Perovskite precursor solution, method for manufacturing solar cell, and solar cell

Abstract

A perovskite precursor solution according to one aspect of the present invention contains: a solvent; a perovskite precursor that forms a perovskite compound which performs photoelectric conversion; a hole transport layer-forming compound that forms a self-assembled monolayer which has hole-selective permeability; and an optionally substituted chain hydrocarbon group having 5 or more carbon atoms and an ionic functional group.

Description

Perovskite precursor liquid, solar cell manufacturing method, and solar cell

[0001] The present invention relates to a perovskite precursor liquid, a solar cell manufacturing method, and a solar cell.

[0002] The use of solar cells is expanding as an energy source with a low environmental impact. Perovskite solar cells, which have a photoelectric conversion layer primarily composed of a perovskite compound, are known as one type of solar cell. A basic perovskite solar cell is formed by stacking a first electrode layer, a first charge transport layer, a perovskite photoelectric conversion layer, a second charge transport layer, and a second electrode layer, in this order, on a substrate. Furthermore, because perovskite solar cells have a different absorption wavelength than solar cells that use a crystalline silicon substrate as a photoelectric conversion layer, they can also be stacked on crystalline silicon solar cells. The charge transport layer selectively passes electrons or holes, but also creates electrical resistance that generates internal losses. Therefore, to reduce electrical resistance, a technique has been proposed in which a thin charge transport layer is formed using a self-assembled monolayer composed of a charge-selective carbazole compound or the like (see, for example, Patent Document 1).

[0003] Generally, forming a self-assembled monolayer requires applying a material solution thinly and evenly by spin coating or the like. When enlarging a solar cell, it is difficult to employ spin coating, and it is desirable to apply the material by methods such as die coating or bar coating. Furthermore, since perovskite photoelectric conversion layers are generally also formed by coating, forming the first charge transport layer by coating requires repeated coating and drying. It has been reported that, in order to efficiently manufacture solar cells, a carbazole compound that forms a hole-selective self-assembled monolayer is incorporated into a perovskite precursor solution and then applied, whereby the carbazole compound forms a self-assembled monolayer at the interface of the coating film with the electrode layer, thereby simultaneously forming a hole transport layer and a perovskite photoelectric conversion layer (see, for example, Non-Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2023-46212

[0005] "Co-deposition of hole-selective contact and absorber for improving the processability of perovskite solar cells", Nature Energy, 2023, vol. 8, p. 462-472

[0006] When a carbazole compound is blended into a perovskite precursor liquid as in Non-Patent Document 1, it is necessary to blend an excess amount of the carbazole compound relative to the coating area in order to form a continuous hole transport layer. As a result of the inventors' investigations, it was confirmed that an excess amount of the carbazole compound in the precursor solution forms a layer on the surface of the coating film and can inhibit electron transport.

[0007] An object of the present invention is to provide a perovskite precursor liquid that can simultaneously form a hole transport layer, a photoelectric conversion layer, and a passivation layer while suppressing the formation of a layer that inhibits electron transport, a solar cell manufacturing method, and a solar cell that can be easily manufactured.

[0008] (1) A perovskite precursor liquid according to a first aspect of the present invention includes a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer that has hole selective permeability, and an organic compound that has a chain hydrocarbon group having 5 or more carbon atoms that may be substituted and an ionic functional group.

[0009] (2) In the perovskite precursor liquid of (1), the ionic functional group may be any one of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphonic acid group, a phosphoric acid group, a hydroxyl group, a carboxyl group, and a sulfonyl group.

[0010] (3) In the perovskite precursor liquid of (1), the organic compound may be a halide salt.

[0011] (4) In the perovskite precursor liquids of (1) to (3), the perovskite precursor may contain a metal halide including at least one of a lead halide and a tin halide, and a halogenated organic compound or an alkali metal halide, and the molar concentration of the metal moiety of the metal halide may be in excess of the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal by 0.5 mol % or more and 10 mol % or less.

[0012] (5) The perovskite precursor liquids (1) to (4) may further contain an organic hydrochloride that promotes the growth of crystals of the perovskite compound.

[0013] (6) The perovskite precursor liquids (1) to (5) may further contain at least one of a fluorine-containing organic compound, piperazine, or a piperazine derivative, and a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle.

[0014] (7) In the perovskite precursor liquid of (6), the fluorine-containing organic compound may have at its terminal at least one of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphate group, a phosphonate group, a hydroxyl group, a carboxyl group, a sulfonyl group, or an ionized form thereof, and may have a carbon skeleton containing an alkyl chain or benzene in which hydrogen is substituted with fluorine or a trifluoromethyl group.

[0015] (8) A solar cell manufacturing method according to a second aspect of the present invention includes the steps of: applying the perovskite precursor liquid to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

[0016] (9) A solar cell according to a third aspect of the present invention includes a plate- or sheet-like substrate, a first electrode layer laminated on one main surface of the substrate, a hole transport layer laminated on the first electrode layer and made of a film of a hole transport layer-forming compound having hole selective permeability, a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound, an excess material layer partially laminated on the photoelectric conversion layer and containing the hole transport layer-forming compound, a passivation layer laminated in a region of the photoelectric conversion layer where the excess material layer is not present and containing an organic compound having a chain hydrocarbon group having 5 or more carbon atoms which may be substituted and an ionic functional group, and a second electrode layer laminated on the one side of the excess material layer and the passivation layer.

[0017] (10) In the solar cell of (8), the photoelectric conversion layer may have an impurity film containing a halide of a metal atom in the perovskite compound at the grain boundary of the crystal of the perovskite compound.

[0018] (11) The solar cell of (8) to (9) may further include an electron transport layer laminated between the excess material layer and the passivation layer and the second electrode layer.

[0019] (12) A perovskite precursor liquid according to a fourth aspect of the present invention includes a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer having hole selective permeability, and at least one of a piperazine derivative and a piperazine derivative.

[0020] (13) In the perovskite precursor liquid of (12), the piperazine derivative may be a halide salt.

[0021] (14) In the perovskite precursor liquids of (12) and (13), the piperazine derivative may have an alkyl chain or a fluorine-containing organic group bonded to one of the nitrogen atoms.

[0022] (15) The perovskite precursor liquids (12) to (14) may further contain a fluorine-containing organic compound.

[0023] (16) In the perovskite precursor liquids of (12) to (15), the fluorine-containing organic compound may have at its terminal at least one of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphate group, a phosphonate group, a hydroxyl group, a carboxyl group, a sulfonyl group, or an ionized form thereof, and may have a carbon skeleton containing an alkyl chain or benzene in which hydrogen is substituted with fluorine or a trifluoromethyl group.

[0024] (17) In the perovskite precursor liquids of (11) to (16), the perovskite precursor may contain a metal halide including a lead halide, and a halogenated organic compound or an alkali metal halide, and the molar concentration of the metal may be in excess of the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal by 0.5 mol % or more and 10 mol % or less.

[0025] (18) (11) to (17) The perovskite precursor liquid described above may further contain a hydrochloride that promotes the growth of crystals of the perovskite compound.

[0026] (19) A solar cell manufacturing method according to a fifth aspect of the present invention includes the steps of: applying the perovskite precursor liquid to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

[0027] (20) A solar cell according to a sixth aspect of the present invention includes a plate- or sheet-like substrate, a first electrode layer laminated on one main surface of the substrate, a hole transport layer laminated on the first electrode layer and made of a film of a hole transport layer-forming compound having hole selective permeability, a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound, an excess material layer partially laminated on the photoelectric conversion layer and made of the hole transport layer-forming compound, a passivation layer containing at least one of piperazine and a piperazine derivative laminated in a region of the photoelectric conversion layer where the excess material layer is not present, and a second electrode layer laminated on the one side of the excess material layer and the passivation layer.

[0028] (21) In the solar cell of (19), the photoelectric conversion layer may have an impurity film containing a halide of a metal atom in the perovskite compound at the grain boundary of the crystal of the perovskite compound.

[0029] (22) The solar cell of (19) to (20) may further include an electron transport layer laminated between the excess material layer and the passivation layer and the second electrode layer.

[0030] (23) A perovskite precursor liquid according to a seventh aspect of the present invention includes a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer, and a polymer passivation compound that has a repeating unit having a nitrogen-containing heterocycle.

[0031] (24) In the perovskite precursor liquid of (23), the polymer passivation compound may have a polyvinyl skeleton.

[0032] (25) In the perovskite precursor liquids of (23) and (24), the nitrogen-containing heterocycle may be any one of pyridine, pyrrolidone, phthalimide, caprolactam, imidazole, imidazolium, triazole, thiazole, piperidium, and derivatives thereof.

[0033] (26) In the perovskite precursor liquids of (23) to (25), the perovskite compound is an ABX compound in which X is a halogen atom. ３ The molar concentration of X may be higher than the molar concentration of at least one of A and B.

[0034] (27) A solar cell manufacturing method according to an eighth aspect of the present invention includes the steps of: applying the perovskite precursor liquid to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

[0035] (28) A solar cell according to a ninth aspect of the present invention includes a plate- or sheet-like substrate, a first electrode layer laminated on one main surface of the substrate, a hole transport layer laminated on the first electrode layer and consisting of a film of a hole transport layer-forming compound, a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound, an excess material layer partially laminated on the photoelectric conversion layer and consisting of the hole transport layer-forming compound, a passivation layer laminated in a region of the photoelectric conversion layer where the excess material layer is absent and containing a polymer passivation compound having a repeating unit having a nitrogen-containing heterocycle, and a second electrode layer laminated on the one side of the excess material layer and the passivation layer.

[0036] (29) In the solar cell of (28), the passivation layer may contain a halide of the polymer passivation compound.

[0037] The present invention provides a perovskite precursor liquid that can simultaneously form a hole transport layer, a photoelectric conversion layer, and a passivation layer while suppressing the formation of a layer that inhibits electron transport, a solar cell manufacturing method, and a solar cell that can be easily manufactured.

[0038] Fig. 1 is a schematic cross-sectional view showing the configuration of a solar cell according to a first embodiment of the present invention; Fig. 2 is a flowchart showing the steps of a solar cell manufacturing method according to the first embodiment of the present invention; Fig. 3 is a schematic cross-sectional view showing the configuration of a solar cell according to a second embodiment of the present invention; Fig. 4 is a flowchart showing the steps of a solar cell manufacturing method according to the second embodiment of the present invention; Fig. 5 is a schematic cross-sectional view showing the configuration of a solar cell according to a third embodiment of the present invention; Fig. 6 is a flowchart showing the steps of a solar cell manufacturing method according to the third embodiment of the present invention.

[0039] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing the configuration of a solar cell 1 according to a first embodiment of the present invention. Note that the dimensions of various components in the drawing have been adjusted for ease of viewing.

[0040] The solar cell 1 comprises a plate- or sheet-shaped substrate 10, a first electrode layer 20 laminated on one main surface (the lower side in Figure 1) of the substrate 10, a hole transport layer 30 laminated on one surface of the first electrode layer 20, a photoelectric conversion layer 40 laminated on one surface of the hole transport layer 30, an excess material layer 50 partially laminated on one surface of the photoelectric conversion layer 40, a passivation layer 60 laminated in an area of ​​the one surface of the photoelectric conversion layer 40 where the excess material layer 50 is not present, an electron transport layer 70 laminated on one side of the excess material layer 50 and the passivation layer 60, and a second electrode layer 80 laminated on one side of the electron transport layer 70.

[0041] The substrate 10 is a structure that supports the other layers and ensures the strength of the solar cell 1. When the solar cell 1 receives light from the substrate 10 side, the substrate 10 is formed from a transparent material. Specifically, the substrate 10 may be formed from glass or a resin such as polyimide, polyamide, or polyethylene terephthalate. When the solar cell 1 receives light from the second electrode layer 80 side, the substrate 10 may be formed from a composite material including a metal layer.

[0042] The first electrode layer 20 collects holes generated in the photoelectric conversion layer 40 through the hole transport layer 30 and outputs them to the outside. The first electrode layer 20 may be formed of a transparent conductive oxide (TCO) having electrical conductivity and optical transparency. Examples of transparent conductive oxides that can be used to form the first electrode layer 20 include indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof. Among these, indium-based composite oxides containing indium oxide, zinc oxide, tungsten oxide, molybdenum oxide, or the like as their main components, and fluorine-doped tin oxide are preferred. From the viewpoints of high electrical conductivity and transparency, indium oxide is particularly preferred. The first electrode layer 20 is preferably subjected to a surface treatment, such as ozone treatment, to improve the formability of the hole transport layer 30. The first electrode layer 20 may have a multilayer structure having a p-type oxide semiconductor layer, for example, containing nickel oxide, niobium oxide, or the like as its main component, on its surface.

[0043] The hole transport layer 30 is formed from a film of a hole transport layer-forming compound that forms a self-assembled monolayer (SAM). The hole transport layer 30 transports only holes, among the positive and negative photocarriers (holes and electrons) generated in the photoelectric conversion layer 40, to the first electrode layer 20. The hole transport layer-forming compound preferably has a highest occupied molecular orbital close to the valence band of the perovskite compound that performs photoelectric conversion, to facilitate hole transport. Furthermore, the lowest unoccupied molecular orbital is preferably smaller than the conduction band, to block electrons. The hole transport layer-forming compound that forms the hole transport layer 30 preferably has a functional group capable of transporting holes, such as a carbazole-based, phenothiazine-based, or dimethylacridine-based compound, and a self-assembled terminal group that chemically bonds to the substrate, such as phosphoric acid or carboxylic acid. In order to impart passivation properties to the hole transport layer 30, it is preferable to have a linear structure such as an alkyl chain between the functional group and the self-assembling terminal group. The alkyl chain between the functional group and the self-assembling terminal group preferably has four or more carbon atoms. Specifically, examples of the hole transport layer-forming compound that forms the hole transport layer 30 include Me-4PACz ([4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid), MeO-4PACz ([4-(3,6-Dimethoxy-9H-carbazol-9-yl)butyl]phosphonic Acid), and DMAcPA ((4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid).

[0044] The photoelectric conversion layer 40 contains a perovskite compound that performs photoelectric conversion and absorbs incident light to generate photocarriers. The perovskite compound contained in the photoelectric conversion layer 40 contains an organic atom A containing at least one of an alkali metal (Am), a monovalent organic ammonium ion, and an amidinium ion, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of an iodide ion I, a bromide ion Br, a chloride ion Cl, and a fluoride ion F, and the perovskite compound contains an ABX ３The alkali metal at the A site may be potassium K, cesium Cs, rubidium Rb, or the like, and the organic atom A may be methylammonium MA (CH ３ NH ３ ), Formamidinium FA (CH ３ N ２ ) and the like. Examples of the metal atom B include lead (Pb) and tin (Sn). It is preferable to contain at least one of lead (Pb) and tin (Sn), and a mixture thereof is also acceptable. The halogen atom X is preferably at least one of iodide (I), bromide (Br), and chloride (Cl).

[0045] Specifically, preferred perovskite compounds include, for example, MAPbI ３ , MAPbBr ３ , MAPbCl ３ Methylammonium lead halides (MAPbX) such as ３ ), and FAPbI ３ , FAPbBr ３ , FAPbCl ３ Formamidinium lead halide (FAPbX) ３ The halogen atom X may contain multiple types. FA, which contains both methylammonium and formamidinium, is also suitable. ｙ MA １－ｙ PbX ３ In addition, when an alkali metal is contained, Am ｙ FA ｚ MA １－ｙ－ｚ PbIX, Am ｙ FA １－ｙ Am may be a single element selected from the group consisting of Cs, Rb, and K, or may contain multiple elements (y and z are any positive integers).

[0046] The photoelectric conversion layer 40 contains Pb, PbI, and the like at the grain boundaries of the crystals of the perovskite compound. ２ , PbBr ２ , PbCl ２, or the like. In order to form such an impurity film 41, the metal B in the perovskite compound preferably contains at least one of lead (Pb) and tin (Sn). By having the photoelectric conversion layer 40 have the impurity film 41 containing the metal atom B and a metal compound, it is possible to prevent the hole transport layer-forming compound that forms the hole transport layer 30 and the material that forms the passivation layer 60 from being left behind at the grain boundaries of the crystals of the perovskite compound during the formation of the photoelectric conversion layer 40, thereby improving the photoelectric conversion efficiency.

[0047] The excess material layer 50 is formed from a material containing the same hole transport layer-forming compound as that forming the hole transport layer 30. The excess material layer 50 may be composed solely of the hole transport layer-forming compound, or may contain other materials contained in the perovskite precursor liquid. When the excess material layer contains a hole transport layer-forming compound, the weight content of the hole transport layer-forming compound in the excess material layer 50 is preferably 10% or more, more preferably 30% or more. Furthermore, the weight content of the hole transport layer-forming compound is preferably 90% or less, more preferably 70% or less. The weight content in the excess material layer can be calculated based on the composition of the excess material layer measured by a combination of transmission electron microscope observation and energy dispersive X-ray analysis, for example. The hole transport layer-forming compound used for the hole transport layer 30 has a lowest unoccupied molecular orbital (LOM) lower than the conduction band of the perovskite compound (close to the vacuum level) in order to block electron transport. Therefore, if the hole transport layer-forming compound exists between the photoelectric conversion layer 40 and the electron transport layer, the excess material layer 50 may hinder electrons generated in the photoelectric conversion layer 40 from reaching the electron transport layer, potentially acting as a resistor. For this reason, it is necessary to ensure that the excess material layer 50 is formed in an appropriate state. For example, when the hole transport layer 30 and the photoelectric conversion layer 40 are formed using the same process, in order to form a seamless hole transport layer 30 that covers the entire surface of the first electrode layer 20, it is preferable to use a perovskite precursor liquid in which the concentration of the hole transport layer-forming compound is adjusted so that the number of hole transport layer-forming compounds is slightly greater than the number of hole transport compounds required to densely cover the coated surface. Furthermore, a material contained in the perovskite precursor liquid may be included in the excess material layer 50 to less likely hinder the transport of electrons passing through the excess material layer 50. A simple method for understanding the growth state of the hole transport layer-forming compound on the TCO surface is to assume that the molecular length is the unit (lattice constant) of the monolayer, estimate the number of hole transport-forming compounds per coating area, and determine the concentration so that the number of hole transport-forming compounds contained in the coating film is greater than that. In the case of a halide, the molecular length of an ion that does not contain a halogen can be used as the unit.

[0048] The passivation layer 60 prevents photocarrier recombination at the interface with the photoelectric conversion layer 40 and promotes the arrival of electrons at the electron transport layer 70. The passivation layer 60 is formed so as to share the surface of the excess material layer 50 and the photoelectric conversion layer 40, preventing the excess material layer 50 from covering the entire surface of the photoelectric conversion layer 40 and reducing the photoelectric conversion efficiency. The passivation layer 60 contains an organic compound (hereinafter referred to as a "specific organic compound") having an optionally substituted chain hydrocarbon group having 5 or more carbon atoms and an ionic functional group. The term "optionally substituted chain hydrocarbon group" includes a chain hydrocarbon group in which a hydrogen atom has been substituted with another atom or group. Specific examples of the specific organic compound include n-octylphosphocholine, 2,8-dimethyl-5-nonylphosphocholine, 10-undecylenyl-1-phosphocholine, n-octylammonium iodide, and L-α-phosphotidylcholine. The deposition of the specific organic compound on the surface can be confirmed by time-of-flight secondary ion mass spectrometry.

[0049] The specific organic compound is mixed in a solvent containing aprotic polar solvents such as dimethylformamide (DMF), N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), and acetonitrile, which are used to form the photoelectric conversion layer 40. Larger materials are less susceptible to the crystallization of the perovskite material and are extruded to the surface and interface. In this process, the use of alkyl chains that interact with each other and have an orientation effect facilitates two-dimensional alignment. Furthermore, the ionic end facilitates attachment to defects on the surface of the perovskite material, allowing for control of molecular orientation. Poor orientation can result in poor coverage, such as growth by folding over each other, resulting in poor passivation and resistance, making it difficult to transport electrons. The carbon number of the chain hydrocarbon is preferably 5 or more, and preferably 24 or less. It is important to have a size that is less susceptible to crystallization; the longer the carbon number, the easier the orientation; more preferably, 8 or more carbon atoms. On the other hand, a larger carbon number and longer length result in poor orientation. The chain hydrocarbon group may be linear or branched. Having a sufficient number of carbon atoms prevents incorporation into the crystals of the perovskite material. The short carbon number of each chain hydrocarbon reduces electrical resistance. It is preferable for the chain to partially contain double chains (alkene), triple chains (alkyne), or aromatic rings. The presence of π bonds, such as double chains, triple chains, or aromatic rings, reduces insulating properties even when the hydrocarbon group is long. For example, L-α-Phosphatidylcholine is bifurcated and contains chain hydrocarbons with 15 carbon atoms and chain hydrocarbons with 17 carbon atoms. The chain hydrocarbons with 17 carbon atoms require partial double chains. Furthermore, forming a halide facilitates ionization when dissolved in a solvent, and the halogen ions also act to fill defects in the perovskite material, preventing a decrease in performance.

[0050] The ionic functional group binds to defects in the crystal of the perovskite compound, thereby preventing the recombination of photocarriers. Because defects in the crystal of the perovskite compound can be both positive and negative, the ionic functional group may form either a cation or anion. Specifically, the ionic functional group is preferably any of an amino group, a hydrazine group, a trialkylamino group, a phosphonic acid group, a phosphate group, a hydroxyl group, a carboxyl group, and a sulfonyl group. In particular, the presence of an ionic functional group that forms a zwitterion, such as a phosphocholine group, which has both a cation and an anion, is more preferable because it can compensate for defects with both charges on the perovskite surface.

[0051] In addition to the specific organic compound, the passivation layer 60 may further contain at least one of a fluorine-containing organic compound, piperazine and piperazine derivatives, and a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle. Since a single material alone may not be sufficiently deposited on the perovskite layer surface, mixing it with a material deposited by a different method and having different passivation properties can more reliably cover the surface and improve passivation properties.

[0052] Fluorine-containing organic compounds have high surface deposition properties and high electron transport capabilities. However, they have low surface energy and poor adhesion to the materials grown on them. Furthermore, when formed by coating, they tend to exhibit lyophobic properties, which can lead to coating defects. Therefore, combining them with specific organic compounds can improve adhesion and coatability.

[0053] The fluorine-containing organic compound preferably has a carbon skeleton containing an alkyl chain or benzene, with some hydrogen atoms substituted with fluorine, trifluoromethyl groups, or the like. The carbon skeleton more preferably contains consecutive carbon atoms bonded to fluorine. When the fluorine-containing organic compound has a benzene skeleton, it is preferable that five of the six hydrogen atoms in the benzene are substituted with fluorine or trifluoromethyl groups, with one hydrogen atom connected to a terminal lyophilic group. The greater the number of fluorine and trifluoromethyl group substitutions, the higher the lyophobicity and the greater the effect of selectively orienting the compound toward the surface. Therefore, when substituted with fluorine, it is preferable to have a pentafluorobenzene structure in which all hydrogen atoms except one connected to the terminal are substituted with fluorine. When the fluorine-containing organic compound has an alkyl chain skeleton, it is preferable that the end of the alkyl chain has a trifluoromethyl group or a phenyl group containing fluorine or trifluoromethyl groups, and the end of the alkyl chain has a lyophilic group. The fluorine-containing end faces the electron transport layer, and the end containing the lyophilic group faces the perovskite surface. The linear skeleton, excluding the end and terminal, preferably has from 1 to 17 carbon atoms. More preferably, the number of carbon atoms is 5 or more and 16 or less. To promote the formation of the passivation layer 60 by self-organization, the longer the alkyl chain, the better the orientation and passivation properties. However, the longer the alkyl chain, the higher the insulating properties and the lower the conductivity. Therefore, by adding an alkyl chain longer than the upper limit, sufficient orientation can be achieved, and by keeping the alkyl chain length below the lower limit, both passivation properties and conductivity can be achieved. When the fluorine-containing organic compound has an alkyl chain skeleton and a trifluoromethyl group at the end, it is preferable that the alkyl chain continuing from the end contains consecutive fluorinated carbons. More preferably, all carbons except for one or two adjacent to the end are fluorinated. Continuous fluorination enhances lyophobicity and allows for more selective deposition on the surface, promoting the formation of the passivation layer 60. Another example of a fluorine-containing organic compound having an alkyl chain skeleton is a polymer structure.The partially fluorinated polymer structure, containing a large amount of fluorine, is more likely to be oriented planarly on the surface, unlike structures in which the fluorine-containing end faces the electron transport layer and the lyophilic end faces the perovskite surface. When the fluorine-containing organic compound has an alkyl chain skeleton and a phenyl group at the end containing fluorine or trifluoromethyl groups, the greater the number of fluorine and trifluoromethyl group substitutions, as described above. Therefore, when the hydrogen atoms of the phenyl group are substituted with fluorine, pentafluorobenzene is preferred. Furthermore, the combination of the phenyl group containing fluorine and trifluoromethyl groups with the alkyl chain can promote more selective deposition on the surface than when the compound has only a benzene skeleton. Furthermore, the fluorine-containing organic compound preferably has at least one lyophilic group at the end, specifically, an amino group, a hydrazine group, a trialkylamino group, a phosphate group, a phosphonate group, a hydroxyl group, a carboxyl group, a sulfonyl group, or an ionized form thereof. These compounds have lyophilicity toward the aprotic polar solvent used to form the photoelectric conversion layer 40, and by combining them with a fluorine-containing skeleton that is lyophobic, they can be positioned on the surface of the photoelectric conversion layer 40 even before the drying process. Having a linear skeleton, lyophilic groups, or both facilitates alignment of the fluorine-containing organic compounds, allowing for the formation of thin, uniform films and reduced series resistance. Ionization of these terminal groups can compensate for defects such as iodine defects, lead defects, and halogen defects on the surface of the perovskite layer, thereby improving performance. Multiple types of fluorine-containing organic compounds may also be used. These terminal groups may also be ionized in the solvent. It is more preferable for the fluorine-containing organic compound to have both cationic and anionic terminal groups to compensate for defects with different charges, such as iodine defects, lead defects, and halogen defects, on the surface of the perovskite layer. Examples of terminal groups having both cationic and anionic terminal groups include phosphocholine groups and carbamic acid groups.Furthermore, the specific organic compound and the fluorine-containing organic compound are likely to be oriented due to interactions between the individual molecules and at the film boundaries between the specific organic compound, which is likely to be charged with cations, and the fluorine-containing compound, which is likely to be charged with anions, making it possible to form a dense passivation layer. In particular, by selecting a fluorine-containing organic compound that has a chain structure similar to that of the specific organic compound, orientation becomes even easier.

[0054] Specific examples of fluorine-containing organic compounds include those having a benzene skeleton substituted with fluorine and a trifluoromethyl group, such as 4-fluorophenethylamine hydroiodide (FPEAI), 4-(trifluoromethyl)phenylammonium hydroiodide, 2,6-difluoroaniline, 3,4,5-trifluoroaniline, pentafluorophenylphosphonic acid (5FPAc), pentafluorophenylhydrazine (5FPHZ), and pentafluorobenzene-amino-carboxylic acid (carbamic acid) hydroiodide. When the fluorine-containing organic compound has an alkyl chain skeleton, examples of compounds having a trifluoromethyl group at the end and a lyophilic end include 1H,1H-undecafluorohexylamine (CF ３ (CF ２ ) ４ CH ２ NH ２ ), 1H,1H-pentadecafluorooctylamine (CF ３ (CF ２ ) ６ CH ２ NH ２ ), Fos-Choline-8 (fluoride) (registered trademark: C １３ H １７ F １３ NO ４ P), 2,2,2-trifluoroethylamine (CF ３ CH ２ NH ２Examples of fluorine-containing organic compounds include 12-pentafluorophenoxydodecylphosphonic acid (C ), 3,3,4,4,5,5,6,6-nonafluorohexylphosphonic acid (FHPA), and polyvinylidene fluoride (PVDF) as a polymer structure. When the fluorine-containing organic compound has an alkyl chain skeleton, examples of fluorine-containing organic compounds having a phenyl group containing fluorine or a trifluoromethyl group include 12-pentafluorophenoxydodecylphosphonic acid (C ). １８ H ２６ F ５ O ４ P), etc. The deposition of fluorine-containing organic compounds on the surface as a passivation layer can be confirmed by observing the contact angle. For example, when evaluated with chlorobenzene, the contact angle increases with the addition of a small amount of linear fluoroalkyl chains, highly lyophilic 1H,1H-undecafluorohexylamine, (fluorinated) Fos-Choline-8, etc.

[0055] While piperazine compounds exhibit a high passivation effect on the perovskite surface, they have low solubility in solvents, making it difficult to dissolve them in a sufficient amount to cover the surface. If any undissolved portions remain, they become impurities, which can lead to poor solar cell performance. Therefore, combining them with specific compounds can produce a synergistic effect.

[0056] Piperazine compounds tend to be poorly soluble at room temperature in solvents used to form the photoelectric conversion layer 40, including aprotic polar solvents such as dimethylformamide (DMF), N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and acetonitrile. Therefore, compared to the excess material layer 50, they are less likely to contribute to the crystal growth of the perovskite material and precipitate on the surface and grain boundaries of the photoelectric conversion layer 40. The crystallization process is known to occur from the surface, with the poorly soluble piperazine compound precipitating on the surface first, followed by the perovskite compound containing the hole transport compound. By precipitating on the surface, the piperazine compound facilitates electron transport while maintaining passivation properties. In particular, forming a halide salt of the piperazine compound and turning it into an ionic material increases its solubility and facilitates surface deposition. Furthermore, having a hydrophobic group, such as an alkyl chain or a fluorine-containing organic group, bonded to one of the nitrogen groups further promotes surface deposition. The fluorine-containing organic group is preferably a fluorinated alkyl group. Here, the "piperazine compound" refers to at least one of piperazine and piperazine derivatives (including halide salts) represented by the following chemical formulas 1 to 3, and may also be a mixture of two or more of these. In the formulas, R1 to R8 are hydrogen or any substituent, RA1 to RA4 are hydrogen or an alkyl group, and X is a halogen. Deposition of the piperazine compound on the surface can be confirmed by time-of-flight secondary ion mass spectrometry.

[0057] Specific examples of piperazine derivatives include piperazine-1,4-diium iodide, piperazinium iodide, pentylpiperazine hydrochloride, and 1-(2-fluoroethyl)piperazine dihydrochloride.

[0058]

[0059]

[0060]

[0061] Polymer passivation compounds with repeating units containing nitrogen-containing heterocycles have the advantage that nitrogen ions easily combine with halogen ions to form polymer passivation halides, which then compensate for halogen defects that occur on the surface during perovskite compound formation. However, they can also cause aggregation, which is difficult to control, and by combining them with specific monomolecular organic compounds, a denser passivation layer can be created.

[0062] Because polymer passivation compounds having repeating units with nitrogen-containing heterocycles are polymers with large sizes, they are not incorporated into the perovskite crystals and preferentially precipitate on the surface when the photoelectric conversion layer 40 is formed using the perovskite precursor liquid described below. Therefore, the formation of the excess material layer 50 can be suppressed, allowing the passivation layer 60 to be formed. To ensure the formation of the passivation layer 60, the weight-average molecular weight of the polymer passivation compound is preferably 5,000 to 5,000,000. A molecular weight of 10,000 or more is more preferable to ensure that the polymer is not incorporated into the perovskite compound, and a molecular weight of 2.5 million or less is more preferable to maintain solubility in the solvent. Furthermore, by having a nitrogen-containing heterocycle in the repeating unit, the polymer passivation compound prevents recombination and efficiently transmits electrons. Polymer passivation halides may also be used. Polymer passivation compounds having repeating units with nitrogen-containing heterocycles are more likely to form polymer passivation compounds with halogen ions in the precursor liquid. By creating a polymer passivation halide, it is possible to compensate for halogen defects that occur due to aging on the surface of perovskite compounds, thereby improving the reliability of solar cell characteristics.

[0063] Preferred nitrogen-containing heterocycles for polymer passivation compounds include pyridine, pyrrolidone, phthalimide, caprolactam, imidazole, imidazolium, triazole, thiazole, piperidium, and their derivatives. The polymer passivation compound preferably has a larger band gap than the perovskite compound. More preferably, the highest occupied molecular orbital of the polymer passivation compound is larger than the valence band of the perovskite compound (farther from the vacuum level), and the lowest unoccupied molecular orbital of the polymer passivation compound is smaller than the conduction band of the perovskite compound (closer to the vacuum level). Furthermore, by using a highly conductive heterocycle with an alkyl chain composed of locally highly insulating vinyl groups, carriers can be efficiently transported while maintaining passivation properties.

[0064] Furthermore, pyrrolidone, phthalimide, and caprolactam have oxygen in their skeletons, and in skeletons containing hydrogen halide ions, and pyridine, imidazole, imidazolium, triazole, and thiazole, nitrogen ions are easily converted into halogen ions to form polymer passivation halides. Therefore, during the formation of the passivation layer from the precursor liquid, halogen ions not used in the formation of the perovskite compound are absorbed to partially form polymer passivation halides. The polymer passivation halides compensate for halogen defects that occur on the surface during the formation of the perovskite compound, improving the passivation properties of the perovskite compound surface. Furthermore, in the completed solar cell, the polymer passivation halides can compensate for halogen defects on the surface of the perovskite compound that occur due to aging, thereby improving the reliability of the solar cell's characteristics. Therefore, if the molar concentration of halogen ions X in the precursor liquid is 1% or more in excess of the molar concentration of at least one of the materials involved in the A site and B site of the perovskite compound, a halide can be effectively formed with the polymer passivation compound. Furthermore, if the molar concentration is 3% or more, halogen ions can be incorporated more effectively. Furthermore, an excess of 20% or less is preferable, which can suppress defect formation in the perovskite compound. Furthermore, if the excess amount is 10% or less, defect formation can be suppressed even more effectively. A precursor liquid containing excess halogen can also be formed by adding a halide of the polymer passivation compound to the precursor. From the perspective of improving reliability, the polymer passivation halide in the passivation layer after solar cell formation is preferably formed in 1% or more of the total number of repeating units of the polymer passivation compound. Furthermore, if the polymer passivation halide is formed in 5% or more, defects occurring in the perovskite compound can be more effectively compensated for. Furthermore, if the polymer passivation halide accounts for 90% or less of the total number of repeating units of the polymer passivation compound, the polymer passivation compound can be maintained in a stable state without steric hindrance. Furthermore, by keeping the density at 80% or less, a more stable state can be maintained.

[0065] The repeating unit of the polymeric passivation compound may be an alkyl unit. That is, the repeating unit of the polymeric passivation compound may be an alkyl unit substituted with a nitrogen-containing heterocycle. A typical example of the polymeric passivation compound is a compound having a polyvinyl skeleton obtained by vinyl polymerization of a monomer having a nitrogen-containing heterocycle and a vinyl group. That is, the polymeric passivation compound may have a nitrogen-containing heterocycle bonded to every two carbon atoms of the alkyl chain. Because the polymeric passivation compound is a compound with an alkyl chain as its main chain, the polymer can be synthesized relatively easily and the desired molecular weight can be obtained, thereby more reliably forming the passivation layer 60. Furthermore, the presence of the alkyl chain facilitates orientation control and allows for a uniform arrangement of the heterocycles. Furthermore, in addition to a structure having a nitrogen-containing heterocycle or a vinyl skeleton, the polymeric passivation compound may also include a repeating structure of other skeletons, such as a fluorinated alkyl chain skeleton. For example, a skeleton having a fluorinated alkyl chain may be included as a branch of the alkyl chain between the poly(vinylimidazole) skeletons. Fluorinated alkyl chains tend to exhibit lyophobicity and can be more selectively deposited on the surface of the perovskite compound.

[0066] Examples of polymer passivation compounds having repeating units of alkyl units substituted with nitrogen-containing heterocycles include poly(vinylpyrrolidone), poly(4-vinylpyridine), poly(2-vinylpyridine), poly(1-vinylimidazole), poly(2-vinylimidazole), poly(4-vinylimidazole), poly(vinylazole), poly(vinylphthalimide), poly(vinylimidazole), poly(vinylcaprolactam), poly(vinyltriazole), poly(5-vinylthiazole), and poly(4-methyl-5-vinylthiazole). Examples of halides include poly(vinylpyrrolidone) iodine complexes.

[0067] In addition to the specific organic compound, the passivation layer 60 may contain two or more of the following: a fluorine-containing organic compound, piperazine and piperazine derivatives, and a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle. By using an appropriate combination, it is possible to obtain a higher effect than if a single compound were used.

[0068] If the coverage of the photoelectric conversion layer 40 with the passivation layer 60 is 50% or more, electron transport can be performed effectively. If it is 90% or more, this effect is further enhanced, which is preferable. Furthermore, if it is 99% or less, resistance loss caused by partial thickening of the polymer passivation compound can be reduced. Furthermore, if it is 95% or less, resistance loss can be suppressed even more effectively.

[0069] The electron transport layer 70 selectively transmits electrons and transfers them to the second electrode layer 80. The electron transport layer 70 is formed of a material mainly composed of, for example, fullerene. Examples of fullerene include C60, C70, and their hydrides, oxides, metal complexes, and derivatives to which alkyl groups or the like are added, such as PCBM ([6,6]-Phenyl-C61-Butyric Acid Methyl Ester). In addition, a hole blocking layer made of pasocuproine (BCP), lithium fluoride (LiF), or tin oxide (SnO ２ ), aluminum-doped zinc oxide (ZnO), titanium oxide (TiO ２ The inorganic oxide layer may be doped with another metallic material.

[0070] When the solar cell 1 receives light from the side of the substrate 10, the second electrode layer 80 preferably includes a metal layer made of, for example, copper in order to reduce electrical resistance. When the solar cell 1 receives light from the side of the second electrode layer 80, the second electrode layer 80 can be made of a transparent conductive oxide.

[0071] The solar cell 1 having the above configuration is manufactured by a solar cell manufacturing method according to one embodiment of the present invention, as shown in Fig. 2. The solar cell manufacturing method of this embodiment includes a first electrode layer forming step (step S1), a precursor liquid applying step (step S2), a crystallization step (step S3), an electron transport layer forming step (step S4), and a second electrode layer forming step (step S5).

[0072] In the first electrode layer formation step of step S1, a first electrode layer 20 is formed on one main surface of the substrate 10. The first electrode layer 20 can be deposited using a vacuum film-forming technique such as sputtering. In the first electrode layer step, it is preferable to modify the surface of the deposited first electrode layer 20 to facilitate the formation of the hole transport layer 30 in the next step. Specific methods for modifying the surface of the first electrode layer 20 include, for example, surface hydroxylation by ultraviolet-ozone treatment or ozone water washing, film formation by vacuum film-forming techniques such as sputtering of oxides such as nickel oxide, which are prone to grow self-assembled films, film formation by coating techniques of oxide nanoparticles, and heat treatment to activate the surface and remove impurities to facilitate the growth of self-assembled films.

[0073] In the precursor liquid application step of step S2, the perovskite precursor liquid is applied to the first electrode layer 20. The perovskite precursor liquid can be applied using, for example, a die coater, a bar coater, or the like. The perovskite precursor liquid applied in the precursor liquid application step is itself one embodiment of the perovskite precursor liquid according to the present invention.

[0074] The perovskite precursor liquid contains a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer that has hole selective permeability, and a specific organic compound. Preferably, the perovskite precursor liquid further contains an organic hydrochloride that promotes crystal growth of the perovskite compound.

[0075] As the solvent, for example, polar aprotic solvents such as DMF, DMSO, NMP, GBL, acetonitrile, etc. may be used alone or as a mixture of two or more kinds, and may further contain other kinds of solvents.

[0076] The perovskite precursor is a mixture of a metal halide BX and an AX composed of an organic halide compound or an alkali metal halide, in a predetermined ratio. The molar concentration of the metal atom B (the metal portion of the metal halide) is preferably in excess of 0.5 mol % to 10 mol % relative to the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal. This expels other materials to the interfaces between the front and back of the perovskite precursor liquid during the crystallization process, preventing other materials from being left behind in the impurity film 41 formed between the crystals of the perovskite compound, and suppressing a decrease in photoelectric conversion efficiency due to the remaining other materials.

[0077] As described above, the hole transport layer-forming compound is a material that forms a self-assembled monolayer having hole selective permeability. When the perovskite precursor liquid is applied onto the first electrode layer 20, the hole transport layer-forming compound preferentially self-assembles at the interface with the first electrode layer 20 to form a film (hole transport layer 30). The remaining hole transport layer-forming compound that has formed a film at the interface with the first electrode layer 20 also self-assembles on the surface of the perovskite precursor liquid coating (the side opposite the first electrode layer 20) to form a film (excess material layer 50). The concentration of the hole transport layer-forming compound in the perovskite precursor liquid can be 0.1 mmol / L or more and 5.0 mmol / L or less. A concentration of 0.5 mmol / L or more and 2.0 mmol / L or more is more preferable. Within the range that can cover the substrate surface, a lower concentration can suppress the formation of the excess material layer 50.

[0078] The specific organic compound aggregates into a film on the surface of the coating film of the perovskite precursor liquid and partially covers the surface of the layer of perovskite compound (photoelectric conversion layer 40) generated from the perovskite precursor, thereby forming a passivation layer 60 that suppresses the recombination of photocarriers (holes and electrons) at the interface of the photoelectric conversion layer 40. Furthermore, the specific organic compound inhibits the growth of a film of the hole transport layer-forming compound on the surface of the coating film of the perovskite precursor liquid, thereby reliably forming a region where the excess material layer 50 is absent and where the passivation layer 60 is present. The concentration of the specific organic compound in the perovskite precursor liquid may be 1 μmol / L or more and 5 mmol / L or less. A more preferred range is 50 μmol / L or more and 2 mmol / L or less. To achieve high performance, a high coverage of the surface of the specific organic compound is preferred, and more preferably, the specific organic compound covers substantially the entire surface (e.g., 90% or more of the region), thereby suppressing the inhibition of electron transport by the hole transport layer-forming compound. On the other hand, increasing the concentration of the specific organic compound to improve coverage can result in the compound being incorporated into the perovskite compound and acting as an impurity, making recombination more likely. Furthermore, forming multiple layers can create resistance, potentially reducing performance. Therefore, as with the hole transport layer-forming compound, the molecular length is assumed to be the unit (lattice constant) of the monomolecular film, the number of specific organic compounds per coating area is estimated, and the concentration is determined so that the number of specific organic compounds contained in the coating film is smaller than that. When the specific organic compound is an ionic material, the molecular weight is determined by the ions contained in the specific organic compound. The passivation layer 60 and excess material layer 50 may not cover the entire surface of the photoelectric conversion layer 40. In such cases, an additional passivation layer may be formed separately. The additional passivation layer may be formed from a solution of an organic compound, or may be formed by vapor deposition of an inorganic material such as lithium fluoride or magnesium difluoride.

[0079] Some organic hydrochlorides have the function of promoting the crystallization of perovskite compounds and increasing the particle size of the perovskite crystals. For example, methylammonium hydrochloride (MACl), formamidinium hydrochloride (FACl), methylenediaminium hydrochloride (MDACl), etc.２ ) and others. In these organic hydrochlorides, only the organic portion remains in the perovskite crystal, while the hydrochloric acid portion functions to bond the crystal grains. This reduces the area of ​​the grain boundaries in the photoelectric conversion layer 40, suppresses the generation of impurities between the perovskite crystals, and achieves high photoelectric conversion efficiency. It is preferable that the portion other than the hydrochloride salt is smaller in size than the crystal lattice of the perovskite crystal and has an amino group. The concentration of the hydrochloride salt in the perovskite precursor liquid can be 0.05 mol% or more and 40 mol% or less relative to the molar concentration of the metal ions located at the center (B site) of the perovskite compound crystal. Chlorides containing alkyl metals may also have a similar effect. Examples include cesium chloride (CsCl) and rubidium chloride (RbCl).

[0080] In the crystallization process of step S3, the solvent is volatilized from the coating film of the perovskite precursor liquid, drying the coating film, and the perovskite precursor reacts to produce crystals of the perovskite compound. This forms a photoelectric conversion layer 40 primarily composed of the perovskite compound, which fixes the hole transport layer 30, the excess material layer 50, and the passivation layer 60. Furthermore, as the crystals of the perovskite compound grow, an impurity film 41 containing excess metal B and metal compounds is formed between the crystal grains of the perovskite compound. Because the crystals of the perovskite compound grow from the surface side (the side opposite the first electrode layer 20), the impurity film 41 also grows from the surface side toward the first electrode layer 20. Methods for promoting the production of crystals of the perovskite compound in the perovskite precursor liquid film include, for example, poor solvent quenching, vacuum quenching, gas quenching, and laser treatment. If the crystallization of the perovskite compound is too fast, the specific organic compound will finish crystal growth before reaching the surface. Therefore, it is preferable to slow down the crystallization of the perovskite compound to facilitate sufficient growth on the surface. From this perspective, vacuum quenching or gas quenching is more preferable. In the crystallization process of step S3, the dried coating film of the perovskite precursor liquid may be further heated. Heating is a preferable method for removing the hydrochloric acid portion of the organic hydrochloride.

[0081] In the electron transport layer forming step S4, the electron transport layer 70 is formed by a method such as coating or vacuum deposition. A hole blocking layer may be formed on the electron transport layer 70 by vacuum deposition or atomic deposition.

[0082] In the second electrode forming step S5, the second electrode layer 80 is formed by a method such as sputtering, vacuum deposition, plating, or coating depending on the forming material.

[0083] As described above, the perovskite precursor liquid according to one embodiment of the present invention contains a perovskite precursor, a hole transport layer-forming compound, and a specific organic compound, and therefore can simultaneously form the hole transport layer 30 and the photoelectric conversion layer 40 on the first electrode layer 20 by a single coating operation, while also forming a passivation layer 60 on the surface of the photoelectric conversion layer 40, thereby preventing the photoelectric conversion layer 40 from being completely covered with an excess material layer 50 that inhibits electron transport. Therefore, the solar cell manufacturing method according to one embodiment of the present invention can easily manufacture a solar cell 1 having a relatively high photoelectric conversion efficiency.

[0084] 3 is a schematic cross-sectional view showing the configuration of a solar cell 101 according to a second embodiment of the present invention. The solar cell 101 includes a plate- or sheet-shaped substrate 110, a first electrode layer 120 laminated on one main surface (the lower side in FIG. 3 ) of the substrate 110, a hole transport layer 130 laminated on one surface of the first electrode layer 120, a photoelectric conversion layer 140 laminated on one surface of the hole transport layer 130, an excess material layer 150 partially laminated on one surface of the photoelectric conversion layer 140, a passivation layer 160 laminated in an area of ​​the one surface of the photoelectric conversion layer 140 where the excess material layer 150 is not present, an electron transport layer 170 laminated on one side of the excess material layer 150 and the passivation layer 160, and a second electrode layer 180 laminated on one side of the electron transport layer 170.

[0085] The substrate 110 is a structure that supports the other layers and ensures the strength of the solar cell 101. When the solar cell 101 receives light from the substrate 110 side, the substrate 110 is formed from a transparent material. Specifically, the substrate 110 may be formed from glass, a resin such as polyimide, polyamide, or polyethylene terephthalate, or the like. Furthermore, when the solar cell 101 receives light from the second electrode layer 180 side, the substrate 110 may be formed from a composite material including a metal layer, or the like.

[0086] The first electrode layer 120 collects holes generated in the photoelectric conversion layer 140 through the hole transport layer 130 and outputs them to the outside. The first electrode layer 120 may be formed of a transparent conductive oxide (TCO) having electrical conductivity and optical transparency. Examples of transparent conductive oxides that can be used to form the first electrode layer 120 include indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof. Among these, indium-based composite oxides containing indium oxide, zinc oxide, tungsten oxide, molybdenum oxide, or the like as their main components, and fluorine-doped tin oxide are preferred. From the viewpoints of high electrical conductivity and transparency, indium oxide is particularly preferred. The first electrode layer 120 is preferably subjected to a surface treatment, such as ozone treatment, to improve the formability of the hole transport layer 130. The first electrode layer 120 may have a multilayer structure having a p-type oxide semiconductor layer, for example, containing nickel oxide, niobium oxide, or the like as its main component, on its surface.

[0087] The hole transport layer 130 is formed from a film of a hole transport layer-forming compound that forms a self-assembled monolayer (SAM). The hole transport layer 130 transports only holes, of the positive and negative photocarriers (holes and electrons) generated in the photoelectric conversion layer 140, to the first electrode layer 120. The hole transport layer-forming compound preferably has a highest occupied molecular orbital close to the valence band of the perovskite compound that performs photoelectric conversion, to facilitate hole transport. Furthermore, the lowest unoccupied molecular orbital is preferably smaller than the conduction band, to block electrons. The hole transport layer-forming compound that forms the hole transport layer 130 preferably has a functional group capable of transporting holes, such as a carbazole-based, phenothiazine-based, or dimethylacridine-based compound, and a self-assembled terminal group that chemically bonds to the substrate, such as phosphoric acid or carboxylic acid. In order to impart passivation properties to the hole transport layer 130, it is preferable to have a linear structure such as an alkyl chain between the functional group and the self-assembled terminal group. The alkyl chain preferably has four or more carbon atoms. Specifically, examples of the hole transport layer-forming compound that forms the hole transport layer 130 include Me-4PACz ([4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid), MeO-4PACz ([4-(3,6-Dimethoxy-9H-carbazol-9-yl)butyl]phosphonic Acid), and DMAcPA ((4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid).

[0088] The photoelectric conversion layer 140 contains a perovskite compound that performs photoelectric conversion, absorbing incident light to generate photocarriers. The perovskite compound contained in the photoelectric conversion layer 140 includes an organic atom A containing at least one of an alkali metal (Am), a monovalent organic ammonium ion, and an amidinium-based ion, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of an iodide ion I, a bromide ion Br, a chloride ion Cl, and a fluoride ion F, and can be represented by the formula ABX3. Examples of the alkali metal at the A site include potassium K, cesium Cs, and rubidium Rb, and examples of the organic atom A include methylammonium MA (CH ３ NH ３ ), Formamidinium FA (CH ３ N ２ The metal atom B may be lead (Pb) or tin (Sn), and preferably is mainly lead. The halogen atom X is preferably at least one of iodide (I), bromide (Br), and chloride (Cl).

[0089] Specifically, preferred perovskite compounds include, for example, MAPbI ３ , MAPbBr ３ , MAPbCl ３ Methylammonium lead halides (MAPbX) such as ３ ), and FAPbI ３ , FAPbBr ３ , FAPbCl ３ Formamidinium lead halide (FAPbX) ３ The halogen atom X may contain multiple types. FA, which contains both methylammonium and formamidinium, is also suitable. ｙ MA １－ｙ PbX ３ In addition, when an alkali metal is contained, Am ｙ FA ｚ MA １－ｙ－ｚ PbIX, Am ｙ FA １－ｙ Am may be a single element selected from the group consisting of Cs, Rb, and K, or may contain multiple elements (y and z are any positive integers).

[0090] The photoelectric conversion layer 140 contains Pb, PbI, and the like at the grain boundaries of the crystals of the perovskite compound. ２ , PbBr ２ , PbCl ２ , or the like. In order to form such an impurity film 141, the metal B in the perovskite compound is preferably lead (Pb). By having the photoelectric conversion layer 140 have the impurity film 141 containing the metal atom B and a metal compound, it is possible to prevent the hole transport layer-forming compound that forms the hole transport layer 130 and the material that forms the passivation layer 160 from being left behind in the grain boundaries of the crystals of the perovskite compound during the formation of the photoelectric conversion layer 140, thereby improving the photoelectric conversion efficiency.

[0091] The excess material layer 150 is formed from the same hole transport layer-forming compound as that forming the hole transport layer 130. The hole transport layer-forming compound used for the hole transport layer 130 has the lowest unoccupied molecular orbital below the conduction band of the perovskite compound in order to block electron transport, making it difficult for electrons to reach the electron transport layer and acting as a resistor. Ideally, it is preferable that the excess material layer 150 is not formed, but when the hole transport layer 130 and the photoelectric conversion layer 140 are formed in the same process, it is necessary to blend a slightly larger amount of the hole transport layer-forming compound in order to form a continuous hole transport layer 130 that covers the entire surface of the first electrode layer 120, and the excess hole transport layer-forming compound forms the excess material layer 150. Since it is difficult to accurately grasp the growth state of the hole transport layer-forming compound on the TCO surface, we simply assume that the molecular length is the unit (lattice constant) of the monomolecular film, estimate the number of hole transport-forming compounds per coating area, and determine the concentration so that the number of hole transport-forming compounds contained in the coating film is larger than that.

[0092] The passivation layer 160 prevents the recombination of photocarriers at the interface with the photoelectric conversion layer 140 and promotes the arrival of electrons at the electron transport layer 170. The passivation layer 160 is also formed so as to share the surface of the excess material layer 150 and the photoelectric conversion layer 140, preventing the excess material layer 150 from covering the entire surface of the photoelectric conversion layer 140 and reducing the photoelectric conversion efficiency. The passivation layer 160 contains a piperazine compound and tends to be poorly soluble at room temperature in solvents including aprotic polar solvents such as dimethylformamide (DMF), N-methylpyrrolidone (NMP), γ-butyrolactone (GBL), and acetonitrile, which are used to form the photoelectric conversion layer 140. Therefore, compared to the excess material layer 150, the passivation layer 160 is less likely to be involved in the crystal growth of the perovskite material and precipitates on the surface and grain boundaries of the photoelectric conversion layer 140. The crystallization process is known to occur from the surface, with the poorly soluble piperazine compound precipitating on the surface first, followed by the perovskite compound containing the hole transport compound. By precipitating on the surface, the piperazine compound facilitates electron transport while maintaining passivation properties. In particular, forming a halide salt of the piperazine compound and making it an ionic material increases its solubility and facilitates surface deposition. Furthermore, having a hydrophobic group such as an alkyl chain or a fluorine-containing organic group bonded to one of the nitrogen groups further promotes surface deposition. The fluorine-containing organic group is preferably a fluorinated alkyl group. Here, the "piperazine compound" refers to at least one of piperazine and piperazine derivatives (including halide salts) represented by the following chemical formulas 1 to 3, and may also be a mixture of multiple types thereof. In the formulas, R1 to R8 are hydrogen or any substituent, RA1 to RA4 are hydrogen or an alkyl group, and X is a halogen. The deposition of the piperazine compound on the surface can be confirmed by time-of-flight secondary ion mass spectrometry.

[0093] Specific examples of piperazine derivatives include piperazine-1,4-diium iodide, piperazinium iodide, pentylpiperazine hydrochloride, and 1-(2-fluoroethyl)piperazine dihydrochloride.

[0094]

[0095]

[0096]

[0097] The passivation layer 160 preferably further contains a fluorine-containing organic compound. Fluorine-containing organic compounds have high surface deposition properties and high electron transport capabilities. On the other hand, they have low surface energy and poor adhesion to materials grown on them. Furthermore, when formed by coating, they tend to exhibit lyophobicity, resulting in coating defects. Therefore, by combining them with a specific organic compound, adhesion and coating properties can be improved.

[0098] The fluorine-containing organic compound preferably has a carbon skeleton containing an alkyl chain or benzene, with some hydrogen atoms substituted with fluorine, trifluoromethyl groups, or the like. The carbon skeleton more preferably contains consecutive carbon atoms bonded to fluorine. When the fluorine-containing organic compound has a benzene skeleton, it is preferable that five of the six hydrogen atoms in the benzene are substituted with fluorine or trifluoromethyl groups, with one hydrogen atom connected to a terminal lyophilic group. The greater the number of fluorine and trifluoromethyl group substitutions, the higher the lyophobicity and the greater the effect of selectively orienting the compound toward the surface. Therefore, when substituted with fluorine, it is preferable to have a pentafluorobenzene structure in which all hydrogen atoms except one connected to the terminal are substituted with fluorine. When the fluorine-containing organic compound has an alkyl chain skeleton, it is preferable that the end of the alkyl chain has a trifluoromethyl group or a phenyl group containing fluorine or trifluoromethyl groups, and the end of the alkyl chain has a lyophilic group. The fluorine-containing end faces the electron transport layer, and the end containing the lyophilic group faces the perovskite surface. The linear skeleton, excluding the end and terminal, preferably has from 1 to 17 carbon atoms. More preferably, the number of carbon atoms is 5 or more and 16 or less. To promote the formation of the passivation layer 160 through self-organization, the longer the alkyl chain, the better the orientation and passivation properties. However, the longer the alkyl chain, the higher the insulating properties and the lower the conductivity. Therefore, by adding an alkyl chain longer than the upper limit, sufficient orientation can be achieved, and by keeping the alkyl chain length below the lower limit, both passivation properties and conductivity can be achieved. When the fluorine-containing organic compound has an alkyl chain skeleton and a trifluoromethyl group at the end, the alkyl chain continuing from the end preferably contains consecutive fluorinated carbon atoms. More preferably, all but one or two carbon atoms adjacent to the end are preferably fluorinated. Continuous fluorination enhances lyophobicity and allows for more selective deposition on the surface, promoting the formation of the passivation layer 160. Another example of a fluorine-containing organic compound having an alkyl chain skeleton is a polymer structure.The partially fluorinated polymer structure, containing a large amount of fluorine, is more likely to be oriented planarly on the surface, unlike structures in which the fluorine-containing end faces the electron transport layer and the lyophilic end faces the perovskite surface. When the fluorine-containing organic compound has an alkyl chain skeleton and a phenyl group at the end containing fluorine or trifluoromethyl groups, the greater the number of fluorine and trifluoromethyl group substitutions, as described above. Therefore, when the hydrogen atoms of the phenyl group are substituted with fluorine, pentafluorobenzene is preferred. Furthermore, the combination of the phenyl group containing fluorine and trifluoromethyl groups with the alkyl chain can promote more selective deposition on the surface than when the compound has only a benzene skeleton. Furthermore, the fluorine-containing organic compound preferably has at least one lyophilic group at the end, specifically, an amino group, a hydrazine group, a trialkylamino group, a phosphate group, a phosphonate group, a hydroxyl group, a carboxyl group, a sulfonyl group, or an ionized form thereof. These compounds have lyophilicity and lyophobicity toward the aprotic polar solvent used to form the photoelectric conversion layer 140. By combining them with a fluorine-containing skeleton, which is lyophilic to the aprotic polar solvent used to form the photoelectric conversion layer 140, they can be positioned on the surface of the photoelectric conversion layer 140 even before the drying process. Having a linear skeleton, lyophilic groups, or both facilitates alignment of the fluorine-containing organic compounds, allowing for the formation of thin, uniform films and reduced series resistance. Ionization of these terminal groups improves performance by compensating for defects such as iodine defects, lead defects, and halogen defects on the perovskite layer surface. Multiple types of fluorine-containing organic compounds may also be used. These terminal groups may also be ionized in the solvent. It is more preferable for the fluorine-containing organic compound to have both cationic and anionic terminal groups to compensate for defects with different charges, such as iodine defects, lead defects, and halogen defects, on the perovskite layer surface. Examples of terminal groups having both cationic and anionic terminal groups include phosphocholine groups and carbamic acid groups.

[0099] Specific examples of fluorine-containing organic compounds include those having a benzene skeleton substituted with fluorine and a trifluoromethyl group, such as 4-fluorophenethylamine hydroiodide (FPEAI), 4-(trifluoromethyl)phenylammonium hydroiodide, 2,6-difluoroaniline, 3,4,5-trifluoroaniline, pentafluorophenylphosphonic acid (5FPAc), pentafluorophenylhydrazine (5FPHZ), and pentafluorobenzene-amino-carboxylic acid (carbamic acid) hydroiodide. When the fluorine-containing organic compound has an alkyl chain skeleton, examples of compounds having a trifluoromethyl group at the end and a lyophilic end include 1H,1H-undecafluorohexylamine (CF ３ (CF ２ ) ４ CH ２ NH ２ ), 1H,1H-pentadecafluorooctylamine (CF ３ (CF ２ ) ６ CH ２ NH ２ ), Fos-Choline-8 (fluoride) (registered trademark: C １３ H １７ F １３ NO ４ P), 2,2,2-trifluoroethylamine (CF ３ CH ２ NH ２ Examples of fluorine-containing organic compounds include 12-pentafluorophenoxydodecylphosphonic acid (C ), 3,3,4,4,5,5,6,6-nonafluorohexylphosphonic acid (FHPA), and polyvinylidene fluoride (PVDF) as a polymer structure. When the fluorine-containing organic compound has an alkyl chain skeleton, examples of fluorine-containing organic compounds having a phenyl group containing fluorine or a trifluoromethyl group include 12-pentafluorophenoxydodecylphosphonic acid (C ). １８ H ２６ F ５ O ４P), etc. The deposition of fluorine-containing organic compounds on the surface as a passivation layer can be confirmed by observing the contact angle. For example, when evaluated with chlorobenzene, the contact angle increases with the addition of a small amount of linear fluoroalkyl chains, highly lyophilic 1H,1H-undecafluorohexylamine, (fluorinated) Fos-Choline-8, etc.

[0100] The electron transport layer 170 selectively transmits electrons and transfers them to the second electrode layer 180. The electron transport layer 170 is formed of a material mainly composed of, for example, fullerene. Examples of fullerene include C60, C70, and their hydrides, oxides, metal complexes, and derivatives to which alkyl groups or the like are added, such as PCBM ([6,6]-Phenyl-C61-Butyric Acid Methyl Ester). In addition, a hole blocking layer made of pasocuproine (BCP), lithium fluoride (LiF), aluminum-doped zinc oxide (ZnO), or titanium oxide (TiO ２ The inorganic oxide layer may be doped with another metallic material.

[0101] When the solar cell 101 receives light from the side of the substrate 110, the second electrode layer 180 preferably includes a metal layer made of, for example, copper in order to reduce electrical resistance. When the solar cell 101 receives light from the side of the second electrode layer 180, the second electrode layer 180 may be made of a transparent conductive oxide.

[0102] Solar cell 101 having the above configuration is manufactured by a solar cell manufacturing method according to one embodiment of the present invention, as shown in Fig. 4. The solar cell manufacturing method of this embodiment includes a first electrode layer forming step (step S11), a precursor liquid applying step (step S12), a crystallization step (step S13), an electron transport layer forming step (step S14), and a second electrode layer forming step (step S15).

[0103] In the first electrode layer formation process of step S11, the first electrode layer 120 is formed on one main surface of the substrate 110. The first electrode layer 120 can be deposited using a vacuum film-forming technique such as sputtering. Furthermore, in the first electrode layer process, it is preferable to modify the surface of the deposited first electrode layer 120 to facilitate the formation of the hole transport layer 130 in the next process. Specific methods for modifying the surface of the first electrode layer 120 include, for example, surface hydroxylation by ultraviolet-ozone treatment or ozone water washing, deposition of oxides such as nickel oxide, which are prone to grow self-assembled monolayers, using vacuum film-forming techniques such as sputtering, deposition using a coating technique for oxide nanoparticles, and heat treatment to activate the surface and remove impurities to facilitate the growth of self-assembled monolayers.

[0104] In the precursor liquid application step of step S12, the perovskite precursor liquid is applied to the first electrode layer 120. The perovskite precursor liquid can be applied using, for example, a die coater, a bar coater, or the like. The perovskite precursor liquid applied in the precursor liquid application step is itself one embodiment of the perovskite precursor liquid according to the present invention.

[0105] The perovskite precursor liquid contains a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer that has hole selective permeability, and a piperazine compound. Preferably, the perovskite precursor liquid further contains hydrochloride that promotes crystal growth of the perovskite compound.

[0106] As the solvent, for example, polar aprotic solvents such as DMF, DMSO, NMP, GBL, acetonitrile, etc. may be used alone or as a mixture of two or more kinds, and may further contain other kinds of solvents.

[0107] The perovskite precursor is a mixture of a metal halide BX and an AX composed of an organic halide compound or an alkali metal halide, in a predetermined ratio. The molar concentration of the metal atom B is preferably in excess of the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal by 0.5 mol % to 10 mol %. This expels other materials to the interfaces between the front and back of the perovskite precursor liquid during the crystallization process, preventing other materials from being left behind in the impurity film 141 formed between the crystals of the perovskite compound, and suppressing a decrease in photoelectric conversion efficiency due to the remaining other materials.

[0108] As described above, the hole transport layer-forming compound is a material that forms a self-assembled monolayer having hole selective permeability. When the perovskite precursor liquid is applied onto the first electrode layer 120, the hole transport layer-forming compound preferentially self-assembles at the interface with the first electrode layer 120 to form a film (hole transport layer 130). The remaining hole transport layer-forming compound that has formed a film at the interface with the first electrode layer 120 also self-assembles on the surface of the perovskite precursor liquid coating (the side opposite the first electrode layer 120) to form a film (excess material layer 150). The concentration of the hole transport layer-forming compound in the perovskite precursor liquid can be 0.1 mmol / L or more and 5.0 mmol / L or less. A concentration of 0.5 mmol / L or more and 2.0 mmol / L or less is more preferable. Within the range that can cover the substrate surface, a lower concentration can suppress the formation of the excess material layer 150.

[0109] The piperazine compound aggregates into a film on the surface of the coating film of the perovskite precursor liquid, partially covering the surface of the layer of perovskite compound (photoelectric conversion layer 140) generated from the perovskite precursor, thereby forming a passivation layer 160 that suppresses the recombination of photocarriers (holes and electrons) at the interface of the photoelectric conversion layer 140. Furthermore, the piperazine compound preferentially precipitates on the surface of the coating film of the perovskite precursor liquid, thereby inhibiting the growth of the film of the hole transport layer-forming compound, thereby reliably forming a region where the excess material layer 150 is absent and the passivation layer 160 is present. The concentration of the piperazine compound in the perovskite precursor liquid can be 1 μmol / L or more and 5 mmol / L or less. A more preferred range is 50 μmol / L or more and 2 mmol / L or less. To achieve high performance, a high coverage of the piperazine compound on the surface is preferable. More preferably, the piperazine compound covers substantially the entire surface (e.g., 90% or more of the area), thereby suppressing the inhibition of electron transport by the hole transport layer. On the other hand, increasing the concentration of the piperazine compound to improve coverage can result in the piperazine compound being incorporated into the perovskite compound and acting as an impurity, making recombination more likely. Furthermore, forming multiple layers can cause resistance, potentially resulting in reduced performance. Therefore, as with the hole transport layer-forming compound, the molecular length is assumed to be the unit (lattice constant) of a monomolecular film, and the number of piperazine compounds per coating area is estimated. The concentration is determined so that the number of piperazine compounds contained in the coating film is smaller than this. When the piperazine compound is an ionic material, the molecular weight is determined by the ions containing the piperazine ring.

[0110] The hydrochloride promotes the crystallization of the perovskite compound and increases the grain size of the perovskite crystals. This reduces the area of ​​the grain boundaries in the photoelectric conversion layer 140 and suppresses a decrease in photoelectric conversion efficiency due to impurities between the perovskite crystals. Examples of hydrochlorides include methylammonium hydrochloride (MACl), formamidinium hydrochloride (FACl), and methylenediaminium hydrochloride (MDACl). ２). The moiety other than the hydrochloride salt is preferably smaller than the crystal lattice of the perovskite crystal and has an amino group. The concentration of the hydrochloride salt in the perovskite precursor liquid can be 0.05 mol% or more and 40 mol% or less relative to the molar concentration of the metal ions located at the center (B site) of the perovskite compound crystal. Chlorides containing alkyl metals can also have a similar effect. Examples include cesium chloride (CsCl) and rubidium chloride (RbCl).

[0111] In the crystallization process of step S13, the perovskite precursor liquid film is dried (the solvent is evaporated), causing the perovskite precursor to react and produce crystals of the perovskite compound. This forms a photoelectric conversion layer 140 primarily composed of the perovskite compound, which fixes the hole transport layer 130, the excess material layer 150, and the passivation layer 160. Furthermore, as the perovskite compound crystals grow, an impurity film 141 containing excess metal B and metal compounds is formed between the perovskite compound crystal grains. Because the perovskite compound crystals grow from the surface side (the side opposite the first electrode layer 120), the impurity film 141 also grows from the surface side toward the first electrode layer 120. Preferred methods for promoting the production of perovskite compound crystals in the perovskite precursor liquid film include, for example, poor solvent quenching, vacuum quenching, gas quenching, and laser treatment. Poor solvent quenching, vacuum quenching, and gas quenching, in which crystallization begins from the surface, are more preferred. Furthermore, in order to facilitate uniform growth of the passivation layer on the surface side of the coating film of the perovskite precursor liquid, it is preferable to cause the crystallization of the perovskite compound to proceed slowly relative to the precipitation of the passivation layer. From this perspective, vacuum quenching and gas quenching are more preferred. In the crystallization step of step S13, the dried coating film of the perovskite precursor liquid may be further heated.

[0112] In the electron transport layer forming step S14, the electron transport layer 170 is formed by a method such as coating or vacuum deposition. A hole blocking layer may be formed on the electron transport layer 170 by vacuum deposition or atomic deposition.

[0113] In the second electrode layer forming step S15, the second electrode layer 180 is formed by a method such as sputtering, vacuum deposition, plating, or coating depending on the material used.

[0114] As described above, the perovskite precursor liquid according to one embodiment of the present invention contains a perovskite precursor, a hole transport layer-forming compound, and a piperazine compound, and therefore can simultaneously form the hole transport layer 130 and the photoelectric conversion layer 140 on the first electrode layer 120 by a single coating operation, while also forming a passivation layer 160 on the surface of the photoelectric conversion layer 140, thereby preventing the photoelectric conversion layer 140 from being completely covered with an excess material layer 150 that inhibits electron transport. Therefore, the solar cell manufacturing method according to one embodiment of the present invention can easily manufacture a solar cell 101 having a relatively high photoelectric conversion efficiency.

[0115] 5 is a schematic cross-sectional view showing the configuration of a solar cell 101 according to a third embodiment of the present invention. The solar cell 201 includes a plate- or sheet-shaped substrate 210, a first electrode layer 220 laminated on one main surface (the lower side in FIG. 5 ) of the substrate 210, a hole transport layer 230 laminated on one surface of the first electrode layer 220, a photoelectric conversion layer 240 laminated on one surface of the hole transport layer 230, an excess material layer 250 partially laminated on one surface of the photoelectric conversion layer 240, a passivation layer 260 laminated in an area of ​​the one surface of the photoelectric conversion layer 240 where the excess material layer 250 is not present, an electron transport layer 270 laminated on one side of the excess material layer 250 and the passivation layer 260, and a second electrode layer 280 laminated on one side of the electron transport layer 270.

[0116] The substrate 210 is a structure that supports the other layers and ensures the strength of the solar cell 201. When the solar cell 201 receives light from the substrate 210 side, the substrate 210 is formed from a transparent material. Specifically, the substrate 210 may be formed from glass, a resin such as polyimide, polyamide, or polyethylene terephthalate, or the like. Furthermore, when the solar cell 201 receives light from the second electrode layer 280 side, the substrate 210 may be formed from a composite material including a metal layer, or the like.

[0117] The first electrode layer 220 collects holes generated in the photoelectric conversion layer 240 through the hole transport layer 230 and outputs them to the outside. The first electrode layer 220 may be formed of a transparent conductive oxide (TCO) having electrical conductivity and optical transparency. Examples of transparent conductive oxides that can be used to form the first electrode layer 220 include indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof. Among these, indium-based composite oxides containing indium oxide, zinc oxide, tungsten oxide, molybdenum oxide, or the like as their main components, and fluorine-doped tin oxide are preferred. In terms of high conductivity and transparency, indium oxide is particularly preferred. The first electrode layer 220 is preferably subjected to a surface treatment, such as ozone treatment, to improve the formability of the hole transport layer 230. The first electrode layer 220 may have a multilayer structure with a p-type oxide semiconductor layer, such as a nickel oxide or niobium oxide, on the surface.

[0118] The hole transport layer 230 is formed from a film of a hole transport layer-forming compound that forms self-assembled monolayers (SAMs) capable of transporting (selectively transmitting) holes. The hole transport layer 230 transports holes, among the positive and negative photocarriers (holes and electrons) generated in the photoelectric conversion layer 240, to the first electrode layer 220. The hole transport layer-forming compound preferably has a highest occupied molecular orbital close to the valence band of the perovskite compound that performs photoelectric conversion to facilitate hole transport. Furthermore, the lowest unoccupied molecular orbital is preferably smaller than the conduction band (close to the vacuum level) to block electrons. The hole transport layer-forming compound that forms the hole transport layer 230 preferably has a functional group capable of transporting holes, such as a carbazole-based, phenothiazine-based, or dimethylacridine-based compound, and a self-assembled terminal group that chemically bonds to the substrate, such as phosphoric acid or carboxylic acid. In order to impart passivation properties to the hole transport layer 230, it is preferable that a linear structure such as an alkyl chain be present between the functional group and the self-assembled terminal group. The alkyl chain preferably has four or more carbon atoms. Specifically, examples of hole transport layer-forming compounds that form the hole transport layer 230 include Me-4PACz ([4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid) and Me-6PACz ([6-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid)).

[0119] The photoelectric conversion layer 240 contains a perovskite compound that performs photoelectric conversion and absorbs incident light to generate photocarriers. The perovskite compound contained in the photoelectric conversion layer 240 contains an organic atomic group A containing at least one of a monovalent organic ammonium ion and an amidinium ion, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of an iodide ion I, a bromide ion Br, a chloride ion Cl, and a fluoride ion F, and the perovskite compound contains an ABX ３ In addition, perovskite compounds in which part or all of the organic atomic group A is substituted with an alkali metal Am are not excluded from the present invention.

[0120] The organic atomic group A is methylammonium MA (CH ３ NH ３ ), Formamidinium FA (CH ３ N ２ ) and the like. Examples of the alkali metal Am include potassium K, cesium Cs, rubidium Rb, and the like. Among these, when the power generation efficiency of the solar cell 201 is important, cesium Cs and rubidium Rb are preferred as the alkali metal Am, and cesium Cs is particularly preferred from the standpoints of cost and availability. Examples of the metal atom B include lead Pb and tin Sn. The amounts of lead and tin are adjusted depending on the required band gap. The halogen atom X is preferably at least one of iodide I, bromide Br, and chloride Cl.

[0121] Specifically, preferred perovskite compounds include, for example, MAPbI ３ , MAPbBr ３ , MAPbCl ３ Methylammonium lead halides (MAPbX) such as ３ ), and FAPbI ３ , FAPbBr ３ , FAPbCl ３ Formamidinium lead halide (FAPbX) ３ The halogen atom X may contain multiple types, and the organic atomic group A may be FA containing both methylammonium and formamidinium. ｙ MA １－ｙ PbX ３ In addition, when the alkali metal Am is contained, Am ｙ FA ｚ MA １－ｙ－ｚ PbI Ｘ , Am ｙ FA １－ｙ PbI Ｘ Am may be a single element selected from Cs, Rb, and K, or may contain a plurality of elements (where y and z are any positive integers).

[0122] The excess material layer 250 is formed from the same hole transport layer-forming compound as that forming the hole transport layer 230. The hole transport layer-forming compound used for the hole transport layer 230 has a lowest unoccupied molecular orbital (LOW) lower than the conduction band of the perovskite compound (close to the vacuum level), which blocks electron transport, making it difficult for electrons to reach the electron transport layer and acting as a resistor. Ideally, it is preferable that the excess material layer 250 is not formed. However, when the hole transport layer 230 and the photoelectric conversion layer 240 are formed using the same process, it is necessary to add a slightly larger amount of hole transport layer-forming compound to form a continuous hole transport layer 230 that covers the entire surface of the first electrode layer 220, and the excess hole transport layer-forming compound forms the excess material layer 250. The excess material layer 250 may be composed solely of the hole transport layer-forming compound, or may include other materials contained in the perovskite precursor liquid. The weight content of the hole transport layer-forming compound in the excess material layer 250 is preferably 10% or more, and more preferably 30% or more. The weight content of the hole transport layer-forming compound in the excess material layer 250 is preferably 90% or less, and more preferably 70% or less. In other words, in the region where the passivation layer is not formed, electron transport is possible when the perovskite compound comes into direct contact with the electron transport layer in part, but it is preferable that the hole transport layer-forming compound is formed on the surface of the perovskite compound, thereby repelling electrons back into the perovskite compound layer, rather than forming a surface containing many defects. The weight content of the hole transport layer-forming compound in the excess material layer can be calculated based on the composition of the excess material layer measured by a combination of transmission electron microscope observation and energy dispersive X-ray analysis, etc. Since it is difficult to accurately grasp the growth state of the hole transport layer-forming compound on the TCO surface, we simply assume that the molecular length is the unit (lattice constant) of the monomolecular film, estimate the number of hole transport-forming compounds per coating area, and determine the concentration so that the number of hole transport-forming compounds contained in the coating film is larger than that.

[0123] The passivation layer 260 prevents photocarrier recombination at the interface with the photoelectric conversion layer 240 and promotes electrons reaching the electron transport layer 270. The passivation layer 260 is formed so as to overlap the surface of the excess material layer 250 and the photoelectric conversion layer 240, preventing the excess material layer 250 from covering the entire surface of the photoelectric conversion layer 240 and reducing the photoelectric conversion efficiency. The passivation layer 260 includes a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle. Because the polymer passivation compound is a polymer and has a large size, when the photoelectric conversion layer 240 is formed using the perovskite precursor liquid described below, it is not incorporated into the perovskite crystal and preferentially precipitates on the surface. Therefore, the formation of the excess material layer 250 can be suppressed to form the passivation layer 260. To ensure the formation of the passivation layer 260, the weight-average molecular weight of the polymer passivation compound is preferably 5,000 to 5,000,000. A molecular weight of 10,000 or more is preferable to ensure that the halogen atoms are not incorporated into the perovskite compound, and a molecular weight of 2.5 million or less is more preferable to maintain solubility in the solvent. Furthermore, the polymer passivation compound has a nitrogen-containing heterocycle in its repeating unit, which prevents recombination and allows electrons to pass efficiently. A polymer passivation halide may also be used. A polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle easily forms a polymer passivation compound with halogen ions in the precursor liquid. By forming a polymer passivation halide, halogen defects that occur due to aging on the surface of the perovskite compound can be compensated for, thereby improving the reliability of solar cell characteristics.

[0124] If the coverage of the photoelectric conversion layer 240 with the passivation layer 260 is 50% or more, electron transport can be performed effectively. If it is 90% or more, this effect is further enhanced, which is preferable. Furthermore, if it is 99% or less, resistance loss caused by partial thickening of the polymer passivation compound can be reduced. Furthermore, if it is 95% or less, resistance loss can be suppressed even more effectively.

[0125] Preferred nitrogen-containing heterocycles for polymer passivation compounds include pyridine, pyrrolidone, phthalimide, caprolactam, imidazole, imidazolium, triazole, thiazole, piperidium, and their derivatives. The polymer passivation compound preferably has a larger band gap than the perovskite compound. More preferably, the highest occupied molecular orbital of the polymer passivation compound is larger than the valence band of the perovskite compound (farther from the vacuum level), and the lowest unoccupied molecular orbital of the polymer passivation compound is smaller than the conduction band of the perovskite compound (closer to the vacuum level). Furthermore, by using a highly conductive heterocycle with an alkyl chain composed of locally highly insulating vinyl groups, carriers can be efficiently transported while maintaining passivation properties.

[0126] Furthermore, pyrrolidone, phthalimide, and caprolactam have oxygen in their skeletons, and in skeletons containing hydrogen halide ions, and pyridine, imidazole, imidazolium, triazole, and thiazole, nitrogen ions are easily converted into halogen ions to form polymer passivation halides. Therefore, during the formation of the passivation layer from the precursor liquid, halogen ions not used in the formation of the perovskite compound are absorbed to partially form polymer passivation halides. The polymer passivation halides compensate for halogen defects that occur on the surface during the formation of the perovskite compound, improving the passivation properties of the perovskite compound surface. Furthermore, in the completed solar cell, the polymer passivation halides can compensate for halogen defects on the surface of the perovskite compound that occur due to aging, thereby improving the reliability of the solar cell's characteristics. Therefore, if the molar concentration of halogen ions X in the precursor liquid is 1% or more in excess of the molar concentration of at least one of the materials involved in the A site and B site of the perovskite compound, a halide can be effectively formed with the polymer passivation compound. Furthermore, if the molar concentration is 3% or more, halogen ions can be incorporated more effectively. Furthermore, an excess of 20% or less is preferable, which can suppress defect formation in the perovskite compound. Furthermore, if the excess amount is 10% or less, defect formation can be suppressed even more effectively. A precursor liquid containing excess halogen can also be formed by adding a halide of the polymer passivation compound to the precursor. From the perspective of improving reliability, the polymer passivation halide in the passivation layer after solar cell formation is preferably formed in 1% or more of the total number of repeating units of the polymer passivation compound. Furthermore, if the polymer passivation halide is formed in 5% or more, defects occurring in the perovskite compound can be more effectively compensated for. Furthermore, if the polymer passivation halide accounts for 90% or less of the total number of repeating units of the polymer passivation compound, the polymer passivation compound can be maintained in a stable state without steric hindrance. Furthermore, by keeping the density at 80% or less, a more stable state can be maintained.

[0127] The repeating unit of the polymeric passivation compound may be an alkyl unit. That is, the repeating unit of the polymeric passivation compound may be an alkyl unit substituted with a nitrogen-containing heterocycle. A typical example of the polymeric passivation compound is a compound having a polyvinyl skeleton obtained by vinyl polymerization of a monomer having a nitrogen-containing heterocycle and a vinyl group. That is, the polymeric passivation compound may have a nitrogen-containing heterocycle bonded to every two carbon atoms of the alkyl chain. Because the polymeric passivation compound is a compound with an alkyl chain as its main chain, the polymer can be synthesized relatively easily and the desired molecular weight can be obtained, thereby more reliably forming the passivation layer 260. Furthermore, the presence of the alkyl chain facilitates orientation control and allows for a uniform arrangement of the heterocycles. Furthermore, in addition to a structure having a nitrogen-containing heterocycle or a vinyl skeleton, the polymeric passivation compound may also include a repeating structure of other skeletons, such as a fluorinated alkyl chain skeleton. For example, a skeleton having a fluorinated alkyl chain may be included as a branch of the alkyl chain between the poly(vinylimidazole) skeletons. Fluorinated alkyl chains tend to exhibit lyophobicity and can be more selectively deposited on the surface of the perovskite compound.

[0128] Examples of polymer passivation compounds having repeating units of alkyl units substituted with nitrogen-containing heterocycles include poly(vinylpyrrolidone), poly(4-vinylpyridine), poly(2-vinylpyridine), poly(1-vinylimidazole), poly(2-vinylimidazole), poly(4-vinylimidazole), poly(vinylazole), poly(vinylphthalimide), poly(vinylimidazole), poly(vinylcaprolactam), poly(vinyltriazole), poly(5-vinylthiazole), and poly(4-methyl-5-vinylthiazole). Examples of halides include poly(vinylpyrrolidone) iodine complexes.

[0129] The electron transport layer 270 transports electrons and transfers them to the second electrode layer 280. The electron transport layer 270 can be formed of a material mainly containing fullerene, for example. Examples of fullerene include C60, C70, and their hydrides, oxides, metal complexes, and derivatives with alkyl groups added thereto, such as PCBM ([6,6]-Phenyl-C61-Butyric Acid Methyl Ester). In addition, a hole blocking layer such as pasocuproine (BCP), lithium fluoride (LiF), or tin oxide (SnO) can be provided between the electron transport layer 270 and the second electrode layer 280. ２ ), aluminum-doped zinc oxide (ZnO), titanium oxide (TiO ２ The inorganic oxide layer may be doped with another metallic material.

[0130] When the solar cell 201 receives light from the side of the base material 210, the second electrode layer 280 preferably includes a metal layer made of, for example, copper in order to reduce electrical resistance. When the solar cell 201 receives light from the side of the second electrode layer 280, the second electrode layer 280 may be made of a transparent conductive oxide.

[0131] The solar cell 201 having the above configuration is manufactured by a solar cell manufacturing method according to one embodiment of the present invention, as shown in Fig. 6. The solar cell manufacturing method of this embodiment includes a first electrode layer forming step (step S21), a precursor liquid applying step (step S22), a crystallization step (step S23), an electron transport layer forming step (step S24), and a second electrode layer forming step (step S25).

[0132] In the first electrode layer formation process of step S21, the first electrode layer 220 is formed on one main surface of the substrate 210. The first electrode layer 220 can be deposited using a vacuum film-forming technique such as sputtering. Furthermore, in the first electrode layer process, it is preferable to modify the surface of the deposited first electrode layer 220 to facilitate the formation of the hole transport layer 230 in the next process. Specific methods for modifying the surface of the first electrode layer 220 include, for example, surface hydroxylation by ultraviolet-ozone treatment or ozone water washing, deposition of oxides such as nickel oxide, which are prone to grow self-assembled monolayers, using a vacuum film-forming technique such as sputtering, deposition using a coating technique for oxide nanoparticles, and heat treatment to activate the surface and remove impurities to facilitate the growth of self-assembled monolayers.

[0133] In the precursor liquid application step of step S22, the perovskite precursor liquid is applied to the first electrode layer 220. The perovskite precursor liquid can be applied using, for example, a die coater, a bar coater, or the like. The perovskite precursor liquid applied in the precursor liquid application step is itself one embodiment of the perovskite precursor liquid according to the present invention.

[0134] The perovskite precursor liquid contains a solvent, a perovskite precursor that forms a perovskite compound that performs photoelectric conversion, a hole transport layer-forming compound that forms a self-assembled monolayer, and a polymer passivation compound. Preferably, the perovskite precursor liquid further contains hydrochloride that promotes crystal growth of the perovskite compound.

[0135] Examples of solvents include amide solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); sulfoxides such as dimethyl sulfoxide (DMSO), diethyl sulfoxide, and dibutyl sulfoxide; esters such as γ-valerolactone (GBL); and aprotic polar solvents such as acetonitrile. These solvents may be used alone or in combination, and may further contain other organic solvents. The boiling points of these organic solvents are preferably as low as possible because they must be distilled off during the formation of perovskite crystals. Specifically, the boiling point under atmospheric pressure is preferably 300°C or less, more preferably 200°C or less, and even more preferably 180°C or less. Furthermore, the polymer passivation compound may be different from the solvent that dissolves the perovskite compound. To grow the polymer passivation compound uniformly on the surface of the perovskite compound, it is preferable that the polymer passivation compound be dispersed in the solvent. Therefore, it is preferable to add a small amount of a non-polar solvent in addition to the polar solvent and mix them. The addition of a small amount of non-polar solvent makes it possible to disperse the polymer passivation compound while preventing the perovskite compound from crystallizing in the liquid. Alternatively, the polymer passivation compound can be dissolved in a non-polar solvent and then added to the solvent in which the perovskite compound and the hole transport layer-forming compound are dissolved. Examples of non-polar solvents include isopropanol.

[0136] As described above, a material that forms a self-assembled monolayer is used as the hole transport layer-forming compound. When the perovskite precursor liquid is applied onto the first electrode layer 220, the hole transport layer-forming compound preferentially self-assembles at the interface with the first electrode layer 220 to form a film (hole transport layer 230). The remaining hole transport layer-forming compound that has formed a film at the interface with the first electrode layer 220 also self-assembles on the surface of the perovskite precursor liquid coating (the side opposite the first electrode layer 220) to form a film (excess material layer 250). The concentration of the hole transport layer-forming compound in the perovskite precursor liquid can be 0.1 mmol / L or more and 5.0 mmol / L or less. A concentration of 0.5 mmol / L or more and 2.0 mmol / L or less is more preferable. Within the range that can cover the substrate surface, a lower concentration can suppress the formation of the excess material layer 250.

[0137] The polymer passivation compound aggregates into a film on the surface of the coating of the perovskite precursor liquid, partially covering the surface of the layer of perovskite compound (photoelectric conversion layer 240) generated from the perovskite precursor, thereby forming a passivation layer 260 that suppresses the recombination of photocarriers (holes and electrons) at the interface of the photoelectric conversion layer 240. The polymer passivation compound has a larger molecular weight than other materials, and because it is a polymer and has a large size, it is not incorporated into the perovskite crystals and is preferentially precipitated on the surface of the photoelectric conversion layer 240. Therefore, by inhibiting the growth of the film of the hole transport layer-forming compound, the precipitation of the excess material layer 250 is suppressed and a region where the passivation layer 260 exists is reliably formed.

[0138] In the crystallization process of step S23, the film of the perovskite precursor liquid is dried (the solvent is evaporated), causing the perovskite precursor to react and produce crystals of the perovskite compound. This forms a photoelectric conversion layer 240 mainly composed of the perovskite compound, which fixes the hole transport layer 230, the excess material layer 250, and the passivation layer 260. Furthermore, if the passivation layer 260 contains a polymer passivation halide, halogen ions desorb from the polymer passivation compound and bond to defects on the surface of the perovskite compound, suppressing carrier recombination.

[0139] As a method for promoting the formation of crystals of the perovskite compound in the perovskite precursor liquid film, for example, poor solvent quenching, vacuum quenching, gas quenching, laser treatment, etc. are preferably employed. Poor solvent quenching, vacuum quenching, and gas quenching, in which crystallization begins from the surface, are more preferred. Furthermore, in order to facilitate uniform growth of a passivation layer on the surface side of the perovskite precursor liquid coating film, it is preferable to slow the crystallization of the perovskite compound relative to the precipitation of the passivation layer. From this perspective, vacuum quenching and gas quenching are more preferred. In the crystallization process of step S23, the dried perovskite precursor liquid coating film may be further heated.

[0140] In the electron transport layer forming step S24, the electron transport layer 270 is formed by a method such as coating or vacuum deposition. A hole blocking layer may be formed on the electron transport layer 270 by vacuum deposition or atomic deposition.

[0141] In the second electrode layer forming step S25, the second electrode layer 280 is formed by a method such as sputtering, vacuum deposition, plating, or coating depending on the material used.

[0142] As described above, the perovskite precursor liquid according to one embodiment of the present invention contains a perovskite precursor, a hole transport layer-forming compound, and a polymer passivation compound, and therefore can simultaneously form the hole transport layer 230 and the photoelectric conversion layer 240 on the first electrode layer 220 by a single coating operation, while also forming the passivation layer 260 on the surface of the photoelectric conversion layer 240, thereby preventing the photoelectric conversion layer 240 from being completely covered with the excess material layer 250 that inhibits electron transport. Therefore, the solar cell manufacturing method according to one embodiment of the present invention can easily manufacture a solar cell 201 having a relatively high photoelectric conversion efficiency.

[0143] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and various modifications and variations are possible. The solar cell according to the present invention may include an additional functional layer. For example, a second passivation layer may be provided between the excess material layer and the passivation layer and the electron transport layer, covering one side of the excess material layer and the passivation layer. This second passivation layer may be formed from the same material as the first passivation layer that is laminated in the region where the excess material layer is absent. Furthermore, the electron transport layer may be omitted from the solar cell according to the present invention. Furthermore, the solar cell according to the present invention may be used to form a tandem solar cell using a photoelectric conversion body such as a crystalline silicon solar cell as a substrate.

[0144] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0145] Example 1 A commercially available glass / ITO substrate (a glass substrate on which a first electrode had been laminated in advance) was used as the substrate. First, a NiOx film was formed as an electron blocking layer. Next, a perovskite precursor liquid was applied, followed by a crystallization process and heating to generate crystals of the perovskite compound, thereby forming a hole transport layer, a photoelectric conversion layer, an excess material layer, and a passivation layer. The crystallization process used a vacuum quenching method. Furthermore, an electron transport layer was formed by applying PCBM, a hole blocking layer was formed by vapor deposition of BCP, and a second electrode was formed by vapor deposition of Ag, thereby producing Example 1 of the solar cell. The perovskite precursor liquid was prepared by dissolving 1.2 mol / L of a perovskite precursor (PbI) in a mixed solvent of DMF and NMP at a volume ratio of 90:10. ２, CsI, FAI), 1.0 mmol / L of Me-4PACz (hole transport layer forming compound), and 0.2 mmol / L of n-octylphosphocholine (specific organic compound) were dissolved in the solution. The perovskite precursor contained FA and Cs in a molar ratio of 90:10 for A site formation, Pb for B site formation, and I as a halogen atom for X site formation. Here, the molecular lengths of Me-4PACz and n-octylphosphocholine can be estimated to be 1 nm and 1.8 nm, respectively, by molecular orbital calculation. Assuming that these are grown densely on the substrate as a unit lattice, Me-4PACz and n-octylphosphocholine each have a molecular length of 9.0 × 10 １４ pieces, 5.0×10 １４ Assuming that the perovskite layer is 500 nm thick, the number of molecules that precipitate from the concentration of Me-4PACz selected here is 1.3 × 10 １５ The number of precipitates calculated from the concentration of n-octylphosphocholine is 2.6 × 10 １４ Therefore, the concentration of Me-4PACz is determined so that it is equal to or greater than the standard close-packed molecular number and equal to or less than the standard close-packed molecular number of n-octylphosphocholine.

[0146] Examples 2 to 5 Solar cell Example 2 was produced under the same conditions as Example 1, except that 0.2 mmol / L of 2,8-dimethyl-5-nonylphosphocholine was used as the specific organic compound. Solar cell Example 3 was produced under the same conditions as Example 1, except that 0.2 mmol / L of 10-undecylenyl-1-phosphocholine was used as the specific organic compound. Solar cell Example 4 was produced under the same conditions as Example 1, except that 0.2 mol / L of n-octylammonium iodide was used as the specific organic compound. Solar cell Example 5 was produced under the same conditions as Example 1, except that 0.13 mol / L of L-α-phosphotidylcholine was used as the specific organic compound.

[0147] Examples 6 and 7 A solar cell of Example 5 was produced under the same conditions as Example 1, except that 10 mol % of MACl was mixed into the perovskite precursor liquid. A solar cell of Example 6 was produced under the same conditions as Example 1, except that the hole transport layer-forming compound was changed from Me-4PACz to DMAcPA.

[0148] Example 8 A solar cell of Example 8 was produced under the same conditions as in Example 5, except that MeO-4PACz was used as the hole transport layer forming material.

[0149] Comparative Example 1 A solar cell of Comparative Example 1 was produced under the same conditions as in Example 1, except that a perovskite precursor liquid not containing an organic compound having a chain hydrocarbon group was used.

[0150] The photoelectric conversion efficiencies of Examples 1 to 8 and Comparative Example 1 were measured, and the ratios to the photoelectric conversion efficiency of Comparative Example 1 were calculated. As a result, Example 1 was 1.15, Example 2 was 1.16, Example 3 was 1.18, Example 4 was 1.08, Example 5 was 1.17, Example 6 was 1.16, Example 7 was 1.10, and Example 8 was 1.18. The photoelectric conversion efficiencies of the solar cells were measured at 25°C and 1000 W / m ２ This was calculated using the current-voltage characteristic measurements shown below. Specifically, the photoelectric conversion efficiency was calculated by dividing the maximum output determined from the current-voltage characteristic measurements by the power generation area.

[0151] Example 9 A solar cell of Example 9 was produced under the same conditions as Example 1, except that the perovskite precursor solution contained, as the perovskite precursor, FA and Cs in a molar ratio of 80:20 for forming the A site, Pb for forming the B site, and I and Br in a molar ratio of 90:10 as halogen atoms for forming the X site, and 1.0 mmol / L of Me-4PACz (a hole transport layer-forming compound) and 0.13 mmol / L of L-α-Phosphatidylcholine were used.

[0152] Example 10 A solar cell of Example 10 was produced under the same conditions as in Example 9, except that 0.3 mmol / L of piperazine-1,4-diium iodide was further added as a piperazine compound.

[0153] (Examples 11 and 12) 2 mM MDAC1 was further added to the perovskite precursor solution. ２ A solar cell of Example 11 was produced under the same conditions as Example 10, except that 2 mM of RbCl was further added to the perovskite precursor liquid. A solar cell of Example 12 was produced under the same conditions as Example 10, except that 2 mM of RbCl was further added to the perovskite precursor liquid.

[0154] Example 13 A solar cell of Example 13 was produced under the same conditions as Example 10, except that 0.5 mmol / L of piperazine compound, piperazine iodide, was added to the perovskite precursor liquid instead of piperazine-1,4-diium iodide.

[0155] Example 14 A solar cell of Example 15 was produced under the same conditions as in Example 10, except that 0.4 mmol / L of 4-fluorophenethylamine hydroiodide, a fluorine-containing organic compound, was blended instead of piperazine-1,4-diium iodide.

[0156] Examples 15 and 16 A solar cell of Example 15 was produced under the same conditions as Example 10, except that 0.4 mmol / L of 4-fluorophenethylamine hydroiodide, a fluorine-containing organic compound, was further blended. A solar cell of Example 16 was produced under the same conditions as Example 13, except that 0.4 mM of 4-fluorophenethylamine hydroiodide, a fluorine-containing organic compound, was further blended.

[0157] Example 17 A solar cell of Example 17 was produced under the same conditions as in Example 10, except that 0.4 mmol of pentafluorophenylphosphonic acid, a fluorine-containing organic compound, was blended in place of piperazine-1,4-diium iodide.

[0158] (Example 18) Furthermore, 2 mM MDAC1 ２ A solar cell of Example 18 was produced under the same conditions as in Example 17, except that the above was additionally blended.

[0159] Example 19 A solar cell of Example 19 was produced under the same conditions as Example 10, except that 0.4 mmol of pentafluorophenylphosphonic acid, a fluorine-containing organic compound, was additionally blended.

[0160] Example 20 A solar cell of Example 20 was produced under the same conditions as in Example 10, except that 0.2 mmol of (fluorinated) Fos-Choline-8, a fluorine-containing organic compound, was blended in place of piperazine-1,4-diium iodide.

[0161] (Example 21) A solar cell of Example 21 was produced under the same conditions as Example 10, except that 0.2 mmol of (fluorinated) Fos-Choline-8 was further added. (Example 22) A solar cell of Example 22 was produced under the same conditions as Example 12, except that 0.1 mg / mL of poly(vinylpyrrolidone)-iodine complex, a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle, was added instead of piperazine-1,4-diium iodide.

[0162] Example 23 A solar cell of Example 23 was produced under the same conditions as in Example 19, except that MeO-4PACz was used instead of Me-4PACz as the hole transport layer forming material.

[0163] Comparative Example 2 A solar cell of Comparative Example 11 was produced under the same conditions as in Example 11, except that a perovskite precursor liquid that did not contain the specific organic compound, other passivation materials, or excess perovskite compound-forming materials was used.

[0164] The photoelectric conversion efficiency was measured for Examples 9 to 23 and Comparative Example 2, and the ratio to the photoelectric conversion efficiency of Comparative Example 2 was calculated. As a result, Example 9 was 1.05, Example 10 was 1.07, Example 11 was 1.08, Example 12 was 1.09, Example 13 was 1.08, Example 14 was 1.07, Example 15 was 1.11, Example 16 was 1.13, Example 17 was 1.04, Example 18 was 1.06, Example 19 was 1.11, Example 20 was 1.07, Example 21 was 1.13, Example 24 was 1.06, and Example 23 was 1.07.

[0165] As described above, it was confirmed that the photoelectric conversion efficiency can be improved by blending a hole transport layer-forming compound and a specific organic substance into a perovskite precursor liquid. Furthermore, it was confirmed that the photoelectric conversion efficiency can be improved by adding a fluorine-containing organic compound, a piperazine compound, or a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle in addition to the specific organic compound.

[0166] (Example 24) A commercially available glass / ITO substrate (a substrate with a first electrode layer laminated thereon, 3 cm square) was used as the substrate. First, a NiOx film was formed as an electron blocking layer. Next, a perovskite precursor liquid was applied, followed by a crystallization process and heating to generate crystals of the perovskite compound, thereby forming a hole transport layer, a photoelectric conversion layer, an excess material layer, and a passivation layer. The crystallization process used a vacuum quenching method. Furthermore, an electron transport layer was formed by application of PCBM, a hole blocking layer was formed by vapor deposition of BCP, and a second electrode layer was formed by laminating Ag by vapor deposition, thereby producing a solar cell of Example 1. The perovskite precursor liquid was prepared by dissolving 1.2 mol / L of a perovskite precursor (PbI) in a mixed solvent of DMF and NMP at a volume ratio of 90:10. ２ , CsI, FAI), 1.0 mmol / L of Me4PACz (a hole transport layer-forming compound), and 0.3 mmol / L of piperazine-1,4-diium iodide were dissolved in the perovskite precursor. The perovskite precursor contained FA and Cs in a molar ratio of 90:10 for the formation of the A site, Pb for the formation of the B site, and I as a halogen atom for the formation of the X site. Here, the molecular lengths of Me-4PACz and piperazine (only the piperazine skeleton is considered) can be estimated by molecular orbital calculation to be 1 nm and 0.3 nm, respectively. Assuming that these are used as a unit cell and grow densely on the substrate, Me-4PACz and piperazine each have a size of 9.0 x 10 １４ pieces, 1.0x10 １６ Assuming that the perovskite layer is 500 nm thick, the number of molecules that precipitate from the concentration of Me-4PACz selected here is 1.3 × 10 １５The number of precipitates of piperazine precipitated from the concentration of piperazine-1,4-diium iodide is 1.5 x 10 １５ Therefore, the concentration of Me-4PACz is determined to be equal to or greater than the standard close-packed molecular number, and the concentration of Piperazine-1,4-diium iodide is determined to be equal to or less than the standard close-packed molecular number.

[0167] Examples 25 to 30 Solar cell Example 25 was produced under the same conditions as Example 24, except that 0.5 mM piperazine iodide was used as the piperazine compound. Solar cell Example 26 was produced under the same conditions as Example 24, except that 0.15 mM piperazine was used as the piperazine compound. Solar cell Example 27 was produced under the same conditions as Example 24, except that 0.5 mM pentylpiperazine hydrochloride was added as the piperazine compound. Solar cell Example 28 was produced under the same conditions as Example 24, except that 0.5 mM 1-(trifluoromethyl)piperazine hydrochloride was added as the piperazine compound. A solar cell of Example 29 was produced under the same conditions as Example 24, except that 10 mol % of MACl was further blended into the perovskite precursor. A solar cell of Example 30 was produced under the same conditions as Example 29, except that DMAcPA was used as the hole transport layer-forming compound.

[0168] Comparative Example 3 A solar cell of Comparative Example 3 was produced under the same conditions as in Example 24, except that the perovskite precursor liquid did not contain a piperazine compound.

[0169] The photoelectric conversion efficiencies of Examples 24 to 30 and Comparative Example 3 were measured, and the ratios to the photoelectric conversion efficiency of Comparative Example 3 were calculated. As a result, Example 24 had a photoelectric conversion efficiency of 1.12, Example 25 had a photoelectric conversion efficiency of 1.14, Example 26 had a photoelectric conversion efficiency of 1.06, Example 27 had a photoelectric conversion efficiency of 1.15, Example 28 had a photoelectric conversion efficiency of 1.17, Example 29 had a photoelectric conversion efficiency of 1.14, and Example 30 had a photoelectric conversion efficiency of 1.10.

[0170] Example 31 A solar cell of Example 31 was produced under the same conditions as Example 24, except that the perovskite precursor used contained FA and Cs in a molar ratio of 80:20 for the A site formation, Pb for the B site formation, and I and Br in a molar ratio of 90:10 as halogen atoms for the X site formation.

[0171] Example 32 Furthermore, a solar cell of Example 32 was produced under the same conditions as Example 31, except that 0.4 mM of pentafluorophenylphosphonic acid was used.

[0172] Comparative Example 4 A solar cell of Comparative Example 4 was produced under the same conditions as in Example 31, except that the piperazine compound and other passivation materials were not included.

[0173] The photoelectric conversion efficiencies of Examples 31 and 32 and Comparative Example 4 were measured, and the ratios to the photoelectric conversion efficiency of Comparative Example 4 were calculated. As a result, Example 31 was 1.04, and Example 32 was 1.09.

[0174] As described above, it was confirmed that the photoelectric conversion efficiency can be further improved by blending a hole transport layer-forming compound and a piperazine compound into the perovskite precursor liquid. It was also confirmed that the photoelectric conversion efficiency can be further improved by adding a fluorine-containing organic compound in addition to the piperazine compound.

[0175] (Example 33) A commercially available glass / ITO substrate (a substrate with a first electrode layer laminated thereon, 3 cm square) was used as the substrate. First, a NiOx film was formed as an electron blocking layer. Next, a perovskite precursor liquid was applied, followed by a crystallization process and heating to generate crystals of the perovskite compound, thereby forming a hole transport layer, a photoelectric conversion layer, an excess material layer, and a passivation layer. The crystallization process used a vacuum quenching method. Furthermore, an electron transport layer was formed by applying PCBM, a hole blocking layer was formed by vapor deposition of BCP, and a second electrode layer was formed by laminating Ag by vapor deposition, thereby producing a solar cell of Example 61. The perovskite precursor liquid was prepared by dissolving a 1.2 mol / L perovskite precursor (PbI) containing 5 mol% excess iodine in a mixed solvent of DMF and NMP at a volume ratio of 90:10. ２The perovskite precursor contained FA and Cs in a molar ratio of 90:10 to form the A site, Pb to form the B site, and I as a halogen atom to form the X site.

[0176] Comparative Example 5 A solar cell of Comparative Example 5 was produced under the same conditions as in Example 33, except that a perovskite precursor liquid not containing a poly(vinylpyrrolidone)-iodine complex was used.

[0177] The photoelectric conversion efficiencies of Example 33 and Comparative Example 5 were measured, and the ratio to the photoelectric conversion efficiency of Comparative Example 5 was calculated. As a result, the photoelectric conversion efficiency of Example 33 was 1.17. The photoelectric conversion efficiency of the solar cell was measured at 25°C and 1000 W / m ２ This was calculated using the current-voltage characteristic measurements shown below. Specifically, the photoelectric conversion efficiency was calculated by dividing the maximum output determined from the current-voltage characteristic measurements by the power generation area.

[0178] As described above, it was confirmed that photoelectric conversion efficiency can be improved by blending a hole transport layer-forming compound and a poly(vinylpyrrolidone)-iodine complex, which is a polymer passivation compound having a repeating unit with a nitrogen-containing heterocycle, into a perovskite precursor liquid.

[0179] 1, 101, 201 Solar cell 10, 110, 210 Base material 20, 120, 220 First electrode layer 30, 130, 230 Hole transport layer 40, 140, 240 Photoelectric conversion layer 41, 141 Impurity film 50, 150, 250 Excess material layer 60, 160, 260 Passivation layer 70, 170, 270 Electron transport layer 80, 180, 280 Second electrode layer

Claims

1. A perovskite precursor liquid comprising: a solvent; a perovskite precursor that forms a perovskite compound that performs photoelectric conversion; a hole transport layer-forming compound that forms a self-assembled monolayer having hole selective permeability; and an organic compound that has a chain hydrocarbon group having 5 or more carbon atoms which may be substituted and an ionic functional group.

2. The perovskite precursor liquid according to claim 1, wherein the ionic functional group is any one of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphonic acid group, a phosphoric acid group, a hydroxyl group, a carboxyl group, and a sulfonyl group.

3. The perovskite precursor liquid of claim 1, wherein the organic compound is a halide salt.

4. The perovskite precursor liquid according to any one of claims 1 to 3, wherein the perovskite precursor contains a metal halide including at least one of a lead halide or a tin halide, and an organic halide or an alkali metal halide, and the molar concentration of the metal portion of the metal halide is in excess of the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal by 0.5 mol % or more and 10 mol % or less.

5. The perovskite precursor liquid according to any one of claims 1 to 3, further comprising an organic hydrochloride that promotes crystal growth of the perovskite compound.

6. The perovskite precursor liquid according to any one of claims 1 to 3, further comprising at least one of a fluorine-containing organic compound, piperazine and piperazine derivatives, and a polymeric passivation compound having a repeat unit having a nitrogen-containing heterocycle.

7. The perovskite precursor liquid according to claim 6, wherein the fluorine-containing organic compound has at least one or more of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphate group, a phosphonic acid group, a hydroxyl group, a carboxyl group, a sulfonyl group, or an ionized form thereof at a terminal thereof, and has a carbon skeleton containing an alkyl chain or benzene in which hydrogen is substituted with fluorine or a trifluoromethyl group.

8. A solar cell manufacturing method comprising the steps of: applying a perovskite precursor liquid according to any one of claims 1 to 3 to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

9. A solar cell comprising: a plate-like or sheet-like substrate; a first electrode layer laminated on one main surface of the substrate; a hole transport layer laminated on the first electrode layer and consisting of a film of a hole transport layer-forming compound having hole selective permeability; a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound; an excess material layer partially laminated on the photoelectric conversion layer and containing the hole transport layer-forming compound; a passivation layer laminated in an area of ​​the photoelectric conversion layer where the excess material layer is not present, the passivation layer containing an organic compound having a chain hydrocarbon group having 5 or more carbon atoms which may be substituted and an ionic functional group; and a second electrode layer laminated on the one side of the excess material layer and the passivation layer.

10. The solar cell according to claim 9, wherein the photoelectric conversion layer has an impurity film containing a halide of a metal atom in the perovskite compound at the grain boundaries of the crystals of the perovskite compound.

11. The solar cell of claim 9 or 10, further comprising an electron transport layer disposed between the excess material layer and the passivation layer and the second electrode layer.

12. A perovskite precursor liquid comprising: a solvent; a perovskite precursor that forms a perovskite compound that performs photoelectric conversion; a hole transport layer forming compound that forms a self-assembled monolayer having hole selective permeability; and at least one of piperazine and a piperazine derivative.

13. The perovskite precursor liquid according to claim 12, wherein the piperazine derivative is a halide salt.

14. The perovskite precursor liquid according to claim 12, wherein the piperazine derivative has an alkyl chain or a fluorine-containing organic group bonded to one of the nitrogen atoms.

15. The perovskite precursor liquid according to any one of claims 12 to 14, wherein the perovskite precursor liquid further comprises a fluorine-containing organic compound.

16. The perovskite precursor liquid according to claim 15, wherein the fluorine-containing organic compound has at least one or more of an amino group, a hydrazine group, a trialkylamino group, a phosphocholine group, a phosphate group, a phosphonic acid group, a hydroxyl group, a carboxyl group, a sulfonyl group, and ionized forms thereof at a terminal thereof, and has a carbon skeleton containing an alkyl chain or benzene in which hydrogen is substituted with fluorine or a trifluoromethyl group.

17. A perovskite precursor liquid according to any one of claims 12 to 14, wherein the perovskite precursor contains a metal halide including a lead halide, and a halogenated organic compound or an alkali metal halide, and the molar concentration of the metal is in excess of the sum of the molar concentration of the organic compound and the molar concentration of the alkali metal by 0.5 mol % or more and 10 mol % or less.

18. A perovskite precursor liquid according to any one of claims 12 to 14, further comprising a hydrochloride salt that promotes crystal growth of the perovskite compound.

19. A solar cell manufacturing method comprising the steps of: applying a perovskite precursor liquid according to any one of claims 12 to 14 to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

20. A solar cell comprising: a plate-like or sheet-like substrate; a first electrode layer laminated on one main surface of the substrate; a hole transport layer laminated on the first electrode layer and consisting of a film of a hole transport layer forming compound having hole selective permeability; a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound; an excess material layer partially laminated on the photoelectric conversion layer and consisting of the hole transport layer forming compound; a passivation layer containing at least one of piperazine and a piperazine derivative laminated on an area of ​​the photoelectric conversion layer where the excess material layer is not present; and a second electrode layer laminated on the one side of the excess material layer and the passivation layer.

21. The solar cell according to claim 20, wherein the photoelectric conversion layer has an impurity film containing a halide of a metal atom in the perovskite compound at the grain boundaries of the crystals of the perovskite compound.

22. The solar cell of claim 20 or 21, further comprising an electron transport layer disposed between the excess material layer and the passivation layer and the second electrode layer.

23. A perovskite precursor liquid comprising: a solvent; a perovskite precursor that forms a perovskite compound that performs photoelectric conversion; a hole transport layer forming compound that forms a self-assembled monolayer; and a polymer passivation compound having a repeating unit having a nitrogen-containing heterocycle.

24. The perovskite precursor liquid of claim 23, wherein the polymeric passivation compound has a polyvinyl backbone.

25. The perovskite precursor liquid according to claim 23 or 24, wherein the nitrogen-containing heterocycle is any one of pyridine, pyrrolidone, phthalimide, caprolactam, imidazole, imidazolium, triazole, thiazole, piperidium, and derivatives thereof.

26. The perovskite compound is an ABX compound, in which X is a halogen atom. ３ 25. The perovskite precursor liquid according to claim 24, having a structure, wherein the molar concentration of X is higher than the molar concentration of at least one of A and B.

27. A solar cell manufacturing method comprising the steps of: applying the perovskite precursor liquid according to claim 23 or 24 to a first electrode layer formed on one main surface of a substrate; and volatilizing the solvent from the coating of the perovskite precursor liquid and reacting the perovskite precursor to produce crystals of a perovskite compound.

28. A solar cell comprising: a plate-like or sheet-like substrate; a first electrode layer laminated on one main surface of the substrate; a hole transport layer laminated on the first electrode layer and consisting of a film of a hole transport layer-forming compound; a photoelectric conversion layer laminated on the hole transport layer and containing a perovskite compound; an excess material layer partially laminated on the photoelectric conversion layer and containing the hole transport layer-forming compound; a passivation layer laminated in an area of ​​the photoelectric conversion layer where the excess material layer is absent and containing a polymer passivation compound having a nitrogen-containing heterocycle; and a second electrode layer laminated on the excess material layer and on the one side of the passivation layer.

29. The solar cell of claim 28, wherein the passivation layer comprises a halide of the polymeric passivation compound.

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