely known and actually used in photovoltaic power generation. However, these have the problem of high cost per unit of power due to the need for high-temperature processing and the high price of the material itself. Furthermore, there are supply issues from the perspective of silicon resources.

[0004] On the other hand, solar cells using organic materials (hereinafter referred to as "organic solar cells") do not require high-temperature processing and can be produced using a so-called roll-to-roll method on sheet-like substrates, thus offering the potential for lower costs. However, further improvements in power generation efficiency are desired for the practical application of organic solar cells. In particular, perovskite-type solar cells, which have a perovskite structure crystal as the photoelectric conversion layer, are being developed for practical use because of their excellent photoelectric conversion properties.

[0005] For example, Patent Document 1 describes how constructing a perovskite layer with dense crystals suppresses shunt liquefaction and improves conversion efficiency. Non-Patent Document 1 describes how including polymethyl methacrylate (PMMA) as a leak-preventing layer on top of the perovskite increases conversion efficiency due to the suppression of shunt liquefaction.

[0006] Patent No. 7245527

[0007] F. Wang, et. al. , J. Phys. Chem. C, 2017, 121, 1562

[0008] The photoelectric conversion element described in Patent Document 1 achieves high conversion efficiency by suppressing the occurrence of pinholes and inhibiting shunt liquefaction through the use of a dense crystal group. On the other hand, it is known that crystal grain boundaries have defects that trap carriers. Therefore, although densification of the perovskite layer crystal can suppress shunt liquefaction, it increases carrier trapping, which hinders the improvement of conversion efficiency. Thus, there were challenges in achieving further improvements in conversion efficiency through densification. In addition, the photoelectric conversion element described in Non-Patent Document 1 requires the addition of a leak prevention layer to suppress shunt liquefaction, which presented a productivity challenge.

[0009] Therefore, an object of this disclosure is to provide a photoelectric conversion element with high productivity and improved leak resistance by protecting defects in the perovskite crystal structure with another perovskite crystal structure. Another object of this disclosure is to provide a method for manufacturing a photoelectric conversion element with high productivity and improved leak resistance by protecting defects in the perovskite crystal structure with another perovskite crystal structure.

[0010] The above objectives are achieved by the present disclosure below. Specifically, the present disclosure relates to a photoelectric element having a first electrode, a second electrode, and a photoelectric conversion layer comprising a perovskite crystal disposed between the first electrode and the second electrode, wherein the photoelectric element has a first charge transport layer between the photoelectric conversion layer and the first electrode, and a second charge transport layer between the photoelectric conversion layer and the second electrode, and the photoelectric element is characterized by having crystal A in contact with the second charge transport layer, and crystal B covering the gap between adjacent crystals A, in contact with the first charge transport layer, and not in contact with the second charge transport layer. The present disclosure also relates to a coating solution for forming the above-mentioned photoelectric element, comprising a photoelectric conversion layer precursor, a solvent, and an additive, wherein the photoelectric conversion layer precursor is A １ X １ Compounds represented by B １ X １ ２It comprises at least one selected from the group consisting of compounds represented by A １ is a monovalent cation comprising at least one selected from the group consisting of alkali metal cations and organic ammonium compounds, and the B １ X is a divalent cation comprising at least one selected from the group consisting of lead, tin, bismuth, and silver, and １ The coating solution is a monovalent anion of a halide ion, the solvent contains a plurality of solvent species and has a boiling point of 190°C or less, and the additive is methylammonium chloride. The present disclosure also relates to a method for manufacturing a photoelectric element, comprising the steps of forming a first electrode, forming a second electrode, forming a photoelectric conversion layer between the first electrode and the second electrode containing a perovskite crystal, and forming a first charge transport layer between the photoelectric conversion layer and the first electrode, wherein the photoelectric element has crystal A in contact with the second charge transport layer and crystal B covering the gap between adjacent crystals A, in contact with the first charge transport layer, and not in contact with the second charge transport layer.

[0011] According to this disclosure, it is possible to provide a photoelectric conversion element that has high productivity and improved leakage resistance and conversion efficiency.

[0012] This is an example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion element of the present disclosure. This is another example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion element of the present disclosure. This is an example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion layer of the present disclosure. This is another example of a schematic cross-sectional view in the thickness direction of one embodiment of the photoelectric conversion layer of the present disclosure. This is a schematic side view illustrating a coating apparatus used in a coating method according to one embodiment of the photoelectric conversion layer of the present disclosure.

[0013] <First Embodiment> The first embodiment relates to a photoelectric conversion element. The photoelectric conversion element of the present disclosure is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer having a perovskite structure crystal disposed between the first electrode and the second electrode, wherein the photoelectric conversion element has a first charge transport layer between the photoelectric conversion layer and the first electrode, and a second charge transport layer between the photoelectric conversion layer and the second electrode, and the photoelectric conversion element is characterized by having a crystal A that contacts the second charge transport layer, and a crystal B that covers the gap between adjacent crystals A, and is in contact with the first charge transport layer but not with the second charge transport layer.

[0014] As a result of their investigation, the inventors have found that by having the above-mentioned crystal A and crystal B, a photoelectric conversion element with high productivity, leakage resistance, and excellent conversion efficiency can be obtained. The reason why a photoelectric conversion element with high conversion efficiency can be obtained in this disclosure is not entirely clear, but it is thought to be as follows.

[0015] In the inventors' previous studies, it was estimated that by utilizing a dense group of perovskite crystals, the generation of pinholes was suppressed, shunt liquefaction was inhibited, and high conversion efficiency was achieved. However, while densifying the perovskite layer crystals suppresses shunt liquefaction, it increases carrier traps, which hinders the improvement of conversion efficiency. Therefore, it was found that further improvements in conversion efficiency through further densification are difficult. Furthermore, according to the inventors' studies, in the photoelectric conversion element described in Non-Patent Document 1, it is necessary to add a leak prevention layer to suppress shunt liquefaction, which presents a productivity challenge.

[0016] Therefore, in this disclosure, it is hypothesized that by having crystal A having a perovskite structure and crystal B having a perovskite structure that covers the gap between adjacent crystals A, productivity is improved because there is no need to add a new leak prevention layer, carrier trapping and shunt liquefaction are suppressed, and this contributes to an increase in conversion efficiency.

[0017] As described above, the effects of this disclosure can be achieved through the synergistic effects of each component constituting this disclosure.

[0018] The present disclosure will be described in detail below with reference to preferred embodiments. The present disclosure is not limited to the embodiments described below, and the scope of the present disclosure also includes modifications, improvements, etc., to the extent appropriate to the embodiments described below, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the present disclosure.

[0019] In this specification, "layer" refers not only to layers with clear boundaries or flat, thin films, but also to layers with gradually changing elemental concentrations and layers that can form complex structures together with other layers. Elemental analysis of a layer can be performed, for example, by conducting TOF-SIMS / FE-TEM / EDS radiation analysis on a cross-section of a photoelectric conversion element to confirm the elemental distribution of specific elements.

[0020] The photoelectric conversion element of the present disclosure comprises a first electrode, a second electrode, and a photoelectric conversion layer containing a perovskite crystal disposed between the first electrode and the second electrode. Figure 1 shows a schematic cross-sectional view illustrating the configuration of one embodiment of the photoelectric conversion element of the present disclosure. The substrate 2 has a second electrode 3, a second charge transport layer 4, a photoelectric conversion layer 5, a first charge transport layer 6, and a first electrode 7. One of the first electrode 7 and the second electrode 3 is a positive electrode and the other is a negative electrode, and current can be extracted by connecting the first electrode 7 and the second electrode 3 to an external circuit. One of the first charge transport layer 6 and the second charge transport layer 4 is a hole transport layer and the other is an electron transport layer. The photoelectric conversion layer 5 is excited by light incident through the substrate 2, the second electrode 3 and the second charge transport layer 4, or the first electrode 7 and the first charge transport layer 6, generating electrons or holes. In other words, the photoelectric conversion layer 5 generates an electric current between the first electrode 7 and the second electrode 3.

[0021] The second charge transport layer 4 is a layer positioned between the photoelectric conversion layer 5 and the two electrodes 3 and 7. Multiple layers of the second charge transport layer 4 and the photoelectric conversion layer 5 may be stacked. This configuration can also be called a tandem structure. Alternatively, the photoelectric conversion element may be fabricated on the substrate 2 in the following order: first electrode 7, first charge transport layer 6, photoelectric conversion layer 5, second charge transport layer 4, and second electrode 3.

[0022] The components constituting the photoelectric conversion element of this disclosure are described below. [Photoelectric Conversion Element] The photoelectric conversion element of this disclosure is a photoelectric conversion element having a first electrode, a second electrode, and a photoelectric conversion layer containing a perovskite structure crystal disposed between the first electrode and the second electrode, characterized in that it has a first charge transport layer between the photoelectric conversion layer and the first electrode. Furthermore, in order to improve the photoelectric conversion efficiency, a tandem type in which photoelectric conversion elements are stacked may be used. The photoelectric conversion elements to be stacked are not limited to the type of photoelectric conversion element, but include not only perovskite type solar cells that use a perovskite structure crystal as the photoelectric conversion layer, but also silicon type solar cells, CIGS type solar cells, etc.

[0023] Methods for forming the photoelectric conversion layer and charge transport layer of the photoelectric conversion element disclosed herein include coating methods and vapor deposition methods. Examples of coating methods include immersion coating, spin coating, spray coating, inkjet coating, meniscus coating, screen coating, roll coating, die coating, blade coating, curtain coating, and wire bar coating. The coating method involves preparing the coating solution for each layer, which will be described later, coating the layers in the desired order, and drying them. These film formation methods can be selected according to the requirements of each layer. Each layer will be described below.

[0024] [Substrate] The photoelectric conversion element 1 of the present disclosure may include a substrate 2, for example, a transparent glass substrate made of soda-lime glass or alkali-free glass, a ceramic substrate, or a transparent plastic substrate. When light is taken in from the first electrode 7 side, the substrate 2 can be made of an opaque material, and when light is taken in from the second electrode 3 side, the substrate 2 is made of a transparent material.

[0025] [Electrode] The photoelectric conversion element of the present disclosure has a first electrode and a second electrode. The materials of the first electrode 7 and the second electrode 3 are not particularly limited, and conventionally known materials can be used. For example, metals such as gold, silver, titanium, and copper, sodium, sodium-potassium alloy, lithium, magnesium, carbon, carbon nanotubes, aluminum, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, Al / Al ２ O ３ mixture, Al / LiF mixture. As the transparent electrode material, for example, CuI, ITO (indium tin oxide), SnO ２ , AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), FTO (fluorine-doped tin oxide), ATO (antimony-doped tin oxide) conductive transparent materials, conductive transparent polymers.

[0026] These materials may be used alone or in combination of two or more. At least one of the first electrode 7 and the second electrode 3 on the light incident side is a transparent electrode, and the other may be a transparent electrode or may also serve as a reflective layer formed of a light-reflective material, or may be a transparent electrode provided with a reflective layer on the side opposite to the light incident side. When the first electrode 7 is on the light incident side, the second electrode 3 may be used as a transparent electrode and the substrate 2 may be used as a reflective layer. Note that the transparent electrode may be a patterned electrode.

[0027] [Photoelectric Conversion Layer] The photoelectric conversion element of the present disclosure has a photoelectric conversion layer containing a perovskite-structured crystal disposed between the first electrode and the second electrode, and the photoelectric conversion element has crystal A in contact with the second charge transport layer, and crystal B that covers the voids between adjacent crystal A and is in contact with the first charge transport layer and not in contact with the second charge transport layer. Here, crystal A and crystal B are part of the photoelectric conversion layer, and their composition is basically the same as that of other parts of the photoelectric conversion layer, and they are crystallized.

[0028] Figure 3 is a schematic cross-sectional view showing an example of the configuration of one embodiment of the photoelectric conversion layer of the present disclosure. In one example of the embodiment of the photoelectric conversion layer, perovskite crystal A5A is a crystal adjacent to the first charge transport layer and the second charge transport layer, and perovskite crystal B5B is a crystal adjacent to the first charge transport layer, and the void between adjacent crystals A5A is a sealing void 8 covered by crystal B5B. Here, the first charge transport layer 6 is a hole transport layer, and the second charge transport layer 4 is an electron transport layer.

[0029] Figure 4 is a schematic cross-sectional view showing another example of the configuration of one embodiment of the photoelectric conversion layer of the present disclosure. As in the case of Figure 4, the positions of the first charge transport layer and the second charge transport layer may be reversed compared to the case of Figure 3.

[0030] In the photoelectric conversion element disclosed herein, the surface area of ​​the crystal A in the direction intersecting the layer thickness direction of the photoelectric conversion element is 0.05 μm². ２ Preferably, the above conditions are met, and the thickness of crystal B in the layer thickness direction of the photoelectric conversion element is smaller than the thickness of the first charge transport layer, preferably less than 300 nm. In the photoelectric conversion element of this disclosure, it is preferable that the width of crystal B in the direction intersecting the layer thickness direction of the photoelectric conversion element is larger than the thickness of crystal B in the layer thickness direction of the photoelectric conversion element. By doing so, the photoelectric conversion element of this disclosure can achieve higher productivity and improved leakage resistance and conversion efficiency. In this disclosure, the sizes of crystal A and crystal B can be confirmed by transmission electron microscopy (TEM) observation.

[0031] When the total area is the sum of the area of ​​the surface of crystal A in a direction intersecting the thickness direction of the photoelectric conversion element, the area of ​​the surface of crystal B in a direction intersecting the thickness direction of the photoelectric conversion element, the area of ​​the void in a direction intersecting the thickness direction of the photoelectric conversion element, and the area of ​​the portion where the first charge transport layer and the second charge transport layer are short-circuited in a direction intersecting the thickness direction of the photoelectric conversion element, it is preferable that the ratio of the area of ​​the void in a direction intersecting the thickness direction of the photoelectric conversion element to the total area (defect rate in Table 1) is 0.01% or less. By doing so, the photoelectric conversion element of the present disclosure can achieve higher productivity and improved leakage resistance and conversion efficiency.

[0032] Preferably, the ratio of the area of ​​the surface of the photoelectric conversion layer in a direction intersecting the thickness direction of the photoelectric conversion element to the sum of the area of ​​the surface of crystal A in a direction intersecting the thickness direction of the photoelectric conversion element and the area of ​​the surface of crystal B in a direction intersecting the thickness direction of the photoelectric conversion element is 97% or more. By doing so, the photoelectric conversion element of the present disclosure can achieve higher productivity and improved leakage resistance and conversion efficiency.

[0033] The photoelectric conversion layer 5 has a perovskite crystal structure. The photoelectric conversion layer forms a planar heterojunction with the first charge transport layer or the second charge transport layer, and the perovskite crystal structure used in this disclosure is preferably represented by the following general formula [1]. A ｏ B ｐ X ｑ [1]

[0034] In the above general formula [1], A is a first cation, B is a second cation, and X is a halide anion. o, p, and q satisfy 0 ≤ o ≤ 10, 0 ≤ p ≤ 10, and 0 ≤ q ≤ 20, respectively, and A, B, and X may be composed of a single material or two or more types may be used in combination. Additives may be added within the range in which the above general formula holds true. Preferably, the first cation is an organic cation, and preferably the second cation is a metal cation. In this disclosure, the perovskite crystal structure can be confirmed, for example, by X-ray photoelectron spectroscopy (XPS).

[0035] The above general formula generally forms a three-dimensional perovskite crystal. However, if the constituent cation A is large enough to fit within the three-dimensional perovskite crystal, it can form a two-dimensional perovskite crystal, a 2.5-dimensional perovskite crystal possessing properties of both two and three dimensions, a two-layer crystal with three-dimensional and two-dimensional perovskite structures, or a crystal with a mixed three-dimensional / two-dimensional perovskite structure, all of which function as a photoelectric conversion layer.

[0036] A two-layer crystal of three-dimensional and two-dimensional perovskite refers to a crystal in which three-dimensional and two-dimensional perovskite crystals are stacked as independent, separate layers. A mixed three-dimensional / two-dimensional perovskite refers to a crystal with a structure in which regions or domains of both two-dimensional or 2.5-dimensional layered and three-dimensional perovskite crystals are mixed. Two-dimensional perovskite or 2.5-dimensional perovskite crystals may form RP (Ruddlesden-Popper), DJ (Dion-Jacobson), or ACI (Alternating Cautions in the Interlayer) type perovskite structures.

[0037] In the above general formula [1], the A cation is not particularly limited. The A cation may or may not have substituents, and the following structural formulas are examples.

[0038]

[0039]

[0040] Furthermore, while the inorganic atoms are not particularly limited, lithium, cesium, sodium, potassium, and rubidium are preferred. These organic molecules or inorganic atoms may be used individually, or two or more may be used in combination.

[0041] In the general formula [1] above, B is a cation atom, and examples include lead, tin, bismuth, zinc, titanium, antimony, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, and europium. Among these, lead, tin, bismuth, and silver are preferred from the viewpoint of the stability of the perovskite crystal structure. These atoms may be used individually or in combination of two or more.

[0042] In the general formula [1] above, X is a halogen or chalcogen atom, such as chlorine, bromine, iodine, oxygen, sulfur, selenium, tellurium, or polonium. These halogen or chalcogen atoms may be used individually or in combination of two or more. Among these, halogen atoms are preferred because the inclusion of a halogen in the structure makes the perovskite crystal more soluble in organic solvents, enabling its application to inexpensive printing methods and the like. Furthermore, iodine is more preferred because it narrows the energy band gap of the perovskite crystal.

[0043] Specifically, 3D perovskites, 2D perovskites, and mixed 3D / 2D perovskites are classified as MAPbI ３ ya FAPbCl ３ , FAPbi ３ MAPbI ｘ Br ３－ｘ MAPbI ｘ Cl ３－ｘ , Cs ０．０５ (MA ０．１７ FA ０．８３ ) ０．９５ Pb(I ０．８３ Br ０．１７ ) ３ , {Cs ｘ１ (FA ｘ２ MA １－ｘ２ ) １－ｘ１} ｘ３ Pb(I ｘ４ Br １－ｘ４ ) ｘ５ , Cs ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４、(FAPbI ３ ) ０．９５ (MAPbBr ３ ) ０．０５ 、(FAPbI ３ ) ０．８５ (MAPbBr ３ ) ０．１５ 、CsPbI ３ 、CsPbBr ３ 、Cs ｘ (MA) １－ｘ PbI ３ 、Csx(FA) １－ｘ PbI ３ 、MA ｘ (FA) １－ｘ PbI ３ 、MA ０．１７ FA ０．８３ Pb(I ０．８３ Br ０．１７ ) ３ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、Cs ０．０５ FA ０．８８ MA ０．０７ PbI ２．５６ Br ０．４４ 、Cs ０．１５ FA ０．８５ PbI ２．５５ Br ０．４５ 、(PEA) ２ (MA) ２ Pb ３ I １０ 、(PTA) ２ (MA) ４ Pb ５ I １６ 、(PEA) ２ (MA) ４ Pb ５ I １６ 、(ThMA) ２ (MA) ２ Pb ３ I １０ 、(3BBA) ２ (MA) ２ Pb ３ I １０ 、(ThMA) ２ (FA) ４ Pb ５ I １６ 、(pF-PEA) ２(FA ０．３ MA ０．７ ) ４ Pb ５ I １６ 、(PDMA)FA ２ Pb ３ I １０ 、(3AMPY)(MA) ３ Pb ４ I １３ 、(PDMA)MA ５ Pb ６ I １９ 、(PDMA)MA ３ Pb ４ I １３ 、(BA ０．９ PEA ０．１ ) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ４ Pb ５ I １６ 、(BA) ２ MA ３ Pb ４ I １３ 、CsSnBr ３ 、CsSnI ３ 、FA ０．７５ MA ０．２５ Sn ０．９５ Ge ０．０５ I ３ 、FAMASnGeI ３ 、FASnBr ３ 、FASnI ３ 、MA ２ Sn ３ I ８ 、MASnBr ３ 、MASnGeI ３ 、MASnI ３ are preferred.

[0044] Depending on the purpose, the A site, B site, or X site in the above general formula may be adjusted to be too little or too much, and the combinations of x1 to x5 may be changed according to the purpose. Examples of combinations of x1 to x5 are shown in Table 1. Particularly preferred ranges for the combinations of x1 to x5 are 0.03 ≤ x1 ≤ 0.10, 0.80 ≤ x2 ≤ 0.96, 0.95 ≤ x3 ≤ 1.05, 0.80 ≤ x4 ≤ 0.96, and 2.95 ≤ x5 ≤ 3.05. MACL may also be included as the material for forming the perovskite crystal.

[0045]

[0046] The perovskite crystal described above preferably has a cubic crystal structure in which a metal atom B is arranged at the body center, organic molecules A are arranged at each vertex, and halogen atoms X are arranged at the face centers. Although the details are not clear, it is presumed that having such a structure allows the orientation of the octahedra in the crystal lattice to change easily, thereby increasing the electron mobility in the perovskite crystal and improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0047] The perovskite crystal used in this disclosure is preferably a crystalline semiconductor. A crystalline semiconductor is a semiconductor in which the X-ray scattering intensity distribution can be measured and a scattering peak can be detected. Because the perovskite crystal is a crystalline semiconductor, the electron mobility in the perovskite crystal is increased, improving the photoelectric conversion efficiency of the photoelectric conversion element.

[0048] The thickness of the photoelectric conversion layer according to this disclosure is preferably 200 nm or more and 1000 nm or less. If the thickness is 200 nm or more, light can be sufficiently absorbed, and if it is 1000 nm or less, the generated charge can be transported to each electrode.

[0049] [First Charge Transport Layer] The photoelectric conversion element of this disclosure has a first charge transport layer between the photoelectric conversion layer and the first electrode. In the photoelectric conversion element of this disclosure, it is preferable that the first charge transport layer is a hole transport compound. In this disclosure, the material of the first charge transport layer 6 is not particularly limited, and examples include spirofluorene compounds, triphenylamine compounds, chrysene compounds, pyrene compounds, phthalocyanine compounds, carbazole compounds, fluorene compounds, phenylcyclohexane compounds, benzidine compounds, phenoxazine compounds, phenylenediamine compounds, thiocyanate compounds, and thiophene compounds. In particular, it is preferable that it has an aromatic ring from the viewpoint of compatibility at the film interface, and Spiro-OMeTAD, PTAA, and phthalocyanine compounds are preferred.

[0050] Furthermore, the first charge transport layer 6 may have a dopant as an additive to improve its charge transport capacity. Examples of substances that can be used as dopants include lithium compounds such as bis(trifluoromethanesulfonyl)imide lithium, cobalt compounds such as [tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(3)tris(bis(trifluoromethylsulfonyl)imide)], boron compounds such as tetrakis(pentafluorophenyl)borate, molybdenum compounds such as tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene]molybdenum, organic compounds having a tetracyanoquinodimethane skeleton such as 2,3,4,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, and organic compounds having a pyridine skeleton such as 4-tert-butylpyridine.

[0051] The preferred lower limit of the thickness of the first charge transport layer 6 is 200 nm, and the preferred upper limit is 1000 nm. If the thickness of the first charge transport layer 6 is 200 nm or more, electrons can be sufficiently blocked, and if it is 1000 nm or less, it will not become a resistance during hole transport, and the photoelectric conversion efficiency will be high.

[0052] [Second Charge Transport Layer] As shown in Figures 1 and 2, the photoelectric conversion element of this disclosure has a second charge transport layer 4 between the second electrode 3 and the photoelectric conversion layer 5. That is, the photoelectric conversion element of this disclosure may have a configuration in which the positions of the first charge transport layer and the second charge transport layer are swapped, as shown in the configuration of Figure 2 compared to the configuration of Figure 1.

[0053] In the photoelectric conversion element of this disclosure, it is preferable that the second charge transport layer is an electron transport compound. The material of the second charge transport layer 4 is not particularly limited, and examples include N-type conductive polymers, N-type low molecular weight organic semiconductors, N-type metal oxides, N-type metal sulfides, alkali metal halides, alkali metals, surfactants, and more specifically, cyano group-containing polyphenylene vinylene, boron-containing polymers, vasocuproin, vasophenanthrene, hydroxyquinolinatoaluminum, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic acid compounds, fullerene compounds, perylene compounds, phosphine oxide compounds, phosphine sulfide compounds, fluoro group-containing phthalocyanines, titanium dioxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, and zinc sulfide.

[0054] The thickness of the second charge transport layer 4 is preferably 1 nm at the lower limit and 2000 nm at the upper limit. If the thickness is 1 nm or more, holes can be sufficiently blocked, and if it is 2000 nm or less, it will not become a resistance during electron transport, and the photoelectric conversion efficiency will be high.

[0055] <Application Examples> [Photoelectric Conversion Device] The photoelectric conversion device of the present disclosure has a photoelectric conversion element of the present disclosure. A photoelectric conversion device can be constructed by using multiple photoelectric conversion elements of the present disclosure. When multiple photoelectric conversion elements are connected together, such a photoelectric conversion device can also be called a photoelectric conversion cell or a photoelectric conversion module. The photoelectric conversion elements may be stacked with elements having different absorption wavelengths in order to increase the output voltage. The photoelectric conversion device also has a photoelectric conversion element of the present disclosure and an inverter.

[0056] An inverter may be a converter that converts direct current to alternating current. A photoelectric converter may have a power storage unit connected to a photoelectric converter element. The power storage unit is not limited as long as it can store electricity. Examples include lithium-ion secondary batteries, all-solid-state batteries, and electric double-layer capacitors. To provide functions such as maintaining or increasing the amount of incident light, a surface that is resistant to water and dirt, or a function to collect or guide light may be added.

[0057] <Second Embodiment> The second embodiment relates to a coating solution. The coating solution of the present disclosure is a coating solution for forming a photoelectric conversion element of the present disclosure, comprising a photoelectric conversion layer precursor, a solvent, and an additive, wherein the photoelectric conversion layer precursor is A １ X １ Compounds represented by B １ X １ ２ It comprises at least one selected from the group consisting of compounds represented by A １ is a monovalent cation comprising at least one selected from the group consisting of alkali metal cations and organic ammonium compounds, and the B １ X is a divalent cation comprising at least one selected from the group consisting of lead, tin, bismuth, and silver, and １ The compound is a monovalent anion of a halide ion, the solvent contains multiple solvent species and has a boiling point of 190°C or lower, and the additive is methylammonium chloride.

[0058] X, a component of the precursor １ A １ , B １ These are prepared as precursors to X, A, and B in the above formula [1]. １ A １ , B １ Any of the above-mentioned precursors for X, A, and B in equation [1] can be used.

[0059] [Solvent] In the drying process for producing perovskite crystals, if only solvents with low boiling points are used, the solvent dries quickly, making it easy to achieve a supersaturated state and obtain many crystal nuclei. However, the solvent dries too quickly, preventing sufficient nucleus growth and resulting in smaller perovskite crystals. Perovskite layers composed of small crystals have many crystal interfaces, increasing the opportunities for charge recombination at these interfaces, which in turn reduces the photoelectric conversion efficiency.

[0060] On the other hand, when only high-boiling-point solvents are used, solvent drying is suppressed compared to low-boiling-point solvents, which sustains the saturated concentration state that contributes to crystal growth, resulting in large crystal growth. However, the supersaturated state that generates crystal nuclei is reduced, decreasing the number of crystal nuclei. In perovskite layers composed of a small number of large perovskite crystals, spaces are more likely to form between the perovskite crystals, causing a short circuit between the first and second charge transport layers, resulting in a decrease in photoelectric conversion efficiency.

[0061] Based on the above, the solvent used in the drying process for producing perovskite crystals is preferably a combination of a low-boiling point solvent to obtain sufficient crystal nuclei and a high-boiling point solvent to grow the crystal nuclei. In particular, the low-boiling point solvent is preferably DMF (N,N-dimethylformamide, boiling point 153°C), and the high-boiling point solvent is preferably DMSO (dimethyl sulfoxide, boiling point 189°C).

[0062] [Additives] To obtain even higher photoelectric conversion efficiency, it is desirable to have large crystals with minimal perovskite crystal interfaces while suppressing the appearance of unwanted spaces between crystals. To obtain such crystals, it is necessary to generate and grow a number of crystal nuclei commensurate with the space in which the crystals can grow. Therefore, in the drying process, it is necessary to optimize the generation of crystal nuclei by alleviating the supersaturation state and to increase the crystal growth time by suppressing the drying of the solvent.

[0063] The drying process that generates perovskite crystals using the boiling point of the solvent contributes to some extent to the relaxation of the supersaturation state and an increase in crystal growth time. However, because the solvent volatilizes quickly overall, too many crystal nuclei are generated, leading to the formation of unwanted crystal interfaces. Furthermore, the insufficient growth time makes it difficult to obtain large crystals.

[0064] Therefore, additives that suppress the rate of solvent evaporation become useful. MACL is preferred as an additive that suppresses the rate of solvent evaporation. It is presumed that MACL has the effect of suppressing the rate of solvent evaporation by coordinating chloride ions with solvent molecules. Specific examples of MACL are as described above.

[0065] <Third Embodiment> The third embodiment relates to a method for manufacturing a photoelectric conversion element. The method for manufacturing a photoelectric conversion element according to the present disclosure includes the steps of forming a first electrode, forming a second electrode, forming a photoelectric conversion layer between the first electrode and the second electrode, which includes a perovskite crystal, forming a first charge transport layer between the photoelectric conversion layer and the first electrode, and forming a second charge transport layer between the photoelectric conversion layer and the second electrode, wherein the photoelectric conversion element has a crystal A that contacts the second charge transport layer, and a crystal B that covers the gap between adjacent crystals A, contacts the first charge transport layer, and does not contact the second charge transport layer. The steps of the manufacturing method will be described below.

[0066] [Steps for forming the first electrode and the second electrode] The method for manufacturing a photoelectric conversion element according to the present disclosure includes a step for forming a first electrode and a step for forming a second electrode. In the steps for forming the first electrode and the step for forming the second electrode, an appropriate method can be selected according to the material of the first electrode and the material of the second electrode, respectively. Examples of such methods include, but are not limited to, sputtering vacuum deposition, CVD (vapor deposition), and SPD (spray pyrolysis deposition). The materials of the first electrode and the second electrode are as described above. When either or both of the first and second electrodes are transparent electrodes, the thickness of the transparent electrode is preferably 0.03 μm or more and 3 μm or less.

[0067] When manufacturing solar cells, cutting processes may be performed between each manufacturing step to form circuits. Examples of cutting processes include mechanical patterning and laser patterning.

[0068] [Step of forming the photoelectric conversion layer] The method for manufacturing a photoelectric conversion element according to the present disclosure includes the step of forming a photoelectric conversion layer between a first electrode and a second electrode, the photoelectric conversion layer containing a perovskite crystal structure. The step of forming the photoelectric conversion layer may include the step of applying a liquid containing the above-mentioned photoelectric conversion layer material. Examples of application methods include spin coating, blade coating, slit die coating, screen printing, bar coating, mold making, print transfer, immersion pulling, inkjet, spray, and vacuum deposition. These can be appropriately selected according to the characteristics of the photoelectric conversion layer to be manufactured, such as thickness control and orientation control.

[0069] Annealing may be performed under reduced pressure or in an inert atmosphere (nitrogen or argon atmosphere) to remove the material of the applied photoelectric conversion layer from the liquid or the dispersion medium. The temperature of the annealing treatment is preferably 40°C to 300°C, and more preferably 50°C to 150°C. Annealing is preferable because it can increase the contact area at the interface between the stacked layers, as the materials constituting each layer penetrate each other, thereby increasing the short-circuit current.

[0070] In the method for manufacturing a photoelectric conversion element of the present disclosure, the photoelectric conversion element has a crystal A that contacts the second charge transport layer, and a crystal B that covers the gap between adjacent crystals A, contacts the first charge transport layer, and does not contact the second charge transport layer. As described above, the explanation of crystals A and B is omitted.

[0071] [Steps for forming a first charge transport layer and a second charge transport layer] The method for manufacturing a photoelectric conversion element according to the present disclosure includes the steps of forming a first charge transport layer between a photoelectric conversion layer and a first electrode, and forming a second charge transport layer between a photoelectric conversion layer and a second electrode. The steps for forming the first charge transport layer and the steps for forming the second charge transport layer are preferably methods of applying a liquid containing the material for the first charge transport layer and a liquid containing the material for the second charge transport layer, respectively. Examples of application methods include spin coating, blade coating, slit die coating, screen printing, bar coating, mold making, print transfer, immersion and pull-up, inkjet, spray, and vacuum deposition.

[0072] [Modularization Process] The elements with electrodes formed may be sealed. Examples of sealing methods include sealing with resin or sealing with film. Examples of materials used for sealing include silazane, silicone rubber, resin having a siloxane skeleton, and glass. Furthermore, from the viewpoint of suppressing adhesion between elements that occurs when winding in a roll-to-roll manner, the surface of the sealed elements may be given a hairline finish.

[0073] [Die Coating Process] The method for manufacturing a photoelectric conversion element according to the present disclosure preferably includes a die coating process in the process of forming the photoelectric conversion layer. The die coating process preferably includes the steps of discharging a coating solution containing a photoelectric conversion layer precursor, a solvent, and an additive from a slit nozzle toward a heated and held object to be coated, in a humidity-controlled environment, and applying the coating solution to the object to be coated, and after forming a coating film from the coating solution, annealing the coating film together with the object to be coated.

[0074] The coating process preferably includes the steps of moving the object to be coated and the slit nozzle relative to each other, and supplying gas from a gas blow nozzle toward the surface of the coating liquid applied to the object to be coated, and it is preferable that the direction of gas supply is aligned with the relative movement direction of the object to be coated.

[0075] Figure 5 shows the die coating process 101. The die coating process includes discharging a coating solution 53 containing the photoelectric conversion layer precursor, which will become the photoelectric conversion layer, the solvent, and the additives from a slit nozzle 52 toward the heated and held object to be coated 50 in a humidity-controlled environment, thereby coating the object to be coated 50 with the coating solution 53.

[0076] The step of applying the coating liquid 53 to the object to be coated 50 includes a step of moving the object to be coated 50 and the slit nozzle 52 relative to each other, and supplying gas 56 from the gas blow nozzle 55 towards the coating liquid 53 applied to the object to be coated 50.

[0077] The direction of supply of the gas 56 is aligned with the relative movement direction of the object to be coated 50, and the process includes forming a coating film 54 from the coating liquid 53, and then annealing the coating film 54 together with the object to be coated 50 using the heater plate 58.

[0078] In the method for manufacturing a photoelectric element according to the present disclosure, it is preferable that the concentration of the additive in the coating solution is 35 mol / L or more and 45 mol / L or less. In this disclosure, the concentration of the additive can be confirmed by nuclear magnetic resonance (NMR) or gas chromatography-mass spectrometry (GC-MS). Furthermore, it is preferable that the solvent is composed of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide), and that the ratio (molar ratio) of DMF to DMSO is 3:1 in the coating solution. In this disclosure, the ratio of DMF to DMSO can be confirmed by nuclear magnetic resonance (NMR) or gas chromatography-mass spectrometry (GC-MS). In the method for manufacturing a photoelectric element according to the present disclosure, it is preferable that the humidity-controlled environment has a humidity of 10% or less. The coating solution supply unit 51 supplies the coating solution toward the slit nozzle 52.

[0079] The temperature at which the heater plate 58 heats and maintains the object to be coated 50, which is placed on the support plate 57, is preferably 30°C to 60°C. The distance L1 between the coating liquid discharge portion of the slit nozzle 52 and the object to be coated 50 is 100 μm. In the method for manufacturing the photoelectric conversion element of this disclosure, the relative movement speed in the relative movement step is preferably 5 m / s.

[0080] In the method for manufacturing a photoelectric conversion element according to the present disclosure, in the step of supplying gas, the wind velocity of the gas 56 on the upper surface of the coated film 54 (the surface of the coating liquid) is preferably 50 m / s or more and 70 m / s or less, and the temperature of the gas 56 is preferably 20°C or more and 40°C or less. The gas preferably contains at least one selected from the group consisting of nitrogen, helium, neon, argon, and air.

[0081] The distance L1 between the coating liquid discharge portion of the slit nozzle 52 and the object to be coated 50 is preferably 100 μm, the distance L2 between the gas supply port end of the gas blow nozzle 55 and the object to be coated 50 is preferably 10 mm, the horizontal distance L3 between the coating liquid discharge port end of the slit nozzle 52 and the gas supply port end is preferably 42 mm, and the angle θ between the gas supply port end of the gas blow nozzle 55 and the object to be coated is preferably 35.5°.

[0082] In the method for manufacturing the photoelectric conversion element of the present disclosure, it is preferable that the annealing of the coated film 54 is performed at 100°C for 10 minutes, followed by 150°C for 5 minutes. By doing so, the photoelectric conversion element of the present disclosure can achieve higher productivity and improved leakage resistance and conversion efficiency.

[0083] The present disclosure will be described in further detail below using examples and comparative examples. The present disclosure is not limited in any way by the following examples unless it exceeds the gist of the disclosure.

[0084] (Example 1) [Formation of the second charge transport layer] An ITO-coated glass substrate was cleaned, and tin oxide (2) adjusted to 3% by mass was applied thereon by spin coating. Then, it was heated at 150°C for 30 minutes to form a thin film-like second charge transport layer with a thickness of 15 nm.

[0085] [Formation of the photoelectric conversion layer] 67 mg of methylammonium chloride, 397 mg of methylammonium iodide, and 1152 mg of lead iodide were dissolved in 1396 mg of N,N-dimethylformamide and 493 mg of dimethyl sulfoxide, and the mixture was stirred for 1 hour to prepare a photoelectric conversion layer coating solution. By die-coating this coating solution onto the electron transport layer, MAPbI ３ A photoelectric conversion layer consisting of the following was formed.

[0086] The concentration of the additive in the coating solution is 40 mol / L, the solvent is composed of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide), the ratio (molar ratio) of DMF to DMSO is 3:1, the humidity environment is 6%, and the coating solution supply unit 51 supplies the coating solution toward the slit nozzle 52.

[0087] The heater plate 58 heated and held the object to be coated 50, which was placed on the support plate 57, at a temperature of 56°C. The distance L1 between the coating liquid discharge portion of the slit nozzle 52 and the object to be coated 50 was 100 μm. The relative moving speed was 5 m / s. The air velocity of the gas 56 on the upper surface of the coated film 54 was 53 m / s. The temperature of the gas 56 was 25°C. The distance L2 between the gas supply port end of the gas blow nozzle 55 and the object to be coated 50 was 10 mm. The horizontal distance L3 between the coating liquid discharge port end of the slit nozzle 52 and the gas supply port end was 42 mm. The angle θ between the gas supply port end of the gas blow nozzle 55 and the object to be coated was 35.5°. The coated film 54 was annealed at 100°C for 10 minutes, followed by 150°C for 5 minutes, to form a photoelectric conversion layer with a thickness of 220 nm.

[0088] [Formation of the first charge transport layer] 0.15 g of Spiro-OMeTAD, as the material for the first charge transport layer, was dissolved in 2.2 g of chlorobenzene. To this chlorobenzene solution, 36 μL of an acetonitrile solution obtained by dissolving 0.2 g of bis(trifluoromethanesulfonyl)imide lithium in 0.3 g of acetonitrile and 60 μL of 4-tert-butylpyridine (TBP) were added and mixed.

[0089] Furthermore, 58 μL of an acetonitrile solution obtained by dissolving 0.11 g of [Tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(3)tris(bis(trifluoromethylsulfonyl)imide)] in 0.3 g of acetonitrile was mixed to prepare the material solution for the first charge transport layer. This solution was then applied to the above photoelectric conversion layer by spin coating to form a hole transport layer that would become the first charge transport layer with a thickness of 285 nm.

[0090] [Formation of the first electrode] On the first charge transport layer, a layer with a thickness of 80 nm and an area of ​​0.09 cm² is formed. ２ Gold electrodes were formed by vacuum deposition to obtain a photoelectric conversion element.

[0091] (Example 2) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the thickness of the photoelectric conversion layer was set to 984 nm.

[0092] (Example 3) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the MACL concentration was 45 mol / L.

[0093] (Example 4) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the gas temperature was set to 20°C.

[0094] (Example 5) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the gas temperature was set to 40°C.

[0095] (Example 6) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the gas wind speed was set to 66 m / s.

[0096] (Example 7) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the temperature of the coated object was set to 32°C.

[0097] (Example 8) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the first charge transport layer was an electron transport layer and the second charge transport layer was a hole transport layer.

[0098] (Comparative Example 1) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the gas wind speed was set to 40 m / s.

[0099] (Comparative Example 2) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the gas wind speed was set to 76 m / s.

[0100] (Comparative Example 3) A photoelectric conversion element was obtained in the same manner as in Example 1, except that the solvent was composed of DMF and NMP (N-methyl-2-pyrrolidone), and the ratio (molar ratio) of DMF to NMP was 9:11.

[0101] [Evaluation] The following evaluations were performed on the photoelectric conversion elements obtained in each example and each comparative example. [Common evaluation items] The photoelectric conversion elements were cut and fixed to an inclined sample stage, and then confirmed by cross-sectional observation using a SEM (device: Carl Zeiss K.K., SmartSEM). In the observation, the photoelectric conversion layer and other layers were distinguished by the difference in contrast of the observed image and compositional analysis using the SEM-EDX function, and image processing was performed on images taken at a magnification of 50,000 times.

[0102] [Presence or absence of crystals A and B] Crystals A and B in the photoelectric conversion layer were identified by image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the presence or absence of crystals A and B was determined. The results are shown in Table 2.

[0103] [Presence or absence of crystal B covering the gaps between crystals A] Crystals A and B in the photoelectric conversion layer were identified by image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the presence or absence of crystal B covering the gaps between crystals A was determined. The results are shown in Table 2.

[0104] [Crystal Area of ​​Crystal A] The crystal area of ​​crystal A in the photoelectric conversion layer was measured using image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the average of these five average points was taken as the crystal area of ​​crystal A in the photoelectric conversion layer. The results are shown in Table 2.

[0105] [Measurement of the Thickness and Width of Crystal B] The thickness and width of crystal B in the photoelectric conversion layer were measured using image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the average of these five average points was taken as the thickness and width of crystal B in the photoelectric conversion layer. The results are shown in Table 2.

[0106] [Measurement of Average Film Thickness] The average film thickness of the charge transport layer and photoelectric conversion layer was measured using image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the average of these five average values ​​was taken as the average film thickness of the charge transport layer and photoelectric conversion layer. The results are shown in Table 2.

[0107] [Defect Rate of Photoelectric Conversion Layer] Using image processing obtained from the above common evaluation items, the area of ​​crystal A in the photoelectric conversion layer, the area of ​​crystal B, the area of ​​the void sealed by crystal B, and the area of ​​the void where the first charge transport layer and the second charge transport layer are short-circuited were measured. Five locations were randomly photographed, and the average of these five average points was taken as the average area for each component.

[0108] The total area was calculated by adding the average area of ​​crystal A, the average area of ​​crystal B, and the average void area sealed by crystal B. The defect rate was defined as the ratio of the average void area to the total area. The results are shown in Table 2.

[0109] [Area of ​​crystal A and crystal B in the photoelectric conversion layer] The crystal area, the area of ​​crystal A, and the area of ​​crystal B constituting the photoelectric conversion layer were measured using image processing obtained from the above common evaluation items. Five locations were randomly photographed, and the average of these five average points was taken as the average area for each crystal. The ratio of the sum of the average area of ​​crystal A and the average area of ​​crystal B to the average crystal area was defined as the abundance of crystal A and crystal B. The results are shown in Table 2.

[0110] [Evaluation of power generation efficiency] In Example 1, a power supply (KEITHLEY, Model 236) was connected between the electrodes of the photoelectric conversion element, and the intensity was set to 100 mW / cm. ２ The photoelectric conversion efficiency was evaluated by irradiating a constant amount of light using a solar simulator (manufactured by Yamashita Densou Co., Ltd.) and measuring the generated current and voltage. The series resistance was approximated by calculating the reciprocal of the slope near Voc in the obtained current-voltage curve, and the shunt resistance was approximated by calculating the reciprocal of the slope near Jsc in the obtained current-voltage curve.

[0111] Examples 2-6 and Comparative Examples 1-3 were evaluated in the same manner as Example 1, and the photoelectric conversion efficiency was determined. The results are shown as relative values ​​with the result of Example 1 set to 1. A relative value of 0.80 or higher was considered good. The results are shown in Table 2.

[0112]

[0113] This disclosure is not limited to the embodiments described above, and various modifications and alterations are possible without departing from the spirit and scope of this disclosure. Accordingly, the following claims are attached to make the scope of this disclosure public.

[0114] This application claims priority based on Japanese Patent Application No. 2024-197706, filed on November 12, 2024, and all of its contents are incorporated herein by reference.

[0115] 1 Photoelectric element 2 Substrate 3 Second electrode 4 Second charge transport layer 5 Photoelectric layer 5A Crystal A 5B Crystal B 6 First charge transport layer 7 First electrode 8 Sealing void 50 Object to be coated 51 Coating liquid supply unit 52 Slit nozzle 53 Coating liquid 54 Coating film 55 Gas blow nozzle 56 Gas 57 Support plate 58 Heater plate

Claims

1. A photoelectric conversion element comprising a first electrode, a second electrode, and a photoelectric conversion layer comprising a perovskite crystal disposed between the first electrode and the second electrode, wherein the photoelectric conversion element comprises a first charge transport layer between the photoelectric conversion layer and the first electrode, a second charge transport layer between the photoelectric conversion layer and the second electrode, and the photoelectric conversion element comprises a crystal A that contacts the second charge transport layer, and a crystal B that covers the gap between adjacent crystals A, contacts the first charge transport layer, and does not contact the second charge transport layer.

2. The area of ​​the surface of crystal A in the direction intersecting the layer thickness direction of the photoelectric conversion element is 0.05 μm². ２ The photoelectric conversion element described in claim 1 is as described above.

3. The photoelectric conversion element according to claim 1 or 2, wherein the thickness of the crystal B in the layer thickness direction of the photoelectric conversion element is less than the thickness of the first charge transport layer, and less than 300 nm.

4. The photoelectric conversion element according to any one of claims 1 to 3, wherein the width of the crystal B in the direction intersecting the layer thickness direction of the photoelectric conversion element is greater than the thickness of the crystal B in the layer thickness direction of the photoelectric conversion element.

5. The photoelectric conversion element according to any one of claims 1 to 4, wherein the thickness of the photoelectric conversion layer is 200 nm or more and 1000 nm or less.

6. When the total area is the sum of the area of ​​the surface of crystal A in a direction intersecting the thickness direction of the photoelectric conversion element, the area of ​​the surface of crystal B in a direction intersecting the thickness direction of the photoelectric conversion element, the area of ​​the void in a direction intersecting the thickness direction of the photoelectric conversion element, and the area of ​​the portion where the first charge transport layer and the second charge transport layer are short-circuited in a direction intersecting the thickness direction of the photoelectric conversion element, the ratio of the area of ​​the void in a direction intersecting the thickness direction of the photoelectric conversion element to the total area is 0.01% or less. A photoelectric conversion element according to any one of claims 1 to 5, wherein the ratio of the area of ​​the surface of the photoelectric conversion layer in a direction intersecting the thickness direction of the photoelectric conversion element to the area of ​​the surface of the crystal A in a direction intersecting the thickness direction of the photoelectric conversion element and the area of ​​the surface of the crystal B in a direction intersecting the thickness direction of the photoelectric conversion element is 97% or more.

7. The photoelectric conversion layer forms a planar heterojunction with the first charge transport layer or the second charge transport layer, and the photoelectric conversion layer is based on the general formula A ｏ B ｐ X ｑ The photoelectric element according to any one of claims 1 to 6, wherein the first cation is an organic cation and the second cation is a metal cation.

8. A coating solution for forming a photoelectric conversion element according to any one of claims 1 to 7, comprising a photoelectric conversion layer precursor, a solvent, and an additive, wherein the photoelectric conversion layer precursor is A １ X １ a compound represented by, and B １ X １ ２ a compound represented by, and contains at least one selected from the group consisting of, the A １ is a monovalent cation containing at least one selected from the group consisting of an alkali metal cation and an organic ammonium, the B １ is a divalent cation containing at least one selected from the group consisting of lead, tin, bismuth, and silver, the X １ is a monovalent anion of a halide ion, the solvent contains a plurality of solvent species and has a boiling point of 190 ° C or lower, and the additive is methylammonium chloride, the coating solution.

9. A method for manufacturing a photoelectric element, comprising the steps of: forming a first electrode; forming a second electrode; forming a photoelectric conversion layer between the first electrode and the second electrode, which includes a perovskite crystal; forming a first charge transport layer between the photoelectric conversion layer and the first electrode; and forming a second charge transport layer between the photoelectric conversion layer and the second electrode, wherein the photoelectric element has a crystal A that contacts the second charge transport layer, and a crystal B that covers the gap between adjacent crystals A, contacts the first charge transport layer, and does not contact the second charge transport layer.

10. The method for manufacturing a photoelectric element according to claim 9, wherein the step of forming the photoelectric conversion layer includes a die-coating step, the die-coating step includes discharging a coating solution containing a photoelectric conversion layer precursor, a solvent, and an additive from a slit nozzle toward a heated and held object to be coated, in a humidity-controlled environment, and coating the object with the coating solution; and after forming a coating film from the coating solution, annealing the coating film together with the object to be coated.

11. The method for manufacturing a photoelectric conversion element according to claim 10, wherein the coating step includes the steps of moving the object to be coated and the slit nozzle relative to each other, and supplying gas from a gas blow nozzle toward the surface of the coating liquid applied to the object to be coated, wherein the direction of the gas supply is aligned with the relative movement direction of the object to be coated.

12. The method for manufacturing a photoelectric element according to claim 10 or 11, wherein the concentration of the additive in the coating solution is 35 mol / L or more and 45 mol / L or less.

13. The method for manufacturing a photoelectric element according to any one of claims 10 to 12, wherein the solvent is composed of DMF and DMSO, and the ratio (molar ratio) of DMF to DMSO is 3:

1.

14. The method for manufacturing a photoelectric conversion element according to any one of claims 10 to 13, wherein the humidity-controlled environment has a humidity of 10% or less, and the temperature for heating and holding is 30°C or more and 60°C or less.

15. The method for manufacturing a photoelectric conversion element according to claim 11, wherein in the step of moving the elements relatively, the speed of movement is 5 m / s.

16. The method for manufacturing a photoelectric conversion element according to claim 11 or 15, wherein in the step of supplying the gas, the air velocity of the gas on the surface of the coating liquid is 50 m / s or more and 70 m / s or less.

17. The method for manufacturing a photoelectric conversion element according to claim 11, 15, or 16, wherein in the step of supplying the gas, the temperature of the gas is 20°C or higher and 40°C or lower.

18. The method for manufacturing a photoelectric conversion element according to claim 11, 15, 16, or 17, wherein the distance L1 between the coating liquid discharge portion of the slit nozzle and the object to be coated is 100 μm, the distance L2 between the gas supply port end of the gas blow nozzle and the object to be coated is 10 mm, the horizontal distance L3 between the coating liquid discharge port end of the slit nozzle and the gas supply port end is 42 mm, and the angle θ between the gas supply port end of the gas blow nozzle and the object to be coated is 35.5°.

19. The method for manufacturing a photoelectric conversion element according to any one of claims 10 to 18, wherein the annealing step is performed at 100°C for 10 minutes, followed by 150°C for 5 minutes.

20. The method for manufacturing a photoelectric element according to claim 11, 15, 16, 17, or 18, wherein the gas comprises at least one selected from the group consisting of nitrogen, helium, neon, argon, and air.

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