Coating agent for forming a large-area perovskite thin film and method for forming a large-area perovskite thin film using the same

Abstract

The present invention relates to a method for forming a large-area perovskite thin film capable of manufacturing a large-area uniform perovskite thin film without using an anti-solvent, a coating agent used therefor, and a perovskite solar cell including the same as a light absorption layer.

Description

Technical Field

[0001] The present invention relates to a method for forming a large-area perovskite thin film capable of manufacturing a large-area uniform perovskite thin film without using an anti-solvent, a coating agent used therefor, and a perovskite solar cell including the same as a light absorption layer.

Background Art

[0002] In order to solve the depletion of fossil energy and the global environmental problems caused by its use, research on renewable and clean alternative energy sources such as solar energy, wind power, and hydropower has been actively conducted.

[0003] Among these, the interest in solar cells that directly convert electrical energy from sunlight has increased significantly. Here, a solar cell means a cell that absorbs light energy from sunlight and generates a current-voltage using the photovoltaic effect that generates electrons and holes.

[0004] Currently, it is possible to manufacture n-p diode type single-crystalline silicon (Si) substrate solar cells with a light energy conversion efficiency exceeding 20%, and they are actually used for solar power generation. There are also solar cells using compound semiconductors such as gallium arsenide (GaAs) that are even more excellent in conversion efficiency. However, such inorganic semiconductor-based solar cells require materials purified to a very high purity for high efficiency, so a lot of energy is consumed in the purification of elemental materials, and expensive process equipment is required in the process of forming single crystals or thin films using elemental materials, and there is a limit to reducing the manufacturing cost of solar cells, which has become an obstacle to large-scale utilization.

[0005] Therefore, in order to manufacture solar cells at low cost, it is necessary to significantly reduce the cost of the materials or manufacturing processes that are core to solar cells. Research has been conducted on perovskite solar cells that can be manufactured with inexpensive materials and processes as an alternative to inorganic semiconductor-based solar cells.

[0006] The general structural formula of the perovskite structure is the AMX3 structure, which has a structure where anions are located at the X site, large cations are located at the A site, and small cations are located at the M site.

[0007] Such perovskite compounds are excellent in electrical conductivity, charge mobility, and optical properties, have a wide range of applications, and have various characteristics including long lifespan, a high absorption wavelength spectrum due to a small energy bandgap, and a wide charge-carrier diffusion length. At the same time, they have the advantages of being economical in terms of material price, being manufacturable as a solution, having low process costs, and being manufacturable at low temperatures, and are attracting attention as promising materials for renewable energy applications. In particular, research continues on using this as a light absorber for use in perovskite solar cells.

[0008] Currently, many small-area (roughly 2.5x2.5 cm 2 ) perovskite thin films are manufactured by a method based on the spin-coating technique, where after uniformly coating a perovskite solution through spin-coating, crystallization is carried out using an anti-solvent.

[0009] In principle, the spin-coating method has limitations in large-area coating and mass production technology, so methods for forming thin films in large-area processes generally use blade coating, slot die coating, inkjet printing, spray coating, etc.

[0010] However, conventional perovskite thin films formed through the above large-area coating have poor thin-film uniformity and thermal stability, and since an anti-solvent treatment process is carried out, there are limitations in the mass productivity of perovskite, such as the generation of waste due to the use of the anti-solvent.

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been devised to overcome the above-described problems, and by introducing a coating agent having an optimal composition for forming a large-area perovskite thin film, a method for forming a large-area perovskite thin film with excellent uniformity without performing a poor solvent treatment step, and a coating agent used therefor are to be provided.

Means for Solving the Problems

[0012] In order to solve the above-described problems, the present invention relates to a coating agent for forming a large-area perovskite thin film, and the perovskite thin film contains a perovskite compound represented by the following Chemical Formula 1 and includes a perovskite precursor, a crystallization improver, a Lewis base, and a solvent.

[0013] [Chemical Formula 1] A m A’ 1-m B(X n X’ 1-n )3

[0014] In Chemical Formula 1, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium), or EDA (Ethylenediamine), A’ is Cs + , Na + , K + , NH4 + or Rb + , B is Pb 2+ , Sn 2+ , Pd 2+ , Cu 2+ , Ge 2+ , Sr 2+ , Cd 2+ , Ca 2+ , Ni 2+ , Mn 2+ , Fe 2+ , Co 2+ , Sn 2+ , Yb 2+ or Eu 2+ , and each of X and X’ is independently Cl - , Br - or I -where m and n are rational numbers satisfying 0 < m ≤ 1 and 0 < n ≤ 1, and preferably, m and n are rational numbers satisfying 0.7 ≤ m ≤ 0.9 and 0.1 ≤ n ≤ 0.3.

[0015] In a preferred embodiment of the present invention, the perovskite precursor may include an organic halide represented by the following Chemical Formula 2, a monovalent metal halide represented by the following Chemical Formula 3, a divalent metal halide represented by the following Chemical Formula 4, and a divalent metal halide represented by the following Chemical Formula 5.

[0016] [Chemical Formula 2] AX

[0017] In Chemical Formula 2, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium), or EDA (Ethylenediamine), and X is Br - or I - .

[0018] [Chemical Formula 3] A’X

[0019] In Chemical Formula 3, A’ is Cs + , Na + , K + , NH4 + or Rb + , and X is Cl - , Br - or I - .

[0020] [Chemical Formula 4] BX2

[0021] [Chemical Formula 5] BX’2

[0022] In Chemical Formulas 4 and 5, B is Pb 2+ , Sn 2+ , Pd 2+ , Cu 2+ , Ge 2+ , Sr 2+ , Cd2+ , Ca 2+ , Ni 2+ , Mn 2+ , Fe 2+ , Co 2+ , Sn 2+ , Yb 2+ or Eu 2+ and each of X and X’ is independently Cl - , Br - or I - and X and X’ are different halogen anions from each other.

[0023] In a preferred embodiment of the present invention, the crystallization improver may contain one or more selected from CH3NH3Cl (MACl), CH3NH3Br, and CH3NH3I.

[0024] In a preferred embodiment of the present invention, the Lewis base may contain one or more selected from DMPU (N,N-Dimethyl-propyleneurea), HMPA (Hexamethylphosphoramide), and NMP (N-Methyl-2-pyrrolidone).

[0025] In a preferred embodiment of the present invention, the solvent may contain one or more selected from DMF (dimethylformamide), gamma-butyrolactone (γ-butyrolactone), 2-methoxyethanol (2-Methoxyethanol), DMSO (Dimethyl sulfoxide), and NMP (N-Methyl-2-pyrrolidinone).

[0026] In a preferred embodiment of the present invention, the coating agent of the present invention may contain 15 to 30 mol% of the crystallization improver and 40 to 100 mol% of the Lewis base with respect to 100 mol% of the perovskite precursor.

[0027] In a preferred embodiment of the present invention, the coating agent of the present invention may contain the solvent and the Lewis base in a volume ratio of 1:0.06 to 0.25.

[0028] Another object of the present invention relates to a method for forming a large-area (area of 200 cm 2 or more) perovskite thin film, which includes a first step of preparing a coating solution containing the above-mentioned coating agent for thin film formation; a second step of coating and drying the coating solution on top of a substrate to form a wet-thin film containing perovskite crystallized in an intermediate phase; and a third step of performing an annealing process on the wet thin film to form a large-area perovskite thin film containing the perovskite compound represented by Chemical Formula 1.

[0029] In a preferred embodiment of the present invention, the top of the substrate on which the coating solution is coated can be a Si thin film layer, a hole transport layer, an electron transport layer, and / or a passivation layer.

[0030] In a preferred embodiment of the present invention, the coating process can be performed by blade coating, slot die coating, bar coating, inkjet coating, or spray coating.

[0031] In a preferred embodiment of the present invention, the drying can be performed together with the coating process or after the completion of the coating process.

[0032] In a preferred embodiment of the present invention, the drying is performed in a blowing owing process to evaporate the solvent of the coating agent.

[0033] In a preferred embodiment of the present invention, the drying is performed by drying with an inert gas such as N2 or Ar or by a knife blowing process through an air knife, and the solvent of the coating agent can be evaporated.

[0034] In a preferred embodiment of the present invention, the firing can be performed by heat treatment at 120 to 180 °C for 5 to 20 minutes.

[0035] Still another object of the present invention relates to a perovskite solar cell including a perovskite thin film formed by the above method using the coating agent as a light absorption layer (or a photoactive layer).

[0036] In a preferred embodiment of the present invention, the perovskite solar cell can be a tandem solar cell.

[0037] In a preferred embodiment of the present invention, it can be a tandem solar cell including an upper cell including a perovskite thin film formed with the above-described coating agent for forming a large-area perovskite thin film as a light absorption layer, and a lower cell including Si, Cu(In,Ga)Se3, CdTe or a perovskite compound as a light absorption layer.

Advantages of the Invention

[0038] The method for forming a perovskite thin film using the coating agent of the present invention is environmentally friendly and excellent in mass productivity without performing a poor solvent treatment step. Further, the perovskite thin film produced by the coating agent and the forming method of the present invention is excellent in uniformity and thermal stability, and a perovskite solar cell having high energy conversion efficiency can be produced by introducing this into the light absorption layer of the solar cell.

Brief Description of the Drawings

[0039]

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Figure 3

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Figure 6b

Figure 7

Embodiments for Carrying Out the Invention

[0040] Hereinafter, the present invention will be described in more detail based on a method for forming a large-area perovskite thin film. Here, the large area means an area of 200 cm 2 or more, preferably 250 cm 2 or more.

[0041] The present invention can form and obtain a large-area perovskite thin film by performing the following steps: a first step of preparing a coating solution containing a coating agent for forming a perovskite thin film; a second step of coating and drying the coating solution on top of a substrate to form a wet-thin film containing perovskite crystallized in an intermediate phase; and a third step of annealing the wet-thin film to form a large-area perovskite thin film containing a perovskite compound represented by Chemical Formula 1 below.

[0042] [Chemical Formula 1] A m A’ 1-m B(X n X’ 1-n )3

[0043] In Chemical Formula 1, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium), or EDA (Ethylenediamine), preferably FA, GA, or EDA, and more preferably FA. Also, A’ in Chemical Formula 1 is Cs + , Na + , K + , NH4 + or Rb + , preferably Cs + , Na + or K + , and more preferably Cs + .

[0044] B in Chemical Formula 1 is Pb 2+ , Sn 2+ , Pd 2+ , Cu 2+ , Ge 2+ , Sr 2+ , Cd 2+ , Ca 2+ , Ni 2+ , Mn 2+ , Fe 2+ , Co 2+ , Sn 2+ , Yb 2+ or Eu 2+and preferably Pb 2+ , Sn 2+ , Pd 2+ or Cu 2+ and more preferably Pb 2+ or Sn 2+ .

[0045] Also, each of X and X' in Chemical Formula 1 is independently Cl - , Br - or I - , and preferably, X is I - and X' is Br - . And m and n in Chemical Formula 1 are rational numbers satisfying 0 < m ≤ 1 and 0 < n ≤ 1, and preferably rational numbers satisfying 0.7 ≤ m ≤ 0.9 and 0.1 ≤ n ≤ 0.3.

[0046] Generally, the A m A' 1-m site is formed by mixing a monovalent organic cation with a monovalent inorganic cation to form a monovalent cation. Specifically, in Chemical Formula 1, A may include an amine, ammonium, Group 1 metal, Group 2 metal, and / or other cation or cation-like compound, and may include, for example, formamidinium (hereinafter "FA"), methylammonium (hereinafter "MA"), and FAMA.

[0047] MA-based perovskites with a large composition ratio of MA can be coated without an antisolvent and are suitable from the perspective of mass production, but have a fatal problem that thermal stability cannot be ensured.

[0048] Note that the currently most efficient FA-based perovskites have poor phase stability, the antisolvent-free process is limited, and it is currently difficult to coat a uniform large-area thin film.

[0049] According to one embodiment of the present invention, A m A' 1-m B(X n X' 1-n)In the structure of 3, in order to ensure the thermal stability of the light absorption layer, an attempt was made to solve the phase stability issue of the FA-based perovskite through the optimization of the mixed composition without adding methylammonium (MA). Specifically, in the present invention, a small amount of Group 1 metal cations was introduced into the MA-free base metal halide perovskite to stabilize the crystal structure and ensure phase stability without reducing the thermal stability of the perovskite.

[0050] Due to the above-described effects, the composition (1 - m) of the Group 1 metal cation is controlled to be 0.1 or more. Considering the bandgap of the tandem device, the composition (1 - m) of the metal cation can be controlled to be 0.3 or less. Thereby, the bandgap of the perovskite material can be 1.50 eV to 1.80 eV, preferably 1.55 eV to 1.72 eV.

[0051] The coating agent for forming a perovskite thin film of the present invention contains a perovskite precursor, a crystallinity improver, a Lewis base, and a solvent.

[0052] Among the coating agent compositions, the perovskite precursor includes an organic halide represented by the following Chemical Formula 2, a monovalent metal halide represented by the following Chemical Formula 3, a divalent metal halide represented by the following Chemical Formula 4 (the first divalent metal halide), and a divalent metal halide represented by the following Chemical Formula 5 (the second divalent metal halide).

[0053] [Chemical Formula 2] AX

[0054] In Chemical Formula 2, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium), or EDA (Ethylenediamine), preferably FA, GA, or EDA, and more preferably FA. And X in Chemical Formula 2 is Br - or I - is.

[0055] [Chemical Formula 3] A’X

[0056] In Chemical Formula 3, A’ is Cs + , Na + , K + , NH4 + or Rb + and preferably Cs + , Na + or K + and more preferably Cs + . And in Chemical Formula 3, X is Br - or I - .

[0057] [Chemical Formula 4] BX2

[0058] [Chemical Formula 5] BX’2

[0059] In Chemical Formulas 4 and 5, B is Pb 2+ , Sn 2+ , Pd 2+ , Cu 2+ , Ge 2+ , Sr 2+ , Cd 2+ , Ca 2+ , Ni 2+ , Mn 2+ , Fe 2+ , Co 2+ , Sn 2+ , Yb 2+ or Eu 2+ and preferably Pb 2+ , Sn 2+ , Pd 2+ or Cu 2+ and more preferably Pb 2+ or Sn 2+ . And each of X in Chemical Formula 4 and X’ in Chemical Formula 5 is independently Cl - , Br - or I - and preferably Br - or I - , and X and X’ are different halogen anions from each other.

[0060] Among the components of the perovskite coating agent, the crystallinity improver increases the phase stability of perovskite, increases the size of perovskite crystal particles, and plays a role in improving crystallinity. The coating agent may contain 15 to 40 mol%, preferably 15.5 to 25.0 mol% of the crystallinity improver based on 100 mol% of the perovskite precursor.

[0061] At this time, when the crystallinity improver is contained in an amount less than 15 mol%, there may be a problem that perovskite crystals are not crystallized to a sufficient size. When it exceeds 40 mol%, crystals may be formed non-uniformly, and there may be a problem that the surface of the perovskite thin film is formed very non-uniformly.

[0062] The crystallinity improver may contain one or more selected from CH3NH3Cl (MACl), CH3NH3Br (MABr), and CH3NH3I (MAI). Preferably, it may contain one or more selected from MACl and MABr. Preferably, it may contain MACl.

[0063] When performing three-stage annealing in the thin film formation process, the crystallinity improver is decomposed and removed. Taking MACl as an example, it is removed in the form of MA gas and HCl during the annealing process and does not remain in the perovskite crystal.

[0064] Among the components of the perovskite coating agent in the first stage, the Lewis base is added to increase the phase stability of perovskite and prevent pinhole formation in the thin film. A polar aprotic compound can be used. Preferably, it may contain one or more selected from DMPU (N,N-Dimethyl-propyleneurea), HMPA (Hexamethylphosphoramide), and NMP (N-Methyl-2-pyrrolidone). Preferably, it may contain DMPU.

[0065] The Lewis base is preferably contained in an amount of 40 to 100 mol%, preferably 40 to 90 mol%, more preferably 50 to 85 mol%, based on 100 mol% of the perovskite precursor in the coating agent. At this time, if the content of the Lewis base is less than 40 mol%, the binding energy of the perovskite crystal intermediate phase in the wet thin film formed through drying in the thin film forming process is weak, and the perovskite crystal phase may not be formed well, and the uniformity of the thin film may not be good. If it exceeds 100 mol%, on the contrary, the perovskite crystallization may not be smooth due to supersaturation, and thus a problem of forming a non-uniform thin film may occur. Therefore, in the present invention, the content of the Lewis base in the coating agent is controlled within the above range.

[0066] The solvent in the perovskite coating agent composition may contain one or more selected from DMF (dimethylformamide), γ-butyrolactone, 2-methoxyethanol, DMSO (dimethyl sulfoxide), and NMP (N-methyl-2-pyrrolidinone). Preferably, it may contain one or more selected from DMF, γ-butyrolactone, and 2-methoxyethanol, and more preferably, it may contain DMF.

[0067] And the usage amount of the solvent in the coating agent is preferably such that the volume ratio of the solvent and the Lewis base is 1:0.06 to 0.25, preferably 1:0.10 to 0.22, and more preferably 1:0.10 to 0.18. When the content of the solvent is too much with respect to the Lewis base, pinholes may occur in the thin film. When the content of the solvent is too little with respect to the Lewis base, coatability cannot be ensured, and there may be a problem that the surface roughness increases significantly. Therefore, in the present invention, the content of the solvent in the coating agent is controlled within the above range.

[0068] Next, the two-stage substrate in the method for forming a large-area perovskite thin film of the present invention means the object to which the coating liquid in the first stage is coated, and the coating liquid can be coated on the upper part of the Si thin film, the upper part of the hole transport layer, the upper part of the electron transport layer, or the upper part of the passivation layer.

[0069] And the coating step in the two stages can be performed by blade coating, slot die coating, bar coating, inkjet coating, or spray coating, and preferably, it can be performed by blade coating, slot die coating, or bar coating.

[0070] Also, the drying in the two stages can be performed together with the coating step or separately after the completion of the coating step. As a preferable example of the drying method, drying can be performed through an inert gas such as N2 or Ar or drying through an air knife, and the solvent in the coating agent can be evaporated through drying, and a wet-thin film containing perovskite crystallized in the mesophase is formed.

[0071] Next, the three-stage annealing in the method for forming a large-area perovskite thin film of the present invention can be performed by heat treatment at 120 to 180 °C for 5 to 20 minutes, and preferably, it can be performed by heat treatment at 130 to 160 °C for 7 to 15 minutes. During the annealing process, as described above, the crystallization improver is removed by gasification or the like. For example, a perovskite thin film is formed by reactions such as the following Reaction Formulas 1 to 5, and the crystallization improver can be evaporated and removed.

[0072] [Reaction Formula] 1. PbCl2 + FAI + 2MAI → FAPbl3 + MACI (evaporation and removal) 2. PbI2 + FAI + MACl → FAPbl3 + MACI (evaporation and removal) 3. PbI2 + FABr + MACl → FAPbl2Br + MACI (evaporation and removal) 4. PbCl2 + FABr + 2MABr → FAPbBr3 + MACI (removed by evaporation) 5. PbBr2 + FABr + 2MAI → FAPbBr3 + MAI (removed by evaporation)

[0073] By performing the above-described steps 1 to 3, a large-area thin film that is uniform and has excellent thermal stability and contains the perovskite compound represented by Chemical Formula 1 can be manufactured in a mass production process.

[0074] The present invention can provide a perovskite solar cell having excellent power conversion efficiency (PCE) by forming a light absorption layer of a solar cell using the above-described coating agent and method for forming a perovskite thin film. The solar cell of the present invention can be a pin-structured perovskite solar cell, an inverted-structured perovskite solar cell, a tandem-type perovskite solar cell, or a tandem-type silicon / perovskite heterojunction solar cell.

[0075] For example, in a tandem solar cell composed of a silicon lower cell and a perovskite upper cell, the light absorption layer of the upper cell can be formed as a perovskite light absorption layer by the above-described coating agent and method of the present invention.

[0076] Also, in a tandem solar cell composed of a lower cell containing Cu(In, Ga)Se3, CdTe, or a perovskite compound as a light absorption layer and a perovskite upper cell, the light absorption layer of the upper cell can be formed as a perovskite light absorption layer by the above-described coating agent and method of the present invention.

[0077] The recombination layer is a layer that induces the recombination of electrons and holes generated in the lower cell and the light absorption layer described later. It can be a transparent thin film deposited with ITO (Induim Tin Oxide), FTO (Fluorine doped Tin Oxide), ATO (Sb2O3 doped Tin Oxide), GTO (Gallium doped Tin Oxide), ZTO (tin doped zinc oxide), ZTO:Ga (gallium doped ZTO), IGZO (Indium gallium zinc oxide), IZO (Indium doped zinc oxide) or AZO (Aluminu m doped zinc oxide).

[0078] Also, as an example of the formation of the recombination layer, when using a silicon solar cell doped with n or p-type impurities as the lower cell, after treating the silicon solar cell doped with n or p-type impurities with hydrofluoric acid to remove the SiOx oxide film, and then removing the residual hydrofluoric acid using ultrapure water, the recombination layer can be formed on the upper end of the silicon solar cell with the oxide film removed through a sputtering process.

[0079] The hole transport layer (HTL) may contain an inorganic and / or organic hole transporting material. The inorganic hole transporting material may contain one or more selected from nickel oxide (NiO x ), CuSCN, CuCrO2 and CuI.

[0080] The organic hole transporting material is a carbazole derivative, a polyarylalkane derivative, a phenylenediamine derivative, an arylamine derivative, an amino-substituted chalcone derivative, a styrylanthracene derivative, a fluorene derivative, a hydrazone derivative, a stilbene derivative, a silazane derivative, an aromatic tertiary amine compound, a styrylamine compound, an aromatic dimethylidine-based compound, a porphyrin-based compound, a phthalocyanine-based compound, a polythiophene derivative, a polypyrrole derivative, a polyparaphenylenevinylene derivative, pentacene, coumarin 6 (3-(2-benzothiazolyl)-7-(diethylamino)coumarin), ZnPC (zinc phthalocyanine), CuPC (copper phthalocyanine), TiOPC (titanium oxide phthalocyanine), Spiro-MeOTAD (2,2’,7,7’-tetrakis(N,N-p-dimethoxyphenylamino)-9,9’-spirobifluorene), F16CuPC (copper(II)1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H, 31H-phthalocyanine), SubPc (boron subphthalocyanine chloride) and N3 (cis-di(thiocyanato)-bis(2,2’-bipyridyl-4,4’-dicarboxylic acid)-ruthenium(II), P3HT (poly[3-hexylthiophene]), MDMO-PPV (poly[2-methoxy-5-(3’,7’-dimethyloctyloxyl)]-1,4-phenylene vinylene), MEH-PPV (poly[2-methoxy-5-(2’’-ethylhexyloxy)-p-phenylene vinylene]), P3OT (poly(3-octyl thiophene)), POT (poly(octyl thiophene)), P3DT (poly(3-decyl thiophene)), P3DDT (poly(3-dodecyl thiophene)), PPV (poly(p-phenylene vinylene)), TFB (poly(9,9’-dioctylfluorene-co-N-(4-butylphenyl)diphenyl, amine), Polyaniline, Spiro-MeOTAD ([2,22’,7,77’-tetrkis(N,N-di-pmethoxyphenyl amine)-9,9,9’-spirobi fluorine]), CuSCN, CuI, PCPDTBT (Poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl]]), Si-PCPDTBT (poly[(4,4’-bis(2-ethylhexyl)dithieno[3,2-b:2’,3’-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl]), PBDTTPD (poly((4,8-diethylhexyloxyl), PFDTBT (poly[2,7-(9-(2-ethylhexyl)-9-hexyl- (fluorene)-alt-5,5-(4’,7-di-2-thienyl-2’,1’,3’-benzothiadiazole)), PFO-DBT (poly[2,7-(9,9-(dioctyl-fluorene)-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole)]), PSiFDTBT (poly[(2,7-dioctylsilafluorene)-2,7-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5’-diyl]), PCDTBT (Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]), PFB (poly(9,9’-dioctylfluorene-co-bis(N,N’-(4-butylphenyl))bis(N,N’-phenyl-1,4-phenylene)diamine), F8BT (poly(9,9’-dioctylfluorene-cobenzothiadiazole), PEDOT (poly(3,4-ethylenedioxythiophene)), PEDOT:PSS poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate), PTAA (poly(triarylamine)), 2-PACz, and / or MeO-2PACz may be included.

[0081] And, as a method for forming the hole transport layer, a coating method, a vacuum evaporation method, etc. may be mentioned, and as the coating method, a gravure coating method, a bar coating method, a printing method, a spraying method, a spin coating method, a dipping method, a die coating method, etc. may be mentioned.

[0082] Next, the light absorption layer may include a perovskite crystal represented by the chemical formula 1 as a large-area thin film layer formed through the coating agent and method of the present invention described above.

[0083] Note that a protective layer (not shown) may be further included between the hole transport layer and the light absorption layer. Specifically, the protective layer may contain a substance having a strong binding force between a carbazole body with strong hole collection ability and a phosphonic acid group, or preferably, may contain SAM substances such as 2-PACz, MeO-2PACz, Br-2PACz, Me-4PACz, MeO-4PACz, 6-PACz, etc.

[0084] Examples of the method for forming the protective layer include a coating method and / or a vacuum evaporation method. Examples of the coating method include a gravure coating method, a bar coating method, a printing method, a spraying method, a spin coating method, a blade coating method, a dipping method, and a die coating method. Preferably, the protective layer can be formed on one surface of the hole transport layer through a vacuum evaporation method.

[0085] Next, the electron transport layer may contain an inorganic substance (e.g., a metal oxide) and / or an organic substance. The electron transport layer may be a flat metal oxide layer, a metal oxide layer having surface irregularities, a composite metal oxide layer in which nanostructures (including metal oxide particles, nanowires, and / or nanotubes) of the same or different metal oxides are formed on the surface of a thin film-shaped metal oxide, or a porous metal oxide layer. Preferably, it may contain a compact metal oxide layer and a meso-porous metal oxide layer. As a preferable example, it may contain SnO2, TiO2, ZnO, etc. Also, as the organic substance, PCBM may be included.

[0086] Note that a buffer layer may be further included between the electron transport layer and the light absorption layer. The buffer layer is a layer formed for improving interface defects and transport ability, and may contain one or more selected from C60, PCBM and PC71BM.

[0087] As a method for forming the buffer layer, a coating method and / or a vacuum deposition method can be mentioned. Examples of the coating method include a gravure coating method, a bar coating method, a printing method, a spraying method, a spin coating method, a blade coating method, a dipping method, and a die coating method. According to one embodiment, a protective layer can be formed on one surface of the light absorption layer through a vacuum deposition method.

[0088] Among the components of the solar cell, the upper electrode (or source electrode) can be formed by coating or depositing one or more substances selected from Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C, and conductive polymers.

[0089] In addition, the solar cell can further include a passivation layer between the light absorption layer and the electron transport layer.

[0090] Hereinafter, the present invention will be described more specifically based on examples. However, the following examples do not limit the scope of the present invention and should be construed as helping to understand the present invention.

Examples

[0091] Example 1: Production of a perovskite coating agent and a perovskite thin film After introducing the solvent DMF into a three-necked flask, a perovskite precursor was introduced and stirred to dissolve it.

[0092] At this time, the perovskite precursor was introduced by mixing FAI powder (organic halide), CsBr powder (metal halide), PbI2 powder, and PbBr2 powder in a molar ratio of 1:1:0.25:0.25.

[0093] Then, 25 mol% of CH3NH3Cl (crystallinity improver) and 50 mol% of DMPU (N,N-Dimethyl-propyleneurea, Lewis base) were introduced and stirred with respect to 100 mol% of the perovskite precursor to produce a coating agent for forming a thin film.

[0094] Next, on the upper part of one side of a 16×16 cm 2 ITO glass substrate, blade coating was performed using a blade coater, and then N2 blowing through an air knife was carried out to dry the coating agent, forming a wet-thin film containing perovskite crystallized in the mesophase.

[0095] Next, the glass substrate on which the wet thin film was formed was annealed at 150 °C for 10 minutes to form a perovskite thin film containing a perovskite compound represented by the following Chemical Formula 1-1 with a thickness of 550 nm.

[0096] [Chemical Formula 1-1] A m A’ 1-m B(X n X’ 1-n )3

[0097] In Chemical Formula 1-1, A is FA (Formamidinium), A’ is Cs + and B is Pb 2+ and X is I - and X’ is Br - and m = 0.8, n = 0.8.

[0098] Comparative Example 1 A perovskite coating agent and a perovskite thin film were formed on the glass substrate in the same manner as in Example 1, but no Lewis base was used during the production of the coating agent.

[0099] Comparative Example 2 The perovskite coating agent was formed in the same manner as in Example 1, and a perovskite thin film was formed on the glass substrate using this agent. However, during the production of the coating agent, 50 mol% of DMSO (Dimethyl sulfoxide), which is a substance showing the highest level of efficiency in current spin coating, was used as the Lewis base instead of DMPU.

[0100] [Table 1] [Table 1]

[0101] Experimental Example 1: Measurement of PL mapping (microphotoluminescence mapping) PL mapping of the perovskite thin films produced in Example 1 and Comparative Examples 1 to 2 was performed, and the results are shown in Fig. 1.

[0102] In Fig. 1, a is the measurement image for the thin film surface of Comparative Example 1, b is that of Comparative Example 2, and c is that of Example 1. In the case of Comparative Example 1, although the thin film surface appears uniform, since the perovskite thin film is not formed overall, it rather appears uniform.

[0103] In the case of Comparative Example 2, it was confirmed that there is a problem that perovskite is locally well formed, and there are regions where the perovskite is well formed (white parts) and regions where the perovskite is not well formed and not coated (black parts). On the other hand, in Example 1, it was confirmed that a perovskite thin film with a uniform surface was formed overall.

[0104] Experimental Example 2: Measurement of SEM (scanning electron microscope) SEM measurements were performed on the perovskite thin films produced in Example 1 and Comparative Examples 1 to 2, and the results are shown in Fig. 2a (Comparative Example 1), Fig. 2b (Comparative Example 2), and Fig. 2c (Example 1).

[0105] Referring to Fig. 2a, in the case of the large-area perovskite thin film of Comparative Example 1 produced without using a Lewis base, it was confirmed that a large number of pinholes were formed and there was a problem that coverage could not be ensured over the entire area.

[0106] Also, referring to Fig. 2b, in the large-area perovskite thin film of Comparative Example 2 using DMSO as a Lewis base, although there were some parts (f) where some excellent thin films were formed, similar to Comparative Example 1, a large number of pinholes occurred and there was a problem that thin films were not formed (d, e).

[0107] In contrast, referring to g, h, and i in Fig. 2c, the large-area perovskite thin film of Example 1 was generally excellent in thin film uniformity and there was no pinhole generation. This is because the thin film was uniformly coated by DMPU (Lewis base) with a strong binding energy to the perovskite precursor, and the perovskite crystallinity and binding force were improved. Therefore, it was confirmed that even though large-area coating was performed, no pinholes were formed and a uniform thin film could be formed. Experimental Example 3: Measurement of UV-Vis (Ultraviolet-visible spectroscopy) and XRD (X-ray diffraction)

[0108] UV-Vis measurement was performed on the perovskite thin film produced in Example 1, and the results are shown in Fig. 3a (absorbance) and Fig. 3b (energy band gap).

[0109] The energy band gap is calculated based on the measured absorbance value.

[0110] The energy band gap (E g ) was 1.682 eV, and it was confirmed that this value satisfies the energy band gap (1.5 eV ≤ Eg ≤ 1.8 eV) required for the perovskite light absorption layer of the upper cell element of the tandem-type silicon / perovskite heterojunction solar cell.

[0111] In addition, XRD measurement was performed on the perovskite thin film produced in Example 1, and the results are shown in Fig. 3c. From the XRD measurement results, it was confirmed that the perovskite crystals in the cubic phase in the thin film were well formed.

[0112] Examples 2 to 5 and Comparative Example 3 A perovskite coating agent was used to form a perovskite thin film on the glass substrate in the same manner as in Example 1. As shown in Table 2 below, in Example 2, 40 mol% of the Lewis base DMPU was used during the production of the coating agent, in Example 3, 60 mol% of DMPU was used, in Example 4, 80 mol% of DMPU was used, and in Example 5, 100 mol% of DMPU was used. In Comparative Example 3, 20 mol% of DMPU was used.

[0113] [Table 2]

Table 2

[0114] Experimental Example 4: Measurement by SEM (scanning electron microscope) To confirm the perovskite thin film formation state depending on the mol% of the Lewis base, SEM measurement was performed on the cross-sections of the thin films produced in Examples 2 to 5 and Comparative Examples 1 and 3, and the image measurement results are shown in Figs. 4a to 4f. (a: Comparative Example 1, b: Comparative Example 3, c: Example 2, d: Example 3, e: Example 4, f: Example 5)

[0115] Referring to Fig. 4, in Comparative Example 1 (0 mol%) and Comparative Example 3 (20 mol%) where the Lewis base DMPU content was less than 40 mol%, cavity-shaped pinholes were present and it was confirmed that the thin film was formed non-uniformly. In contrast, in Examples 2 to 5 where the DMPU content was 40 to 100 mol%, it was confirmed that no pinholes were present and a uniform thin film was formed.

[0116] Examples 6 to 8 and Comparative Example 4: Production of Perovskite Thin Films Depending on the Content of Crystallinity Improver A perovskite coating agent was prepared and a perovskite thin film was formed on the glass substrate in the same manner as in Example 1. However, as shown in Table 3 below, in Examples 6, 7, and 8, 30, 20, and 15 mol% of the crystallinity improver CH3NH3Cl were used, respectively, and in Comparative Example 4, 10 mol% of the crystallinity improver CH3NH3Cl was used to produce perovskite thin films, respectively.

[0117] [Table 3]

Table 3

[0118] Experimental Example 5: Measurement of Performance of Solar Cell Element While varying the content of the crystallinity improver MACl in the range of 30 to 10 mol%, opaque elements were fabricated and IV measurements were performed, and the results are shown in Table 4 and Figure 5. Referring to Table 4 and Figure 5 below, from 15 to 30 mol% in Examples 6 to 8, almost the same average efficiency was shown, and at 25 mol%, the deviation was also the smallest at 18.35%. This is the role of the generally known crystallinity improver to assist particle growth, so it can be said that the perovskite characteristics are dense and large particles are formed. On the other hand, in the case of Comparative Example 4 where the content of the crystallinity improver did not reach 15 mol%, terminal characteristics (V oc , J sc , FF) were not ensured, and it was confirmed that the final conversion efficiency did not reach that of Example 1 and Examples 6 to 8.

[0119] [Table 4]

Table 4

[0120] Production Example 1-1: Production of Perovskite Solar Cell An opaque perovskite solar cell single element was fabricated using the coating agent for forming a perovskite thin film produced in Example 1 (Active area: 0.096 cm 2 ). Specifically, the structure of the opaque single element is, in order on an organic substrate vapor-deposited with ITO (100 nm), NiOx (17 nm), 2PACz (1 nm), perovskite thin film (550 nm), LiF (1 nm), C60 (13 nm), BCP (8 nm), and Ag electrode (200 nm).

[0121] Production Example 1-2: Fabrication of Perovskite Solar Cells Although a perovskite solar cell single element was fabricated in the same manner as in Production Example 1, an opaque perovskite solar cell single element was fabricated using the coating agents of Examples 2 to 5, Comparative Example 1, and Comparative Example 3 instead of Example 1 (Active area: 0.096 cm 2 ), and Production Examples 1-2 to 1-5, Comparative Production Example 1-1, and Comparative Production Example 1-2 were each carried out (see Table 5 below).

[0122] Production Example 2: Fabrication of Tandem-Type Silicon / Perovskite Heterojunction Solar Cells A silicon / perovskite heterojunction solar cell tandem element was fabricated using the coating agent for forming a perovskite thin film produced in Example 1 (Active area: 242.74 cm 2 ). The structure of the fabricated tandem element is in the order of ITO (20 nm) / NiOx (17 nm) / 2PACz (1 nm), perovskite thin film (550 nm) / LiF (1 nm) / C60 (13 nm) / SnOx (6 nm) / ITO (50 nm) / Ag (200 nm) on the Si lower element.

[0123] Experimental Example 6: Measurement of Performance of Solar Cell Elements The current-voltage characteristics and efficiency of the solar cells produced in Production Examples 1-1 to 1-5, Comparative Production Examples 1-1 to 1-2, and Production Example 2 were measured, and the results are shown in Tables 5 and 6 below. Performance measurement graphs are shown in Fig. 6a (single element, Production Example 1-1), Fig. 6b (single element, Production Examples 1-2 to 1-5, Comparative Production Examples 1-1 to 1-2), and Fig. 7 (tandem element).

[0124] [Table 5]

Table 5

[0125] [Table 6]

Table 6

[0126] Referring to Tables 5 and 6 above, it was confirmed that Comparative Production Examples 1-1 and 1-2, in which a perovskite coating layer using less than 40 mol% of the Lewis base DMPU was introduced into the light absorption layer, had a photoelectric conversion efficiency of less than 10.50%, and had a relatively very low photoelectric conversion efficiency compared to Production Examples 1-1 to 1-5.

[0127] In contrast, it was confirmed that Production Examples 1-1 to 1-5 had a photoelectric conversion efficiency of 15.0% or more, preferably 16.0% or more, and Production Example 1-1 including a light absorption layer formed of the coating agent of Example 1 in which the DMPU usage amount was 50 mol% showed the most excellent solar cell performance.

[0128] Based on the above Examples and Experimental Examples, it was confirmed that a large-area perovskite thin film without pinholes and ensuring uniformity could be commercially produced, and it was confirmed that the perovskite solar cell produced using this had a high photoelectric conversion efficiency.

Claims

1. A coating agent for forming a thin film containing a perovskite compound represented by the following Chemical Formula 1, characterized in that it contains a perovskite precursor, a crystallization improver, a Lewis base, and a solvent; a coating agent for forming a large-area perovskite thin film; [Chemical Formula 1]

2. A ｍ A' １－ｍ B(X ｎ X' １－ｎ ) ３ In Chemical Formula 1, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium) or EDA (Ethylenediamine), and A’ is Cs ＋ , Na ＋ , K ＋ , NH ４ ＋ or Rb ＋ , B is Pb ２＋ , Sn ２＋ , Pd ２＋ , Cu ２＋ , Ge ２＋ , Sr ２＋ , Cd ２＋ , Ca ２＋ , Ni ２＋ , Mn ２＋ , Fe ２＋ , Co ２＋ , Sn ２＋ , Yb ２＋ or Eu ２＋ , X and X’ are each independently Cl － , Br － or I － , and m and n are rational numbers satisfying 0.7 ≤ m ≤ 0.9 and 0.1 ≤ n ≤ 0.

3. The perovskite precursor contains an organic halide represented by the following Chemical Formula 2, a monovalent metal halide represented by the following Chemical Formula 3, a divalent metal halide represented by the following Chemical Formula 4, and a divalent metal halide represented by the following Chemical Formula 5. The coating agent for forming a large-area perovskite thin film according to Claim 1; [Chemical Formula 2] AX [Chemical Formula 3] In Chemical Formula 2, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium), or EDA (Ethylenediamine), and X is Br － or I － and A'X [Chemical Formula 4] In Chemical Formula 3, A' is Cs ＋ , Na ＋ , K ＋ , NH ４ ＋ or Rb ＋ , and X is Cl － , Br － or I － . [Chemical Formula 5] BX ２

3. BX' ２ In Chemical Formula 4 and Chemical Formula 5, B is Pb ２＋ , Sn ２＋ , Pd ２＋ , Cu ２＋ , Ge ２＋ , Sr ２＋ , Cd ２＋ , Ca ２＋ , Ni ２＋ , Mn ２＋ , Fe ２＋ , Co ２＋ , Sn ２＋ , Yb ２＋ or Eu ２＋ ; each of X and X' is independently Cl － , Br － or I － ; and X and X' are different halogen anions from each other. The Lewis base contains one or more selected from DMPU (N,N-Dimethyl-propyleneurea), HMPA (Hexamethylphosphoramide), and NMP (N-Methyl-2-pyrrolidone), and the solvent contains one or more selected from DMF (dimethylformamide), gamma-butyrolactone, 2-methoxyethanol, DMSO (Dimethyl sulfoxide), and NMP (N-Methyl-2-pyrrolidinone). The coating agent for forming a large-area perovskite thin film according to Claim 1. The crystallization improver contains one or more selected from CH ３ NH ３ Cl, CH ３ NH ３ Br, and CH ３ NH ３ I, and

4. The coating agent for forming a large-area perovskite thin film according to Claim 1, characterized in that it contains 15 to 30 mol% of the crystallization improver and 40 to 100 mol% of the Lewis base with respect to 100 mol% of the perovskite precursor.

5. The coating agent for forming a large-area perovskite thin film according to Claim 3, characterized in that it contains the solvent and the Lewis base in a volume ratio of 1:0.06 to 0.

25.

6. A first step of preparing the coating agent according to any one of Claims 1 to 5; a second step of coating and drying the coating agent on the upper part of a substrate to form a wet thin film containing perovskite crystallized in an intermediate phase; and ​ ​ Area of 200 cm ２ The method for forming a large-area perovskite thin film with an area of 200 cm or more, ​ ​ Performing an annealing process on the wet thin film to form a large-area perovskite thin film containing a perovskite compound represented by the following Chemical Formula 1; A method for forming a large-area perovskite thin film, characterized by performing a process including the above three steps; [Chemical Formula 1] A ｍ A' １－ｍ B(X ｎ X' １－ｎ ) ３ In Chemical Formula 1, A is FA (Formamidinium), EA (Ethylamine), GA (Guanidinium) or EDA (Ethylenediamine), and A' is Cs ＋ , Na ＋ , K ＋ , NH ４ ＋ or Rb ＋ , B is Pb ２＋ , Sn ２＋ , Pd ２＋ , Cu ２＋ , Ge ２＋ , Sr ２＋ , Cd ２＋ , Ca ２＋ , Ni ２＋ , Mn ２＋ , Fe ２＋ , Co ２＋ , Sn ２＋ , Yb ２＋ or Eu ２＋ , X and X' are each independently Cl － , Br － or I － , and m and n are rational numbers satisfying 0.7 ≤ m ≤ 0.9 and 0.1 ≤ n ≤ 0.

3.

7. The method for forming a large-area perovskite thin film according to claim 6, wherein the upper part of the substrate coated with the coating agent is a Si thin film layer, a hole transport layer, an electron transport layer, or a passivation layer.

8. The method for forming a large-area perovskite thin film according to claim 6, wherein the coating step is performed by blade coating, slot die coating, bar coating, inkjet coating, or spray coating.

9. The method for forming a large-area perovskite thin film according to claim 6, wherein the drying is performed together with the coating step or after the completion of the coating step.

10. The method for forming a large-area perovskite thin film according to claim 9, wherein the drying is performed by a knife blowing process to evaporate the solvent.

11. The method for forming a large-area perovskite thin film according to claim 6, wherein the firing is performed by heat treatment at 120 to 180 °C for 5 to 20 minutes.

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