Electron carrier for electron transport layer of perovskite solar cell, coating agent for electron transport layer containing same, electron transport layer and perovskite solar cell

Abstract

The present invention relates to a coating agent for forming an electron transport layer (or electron transfer layer), which provides surface-modified metal oxide nanoparticles as a dispersion-type coating agent, and relates to an inverted perovskite-based electron transport layer formed using the coating agent.

Description

[Technical Field]

[0001] The present invention relates to a coating agent for forming an electron transport layer (ETL) of a perovskite solar cell, an electron carrier used therein, an electron transport layer formed from the coating agent, and a perovskite solar cell including the same.

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0118424, filed on September 20, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] In order to solve the global environmental problems caused by the depletion and use of fossil fuels, active research is being conducted into renewable and clean alternative energy sources such as solar energy, wind power, and hydropower.

[0004] Among these, interest in solar cells that directly convert sunlight into electrical energy is increasing. Here, a solar cell refers to a cell that generates current and voltage using the photovoltaic effect, which absorbs light energy from sunlight and generates electrons and holes.

[0005] Currently, it is possible to manufacture np diode-type silicon (Si) single crystal-based solar cells with a light energy conversion efficiency of over 20% and they are actually being used for solar power generation, and there are also solar cells that use compound semiconductors such as gallium arsenide (GaAs) that have even better conversion efficiency. However, these inorganic semiconductor-based solar cells require highly refined materials to achieve high efficiency, which consumes a lot of energy to refine the raw materials, and the process of turning the raw materials into single crystals or thin films requires expensive processing equipment, which places a limit on how much the manufacturing cost of solar cells can be reduced and has been an obstacle to their large-scale use.

[0006] Therefore, in order to manufacture solar cells at low cost, it is necessary to significantly reduce the costs of the materials or manufacturing processes used as the core of solar cells. As such, research is being conducted on perovskite solar cells, which can be manufactured using low-cost materials and processes, as an alternative to inorganic semiconductor-based solar cells.

[0007] In recent years, perovskite solar cells have been developed that use the perovskite-structured halide compound (NH3CH3)PbX3 (X = I, Br, Cl) as a photoactive material, and research is underway for their commercialization. The general structural formula of perovskite is the ABX3 structure, where X is an anion, A is a large cation, and B is a small cation.

[0008] Perovskite solar cells, organometallic halide compounds with the molecular formula (CH3NH3)PbX3, were first used as photoactive materials in solar cells in 2009. Since then, solid-state perovskite solar cells, with the same structure as they are today, have been developed in 2012, resulting in rapid improvements in efficiency. Conventional perovskite solar cells use a metal oxide as the electron transport layer and an organic or polymeric material, such as spiro-OMETAD, as the hole transport layer (HTL). Specifically, a porous or thin metal oxide film is fabricated on a transparent electrode, such as FTO, and then coated with the perovskite material. This is followed by a hole transport layer, and then an electrode layer, such as gold (Au) or silver (Ag), is evaporated onto the film.

[0009] Key challenges for the commercialization of perovskite solar cells are ensuring stability and flexible technology. Conventional electron transport layers formed using metal oxides on top of the photoactive layer require a metal oxide to be deposited or coated on top of the photoactive layer (or light-absorbing layer), followed by a separate organic binder coating layer. However, depositing a metal oxide is a complex manufacturing process, significantly increasing manufacturing costs. Furthermore, the physical and chemical energy generated during the deposition process can potentially damage the light-absorbing layer. Furthermore, the organic binder coating layer requires high-temperature heat treatment to form the coating, but perovskite materials decompose at temperatures above 200°C, reducing the flexibility of the solar cell and limiting the range of applications for perovskite solar cells. Furthermore, when a dispersant is used to form a uniform thin film of the electron transport layer, a high-temperature heat treatment (above 500°C) is required to remove the dispersant, which can also damage the perovskite layer.

[0010] Furthermore, when a passivation layer made of a fullerene-based material is formed between the perovskite light-absorbing layer and the electron transport layer, damage to the light-absorbing layer can be prevented to some extent. However, depending on the material of the electron transport layer, the electron carrier may react with the fullerene in the passivation layer, damaging the passivation layer and reducing the performance of the solar cell element. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been devised to overcome the above-mentioned problems, and provides a perovskite solar cell with excellent performance by using metal oxide nanoparticles whose surface has been modified with a specific material as an electron carrier for an electron transport layer (or electron transport layer, ETL (Electron Transporting Layer)) and a coating agent for forming the electron transport layer using the same, and forming a coating agent and electron transport layer manufactured in a dispersion type using the same. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the present invention relates to an electron carrier for an electron transport layer (ETL) of a perovskite solar cell, which comprises metal oxide nanoparticles whose surface has been modified with a phosphonium salt represented by the following Chemical Formula 1:

[0013] [ka]

[0014] In Chemical Formula 1, R 1 ~R 4 are independently C1 to C 10 Straight chain alkyl groups, C3 to C 10 wherein X is a branched alkyl group, a phenyl group, or a benzyl group, and X is a halogen atom or —OH.

[0015] In a preferred embodiment of the present invention, the metal oxide nanoparticles may comprise an oxide of a metal including one or more selected from tin (Sn), zirconium (Zr), strontium (Sr), zinc (Zn), vanadium (V), molybdenum (Mo), tungsten (W), niobium (Nb), aluminum (Al), and gallium (Ga).

[0016] In a preferred embodiment of the present invention, the metal oxide nanoparticles may include at least one selected from SnO2, ZnO, TiO2, CeO2, ZrO2, WO3, Zn2SnO4, BaSnO3, and SrTiO3.

[0017] In one preferred embodiment of the present invention, the metal oxide nanoparticles may have a particle size of 2 to 100 nm.

[0018] In a preferred embodiment of the present invention, the electron carrier of the present invention may contain 85.0 to 95.0 wt % of the metal oxide nanoparticles based on the total weight, and the remaining amount of the surface modifying component.

[0019] Another object of the present invention relates to a coating agent for an electron transport layer of a perovskite solar cell, which is a dispersion in which the above-mentioned electron carrier is dispersed, and includes an organic solvent and the above-mentioned electron carrier dispersed in the organic solvent.

[0020] As a preferred embodiment of the present invention, the coating agent for the electron transport layer of the solar cell of the present invention may contain 0.30 to 2.00% by weight of an electron carrier and the remaining amount of an organic solvent.

[0021] In a preferred embodiment of the present invention, the organic solvent may have a dielectric constant of 20 or less.

[0022] In a preferred embodiment of the present invention, the organic solvent may include at least one selected from the group consisting of isopropyl alcohol, butyl alcohol, 2,2,2-trifluoroethanol, chlorobenzene, and ethyl acetate.

[0023] Another object of the present invention relates to an electron transport layer of a perovskite solar cell, which includes a coating layer formed from the above-mentioned coating agent.

[0024] In one preferred embodiment of the present invention, the electron transport layer may have a thickness of 10 to 100 nm.

[0025] In one preferred embodiment of the present invention, the electron transport layer may have a light transmittance of 88.0% or more for a wavelength of 500 to 550 nm when the electron transport layer has a thickness of 10 to 15 nm.

[0026] Another object of the present invention relates to a perovskite solar cell including the electron transport layer, in which the electron transport layer as set forth in claim 8 may be formed directly on the upper surface of the perovskite light-absorbing layer, or a passivation layer may be formed between the perovskite light-absorbing layer and the electron transport layer as set forth in claim 8. [Effects of the Invention]

[0027] The coating agent for forming an electron transport layer of the present invention can form an ultra-thin film through a low-temperature heat treatment at 200°C or less without a high-temperature treatment process for forming a thin film, thereby preventing damage to the perovskite light absorption layer. Furthermore, since there is no chemical reaction between the surface modification component of the electron carrier in the coating agent and the fullerene material of the passivation layer, damage to the passivation layer can be prevented. In addition, the electron transport layer formed from the coating solution of the present invention has high thin film uniformity, which contributes to the V of solar cells. oc It has excellent open-circuit voltage and fill factor, and high light transmittance. sc This provides a solar cell with excellent photoelectric conversion efficiency due to its excellent short-circuit current. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a TEM image of the SnO2 nanoparticles produced in Example 1. [Figure 2] FIG. 2 is an XRD measurement graph of the SnO2 nanoparticles produced in Example 1. [Figure 3] FIG. 3 is a graph showing FT-IR measurements of the unmodified SnO2 nanoparticles (control SnO2) and the surface-modified SnO2 nanoparticles prepared in Example 1. [Figure 4]Figure 4 is a TGA measurement graph of unmodified SnO2 nanoparticles (control SnO2) and surface-modified SnO2 nanoparticles prepared in Example 1. Figure 4(a) is a photograph of a solution in which unmodified SnO2 nanoparticles were dispersed in isopropane alcohol, and (b) is a photograph of the coating solution for forming the electron transport layer prepared in Example 1. [Figure 5] FIG. 5 is a graph showing the dynamic light scattering particle size analysis measurement results for Example 2-1 (TBPH), Comparative Example 2-2 (TBAH), and Comparative Example 2-3 (TMAH) performed in Experimental Example 2. [Figure 6] FIG. 6 shows the results of measuring the current density of the inverted structure perovskite solar cells produced in Production Example 1 (TPBH), Comparative Production Example 2 (TBAH), and Comparative Production Example 3 (TMAH) in Experimental Example 2. [Figure 7] FIG. 7 shows the results of measuring the current density of the silicon / perovskite tandem solar cells produced in Production Example 4 (TPBH), Comparative Production Example 2 (TBAH), and Comparative Production Example 3 (TMAH) in Experimental Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will now be described in more detail.

[0030] The present invention relates to an electron carrier applied to the electron transport layer (ETL) of an inverted-structure perovskite solar cell, and a dispersion-type coating agent using the same.

[0031] The electron carrier of the present invention comprises metal oxide nanoparticles whose surface has been modified with a phosphonium salt represented by the following Chemical Formula 1.

[0032] [ka]

[0033] In Chemical Formula 1, R 1 ~R4 Each of these is independent of each other, C1 to C 10 Straight chain alkyl groups, C3 to C 10 a branched alkyl group, a phenyl group or a benzyl group, preferably a C1 to C 10 A straight-chain alkyl group of C3 to C5, a phenyl group or a benzyl group is more preferred.

[0034] In addition, in Chemical Formula 1, X is a halogen atom or —OH, and is preferably —Cl, —Br, —I or —OH.

[0035] The electron carrier of the present invention is easily bonded to metal oxide nanoparticles due to the high reactivity of the phosphonium cations by surface-modifying the metal oxide nanoparticles with the phosphonium salt. The phosphonium cations are uniformly dispersed in organic solvents due to the repulsive force between the substituents and the steric effect, and form a uniform ultra-thin film (10 to 100 nm) upon coating, making them suitable for use as an electron transport layer in solar cells.

[0036] Among the components of the electron carrier, the metal oxide nanoparticles may include an oxide of a metal selected from the group consisting of tin (Sn), zirconium (Zr), strontium (Sr), zinc (Zn), vanadium (V), molybdenum (Mo), tungsten (W), niobium (Nb), aluminum (Al), and gallium (Ga). In a preferred embodiment, the metal oxide nanoparticles may include one or more selected from the group consisting of SnO, ZnO, TiO, CeO, ZrO, WO, ZnSnO, BaSnO, and SrTiO, and more preferably, one or more selected from the group consisting of SnO, ZnO, TiO, CeO, and ZrO.

[0037] The metal oxide nanoparticles may have a particle size of 2 to 100 nm, preferably 2 to 50 nm, and more preferably 2 to 20 nm. If the particle size of the metal oxide nanoparticles exceeds 100 nm, it may be difficult to form a thin, uniform thin film, and if the particle size is less than 2 nm, it may be difficult to manufacture or purchase them.

[0038] The electron carrier can be synthesized by the following method.

[0039] The electron carrier of the present invention can be produced by a process including a first step of producing metal oxide nanoparticles and a second step of reacting the metal oxide with the compound represented by Chemical Formula 1 to produce surface-modified metal oxide nanoparticles.

[0040] More specifically, step 1 may be prepared by carrying out a process including step 1-1 of mixing a metal precursor and ultrapure water to prepare a metal precursor solution, step 1-2 of adding a basic aqueous solution to the metal precursor solution to prepare a reaction solution, and step 1-3 of subjecting the reaction solution to hydrothermal synthesis and obtaining metal oxide nanoparticles from the hydrothermal synthesis product.

[0041] The metal precursor solution in step 1-1 may contain a metal precursor and ultrapure water, and the concentration of the metal precursor in the metal precursor solution may be 0.2 to 2.0 M, preferably 0.3 to 1.5 M. If the metal precursor concentration in the metal precursor solution is less than 0.2 M, the yield of metal oxide nanoparticles may be too low, whereas if the metal precursor concentration in the metal precursor solution is more than 2.0 M, the viscosity of the metal precursor aqueous solution may increase, resulting in non-uniform formation of metal oxide nanoparticles of different sizes during production under the same process conditions, making it difficult to obtain uniform nanoparticles.

[0042] In this case, the metal precursor is an organometallic compound containing at least one metal selected from tin (Sn), zirconium (Zr), strontium (Sr), zinc (Zn), vanadium (V), molybdenum (Mo), tungsten (W), niobium (Nb), aluminum (Al), and gallium (Ga). As a preferred example, the metal precursor may contain a halide of the metal, preferably a chloride of the metal.

[0043] The basic aqueous solution in the first and second steps may contain at least one selected from a KOH aqueous solution, a NaOH aqueous solution, a hydrazine aqueous solution, and an NH4OH aqueous solution. The amount of basic aqueous solution used is determined by adding the basic aqueous solution to the metal precursor solution so that the pH of the reaction solution is 8.0 or higher, preferably about pH 8.0 to 10.0, and more preferably about pH 8.0 to 9.0. If the pH is less than 8, the yield of metal oxide nanoparticles may be too low. If the pH is less than 8, such as between 6.0 and 8.0, the metal precursor solution may gel and become difficult to stir. If the pH is too high, the particle size of the metal oxide particles may become too large.

[0044] The hydrothermal synthesis in steps 1-3 may be carried out using a conventional hydrothermal synthesis method used in the art. The hydrothermal synthesis is preferably carried out at 100-200°C, preferably 110-190°C, and more preferably 120-180°C, for 6-48 hours, preferably 10-24 hours, and more preferably 12-18 hours. If the hydrothermal synthesis temperature is less than 100°C, the crystallinity of the metal oxide may be low. If the temperature exceeds 200°C, the size of the metal oxide particles may increase. Furthermore, if the hydrothermal synthesis time is less than 6 hours, the yield of metal oxide nanoparticles may be too low. If the hydrothermal synthesis time exceeds 48 hours, the size of the hydrothermally synthesized product may become too large. Therefore, it is preferable to carry out the hydrothermal synthesis within the above-mentioned time period.

[0045] The metal oxide nanoparticles obtained by hydrothermal synthesis can be washed repeatedly 3 to 5 times using ultrapure water and ethanol.

[0046] The metal oxide nanoparticles thus obtained may have a particle size of 2 to 100 nm, preferably an average particle size of 2 to 50 nm, more preferably an average particle size of 2 to 20 nm, and even more preferably an average particle size of 2 to 10 nm.

[0047] The metal oxide nanoparticles are as described above.

[0048] Next, the second step is a process for modifying the surface of the metal oxide nanoparticles obtained in the first step, and may include steps of: step 2-1 of mixing the metal oxide nanoparticles, a C3-C5 alcohol, and an aqueous solution containing the compound represented by Chemical Formula 1 to produce a reaction solution; step 2-2 of stirring the reaction solution to perform a reaction; step 2-3 of separating a reaction product from the solution after the stirring reaction and washing the separated reaction product; and step 2-4 of drying the washed reaction product to obtain surface-modified metal oxide nanoparticles.

[0049] The C3-C5 alcohol in the reaction solution prevents the surface-modified SnO2 particles from agglomerating, and 2-propanol is preferably used. The amount of alcohol used is 80 to 200 parts by weight, preferably 100 to 180 parts by weight, per 100 parts by weight of metal oxide nanoparticles. If the amount of C3-C5 alcohol used is less than 80 parts by weight, the surface modification reaction may not proceed well. If the amount exceeds 200 parts by weight, it may be difficult to obtain modified nanoparticles.

[0050] The reaction solution may contain 100 to 220 parts by weight, 120 to 200 parts by weight, or more preferably 130 to 180 parts by weight, of an aqueous solution containing the compound represented by Chemical Formula 1 per 100 parts by weight of metal oxide nanoparticles. If the amount of the aqueous solution containing the compound represented by Chemical Formula 1 used is less than 100 parts by weight, the solvent may not be stirred sufficiently during the surface modification step, resulting in a problem of inconsistent surface modification. If the amount exceeds 220 parts by weight, the stirring reaction time may become too long.

[0051] The content of the compound represented by Chemical Formula 1 in the aqueous solution containing the compound represented by Chemical Formula 1 is 10 to 80 wt %, preferably 30 to 80 wt %, and more preferably 30 to 70 wt %. If the content of the compound represented by Chemical Formula 1 is less than 10 wt %, the degree of modification of the metal oxide surface may be insufficient or uneven, resulting in a problem of the metal oxide particles not being uniformly dispersed in the solvent and settling. If the content exceeds 80.0 wt %, it is uneconomical and may even result in a problem of a decrease in the purity of the electron carrier due to unreacted compound. Therefore, it is preferable to use the compound within the above range.

[0052] The stirring reaction may be carried out at room temperature for 5 minutes to 2 hours, preferably 10 minutes to 1 hour. In this case, if the stirring reaction time is less than 5 minutes, there may be a problem that the stirring is not sufficient, and if it exceeds 2 hours, there is a disadvantage that it is uneconomical.

[0053] The separation and / or washing steps 2 to 4 may be performed by a common method used in the art. In one embodiment, the separation and / or washing may be performed by centrifugation to obtain the stirred reaction product from the reaction solution, and then washing the product with ultrapure water or the like.

[0054] The drying steps 2 to 5 may be carried out by a common method used in the art. In one embodiment, the reaction product obtained after washing may be heated in an oven at 50 to 80°C.

[0055] Such an electron carrier of the present invention may comprise, based on the total weight, 85 to 95% by weight of the metal oxide nanoparticles and the remaining amount of the surface-modifying component, preferably 88 to 94% by weight of the metal oxide nanoparticles and the remaining amount of the surface-modifying component, and more preferably 90.0 to 94.0% by weight of the metal oxide nanoparticles and the remaining amount of the surface-modifying component.

[0056] The coating agent for the electron transport layer (ETL) of the perovskite solar cell of the present invention uses the above-mentioned electron carrier and includes an organic solvent and the electron carrier dispersed in the organic solvent.

[0057] The organic solvent may have a dielectric constant of 20 or less, preferably 5 to 15. Specific examples of such organic solvents include at least one selected from isopropyl alcohol, butyl alcohol, 2,2,2-trifluoroethanol, chlorobenzene, and chloroform, and preferably at least one selected from isopropyl alcohol, 2,2,2-trifluoroethanol, and chlorobenzene may be used alone or in combination.

[0058] If an organic solvent with a dielectric constant of more than 20 is used, the perovskite material, which is the light absorption layer, may be decomposed by the organic solvent during the process of forming the thin electron transport layer.

[0059] The coating agent for ETL of the present invention contains, based on the total weight, 0.30 to 2.00 wt % of the electron carrier and the remaining amount of organic solvent, preferably 0.30 to 1.50 wt % of the electron carrier and the remaining amount of organic solvent, more preferably 0.35 to 1.00 wt % of the electron carrier and the remaining amount of organic solvent.

[0060] If the content of the electron carrier in the coating agent is less than 0.30 wt %, the content of the electron carrier is insufficient, which may result in a problem of the light absorbing layer being exposed during the formation of the ETL thin film. If the content exceeds 2.00 wt %, the thickness of the ETL increases, which may result in a problem of a decrease in the short circuit current (Jsc) and open circuit voltage (Voc) of the solar cell. Therefore, it is preferable to contain the electron carrier within this range.

[0061] The coating agent for forming an ETL of the present invention may be coated by a common coating method such as spin coating, blade coating, bar coating, spray coating, gravure coating, or die coating. In one embodiment, after coating, the coating agent may be heat-treated at 200°C or less to form an ultrathin film having a thickness of 10 to 100 nm, preferably 10 to 70 nm, and more preferably 10 to 50 nm.

[0062] Using the coating agent of the present invention, an inverted structure or pin structure perovskite solar cell can be manufactured as follows.

[0063] The inverted perovskite solar cell of the present invention may be a solar cell having a structure in which a conductive substrate, a drain electrode, a hole transport layer (HTL), a light absorption layer (or photoactive layer), an electron transport layer (ETL), and a source electrode are sequentially stacked.

[0064] The perovskite solar cell may further include a passivation layer between the light absorption layer and the electron transport layer. In this case, the passivation layer may be a C 60 Fullerenes, C 70Fullerenes, C 72 Fullerenes, C 76 Fullerenes and C 84 The fullerene may contain at least one selected from the fullerenes of the formula (II).

[0065] Furthermore, the inverted perovskite solar cell of the present invention may be formed by sequentially stacking a conductive substrate, a drain electrode, a hole transport layer, a light absorption layer, an electron transport layer, and a source electrode to form one set, and the set may be stacked in a single layer or multiple layers.

[0066] The conductive substrate may be a common conductive substrate used in the art, and examples thereof include a transparent plastic substrate made of a material such as polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, aromatic polyester, or polyimide, a glass substrate, a quartz substrate, or a silicon substrate.

[0067] The drain electrode may be made of a material containing at least one selected from a conductive metal, a conductive metal alloy, a metal oxide, and a conductive polymer, and preferred examples thereof include ITO (Indium 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), and / or AZO (Aluminum doped zinc oxide).

[0068] The hole transport layer (HTL) may also include inorganic and / or organic hole transport materials. The inorganic hole transport materials include nickel oxide (NiO x ), CuSCN, CuCrO2, and CuI.

[0069] Examples of the organic hole transport material include carbazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorene derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidine-based compounds, porphyrin-based compounds, phthalocyanine-based compounds, polythiophene derivatives, polypyrrole derivatives, polyparaphenylenevinylene derivatives, pentacene, coumarin 6 (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,Np-dimethoxyphenylamino)-9,9'-spirobifluorene),F16CuP C(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),ポリアニリン(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, Me-2PACz, 4-PACz, MeO-4PACz, Me-4PACz, and / or MeO-2PACz.

[0070] The hole transport layer can be formed by coating, vacuum deposition, or the like. Examples of the coating method include gravure coating, bar coating, printing, spraying, spin coating, dipping, and die coating.

[0071] Furthermore, in the configuration of the solar cell of the present invention, the light absorbing layer may contain a perovskite material generally applied to light absorbing layers of solar cells, and as a preferred example, it may contain a perovskite material represented by the following Chemical Formula 2.

[0072] [ka]

[0073] In Formula 2, C may include, as a monovalent cation, an amine, ammonium, a Group 1 metal, a Group 2 metal, and / or other cations or cation-like compounds, preferably formamidinium (FA), methylammonium (MA), FAMA, CsFAMA, or N(R)4. + (wherein R may be the same or different groups, and R is a linear alkyl group having 1 to 5 carbon atoms, a branched alkyl group having 3 to 5 carbon atoms, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, or an alkyl halide).

[0074] In addition, in Chemical Formula 2, M may contain one or two divalent cations selected from Fe, Co, Ni, Cu, Sn, Pb, Bi, Ge, Ti, Eu, and Zr.

[0075] In addition, in Chemical Formula 2, X may contain at least one halide element and / or Group 16 anion selected from F, Cl, Br, and I as a monovalent anion. In a preferred example, X is I x Br 3-x (0≦x≦3) is also acceptable.

[0076] In addition, a preferred embodiment of the formula 2 is FAPbI x Br 3-x (0≦x≦3), MAPbI x Br 3-x (0≦x≦3), CsMAFAPbI x Br 3-x (0≦x≦3), CH3NH3PbX3 (X=Cl, Br, I, BrI2, or Br2I), CH3NH3SnX3 (X=Cl, Br, or I), CH(=NH)NH3PbX3 (X=Cl, Br, I, BrI2, or Br2I), CH(=NH)NH3SnX3 (X=Cl, Br, or I).

[0077] Furthermore, in the solar cell of the present invention, the light-absorbing layer may be a single layer made of the same perovskite material, or may have a multilayer structure in which multiple layers made of different perovskite materials are stacked.The light-absorbing layer made of one type of perovskite material may contain the one type of perovskite material having a pillar shape such as a columnar, plate, needle, wire, or rod, and another different type of perovskite material.

[0078] Among the components of the solar cell of the present invention, the electron transport layer can be formed on the light absorbing layer by coating the above-described coating agent of the present invention (a dispersion of surface-modified metal oxide nanoparticles dispersed in an organic solvent, i.e., an electron carrier) with a coating liquid, followed by low-temperature heat treatment at 200°C or less, preferably 30 to 100°C or less, to form a thin-film coating layer.

[0079] At this time, the coating may be performed by spin coating, blade coating, bar coating, spray coating, gravure coating, or die coating.

[0080] The electron transport layer is preferably formed to a thickness of 10 to 100 nm, more preferably 10 to 70 nm, and even more preferably 10 to 50 nm. In this case, if the thickness of the electron transport layer exceeds 200 nm, the short-circuit current (J sc ) and open circuit voltage (V oc ) may decrease, so it is preferable to form the film within the above thickness range.

[0081] The surface of the coating layer thus formed, i.e., the electron transport layer, may be formed to have very low roughness, and may satisfy the RMS (root mean square) roughness of 50 nm or less, preferably 5.00 to 30.00 nm, and more preferably 10.00 to 25.00 nm.

[0082] In addition, in the configuration of the solar cell of the present invention, the source electrode may be formed by coating or vapor-depositing at least one material selected from Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C, and conductive polymers.

[0083] The present invention may be applied to heterojunction (tandem) perovskite solar cells. For example, the heterojunction perovskite solar cell may be a solar cell having a structure in which a conductive substrate, a drain electrode, a first light absorbing layer (or a first photoactive layer), a recombination layer, a hole transport layer (HTL), a second light absorbing layer (or a second photoactive layer), an electron transport layer (ETL), and a source electrode are sequentially stacked.

[0084] The first light absorbing layer may be a silicon solar cell or a light absorbing layer comprising a perovskite material as described above.

[0085] When the first light absorbing layer is a silicon solar cell, it may be a p-type silicon layer or an n-type silicon layer, and accordingly the doping layer may be n-type or p-type. When it contains a perovskite material, a hole transport layer and an electron transport layer may be included between the drain electrode and the light absorbing layer, and between the light absorbing layer and the recombination layer, respectively.

[0086] The conductive substrate, drain electrode, hole transport layer, second light absorbing layer, electron transport layer, and source electrode are the same as those described in the inverted structure perovskite solar cell.

[0087] The perovskite solar cell may further include a passivation layer between the second light absorbing layer and the electron transport layer. In this case, the passivation layer may be a C 60 Fullerenes, C 70 Fullerenes, C 72 Fullerenes, C 76 Fullerenes and C 84 The fullerene may contain at least one selected from the fullerenes of the formula (II).

[0088] The present invention will be described in more detail below through examples. However, the following examples should not be construed as limiting the scope of the present invention, but should be construed as being for the purpose of aiding in the understanding of the present invention.

[0089] [Example] Example 1-1: Preparation of coating solution for forming electron transport layer (ETL) (1) Preparation of SnO2 nanoparticles SnCl45H2O was added to a beaker containing ultrapure water and stirred to prepare a metal precursor solution with a SnCl4 concentration of 0.5M. Then, 85 ml of a basic aqueous solution of NH4OH was added to 215 ml of the metal precursor solution to prepare a reaction solution with a pH of approximately 8.0 to 8.5.

[0090] The reactive solution was placed in a pressure vessel (autoclave or hydrothermal reactor) and subjected to hydrothermal synthesis at 120° C. for 12 hours.

[0091] Next, the product obtained by hydrothermal synthesis was washed 3 to 5 times with ultrapure water and ethanol to produce SnO2 nanoparticles.

[0092] The average particle size of the produced SnO2 nanoparticles was 3 to 5 nm.

[0093] In addition, the TEM measurement image of the produced SnO2 nanoparticles is shown in Figure 1, and the XRD measurement results are shown in Figure 2.

[0094] (2) Preparation of electron carriers (surface-modified SnO2 nanoparticles) 5 g of the SnO2 nanoparticles prepared above was placed in a round-bottom flask containing 7.5 mL of 2-propanol and stirred. Then, 7.5 mL of an aqueous solution containing 40 wt% of the compound (TBPH) represented by the following formula 1-1 was added, and a reaction solution was prepared using an ultrasonic grinder.

[0095] [ka]

[0096] In Chemical Formula 1-1, R 1 ~R 4 is an n-butyl group, and said X is -OH.

[0097] Next, the reaction solution was centrifuged to separate the nanoparticles, and then dried in an oven at 60°C to prepare surface-modified SnO2 nanoparticles (electron carriers) as electron carriers.

[0098] Experimental Example 1: FT-IR and TGA analysis of electron carriers The SnO2 nanoparticles prepared in Example 1-1 before and after surface modification were subjected to Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA), and the results are shown in FIGS. 3 and 4.

[0099] (1) Figure 3 shows the results of FT-IR measurements. The black graph shows the SnO2 nanoparticles before surface modification, and the red graph shows the measurement results for the surface-modified SnO2 nanoparticles.

[0100] As can be seen from Figure 3, after surface modification, the -1 ν(CH2) peak, approximately 1460 cm -1 δ as (CH) peak k, approximately 1380 cm -1 It was confirmed that there was a CH2 peak, which confirmed the presence of the modifying component TBPH (tetrabutylphosphonium hydroxide) on the surface of the SnO2 nanoparticles.

[0101] (2) Figure 4 also shows the results of TGA analysis. When SnO2 nanoparticles before and after surface modification were heated to 700°C, the unmodified SnO2 nanoparticles (bare SnO2) (black graph) lost approximately 8% of their initial mass due to the removal of surface-adsorbed moisture and -OH groups. In contrast, the surface-modified SnO2 nanoparticles (TBPH-modified SnO2) showed a rapid mass loss from approximately 200 to 350°C, losing approximately 16% of their mass at 700°C.

[0102] This confirmed that the surface-modified SnO2 nanoparticles contained approximately 8% organic matter compared to unmodified SnO2 nanoparticles, and the electron carrier produced thereby was confirmed to contain 92 wt% SnO2 nanoparticles and 8 wt% surface-modified components.

[0103] Comparative Example 1-1 The SnO2 nanoparticles prepared in Example 1-1(1) were prepared as an electron carrier without any surface modification process.

[0104] Comparative Example 1-2 SnO2 nanoparticles were prepared as produced in Example 1-1 (1).

[0105] Next, 5 g of the SnO2 nanoparticles were placed in a round-bottom flask containing 3 mL of ultrapure water, stirred, and then 7.5 mL of a 40 wt% aqueous solution of TBAH (tetrabutylammonium hydroxide) was added, followed by an ultrasonic grinder to prepare a reaction solution. The reaction solution was then centrifuged to separate the nanoparticles, which were then dried in an oven at 60°C to prepare SnO2 nanoparticles (electron carriers) surface-modified with TBAH.

[0106] Comparative Examples 1-3 SnO2 nanoparticles were prepared as produced in Example 1-1 (1).

[0107] Next, 5 g of the SnO2 nanoparticles were placed in a round-bottom flask containing 3 mL of ultrapure water and stirred, and then 30 mL of a 10 wt% aqueous solution of TMAH (tetramethylammonium hydroxide) was added and the reaction solution was prepared using an ultrasonic grinder. The reaction solution was then centrifuged to separate the nanoparticles, which were then dried in an oven at 60°C to prepare SnO2 nanoparticles (electron carriers) surface-modified with TMAH.

[0108] Example 2-1: Preparation of a dispersion solution of an electron carrier (a coating solution for forming an ETL) 7.0 mg of the electron carrier prepared in Example 1-1 was added to 1.0 ml of 2,2,2-trifluoroethanol (dielectric constant = about 8.5), which has low hydrophilicity, and then an ultrasonic grinder was used to prepare a dispersion-type coating solution for forming an electron transport layer.

[0109] Experimental Example 2: Measurement of coating liquid dispersibility (dispersion stability) The dispersibility of the ETL-forming coating solutions prepared in Example 2-1 and Comparative Examples 2-1 to 2-3 was measured using a dynamic light scattering particle size analyzer, and the results are shown in Table 2 below. A dispersion with a Z-average value of 20.0 nm or less, preferably 17.0 nm or less, was evaluated as having excellent dispersion stability, and the evaluation values ​​in Table 1 are the average values ​​obtained by measuring three repeated experiments. The lower the dispersibility, the more likely it is that the particle size distribution will form multiple peaks rather than a single peak.

[0110] The graphs of the measurement results for Example 2-1 (TBPH), Comparative Example 2-2 (TBAH), and Comparative Example 2-3 (TMAH) are shown in FIG. 5, and Example 2-1, Comparative Example 2-2, and Comparative Example 2-3 all formed a single peak under the same conditions.

[0111] [Table 1]

[0112] Looking at the experimental results in Table 1, the coating solution prepared using unmodified SnO2 nanoparticles showed extremely poor dispersibility, making it impossible to measure. Also, the coating solutions prepared using the nanoparticles of Comparative Examples 1-2 and 1-3 as electron carriers, Comparative Examples 2-2 and 2-3, showed excellent dispersibility compared to Comparative Example 2-1, but tended to show a relatively lower dispersibility compared to Example 2-1.

[0113] Examples 2-2 to 2-3 and Comparative Examples 2-4 to 2-5 The coating liquid for forming the electron transport layer was prepared in the same manner as in Example 2-1, but the types of organic solvents used in preparing the coating liquid were varied as shown in Table 3 below to prepare the coating liquids for forming the ETL, and Examples 2-2 to 2-3 and Comparative Examples 2-4 to 2-5 were carried out (see Table 2).

[0114] [Table 2]

[0115] Experimental Example 2: Manufacturing of ultra-thin films and measurement of surface roughness and light transmittance of coating layers Each of the coating solutions for forming ETL prepared in Examples 2-1 to 2-3 and Comparative Examples 2-4 to 2-5 was spin-coated on a perovskite thin film including a glass substrate and a glass substrate, and then heat-treated at 30°C to prepare an ultra-thin film having a thickness of 10 to 15 nm.

[0116] In addition, the surface roughness of the ultrathin film formed on the perovskite thin film including the glass substrate was measured using a non-contact method and calculated as the root-mean-square (rms) of the roughness. The surface roughness was measured at three random points, and the average value of the surface roughness measured at the three points is shown in Table 4 below.

[0117] In addition, the ultrathin film formed on the glass substrate was scanned with near-infrared light by a UV spectrum measurement method to measure the absorbance and light transmittance (%) of the sample, and the results are shown in Table 3 below. Here, the light transmittance is the light transmittance at a wavelength of 500 to 550 nm.

[0118] [Table 3]

[0119] Looking at the RMS roughness and optical transmittance in Table 3, it was confirmed that Examples 2-1 and 2-2 had very low surface roughness with an RMS roughness of 10.0 to 20.0 nm and excellent optical properties with an optical transmittance of 90% or more. Comparative Example 2-4 showed similar surface roughness and optical properties to Examples 2-1 and 2-2. In contrast, Comparative Example 2-5 had similar optical properties, but when a thin film was formed on top of the perovskite, the perovskite layer was completely dissolved, making it impossible to measure the roughness.

[0120] Manufacturing Example 1: Fabrication of inverted structure perovskite solar cells using surface-modified SnO2 nanoparticles An organic substrate (thickness 1.1 mm, 15.0 Ω / sq) coated with indium tin oxide (ITO) to a thickness of approximately 110 nm as a source electrode was cleaned sequentially with acetone and isopropyl alcohol (IPA) using an ultrasonic cleaner for 1 hour each.

[0121] Next, a hole transport layer (NiO) with a thickness of 20 nm was formed on the ITO substrate through sputtering deposition. x ) was formed.

[0122] Next, a yellow light absorbing layer solution was formed on the hole transport layer by spin coating using a solution of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The solution was then heat-treated at 100°C for 20 minutes to form a NiO x A hole transport layer and a light absorbing layer (CsMAFAPbI) with a perovskite crystal structure of 450-550 nm thickness were x Br 3-x , 0≦x≦3) was formed.

[0123] Next, a <1 nm LiF thin film and a 13 nm thick passivation layer (C60 fullerene) were formed on the light absorption layer using thermal evaporation.

[0124] Next, the coating solution for forming the ETL prepared in Example 2-1 was spin-coated on the top of the passivation layer at 4,000 rpm for 30 seconds, followed by heat treatment at 30° C. to form a 15 nm thick electron transport layer. Next, IZO (Indium-doped Zinc Oxide) was formed as a transparent electrode layer on the top of the hole transport layer using a sputtering device to a thickness of 100 nm.

[0125] Next, 1×10 silver (Ag) was applied to the top of the electron transport layer. -7 An inverted perovskite solar cell was fabricated by forming a source electrode by deposition at a thickness of 200 nm under a pressure of 1000 torr.

[0126] Production Examples 2 to 3 and Comparative Production Examples 1 to 3 Inverted-structure perovskite solar cells were manufactured in the same manner as in Manufacturing Example 1, but instead of the ETL-forming coating liquid of Example 2-1, the ETL-forming coating liquids of Examples 2-2 to 2-7 and Comparative Examples 2-2 to 2-6 were used to form electron transport layers, and solar cells were manufactured, performing Manufacturing Example 2-3 and Comparative Manufacturing Examples 1 to 3, respectively.

[0127] Control group: Solar cells with an electron transport layer formed by ALD deposition As a control, a drain electrode, a hole transport layer, a perovskite light absorption layer, and a passivation layer were formed in the same manner as in Preparation Example 1, and then a 6 nm thick SnO x A vapor deposition layer (electron transport layer) was formed.

[0128] Next, 1×10 silver (Ag) was applied to the top of the electron transport layer. -8 An inverted perovskite solar cell was fabricated by forming a source electrode by evaporation at a pressure of 1000 torr to a thickness of 150 nm.

[0129] Experimental example 2: Performance measurement of semi-transparent solar cells The current-voltage characteristics and efficiency of the semitransparent solar cell manufactured in Manufacturing Example 1 were measured, and the results are shown in Table 4 below. In addition, the short-circuit current density and photoelectric conversion efficiency (PCE) measurement results for Manufacturing Example 1 and the control are shown in Figure 6.

[0130] [Table 4]

[0131] Looking at the performance measurement results of the solar cell in Table 4, Preparation Example 1 exhibited solar cell performance (current-voltage characteristics, fill factor, photoelectric conversion efficiency) similar to that of a solar cell composed of an ETL formed by ALD deposition. In contrast, Comparative Preparation Example 1, in which the ETL was formed using a coating solution containing SnO2 nanoparticles surface-modified with TBAH (Comparative Example 2-2) as the electron carrier material, had a problem of a decrease in fill factor compared to Preparation Example 1. This is because TBAH, a surface-modifying component of the electron carrier, was used to modify the fullerene material (C) of the passivation layer. 60 ) and damage the passivation layer, reducing the performance of the solar cell.

[0132] In contrast, the solar cell of Comparative Preparation Example 2 showed no damage to the passivation layer, but showed slightly lower performance than Preparation Example 1. This can be attributed to the decrease in thin film density and uniformity due to the decreased dispersibility of the dispersion solution used in Preparation Example 1.

[0133] In addition, in Comparative Preparation Example 2, in which the ETL was formed using a coating solution (Example 2-2) that used isopropyl alcohol as the organic solvent in the coating solution for forming the ETL, and in Comparative Preparation Example 3, in which the ETL was formed using a coating solution (Example 2-3) that used chlorobenzene as the organic solvent, the solar cell performance was reduced. This is thought to be due to the problem of reduced thin film uniformity caused by the relatively low dispersibility of the electron carrier in the coating solution for forming the ETL.

[0134] Furthermore, in the case of Comparative Production Example 4, in which the ETL was formed using a coating solution that used ethanol (EtOH) as the organic solvent, it was confirmed that the perovskite photoactive layer was damaged by the organic solvent ethanol, resulting in a problem of reduced performance of the solar cell element.

[0135] Manufacturing Example 4: Fabrication of tandem perovskite solar cells using surface-modified SnO2 nanoparticles A PERC structure cell was used as the lower solar cell.

[0136] The PERC structure cell is made by forming n-type impurities through a POCl process on a silicon substrate on which a lower passivation layer and a lower electrode are formed, which are manufactured by Hanwha Q Cell. ++ An emitter layer is formed.

[0137] Next, n ++ An ITO (Indium Tin Oxide) layer was formed as a recombination layer on the emitter layer using a sputtering device to a thickness of 50 nm.

[0138] Next, a hole transport layer (NiO) with a thickness of 20 nm was formed on the ITO substrate through sputtering deposition. x ) was formed.

[0139] Next, a yellow light absorbing layer solution was formed on the hole transport layer by spin coating using a solution of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The solution was then heat-treated at 100°C for 20 minutes to form a NiO x A hole transport layer and a light absorbing layer (CsMAFAPbI) with a perovskite crystal structure of 450-550 nm thickness were x Br 3-x , 0≦x≦3)) was formed.

[0140] Next, a <1 nm LiF thin film and a 13 nm thick passivation layer (C60 fullerene) were formed on the light absorption layer using thermal evaporation.

[0141] Next, the coating solution for forming the ETL prepared in Example 2-1 was spin-coated on the top of the passivation layer at 4,000 rpm for 30 seconds, followed by heat treatment at 30° C. to form a 15 nm thick electron transport layer. Next, IZO (Indium-doped Zinc Oxide) was formed as a transparent electrode layer on the top of the hole transport layer using a sputtering device to a thickness of 100 nm.

[0142] Next, 1×10 silver (Ag) was applied to the top of the electron transport layer. -7 Tandem perovskite solar cells were fabricated by forming a source electrode by evaporation at a pressure of 1000 torr to a thickness of 200 nm.

[0143] (2) Preparation of the control group (ALD deposition) As a control, a tandem perovskite solar cell was manufactured in the same manner as in Manufacturing Example 4, except that the n of the PERC structure cell, which was the lower solar cell, was ++The same hole transport layer, perovskite light absorption layer, and passivation layer as in Preparation Example 4 were formed on the emitter layer, and then a 6 nm thick SnO layer was deposited on the passivation layer by atomic layer deposition. x A vapor deposition layer (electron transport layer) was formed.

[0144] Next, 1×10 silver (Ag) was applied to the top of the electron transport layer. -8 Tandem perovskite solar cells were fabricated by forming a source electrode by evaporation at a pressure of 1000 torr to a thickness of 150 nm.

[0145] Comparative Examples 6 and 7 Tandem perovskite solar cells were manufactured in the same manner as in Manufacturing Example 4, but the coating liquid for forming the ETL of Comparative Example 2-2 or Comparative Example 2-3 was used instead of the coating liquid for forming the ETL of Example 2-1 to form an electron transport layer, and Comparative Manufacturing Examples 6 and 7 were performed (see Table 5 below).

[0146] Experimental example 3: Performance measurement of silicon-perovskite tandem solar cells The current-voltage characteristics and efficiency of the silicon-perov tandem solar cells fabricated in Preparation Example 4, the control group, and Comparative Preparation Examples 6 and 7 were measured, and the results are shown in Table 5. In addition, the short-circuit current density and photoelectric conversion efficiency (PCE) measurement results for Preparation Example 4 and the control group are shown in Figure 7.

[0147] [Table 5]

[0148] From the performance measurement results of the tandem solar cell element in Table 5 and FIG. 7, it was confirmed that the tandem solar cell element of Preparation Example 1 had excellent photoelectric conversion efficiency.

Claims

1. An electron carrier for an electron transport layer of a perovskite solar cell, comprising metal oxide nanoparticles whose surface has been modified with a phosphonium salt represented by the following Chemical Formula 1: 【Chemical 1】 In Chemical Formula 1, R １ ~R ４ are each independently C １ ~C １０ a linear alkyl group of C ３ ~C １０ is a branched alkyl group, a phenyl group, or a benzyl group, and X is a halogen atom or —OH.

2. 2. The electron carrier for an electron transport layer of a perovskite solar cell according to claim 1, wherein the metal oxide nanoparticles comprise an oxide of a metal including one or more metals selected from the group consisting of tin (Sn), zirconium (Zr), strontium (Sr), zinc (Zn), vanadium (V), molybdenum (Mo), tungsten (W), niobium (Nb), aluminum (Al), and gallium (Ga).

3. 3. The electron carrier for use in the electron transport layer of a perovskite solar cell according to claim 1, wherein the total weight of the electron carrier comprises 85.0 to 95.0 wt % of the metal oxide nanoparticles and the remaining amount of the surface modifying component.

4. The electron carrier for the electron transport layer of a perovskite solar cell according to claim 1, wherein the metal oxide nanoparticles have a particle size of 1 to 100 nm.

5. an organic solvent and the electron carrier according to any one of claims 1 to 4 dispersed in the organic solvent; The organic solvent has a dielectric constant of 20 or less.

6. 6. The coating agent for an electron transport layer of a perovskite solar cell according to claim 5, comprising 0.30 to 2.00 wt % of an electron carrier and the remainder an organic solvent.

7. 6. The coating agent for an electron transport layer of a perovskite solar cell according to claim 5, wherein the organic solvent comprises at least one selected from the group consisting of isopropyl alcohol, butyl alcohol, 2,2,2-trifluoroethanol, chlorobenzene, and chloroform.

8. An electron transport layer of a perovskite solar cell, comprising a coating layer formed from the coating agent according to claim 5.

9. the electron transport layer has a thickness of 10 to 200 nm; The electron transport layer of the perovskite solar cell according to claim 8, wherein the electron transport layer has a light transmittance of 88.0% or more for a wavelength of 500 to 550 nm when the electron transport layer has a thickness of 10 to 15 nm.

10. The electron transport layer according to claim 8 is formed directly on the upper surface of the perovskite light absorbing layer, or A perovskite solar cell, characterized in that a passivation layer is formed between the perovskite light absorbing layer and the electron transport layer according to claim 8.

11. The passivation layer is C ６０ Fullerenes, C ７０ Fullerenes, C ７２ Fullerenes, C ７６ Fullerenes and C ８４ The perovskite solar cell according to claim 10, characterized in that it contains at least one selected from the group consisting of fullerenes.

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