Potassium-doped perovskite and perovskite solar cells

Abstract

To provide a novel potassium-added perovskite and a perovskite solar cell which has high photoelectric conversion efficiency and high stability during light irradiation.SOLUTION: The perovskite solar cell includes at least a substrate 2, a transparent electrode 3, a hole selection layer 4, an active layer 5 comprising the potassium-added perovskite, an electron transport layer 6, an electron selection layer 7, and an electrode 8 in this order. The potassium-added perovskite comprises a potassium ion, an ion comprising a basic additive, and ABX3 (A represents a methylammonium ion, a formamidinium ion, a cesium ion or a rubidium ion; B represents a lead ion; and X represents a chloride ion, a bromide ion or an iodide ion).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a novel potassium-doped perovskite and a perovskite solar cell that has high photoelectric conversion efficiency and high stability during light irradiation. [Background technology]

[0002] A perovskite solar cell is a solar cell that uses a metal halide material having a perovskite structure (hereinafter referred to as "perovskite compound") as the photoelectric conversion layer. In a perovskite solar cell, there is a photoelectric conversion layer made of a perovskite compound having an octahedral crystal structure represented by AMX3 (where A is a monovalent cation, M is a divalent metal cation, and X is a halide ion) between a pair of opposing electrodes. When light is irradiated onto this photoelectric conversion layer, electrons flow to one electrode and holes flow to the other electrode, generating an electromotive force.

[0003] On the other hand, perovskite compounds are highly reactive under heat, temperature, or light. Cs is one of the most stable perovskite materials. 0.05 (Fa 0.85 MA 0.15 ) 0.95 (I 0.85 Br 0.15 )3(FA is formamidinium ion (HC(NH2)2 + ), MA is methylammonium ion (CH3NH3 + ) represents ). ) However, both FA and MA are highly reactive under heat, temperature, or light. Currently, the photoelectric conversion efficiency (PCE) of perovskite solar cells has risen to 25.2%, and stability is gradually improving, but stabilizing the photoelectric conversion layer is crucial for realizing stable perovskite solar cells. Furthermore, since cesium (Cs) is also a rare metal, it is not suitable for large-scale production, and improvements are needed to enhance the practicality of perovskite compounds.

[0004] For example, Non-Patent Document 1 describes a substrate made of glass / ITO / PEDOT:PSS with a CH3NH3PbI3 perovskite layer and fullerene (C60 ) A perovskite solar cell with a planar heterojunction (PHJ) structure formed by a spin-casting method with a layer is disclosed. In the perovskite solar cell, CH3NH3PbI3 perovskite serves as an electron acceptor, and fullerene (C 60 ) acts as an electron donor, and the interface between the CH3NH3PbI3 perovskite layer and the fullerene (C 60 ) layer exhibits a photovoltaic effect under light irradiation.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the perovskite solar cell described in Non-Patent Document 1, although the open-circuit voltage (V OC ) is as high as 0.75V, the short-circuit current density (J SC [[ID=3)2]]) is low, so the PCE is as low as 3.9%, and there is room for improvement towards higher efficiency, such as the thickness of the perovskite layer, or the solvent, solution concentration, preheating temperature or atmosphere during spin-casting.

[0007] In addition, for the practical application of perovskite solar cells, in addition to higher efficiency, it is necessary to pass various reliability tests such as stability during light irradiation and durability at high temperature and high humidity. Therefore, the development of the composition and manufacturing method of perovskite solar cells is very important.

[0008] The present invention aims to provide a novel potassium-doped perovskite and a perovskite solar cell that has high conversion efficiency and stability during light irradiation. [Means for solving the problem]

[0009] The present invention consists of the following: [1] A potassium-doped perovskite having a crystal structure represented as KHoAFAPbI3 (where HoA represents the hydroxylammonium ion and FA represents the formamidinium ion). [2] The device comprises, in this order, a substrate, a transparent electrode, a hole-selective layer, an active layer made of potassium-doped perovskite, an electron transport layer, an electron-selective layer, and an electrode. A perovskite solar cell characterized in that the potassium-doped perovskite comprises potassium ions, ions consisting of a basic additive, and ABX3 (where A represents methylammonium ions, formamidinium ions, cesium ions, or rubidium ions, B represents lead ions, and X represents chloride ions, bromide ions, or iodide ions).

[0010] [3] The perovskite solar cell according to [2], wherein the ion comprising the basic additive is a hydroxylammonium ion, a methoxyammonium ion, a hydrazine ion, or a guanidine ion. [4] The perovskite solar cell according to [2] or [3], wherein, in a total of 100 mol% of potassium ions constituting the potassium-doped perovskite, ions consisting of a basic additive, and ABX3 (where A represents methylammonium ions, formamidinium ions, cesium ions, or rubidium ions, B represents lead ions, and X represents chloride ions, bromide ions, or iodide ions), potassium ions make up 1 to 15 mol%, ions consisting of a basic additive make up 1 to 15 mol%, and ABX3 makes up 80 to 98 mol%.

[0011] [5] The hole-selective layer is composed of a phosphonic acid-based self-assembled monolayer material represented by the following chemical formula ((HO)2P(=O)R; R represents a (9H-carbazol-9-yl)methyl group or a 4-(diphenylamino)phenyl group.), and the perovskite solar cell according to any one of [2] to [4]. [Chemical formula] In the chemical formula, * represents the bonding position. [Advantages of the Invention]

[0012] According to the present invention, by introducing a self-assembled monolayer (SAM) into the hole-selective layer 4 and a potassium-added perovskite into the active layer 5, a perovskite solar cell that achieves both power generation characteristics and light stability can be provided. Specifically, as the potassium-added perovskite, by using both a cation such as methylammonium ion or formamidinium ion and a cation based on a basic additive, a photoelectric conversion efficiency of 18% is shown, and regarding the durability under continuous light irradiation in the atmosphere, even after 100 hours, 75% of the initial photoelectric conversion efficiency can be maintained. In particular, in a potassium-added perovskite having potassium ions and hydroxylammonium ions, using hydroxylamine hydrochloride (NH2OH·HCl) as the basic additive and doping with potassium iodide, the interaction of the perovskite crystal structure is strengthened, the hysteresis due to the voltage sweep direction is reduced, and the reliability of the perovskite solar cell can be improved. [Brief Description of the Drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of a device structure which is an embodiment of the perovskite solar cell of the present invention. [Figure 2]Figure 2(a) shows the materials for each layer of the perovskite solar cell of the present invention used in Examples 1 to 4. Figure 2(b) shows the current density-voltage relationship for the device of Example 1 (FA0.96K0.03HoA0.01PbI3) and the reference example device (FAPbI3).

[0014] [Figure 3] Figure 3(a) shows the current density-voltage relationship of the reference example device, Figure 3(b) shows the current density-voltage relationship of the device in Example 3, Figure 3(c) shows the current density-voltage relationship of the device in Example 2, and Figure 3(d) shows the current density-voltage relationship of the device in Example 4. [Figure 4] Figure 4(a) shows the relationship between current density and voltage for the device of Example 1, and Figure 4(b) shows the relationship between photoelectric conversion efficiency and time when light is continuously irradiated onto the device of Example 1. [Modes for carrying out the invention]

[0015] The potassium-doped perovskite and perovskite solar cell of the present invention will be described in detail below. [Potassium-fortified perovskite] The potassium-doped perovskite of the present invention is a novel compound having a crystal structure represented by KHoAFAPbI3 (HoA represents a hydroxylammonium ion, and FA represents a formamidinium ion). In KHoAFAPbI3, the general formula ABX3 (A: monovalent cation, B: divalent cation, X: halide ion) is such that A is a formamidinium ion (FA + ), B is lead ion (Pb 2+ ), X is an iodide ion (I - Formamidinium lead iodide perovskite (FAPbI3) substituted with hydroxylammonium ions (HoA + ) is added, and further potassium ions (K + It has a doped structure. KHoAFAPbI3 can be synthesized by adding lead(II) iodide (PbI2) to a precursor obtained by reacting formamidine hydroiodide (HC(=NH)NH2·HI) with hydroxylamine hydrochloride (NH2OH·HCl), and then adding potassium iodide (KI).

[0016] Iodide ions (I) that make up KHoAFAPbI3 - The diffusion barrier of ) at room temperature is 0.45 eV, and the diffusion barriers of formamidinium ions and hydroxylammonium ions are approximately 0.57-0.61 eV, which is relatively small compared to ordinary ion conductors. This indicates that in KHoAFAPbI3, iodide ions (I) can be diffused through vacancies in its perovskite structure. - ) as well as the cation molecule formamidinium ion (FA + ) and hydroxylammonium ion (HoA + This indicates that the cation molecules are easily diffused. The cation molecules are thought to rotate within the A sites of the perovskite structure or move to adjacent A sites through vacancies, thereby promoting the induction of an electric field during power generation. Therefore, it is suitable as a material for the active layer 5, which is the photoelectric conversion layer of a perovskite solar cell. Using KHoAFAPbI3 as the material for the active layer 5 contributes to the high durability and high stability of the perovskite solar cell.

[0017] [Perovskite solar cells] The perovskite solar cell of the present invention comprises, in this order, at least a substrate, a transparent electrode, a hole-selective layer, an active layer made of potassium-doped perovskite, an electron transport layer, an electron-selective layer, and a counter electrode. The perovskite solar cell will be described with reference to the drawings. The perovskite solar cell 1 shown in Figure 1 has a transparent electrode 3, a hole-selective layer 4, an active layer 5 made of potassium-doped perovskite, an electron transport layer 6, an electron-selective layer 7, and a counter electrode 8 stacked on a substrate 2.

[0018] First, the basic operation and effects of the perovskite solar cell 1 will be explained. When light is irradiated onto the perovskite solar cell 1, the active layer 5 (hereinafter simply referred to as "active layer 5"), which is made of potassium-doped perovskite, absorbs the light and generates excited electrons and holes. The holes generated in the active layer 5 move to the transparent electrode 3. On the other hand, the excited electrons move to the counter electrode 8. As a result, the perovskite solar cell 1 can extract current from the transparent electrode 3 as the positive electrode and the counter electrode 8 as the negative electrode. The perovskite solar cell 1 of the present invention is an inverted stacked type. Solar cells have a positive electrode and a negative electrode, but an inverted stacked organic thin-film solar cell, such as the perovskite solar cell 1, in which the stacking order is reversed from that of conventional solar cells, is extremely stable, can be produced in the atmosphere, and can maintain its stability even after long-term use.

[0019] In a perovskite solar cell, substrate 2 is positioned on the side where light is incident. From the viewpoint of photoelectric conversion efficiency, substrate 2 is preferably an insulating transparent substrate made of glass, resin, or an organic material. A transparent substrate is a light-transmitting electrode. "Transparent" means having a light transmittance of 50% or more in accordance with the JIS K 7361-1:1997 standard.

[0020] A transparent electrode 3, which serves as the positive electrode, is provided on the surface of the substrate 2. Transparent electrode materials such as fluorine-doped tin oxide (FTO), indium tin oxide (ITO), zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and indium gallium zinc oxide (IGZO) can be used for the transparent electrode 3. Of these, FTO and ITO are preferred because they are conductive and do not impede the transparency of the substrate 2. The transparent electrode 3 is formed by sputtering, thermal deposition, plating, or spray pyrolysis. If necessary, the transparent electrode may be patterned (etched) into a desired shape.

[0021] A hole-selection layer 4 is provided on the surface of the transparent electrode 3, which is placed on the substrate 2. The hole-selection layer 4 improves the flow of holes and enhances the photoelectric conversion efficiency. The hole-selective layer 4 is preferably a self-assembled monolayer (SAM). A SAM is a film obtained by the adsorption of an organic compound, particularly an organic compound having an adsorption group, onto an inorganic material via the adsorption group, and in its adsorption mechanism, only a monolayer is self-assembled between the organic compound and the inorganic material.

[0022] Organic compounds that form SAMs are generally compounds that have an adsorption group capable of binding to an inorganic material, a terminal group on the opposite side that controls the surface energy of the inorganic material, such as an electron-donating group or an electron-withdrawing group, and an aromatic group or a linear or branched carbon chain that connects the adsorption group and the terminal group.

[0023] Examples of the adsorbent groups include phosphonyl groups (-PO(OH)2), carboxyl groups (-COOH), sulfhydryl groups (-SH), carbonyl chlorides (-COCl), carbonyl bromides (-COBr), chlorosilanes (-SiCl), bromosilanes (-SiBr), and alkoxysilanes (-SiOR).

[0024] Examples of the terminal groups include electron-donating groups such as hydroxyl groups, amino groups, (9H-carbazole-9-yl)methyl groups, methoxy groups, 4-(diphenylamino)phenyl groups, and phenoxy groups, as well as electron-withdrawing groups such as trifluoromethyl groups. Examples of the aforementioned aromatic group include the phenylene group. Examples of the carbon chain include linear or branched alkylene groups having 3 to 10 carbon atoms.

[0025] Of these, phosphonic acid derivatives represented by the following general formula RP(=O)(OH)2, wherein R is a (9H-carbazole-9-yl)methyl group or a 4-(diphenylamino)phenyl group, are preferred. [ka] In chemical formulas, * indicates a bond position.

[0026] The hole-selective layer 4 may be formed solely of SAM, or a layer made of SAM and other materials may be formed between the hole-selective layer 4 and the active layer 5. Other materials include, for example, oxides of at least one metal selected from the group consisting of molybdenum, tungsten, vanadium, nickel, and rhenium; poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS); and conductive organic compounds having an arylamine skeleton such as triphenylamine or carbazole.

[0027] The inclusion of SAM in the hole-selective layer 4 reduces the potential barrier at the material interface forming the hole-selective layer 4, facilitating hole injection into the HOMO. This reduces large level mismatches at the interface between the hole-selective layer 4 and the active layer 5, even with continuous light irradiation. As a result, the short-circuit current density (J) SC The attenuation of ) is suppressed, improving the durability of the perovskite solar cell 1.

[0028] For SAM formation, dry processes such as vacuum deposition, sputtering, and molecular beam epitaxy are used; and wet processes such as spin coating, dip coating, and Langmuir-Bludget (LB) are used. Wet processes such as spin coating are preferred from the viewpoint of ease of film formation.

[0029] The thickness of the hole-selective layer 4 is typically 1 to 2000 nm, preferably 1 to 1000 nm, and more preferably 1 to 500 nm. If the thickness of the hole-selective layer 4 is within the above range, it will not create resistance during hole transport, and the photoelectric conversion efficiency will be high.

[0030] The active layer 5 functions to convert light energy into electrical energy using photovoltaic power. The active layer 5 is also called the photoelectric conversion layer. The active layer 5 according to the present invention is made of potassium-doped perovskite. When light is absorbed by the potassium-doped perovskite, excitons are generated and charge separation occurs into holes and electrons.

[0031] Potassium-doped perovskites consist of potassium ions, ions comprising basic additives, and ABX3 (where A represents methylammonium ions, formamidinium ions, cesium ions, or rubidium ions; B represents lead ions; and X represents chloride ions, bromide ions, or iodide ions). Note that A in ABX3 may be a methylammonium ion partially substituted with cesium or rubidium.

[0032] The ions consisting of basic additives are specifically guanidine ions, methoxyammonium ions, hydroxylammonium ions, or hydrazine ions. These ions have a larger ionic radius than A in ABX3 and act as cations in potassium-doped perovskites. Furthermore, these ions have a larger ionic radius than potassium ions produced by potassium ion doping. Basic additives used include guanidine hydroiodide (HN=C(NH2)2·HI), methoxyamine hydrochloride (CH3ONH2·HCl), hydroxylamine hydrochloride (NH2OH·HCl), and hydrazine dihydrochloride (H2NNH2·2HCl).

[0033] In the hole-selective layer 4, when a phosphonic acid derivative is used as the SAM, the basic additive suppresses the decomposition of the phosphonic acid derivative and stabilizes it. When the function of the hole-selective layer 4 is stabilized, the stability of the perovskite solar cell 1 during light irradiation is greatly improved. Furthermore, the improved stability of the phosphonic acid derivative stabilizes the octahedral structure of the potassium-doped perovskite that forms the active layer 5. When NH2OH·HCl is used as the basic additive, the reliability of the perovskite solar cell 1 is significantly improved, suggesting that the hydroxylammonium ion contributes to the deactivation of the SAM and the potassium-doped perovskite surface.

[0034] The active layer 5 can be formed, for example, by spin-coating a solution of formamidine hydroiodide (HC(=NH)NH2·HI) and potassium iodide (KI), along with a basic additive, in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0035] The ratio of potassium ions, ions from the basic additive, and ABX3 that form the potassium-doped perovskite is, in molar ratio, potassium ions:ions from the basic additive:ABX3 = 1~15:1~15:80~98, preferably 1~3:1~5:93~96. The film quality of the potassium-doped perovskite that forms the active layer 5 is evaluated by structural analysis using X-ray diffraction, UV-vis absorption spectroscopy, and observation using scanning electron microscopy (SEM) and atomic force microscopy (AFM).

[0036] By using a potassium-doped perovskite containing potassium ions, basic additives, and ABX3 in the aforementioned ratios as the active layer 5, the photoelectric conversion efficiency of the perovskite solar cell 1 can be improved. The thickness of the active layer 5 is typically 50 to 1000 nm, preferably 300 to 600 nm. If the thickness of the active layer 5 is within this range, it will not create resistance during hole transport, and the photoelectric conversion efficiency will be high.

[0037] The electron transport layer 6 and electron selector layer 7 improve the flow of electrons generated in the active layer 5 to the counter electrode 8, thereby improving the photoelectric conversion efficiency. Specifically, they prevent the movement of holes and prevent short circuits between the negative electrode (counter electrode 8) and the potassium-doped perovskite in the active layer 5.

[0038] Materials used for the electron transport layer 6 and electron selective layer 7 include phenanthroline derivatives such as bathocuproine (BCP) and fullerene (C 60 n-type semiconductor materials such as naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic diimide, perylenetetracarboxylic anhydride, and perylenetetracarboxylic diimide; amine compounds such as amine-based silane coupling agents; and titanium dioxide (TiO2). x These are n-type inorganic oxides such as zinc oxide (ZnO) and gallium(III) oxide (Ga2O3).

[0039] The thickness of the electron transport layer 6 and the electron selective layer 7 is typically 5 to 50 nm. From the viewpoint of preventing leakage current, 5 to 1000 nm is preferred, and from the viewpoint of maintaining high transmittance and low resistance, 5 to 150 nm is more preferred.

[0040] Counter electrode 8 is the negative electrode. The counter electrode 8 can be made of metals such as zinc, platinum, gold, silver, copper, and aluminum, as well as metal oxides such as tin(IV) oxide (SnO2), cadmium oxide (CdO), and ZnO.

[0041] The counter electrode 8 is formed, for example, by bonding, sputtering, chemical vapor deposition (CVD), spray pyrolysis deposition (SPD), and coating methods (e.g., dipping and spin coating). [Examples]

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples. [Example 1] The ITO / glass substrate was ultrasonically cleaned in isopropanol, acetone, and pure water for 1 hour, then dried with a nitrogen flow and treated with ultraviolet light for 30 minutes. Subsequently, a SAM film was deposited on the ITO / glass substrate by spin coating at 3000 rpm for 30 seconds, and then heated at 100°C for 10 minutes. Lead(II) iodide (PbI2) (1.48M) and formamidine hydroiodide (HC(=NH)NH2·HI) (1.48M) were dissolved in a mixed solvent of DMF and DMSO (DMF:DMSO=4:1, vol / vol), and then 1-10 μl of hydroxylamine hydrochloride (NH2OH·HCl) (1.48M) and 1-10 μl of potassium iodide (KI) (1.48M) were added. This mixed solution was spin-coated onto a SAM at 1000 rpm for 10 seconds, and then spin-coated again at 6000 rpm for 30 seconds. 15 seconds after the start of spin-coating, 150 μl of chlorobenzene was added dropwise, and then the substrate was heated at 150°C for 30 minutes to deposit a dark-colored potassium-doped perovskite film. Next, 20nm fullerene (C 60 ), 8nm vasocuproin (BCP), and a 70nm Ag electrode were sequentially deposited under high vacuum.

[0043] The device structure of the obtained perovskite solar cell (substrate 2 / transparent electrode 3 / hole-selective layer 4 / active layer 5 / electron transport layer 6 / electron-selective layer 7 / counter electrode 8) is as follows. Glass / ITO / Self-assembled monolayer (SAM) / FA 0.96 K 0.03 HoA 0.01 PbI3 / C 60 (20nm) / BCP (8nm) / Ag (70nm) FA 0.96 K 0.03 HoA 0.01 In PbI3, FA represents formamidinium ions and HoA represents hydroxylammonium ions. The numbers in parentheses (nm) represent the thickness of the layer.

[0044] The characteristics of the solar cell and its changes over time under continuous light irradiation (1 Sun) were measured. Figure 4(b) shows the relationship between photoelectric conversion efficiency and time when the device is continuously irradiated with light. As shown in Figure 4(b), a photoelectric conversion efficiency of over 18% was obtained with a composition containing hydroxylamine (HoA) in the perovskite layer. When the changes over time under continuous light irradiation (1 Sun) were measured, 75% of the initial conversion efficiency was maintained even after approximately 100 hours, indicating a significant improvement in stability. Furthermore, as shown in Figure 2(b), the hysteresis that appears during voltage sweep is small and does not change regardless of the sweep direction. SC and V OC Since the value remained almost unchanged, it was determined that the effect of hysteresis did not need to be considered. Figure 4(a) shows the current density-voltage relationship of the device.

[0045] [Example 2] In Example 1, a perovskite solar cell device was fabricated in the same manner as in Example 1, except that methoxyamine hydrochloride (CH3ONH2·HCl) was used as the basic additive instead of hydroxylamine hydrochloride (NH2OH·HCl), and the output characteristics were evaluated. Figure 3(c) shows the relationship between the current density and voltage of the device.

[0046] [Example 3] In this study, a perovskite solar cell device was fabricated in the same manner as in Example 1, except that guanidine hydroiodide (HN=C(NH2)2·HI) was used as the basic additive instead of hydroxylamine hydrochloride (NH2OH·HCl), and the output characteristics were evaluated. Figure 3(b) shows the relationship between the current density and voltage of the device.

[0047] [Example 4] In Example 1, a perovskite solar cell device was fabricated in the same manner as in Example 1, except that hydrazine dihydrochloride (H2NNH2·2HCl) was used as the basic additive instead of hydroxylamine hydrochloride (NH2OH·HCl), and the output characteristics were evaluated. Figure 3(d) shows the relationship between the current density and voltage of the device.

[0048] [Reference example] In this study, a perovskite solar cell device was fabricated and its output evaluated in the same manner as in Example 1, except that potassium iodide and basic additives were not used. Figures 2(b) and 3(a) show the current density-voltage relationship of the device. The reference example device exhibited different hysteresis in the forward and reverse sweep directions and had lower reproducibility compared to Examples 1-4.

[0049] Table 1 shows the output characteristics (short-circuit current density (Jsc), open-circuit voltage (Voc), curve factor (FF), photoelectric conversion efficiency (PCE), and hysteresis index (HI)) of the perovskite solar cells of Examples 1 to 4 and the Reference Example. [Table 1]

[0050] As shown in Table 1, devices using potassium-doped perovskite containing both formamidinium ions and cations based on basic additives, as in Examples 1-4, showed improved photoelectric conversion efficiency compared to the control device in the reference example. In particular, the device in Example 1, which used hydroxylamine hydrochloride (NH2OH·HCl) as the basic additive, showed good photoelectric conversion efficiency (17-18%). It was found that the hydroxylammonium ions strengthened the interactions within the perovskite structure, improving stability against light in the atmosphere. As a result, it was found that it is possible to provide a perovskite solar cell that achieves both power generation characteristics and photostability by improving the stability of the perovskite film and the stability of the device against light irradiation without using materials such as methylammonium or cesium as in the conventional method. [Industrial applicability]

[0051] The perovskite solar cell of the present invention is suitable for use in building-integrated solar cells, automotive organic solar cells, or agricultural organic solar cells, as it achieves both light transmittance and power generation characteristics. [Explanation of Symbols]

[0052] 1. Perovskite solar cells 2 circuit boards 3 Transparent electrode 4. Hole-selection layer 5. Active layer consisting of potassium-doped perovskite 6 Electron transport layer 7 Electron-Selective Layer 8 pairs of electrodes

Claims

1. KHoAFAPbi 3 A potassium-doped perovskite having a crystal structure represented by (HoA represents the hydroxylammonium ion, and FA represents the formamidinium ion).

2. At a minimum, the device comprises a substrate, a transparent electrode, a hole-selective layer, an active layer made of potassium-doped perovskite, an electron transport layer, an electron-selective layer, and an electrode, in this order. A perovskite solar cell wherein the potassium-doped perovskite is the potassium-doped perovskite described in claim 1.

3. The potassium ions, hydroxylammonium ions, and ABX constituting the potassium-doped perovskite ３ (A represents formamidinium ion, B represents lead ion, and X represents iodide ion.) In a total of 100 mol%, potassium ions are present at 1-3 mol%, hydroxylammonium ions at 1-3 mol%, and ABX ３ The perovskite solar cell according to claim 2, wherein the content is 93 to 96 mol%.

4. The hole-selective layer is a phosphonic acid-based self-assembled monolayer material represented by the following chemical formula ((HO) ２ A perovskite solar cell according to claim 2 or 3, comprising P(=O)R; where R represents a (9H-carbazole-9-yl)methyl group or a 4-(diphenylamino)phenyl group. 【Chemistry 1】

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