Nickel oxide thin film, manufacturing method therefor, and perovskite solar cell comprising same

Abstract

The present disclosure relates to a nickel oxide thin film manufacturing method, a nickel oxide thin film manufactured thereby, and a perovskite solar cell comprising same, the nickel oxide thin film manufacturing method comprising the steps of: (S1) mixing an organic ligand with a nickel precursor so as to prepare a complex in which nickel and the organic ligand are bound; and (S2) bringing an aqueous solution comprising urea and the complex into contact with a substrate, and then heating same so that a nickel oxide oriented in one direction is deposited on the substrate.

Description

Nickel oxide thin film, method for manufacturing the same, and perovskite solar cell containing the same

[0001] The present disclosure relates to a method for manufacturing a nickel oxide thin film and a perovskite solar cell comprising a nickel oxide thin film manufactured therefrom.

[0002] Perovskite solar cells are attracting attention as next-generation solar cells capable of replacing conventional silicon solar cells, as they possess high efficiency while being manufactured at low cost and through simple processes.

[0003] To improve the quality of perovskite solar cells containing organometal halides of a perovskite structure, also referred to as organic-inorganic perovskite compounds or organometal halide perovskite compounds, it is necessary to enhance the performance of the charge transport layer in contact with the perovskite compound. Among these, the hole transport layer has a decisive influence on the crystallization and shape control of the perovskite compound.

[0004] Conventionally, conductive polymers such as PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)) have been used as hole transport layer materials. However, these materials exhibit non-uniform electrical properties and have low stability due to being easily damaged by moisture and acid.

[0005] To address this, inorganic materials with higher stability compared to organic materials are being developed as new hole transport layer materials. Among them, nickel oxide is attracting attention as a next-generation hole transport layer due to its advantages, such as good compatibility with perovskite compounds in terms of energy levels, high transparency in the visible light region, and the ability to induce efficient hole extraction from perovskite compounds.

[0006] Although coating methods such as the sol-gel method or spin coating are used to deposit nickel oxide thin films, these methods have problems such as difficulty in uniformly depositing nickel oxide thin films at high density, the generation of a large number of defects in the nickel oxide thin films, and poor compatibility with perovskite compounds.

[0007] Recently, a method for manufacturing nickel oxide thin films using Chemical Bath Deposition (CBD) has been developed, but there are limitations in forming high-density thin films because, as a nickel hydroxide dispersion is prepared by simply raising the pH of a nickel precursor solution and then deposited onto a transparent electrode through electrostatic attraction, already aggregated nickel-containing particles are deposited on the substrate to form a thin film.

[0008] The purpose of the present disclosure is to provide a method for manufacturing a uniformly and densely deposited nickel oxide thin film in order to solve the problems of the prior art described above.

[0009] Another objective of the present disclosure is to provide a perovskite solar cell having improved performance and stability.

[0010] A method for manufacturing a nickel oxide thin film according to the present disclosure comprises: (S1) a step of mixing an organic ligand and a nickel precursor to prepare a complex in which nickel and an organic ligand are combined; and (S2) a step of contacting an aqueous solution containing the complex and elements with a substrate and then heating it to deposit a nickel oxide oriented in one direction on the substrate.

[0011] In one example, in step (S2) above, the aqueous solution may be weakly basic.

[0012] In one example, the organic ligand may include an alkanolamine.

[0013] In one example, the organic ligand may include triethanolamine (TEA).

[0014] In one example, the above step (S2) may include: (S2-1) a step of depositing nickel hydroxide on the substrate by first heating the aqueous solution containing the composite and element after contacting it with the substrate; and (S2-2) a step of depositing a nickel oxide thin film on the substrate by second heating the substrate on which the nickel hydroxide has been deposited.

[0015] In one example, the ratio (T1 / T2) of the first heating temperature (T1) and the second heating temperature (T2) may be 0.1 to 0.5.

[0016] In one example, the following Equation 1 can be satisfied.

[0017] [Equation 1]

[0018] 0.9 < k1 / k0 < 1.1

[0019] (In Equation 1 above, k0 represents the pH of the aqueous solution before contact with the substrate, and k1 represents the pH of the aqueous solution after contact with the substrate.)

[0020] In one example, the nickel precursor may be one or more selected from the group comprising nickel sulfate hydrate, nickel nitrate hydrate, nickel acetate hydrate, nickel acetylacetonate hydrate, nickel oxalate hydrate, and nickel chloride hydrate.

[0021] In one example, the substrate may include a transparent conducting oxide (TCO).

[0022] In one example, in step (S2) above, the substrate and the nickel oxide may form a covalent bond.

[0023] The present disclosure comprises a nickel oxide thin film manufactured by the method described above, wherein the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the thin film.

[0024] In one example, the nickel oxide thin film may be used as a hole transport layer for a perovskite solar cell.

[0025] The present disclosure includes a perovskite solar cell comprising nickel oxide manufactured by the method described above.

[0026] A perovskite solar cell according to the present disclosure comprises: a first electrode; a hole transport layer located on the first electrode; and a photoactive layer located on the hole transport layer and containing a perovskite compound, wherein the hole transport layer comprises a nickel oxide thin film in which the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the first electrode.

[0027] In one example, the hole transport layer may satisfy the following Equation 2 in the Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum.

[0028] [Equation 2]

[0029] I1> I2

[0030] (In Equation 2 above, I1 is q=2.65±0.2 Å -1 It refers to the first peak intensity at, and I2 is q=3.0±0.2 Å. -1 (refers to the second peak intensity at)

[0031] In one example, the thickness of the hole transport layer may be 1 to 40 nm.

[0032] In one example, the first electrode may be a transparent electrode.

[0033] In one example, it may further include an electron transport layer located on the photoactive layer; and a second electrode located on the electron transport layer.

[0034] The method for manufacturing a nickel oxide thin film of the present disclosure can produce a nickel oxide thin film with uniform and high density by orienting the nickel oxide in one direction.

[0035] In addition, a nickel oxide thin film can be deposited without damaging the substrate.

[0036] Furthermore, by including the above nickel oxide thin film as a hole transport layer of a perovskite solar cell, the performance and stability of the solar cell can be improved.

[0037] FIG. 1 is a schematic diagram illustrating a method for manufacturing a nickel oxide thin film according to one embodiment of the present disclosure.

[0038] Figure 2 is a GIWAXS analysis spectrum of a nickel oxide thin film prepared by the method according to Example 1 and Comparative Example 1.

[0039] FIG. 3 is an image showing the GIWAXS scattering patterns of nickel oxide thin films prepared according to the methods of (a) Comparative Example 2, (b) Comparative Example 1, and (c) Example 1, respectively.

[0040] Figure 4 shows (a) the GIWAXS scattering pattern and (b) the GIWAXS analysis spectrum of a nickel hydroxide thin film before heat treatment when manufacturing nickel oxide by the method according to Example 1.

[0041] Figure 5 is a scanning electron microscope (SEM) image of a nickel oxide thin film prepared according to the methods of (a) Comparative Example 2, (b) Comparative Example 1, and (c) Example 1, respectively.

[0042] Figure 6 shows (a) a scanning electron microscope (SEM) image and (b) a GIWAXS scattering pattern of a nickel oxide thin film prepared by the method according to Comparative Example 3.

[0043] Figure 7 shows (a) a scanning electron microscope (SEM) image and (b) a GIWAXS scattering pattern of a nickel oxide thin film prepared by the method according to Comparative Example 4.

[0044] FIG. 8 is a graph showing the transmittance of nickel oxide thin films and FTO substrates prepared by the methods according to Example 1, Comparative Example 1, and Comparative Example 2.

[0045] Figure 9 shows the X-ray photoelectron spectroscopy (XPS) spectra of nickel oxide thin films prepared by the methods according to (a) Comparative Example 2, (b) Comparative Example 1, and (c) Example 1, respectively.

[0046] Figure 10 is a graph showing the change in pH of an aqueous solution according to reaction time when manufacturing a nickel oxide thin film by the method according to Example 1.

[0047] Figure 11 is a cross-sectional scanning electron microscope (SEM) image of a perovskite solar cell containing a nickel oxide thin film prepared by the method according to Example 1.

[0048] The nickel oxide thin film of the present disclosure, the method for manufacturing the same, and the perovskite solar cell containing the same are described in detail. The terms used in this specification have been selected to be as widely used as possible in consideration of the functions of the present disclosure; however, these may vary depending on the intent of those skilled in the relevant field, case law, the emergence of new technologies, etc. Unless otherwise defined, technical and scientific terms used may have the meaning commonly understood by those skilled in the art to which this invention pertains.

[0049] In this specification and the appended claims, terms such as “comprising” or “having” mean that the features or components described in the specification exist, and unless specifically limited, do not preclude the possibility that one or more other features or components may be added.

[0050] In this specification and the appended claims, terms such as "first," "second," etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another.

[0051] Singular expressions used in this specification and the appended claims include plural expressions unless the context clearly indicates that they are singular. Additionally, plural expressions include singular expressions unless the context clearly indicates that they are plural.

[0052] Additionally, numerical ranges used herein include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of numerical ranges defined in different forms. Unless otherwise specifically defined in the specification of this disclosure, values ​​outside the numerical range that may occur due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0053] Terms such as "approximately" used in this specification and the appended claims are used to encompass tolerances when tolerances exist.

[0054] Perovskite solar cells are attracting attention as next-generation solar cells capable of replacing conventional silicon solar cells, as they possess high efficiency while being manufactured at low cost and through simple processes.

[0055] To improve the quality of perovskite solar cells containing organometal halides of a perovskite structure, also referred to as organic-inorganic perovskite compounds or organometal halide perovskite compounds, it is necessary to enhance the performance of the charge transport layer in contact with the perovskite compound. Among these, the hole transport layer has a decisive influence on the crystallization and shape control of the perovskite compound.

[0056] Conventionally, conductive polymers such as PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)) have been used as hole transport layer materials. However, these materials exhibit non-uniform electrical properties and have low stability due to being easily damaged by moisture and acid.

[0057] To address this, inorganic materials with higher stability compared to organic materials are being developed as new hole transport layer materials. Among them, nickel oxide is attracting attention as a next-generation hole transport layer due to its advantages, such as good compatibility with perovskite compounds in terms of energy levels, high transparency in the visible light region, and the ability to induce efficient hole extraction from perovskite compounds.

[0058] Although methods such as the sol-gel method and spin coating are used to deposit nickel oxide thin films, these methods have problems such as difficulty in uniformly depositing nickel oxide thin films at high density, the generation of a large number of defects in the nickel oxide thin films, and poor compatibility with perovskite compounds.

[0059] Recently, a method for manufacturing nickel oxide thin films using Chemical Bath Deposition (CBD) has been developed. However, since the nickel hydroxide dispersion is prepared by simply raising the pH of a nickel precursor solution and then deposited onto a transparent electrode through electrostatic attraction, there are limitations in forming high-density thin films because the already aggregated nickel-containing particles are physically adsorbed onto the substrate to form the thin film. Furthermore, when this is used as a hole transport layer, there is a problem of reduced durability and stability of the perovskite solar cell.

[0060] Accordingly, after in-depth research, the applicant developed a method to deposit a nickel oxide thin film at a higher density, in which the nickel oxide is strongly bonded to the substrate without damaging the texture of the substrate with high surface roughness, and at the same time, the nickel oxide is oriented in one direction.

[0061] A method for manufacturing a nickel oxide thin film according to the present disclosure comprises: (S1) a step of mixing an organic ligand and a nickel precursor to prepare a complex in which nickel and an organic ligand are combined; and (S2) a step of contacting an aqueous solution containing the complex and elements with a substrate and then heating to deposit a nickel oxide oriented in one direction on the substrate.

[0062] In the above step (S1), a composite can be prepared by mixing an organic ligand and a nickel precursor to coordinate nickel to the organic ligand. By preparing a composite by coordinating the organic ligand with nickel and then using it to manufacture a nickel oxide thin film, the aggregation of nickel particles in the solution is minimized, allowing the nickel oxide thin film to be uniformly deposited even on a substrate with a rough surface. Additionally, as the nickel oxide is oriented in one direction, a nickel oxide thin film can be manufactured at a high density.

[0063] In one example, the organic ligand may include an alkanolamine. The alkanolamine contains a hydroxyl group (-OH), so that the nickel and the hydroxyl group of the alkanolamine can coordinately bond to form a complex. The hydroxyl group coordinately bonded to the nickel is a hydroxide ion (OH) formed from urea in step (S2) described later. - Nickel oxide can be easily deposited on a substrate by reacting with ). Specifically, the organic ligand may include monoalkanolamine, dialkanolamine, trialanolamine, or a combination thereof, and more specifically, may include trialanolamine with a high hydroxyl group (-OH) content per molecule.

[0064] More specifically, the organic ligand may include triethanolamine (TEA), diethanolamine, ethanolamine, ethylenediaminetetraacetic acid, and triethylamine, and preferably may include triethanolamine (TEA). Triethanolamine not only acts as an organic ligand that forms a complex with nickel, but also prevents nickel particles from aggregating with each other in the solution, thereby enabling high dispersion of nickel in the solution. Accordingly, a nickel oxide thin film having a uniform thickness can be formed on a substrate in step (S2) described later.

[0065] In one example, the nickel precursor may be one or more selected from the group comprising nickel sulfate hydrate, nickel nitrate hydrate, nickel acetate hydrate, nickel acetylacetonate hydrate, nickel oxalate hydrate, and nickel chloride hydrate.

[0066] The above organic ligand and nickel precursor can be mixed in a weight ratio of 0.5 to 2:1, 0.6 to 1.7:1, 0.7 to 1.5:1, 0.8 to 1.3:1, or 0.9 to 1.1:1. When mixed within the above ranges, a complex can be easily formed, and in step (S2), the pH of the aqueous solution can be prevented from rising excessively and becoming strongly basic.

[0067] The above step (S2) is a step of depositing nickel oxide oriented in one direction on a substrate, and the nickel oxide can be deposited on the substrate through the interaction between the elements contained in the aqueous solution and the complex.

[0068] In one example, in step (S2), the aqueous solution may be weakly basic, specifically, the hydrogen ion index (pH) of the aqueous solution may be 6 to 9, 6.5 to 8.5, or 7 to 8. The aqueous solution having weakly basic properties may be such that nickel hydroxide is not formed in advance within the aqueous solution, and upon heating, the element is irreversibly decomposed and hydroxide ions are supplied slowly. Accordingly, a nickel oxide thin film uniformly oriented in one direction can be formed on the substrate without damaging the substrate.

[0069] In one specific example, the following Equation 1 can be satisfied.

[0070] [Equation 1]

[0071] 0.9 ≤ k1 / k0 ≤ 1.1

[0072] In the above Equation 1, k0 represents the pH of the aqueous solution before contact with the substrate, and k1 represents the pH of the aqueous solution after contact with the substrate. Specifically, k1 may represent the pH of the aqueous solution when the aqueous solution is heated by contacting the substrate with the aqueous solution.

[0073] That is, the pH of the aqueous solution can be maintained at a level similar to the initial pH during and after step (S2) is completed. More specifically, k1 / k0 can be 0.9 to 1.1, 0.95 to 1.05, or 0.99 to 1.01, and advantageously, there may be no change in the pH of the aqueous solution.

[0074] (S2) Even while performing step (S2), the pH of the aqueous solution does not change significantly and maintains a weakly basic nature, so that the substrate is not damaged by the aqueous solution or the texture of the substrate is not changed, thereby allowing for the production of a uniform nickel oxide thin film.

[0075] Specifically, the above step (S2) may include: (S2-1) a step of depositing nickel hydroxide on the substrate by first heating the aqueous solution containing the composite and element after contacting it with the substrate; and (S2-2) a step of depositing a nickel oxide thin film on the substrate by second heating the substrate on which the nickel hydroxide has been deposited.

[0076] As shown in FIG. 1, when a substrate is contacted with an aqueous solution containing the complex and urea in step (S2-1) and then heated first, the urea becomes ammonium ions (NH4 + ) and hydroxide ions (OH - It can be irreversibly pyrolyzed. By supplying hydroxide ions at a slow rate through the irreversible pyrolysis reaction of urea, the complex and hydroxide ions react to deposit a nickel hydroxide thin film on the substrate.

[0077] Nickel hydroxide is not formed in advance within the aqueous solution; instead, it is formed and deposited on the substrate through a reaction with hydroxide ions generated by the thermal decomposition reaction of urea after the substrate and the aqueous solution come into contact. This allows the nickel hydroxide to be deposited uniformly on the substrate. In other words, as the nickel hydroxide is deposited on the substrate with a unidirectional orientation in step (S2-1), nickel oxide can also grow with a unidirectional orientation in the subsequent step (S2-2).

[0078] In one example, the aqueous solution may contain urea and a complex in a weight ratio of 1:1 to 8, 1:2 to 6, or 1:3 to 4. When urea and a complex are contained in the above ratios, a thin film in which nickel hydroxide is uniformly deposited at a high density can be formed, and the reaction of urea and a complex to form nickel hydroxide before contact with a substrate can be minimized.

[0079] (S-2) Step is a step of forming a nickel oxide thin film by heating a nickel hydroxide thin film a second time, so that the nickel hydroxide thin film is oxidized and a nickel oxide thin film oriented in one direction can be grown.

[0080] In one example, the ratio (T1 / T2) of the first heating temperature (T1) and the second heating temperature (T2) may be 0.1 to 0.5, 0.15 to 0.4, or 0.2 to 0.3. Since the first heating temperature and the second heating temperature have the ranges described above, during the first heating, irreversible thermal decomposition of the element is induced to supply hydroxide ions into the aqueous solution at a slow rate to deposit a nickel hydroxide thin film on the substrate, and during the second heating, the nickel hydroxide thin film is oxidized to form a nickel oxide thin film.

[0081] The nickel oxide thin film may be chemically bonded to the substrate through covalent bonding. Specifically, the hydroxyl groups of the substrate and the nickel oxide may be covalently bonded through a condensation reaction. For example, if the substrate is FTO (F-doped Tin Oxide), the nickel oxide thin film can be manufactured by bonding in the form of FTO-O-Ni through a dehydration condensation reaction between the hydroxyl groups (-OH), which are functional groups present on the surface of the FTO substrate, and the hydroxyl groups (-OH) of the nickel hydroxide thin film. Since the nickel oxide thin film and the substrate are strongly bonded by covalent bonding, the nickel oxide thin film can be formed with a thin and uniform thickness even on a rough surface, and the nickel oxide thin film can be bonded to the substrate without peeling off for a long period of time, thereby improving durability.

[0082] In one example, the substrate may comprise a transparent conducting oxide (TCO). The transparent conducting oxide is optically transparent and electrically conductive, so it can be utilized as an electrode for solar cells. For example, the transparent conducting oxide may comprise indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), or a combination thereof, and preferably may comprise fluorine-doped tin oxide (FTO).

[0083] As the above substrate is surface-modified to have high surface roughness, it may have low resistance and improved transparency and light trapping performance. Accordingly, when a nickel oxide thin film is formed on a substrate having high surface roughness by the method described above, nickel oxide can be uniformly deposited even on a rough surface. Therefore, electron movement can be effectively blocked without changing the optical properties of the substrate.

[0084] In addition, the substrate may be hydrophilically treated to contain a large amount of hydroxyl groups (-OH) on its surface. As described above, as a large amount of hydroxyl groups (-OH) react with the hydroxyl groups (-OH) of the nickel hydroxide thin film to form covalent bonds, a nickel oxide thin film that is uniformly and strongly bonded to the surface of the substrate can be formed.

[0085] In the nickel oxide thin film manufactured by the above method, the (111) plane of the nickel oxide can be oriented perpendicular to the plane direction of the thin film. Accordingly, when the nickel oxide thin film is used as a hole transport layer for a perovskite solar cell, particularly excellent performance can be provided. Specifically, the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the thin film to produce a high-density nickel oxide thin film, which has high light transmittance while minimizing defects in the thin film, thereby improving the performance of the solar cell.

[0086] The present disclosure includes a perovskite solar cell comprising a nickel oxide thin film manufactured by the method described above. In describing the perovskite solar cell of the present disclosure, the nickel oxide thin film is the same as that described above, so a detailed description is omitted.

[0087] The perovskite solar cell of the present disclosure comprises: a first electrode; a hole transport layer located on the first electrode; and a photoactive layer located on the hole transport layer and containing a perovskite compound, wherein the hole transport layer comprises a nickel oxide thin film in which the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the first electrode.

[0088] As the hole transport layer comprises a nickel oxide thin film in which the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the first electrode, the photoelectric conversion efficiency, fill factor, open-circuit voltage, and short-circuit current density of the perovskite solar cell can be improved. In addition, the stability of the perovskite solar cell can be improved by increasing compatibility with the photoactive layer without compromising the optical properties of the first electrode.

[0089] In one example, the hole transport layer may satisfy the following Equation 2 in the Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum.

[0090] [Equation 2]

[0091] I1> I2

[0092] In Equation 2 above, I1 is q=2.65±0.2 Å -1 It refers to the first peak intensity at, and I2 is q=3.0±0.2 Å. -1 It refers to the second peak intensity at.

[0093] The first peak above may be a peak originating from the (111) plane of the nickel oxide, and the second peak may be a peak originating from the (200) plane of the nickel oxide. That is, if I1 is greater than I2, the nickel oxide thin film may predominantly contain nickel oxide oriented toward the (111) plane. As described above, the (111) plane of the nickel oxide is oriented perpendicular to the plane of the first electrode, thereby forming a high-density nickel oxide thin film. A hole transport layer containing this can improve thermal stability and electrical performance, thereby improving hole extraction performance and improving compatibility with perovskite compounds.

[0094] In one embodiment, the ratio (I1 / I2) of the intensity of the first peak (I1) and the intensity of the second peak (I2) may be 1.01 to 10, 2 to 8, 3 to 7, or 4 to 6. Alternatively, I1 / I2 may be greater than 1, 2 or more, 3 or more, 4 or more, or 5 or more, and as an upper limit may be 10 or less, 9.5 or less, 9 or less, 8.5 or less, 7 or less, 7.5 or less, or 7 or less, and may be a range between any two of these values. Advantageously, the Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum of the hole transport layer may not include the second peak.

[0095] In one example, the thickness of the hole transport layer may be 1 to 40 nm, 5 to 35 nm, 10 to 30 nm, or 15 to 25 nm. Even if the hole transport layer is formed thinly within the above range, electrons generated in the photoactive layer can be effectively blocked.

[0096] The first electrode may be a transparent electrode comprising a transparent conductive oxide (TCO) capable of transmitting sunlight to the photoactive layer. As an example, the substrate used in the manufacture of the nickel oxide thin film may be the first electrode. The first electrode may correspond to a front electrode provided in the direction in which light is received in the solar cell.

[0097] In one example, the photoactive layer may include a perovskite compound that serves to absorb photons from sunlight to generate electron-hole pairs. The perovskite compound may have an ABX3, A2BX4, A3BX5, A4BX6, or ABX4 structure comprising a monovalent organic cation (A), a divalent cation (B), and a halogen anion (X). The monovalent organic cation (A) may include an organic ammonium ion, an organic amidinium ion, an organic phosphonium ion, or a derivative thereof. The divalent cation (B) may include a transition metal, a rare earth metal, an alkaline earth metal, ammonium, or a derivative thereof.

[0098] For example, the above organic ammonium is (CH3NH3) n , ((C x H 2x+1 ) n NH3) n (CH3NH3) n , R(NH2)2(where, R=alkyl), (C n H 2n +1NH3) n , (CF3NH3), (CF3NH3) n , ((C x F 2x+1 ) n NH3) n (CF3NH3) n , ((C x F 2x+1 )nNH3) n , (C n F 2n+1 NH3) nIt may include one selected from the derivatives thereof (n is an integer from 1 to 100, x is an integer from 1 to 3), and the organic amidinium may include formamidinium (FA), acetamidinium, or guamidinium.

[0099] In addition, the above divalent cation (B) is Pb 2+ , Mn 2+ , Cu 2+ , Ga 2+ , Ge 2+ , In 2+ , Al 2+ , Sb 2+ , Bi 2+ , Po 2+ , Sn 2+ , Eu 2+ , Yb 2+ , Ni 2+ , Co 2+ , Fe 2+ , Cr 2+ , Pd 2+ , Cd 2+ , Ca 2+ , Sr 2+ or a combination thereof, and the halogen anion (X) is F - , Cl - , Br - or I - It may include.

[0100] In one example, it may further include an electron transport layer located on the photoactive layer; and a second electrode located on the electron transport layer.

[0101] The electron transport layer above transfers electrons generated in the photoactive layer to the second electrode while blocking the transfer of holes. Porous materials of the tin oxide (SnO2) series, titanium dioxide (TiO2) series, or aluminum oxide (Al2O3) series are mainly used, and may be fullerene (C60), fullerene derivatives, perylene, PBI (Polybenzimidazole), or PTCBI (3,4,9,10-perylene-tetracarboxylic bis-benzimidazole). The fullerene derivative may be PCBM ((6,6)-phenyl-C61-butyric acid-methyl ester) or PCBCR ((6,6)-phenyl-C61-butyric acid cholesteryl ester), but the present disclosure is not limited by the specific material of the electron transport layer.

[0102] The second electrode is formed on an electron transport layer and can serve as a back electrode of a solar cell. The second electrode may include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), aluminum (Al), carbon (C), cobalt sulfide (CoS), copper sulfide (CuS), nickel oxide (NiO), or a combination thereof, but the present disclosure is not limited by the specific material of the second electrode.

[0103] The present invention will be explained in more detail below through examples.

[0104] (Example 1) Ni-TEA CBD NiO x Thin film fabrication

[0105] 20 g of nickel nitrate hexahydrate (Ni(NO3)26H2O) and 20.5 g of triethanolamine (TEA) were added to methyl alcohol in a round-bottom flask and stirred at room temperature for 12 hours to dissolve them. Afterward, the solvent was evaporated to obtain a powder, and the nickel and TEA composite was prepared by washing sequentially with ethyl ether and methyl alcohol. This was named Ni-TEA.

[0106] A Fluorine-Doped Tin Oxide Glass (FTO) substrate was washed with detergent, distilled water, and isopropanol using a vibrator for 15 minutes, and then treated with UV-Ozone for 20 minutes to make the FTO substrate hydrophilic. An aqueous solution containing 1.7 g of Ni-TEA and 0.5 g of urea in 300 mL of distilled water was placed in a heat-resistant container, and the washed FTO substrate was subsequently placed into the container. The heat-resistant container was placed in an oven set at 90 ℃ for 6 hours to allow the reaction to occur. Subsequently, the substrate was removed, washed with distilled water and IPA using a vibrator for 10 minutes each, and then placed in a muffle furnace to be heat-treated at 400 ℃ for 2 hours to deposit a nickel oxide thin film on the substrate. This was then used to create the Ni-TEA CBD NiO x It was named a thin film.

[0107] (Comparative Example 1) Ni CBD NiO x Thin film fabrication

[0108] The procedure was performed in the same manner as in Example 1, except that 1.0 g of nickel nitrate hexahydrate (Ni(NO3)26H2O) was added instead of Ni-TEA during nickel oxide thin film deposition. This was used to create Ni-CBD NiO x It was named a thin film.

[0109] (Comparative Example 2) Spin-coated NiO x Thin film fabrication

[0110] NiO xTo synthesize nanoparticles, 0.05 mol of nickel nitrate hexahydrate (Ni(NO3)26H2O) was dispersed in distilled water to obtain a dark green solution. Then, a 0.1 M aqueous NaOH solution was slowly added to the solution to adjust the pH of the mixed solution to 10. After the reaction, the resulting colloidal precipitate was recovered, washed with distilled water at least three times, dried at 80°C for 24 hours, and then placed in a muffle furnace and calcined at 285°C for 2 hours.

[0111] The FTO (Fluorine-doped tin oxide glass) substrate was washed with detergent, distilled water, and isopropanol using a vibrator for 15 minutes, and then treated with UV-Ozone for 20 minutes to make the FTO substrate hydrophilic. Subsequently, NiO in distilled water x A dispersion of nanoparticles dispersed at 20 mg / mL was spin-coated onto an FTO substrate at 2000 rpm for 30 seconds. NiO x A nickel oxide thin film was deposited on a substrate by heat-treating the coated FTO substrate on a hot plate at 150 °C for 10 minutes. This was spin-coated NiO x It was named a thin film.

[0112] (Comparative Example 3)

[0113] It was prepared in the same manner as in Example 1, but without preparing Ni-TEA, and when depositing the nickel oxide thin film, 100 mL of an aqueous solution was used in which 25 mL of 0.075 M nickel nitrate hexahydrate and 1.5 mL of 3.7 M triethanolamine were mixed in distilled water.

[0114] (Comparative Example 4)

[0115] It was prepared in the same manner as in Example 1, but an aqueous solution with a pH adjusted to 9 was used by adding potassium hydroxide (KOH) instead of adding urea when depositing the nickel oxide thin film.

[0116] <Measurement Method and Measuring Device>

[0117] Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) Analysis: GIWAXS analysis was performed using X-rays with λ = 1.24 Å and a beam size of 500 μm(h) x 60 μm(v) under conditions of an incident angle of 0.1° to 0.2°, and measurements were taken using the Bending Magnet 3C beamline at the Pohang Accelerator Laboratory. Scattering images were collected using a two-dimensional area detector, which was positioned 200 mm from the sample. The surface of the nickel oxide thin film was used as the measurement surface, and the measurement area was 500 μm(h) x 60 μm(v) (length perpendicular to the beam propagation direction x length in the beam direction).

[0118] Scanning Electron Microscope (SEM): The surface of the nickel oxide thin film and the cross-sectional structure of the perovskite solar cell were observed using FEI’s NOVA NANO SEM 450.

[0119] Transmittance: The transmittance of the nickel oxide thin film was measured using a Shimadzu UV-2600i to observe the transmittance of the substrate on which the nickel oxide thin film was deposited and the FTO substrate.

[0120] X-ray Photoelectron Spectroscopy (XPS) Analysis: XPS analysis was performed using the K-Alpha+ from Thermo Fhisher Scientific Messtechnik.

[0121] pH measurement: To measure the hydrogen ion concentration (pH), the change in pH of the aqueous solution was observed using a pH meter (HANNA instruments, HI 2003) during the process of depositing a nickel oxide thin film on a substrate.

[0122] Perovskite Solar Cell Performance Evaluation: To measure the current-voltage characteristics of the perovskite solar cells, an artificial sun simulator (ORIEL class A solar simulator, Newport, 91160s) and a source meter (Keithley, Keithley 2400) were used. Illumination was set to AM 1.5G, and a calibrated silicon reference cell was used at 100 mW / cm². 2 It was corrected to. The step voltage was 20 mV, and the delay time was 20 ms.

[0123] Figure 2 is Example 1 (Ni-TEA CBD NiO x ) and Comparative Example 1 (Ni CBD NiO x This is the GIWAXS spectrum of the nickel oxide thin film. For both Example 1 and Comparative Example 1, the scattering vector (q) value is 2.65±0.2 Å. -1 A first peak attributed to the (111) plane of the nickel oxide was observed at q=3.0±0.2 Å -1 A second peak was observed at the (200) plane of the nickel oxide. In the nickel oxide thin film of Comparative Example 1, the intensity of the first peak was lower than the intensity of the second peak, confirming that the nickel oxide was not oriented. However, in Example 1, the first peak was detected as narrower and stronger compared to the second peak, indicating that the peak intensity was significantly higher. The ratio of the intensity of the first peak to the intensity of the second peak (I1 / I2) was approximately 5.5 for Example 1 and approximately 0.7 for Comparative Example 1, indicating that when the nickel oxide thin film was prepared using the method of Example 1, the intensity of the first peak was significantly improved compared to the second peak. Accordingly, it was confirmed that a high-density nickel oxide thin film with unidirectionally oriented nickel oxide was prepared by combining nickel with an organic ligand to form a composite, and then depositing nickel oxide on a substrate using the composite.

[0124] FIG. 3 shows (a) Comparative Example 2 (Spin-coated NiO), respectively. x ), (b) Comparative Example 1 (Ni CBD NiO x) and (c) Example 1 (Ni-TEA CBD NiO x This is an image illustrating the GIWAXS scattering pattern of the nickel oxide thin film according to ). As shown in FIG. 3, for the nickel oxide thin film of Comparative Example 2 prepared by spin coating, only the diffraction pattern for the (200) crystal plane was detected, and the diffraction pattern for the (111) plane was not detected. In the case of Comparative Example 1, the diffraction pattern for the (111) plane was detected very weakly, indicating that it has low orientation. On the other hand, in the case of Example 1, the direction perpendicular to the plane of the thin film (q z A very strong diffraction pattern for the (111) plane was detected. Accordingly, it was confirmed that when the nickel oxide thin film is manufactured by the method of Example 1, the (111) plane is oriented perpendicular to the plane direction.

[0125] Figure 4 illustrates the results of GIWAXS analysis performed before heat treatment at 400°C when preparing a nickel oxide thin film by the method according to Example 1, showing (a) the GIWAXS scattering pattern and (b) the GIWAXS azimuthal angle profile, respectively. In the area indicated by the dotted line in Figure 4(a), a diffraction pattern corresponding to nickel hydroxide (Ni(OH)2) was detected, indicating that a nickel hydroxide thin film was formed on the substrate before heat treatment at 400°C. Additionally, as shown in Figure 4(b), a strong peak was detected when the azimuthal angle was approximately 90°, confirming that the nickel hydroxide was oriented perpendicular to the plane of the thin film.

[0126] FIG. 5 shows (a) Comparative Example 2 (Spin-coated NiO), respectively. x ), (b) Comparative Example 1 (Ni CBD NiO x ) and (c) Example 1 (Ni-TEA CBD NiO x This is an SEM image of a nickel oxide thin film according to ). When a nickel oxide thin film is deposited by the method of Comparative Example 2, NiO due to the low dispersion force of the dispersion solution xAggregation between nanoparticles occurred, resulting in non-uniform deposition on an FTO substrate with a rough surface. On the other hand, when nickel oxide is deposited on a substrate using the method of Example 1, it is deposited uniformly without damaging the texture of the FTO substrate, and the (111) plane is oriented perpendicular to the plane of the thin film.

[0127] FIG. 6 shows (a) an SEM image and (b) a GIWAXS scattering pattern of a nickel oxide thin film prepared by the method according to Comparative Example 3, and FIG. 7 shows (a) an SEM image and (b) a GIWAXS scattering pattern of a nickel oxide thin film prepared by the method according to Comparative Example 4. Referring to FIG. 6 and FIG. 7, for the nickel oxide thin films deposited by the methods of Comparative Example 3 and Comparative Example 4, only a diffraction pattern for the (200) plane was observed, and there was no diffraction pattern for the (111) plane oriented perpendicular to the plane direction. Since no orientation was observed in the SEM image, it was confirmed that the (111) plane of the nickel oxide thin films prepared by the methods of Comparative Example 3 and Comparative Example 4 was not oriented perpendicular to the plane direction of the thin film.

[0128] FIG. 8 shows FTO (F-doped Tin oxide) glass and Example 1 (Ni-TEA CBD NiO x ), Comparative Example 1 (Ni CBD NiO x ) and Comparative Example 2 (Spin-coated NiO x This is a graph measuring the transmittance of the nickel oxide thin film according to ). In Example 1, even though a nickel oxide thin film was deposited on an FTO substrate, the transmittance was almost similar to the transmittance of the FTO substrate. Accordingly, it was confirmed that the nickel oxide thin film was deposited with a sufficiently thin thickness so as not to reduce the light transmittance of the FTO substrate.

[0129] FIG. 9 shows (a) Comparative Example 2 (Spin-coated NiO), respectively. x ), (b) Comparative Example 1 (Ni CBD NiO x) and (c) Example 1 (Ni-TEA CBD NiO x This is the XPS spectrum of the nickel oxide thin film according to ). As a result of XPS analysis, the nickel oxide thin film of Comparative Example 2 shows peak intensity for nickel with an oxidation state of 3 (Ni 3+ ) and peak intensity of nickel with an oxidation state of 2 (Ni 2+ The ratio of ) (Ni 3+ / Ni 2+ ) was 0.62, indicating that few Ni vacancies were formed; however, when a nickel oxide thin film is prepared by the method of Example 1, Ni 3+ / Ni 2+ It was confirmed that hole transport improved as the value increased to 0.81, and more Ni vacancies affecting hole transport were formed.

[0130] Figure 10 is a graph showing the change in pH of the aqueous solution according to reaction time when a substrate is immersed in the aqueous solution and reacted at 90°C during the preparation of a nickel oxide thin film by the method of Example 1. Before reacting at 90°C, the pH of the aqueous solution was about 7.7, indicating a weakly basic state, and even after reacting at 90°C for 8 hours, the pH of the aqueous solution was about 7.8, maintaining a constant weakly basic state without significant difference from before the reaction.

[0131] On the other hand, although not illustrated in FIG. 10, when nickel oxide thin films were prepared using the methods of Comparative Examples 3 and 4, the pH of the aqueous solution was 9 or higher before and during the reaction at 90°C, exhibiting strong basicity. This indicates that nickel hydroxide (Ni(OH)2) was pre-formed in the aqueous solution before the reaction, and since the nickel hydroxide particles already aggregated in the aqueous solution were converted into a thin film during the deposition reaction, nickel hydroxide molecules were unevenly adsorbed onto the substrate. Therefore, as shown in the GIWAXS analysis results above, it was found that nickel oxide grew in random directions even during high-temperature heat treatment. Furthermore, it was confirmed that the risk of substrate damage significantly increased as the nickel oxide deposition reaction proceeded in a strong basic environment.

[0132] After manufacturing a perovskite solar cell containing the above nickel oxide thin film, its cross-section was observed using a scanning electron microscope and is shown in FIG. 11, and the open-circuit voltage (V oc ), short-circuit current density (J sc The fill factor (FF) and power conversion efficiency (PCE) were measured and are shown in Table 1 below. Perovskite solar cells were fabricated by the following method.

[0133] A perovskite precursor solution was prepared by dissolving 541.2 mg of formamidinium lead iodide (FAPbI3), 5.77 mg of methylammonium chloride (MACl), 20.5 mg of methylammonium lead bromide (MAPbBr3), and 30.6 mg of cesium lead triiodide (CsPbI3) in a solvent containing 0.4 mL of dimethylformamide (DMF) and 0.1 mL of dimethylsulfoxide (DMSO). Subsequently, the perovskite precursor solution was spin-coated onto the nickel oxide thin film at 5000 rpm for 40 seconds. During spin coating, 270 µl of chlorobenzene (CB), an antisolvent, was dropped. After spin coating, a photoactive layer containing an α-phase perovskite compound was prepared by heat treatment at 120°C for 30 minutes. On the photoactive layer, an electron transport layer precursor solution in which PCBM ([6,6]-Phenyl-C61-butyric acid methyl ester) was dispersed in chlorobenzene at 20 mg / mL was spin-coated at 2000 rpm for 20 seconds, followed by heat treatment at 100°C for 5 minutes. Subsequently, an electron transport layer was prepared by spin-coating a solution in which Bathocuproine (BCP) was dispersed in isopropyl alcohol at 0.5 mg / mL at 5000 rpm for 20 seconds, followed by heat treatment at 100°C for 1 minute. Finally, a perovskite solar cell was fabricated by thermally depositing silver (Ag) to a thickness of 120 nm.

[0134] Types of transport layers V oc (V)J sc (mA / cm 2)FF (%) PCE (%) Example 1 1.15 24.3 38 1.49 22.89 Comparative Example 11.10 23.7 38 0.34 21.04 Comparative Example 2 1.09 21.6 7 3.50 17.43 Comparative Example 3 1.02 20.15 7 1.38 14.67 Comparative Example 40.98 19.58 68.04 13.06

[0135] Referring to Fig. 11, it was confirmed that a perovskite solar cell was fabricated by uniformly depositing the nickel oxide thin film of Example 1, i.e., the hole transport layer, on the FTO electrode with a very thin thickness of about 20 nm. In addition, as shown in Table 1 above, the perovskite solar cell containing the nickel oxide thin film of Example 1 as the hole transport layer exhibited the best performance. More specifically, as the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency were all improved compared to Comparative Examples 1 to 3, it was confirmed that the nickel oxide thin film with the (111) plane of the nickel oxide oriented perpendicular to the plane exhibited superior performance. On the other hand, the nickel oxide thin films of Comparative Example 1, prepared by immersing the substrate in an aqueous solution containing a nickel precursor and urea without forming a Ni-TEA composite, and Comparative Example 2, prepared by coating nickel oxide nanoparticles on the substrate by spin coating, showed low performance in perovskite solar cells using them as hole transport layers because the nickel oxide did not have orientation. Comparative Examples 3 and 4 also exhibited low photoelectric conversion efficiencies (PCE) of 14.67% and 13.06%, respectively, because the nickel oxide thin films did not have crystal orientation. In addition to photoelectric conversion efficiency, the open-circuit voltage (V oc ), short-circuit current density (J sc The values ​​of ) and fill factor (FF) were both lower than those of Example 1. Accordingly, it was confirmed that when a nickel oxide thin film is prepared by the method according to the present disclosure, the nickel oxide is oriented in one direction, thereby enabling the realization of a perovskite solar cell with significantly improved performance when used as a hole transport layer.

[0136] As described above, the present invention has been explained by specific details, limited embodiments, and drawings; however, this is provided merely to aid in a more comprehensive understanding of the invention and is not limited to the above embodiments. Those skilled in the art can make various modifications and variations from this description.

[0137] Accordingly, the scope of the present invention is not limited to the described embodiments, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims set forth below, shall be considered to fall within the scope of the concept of the present invention.

Claims

1. (S1) A step of preparing a complex in which nickel and an organic ligand are combined by mixing an organic ligand and a nickel precursor; and (S2) A step of depositing nickel oxide oriented in one direction on the substrate by contacting an aqueous solution containing the above composite and elements with a substrate and then heating; a method for manufacturing a nickel oxide thin film, comprising 2. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein, in step (S2) above, the aqueous solution is weakly basic.

3. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein the above organic ligand comprises an alkanolamine.

4. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein the organic ligand comprises triethanolamine (TEA).

5. In Paragraph 1, The above (S2) step is, (S2-1) A step of depositing nickel hydroxide on a substrate by first heating after contacting an aqueous solution containing the composite and elements with a substrate; and (S2-2) A method for manufacturing a nickel oxide thin film, comprising the step of secondarily heating the substrate on which the nickel hydroxide is deposited to deposit a nickel oxide thin film on the substrate.

6. In Paragraph 5, A method for manufacturing a nickel oxide thin film, wherein the ratio (T1 / T2) of the first heating temperature (T1) and the second heating temperature (T2) is 0.1 to 0.

5.

7. In Paragraph 1, A method for manufacturing a nickel oxide thin film satisfying the following Equation 1. [Equation 1] 0.9 < k1 / k0 < 1.1 (In Equation 1 above, k0 represents the pH of the aqueous solution before contact with the substrate, and k1 represents the pH of the aqueous solution after contact with the substrate.) 8. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein the nickel precursor is one or more selected from the group comprising nickel sulfate hydrate, nickel nitrate hydrate, nickel acetate hydrate, nickel acetylacetonate hydrate, nickel oxalate hydrate, and nickel chloride hydrate.

9. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein the substrate comprises a transparent conducting oxide (TCO).

10. In Paragraph 1, A method for manufacturing a nickel oxide thin film, wherein, in step (S2) above, the substrate and the nickel oxide form a covalent bond.

11. A nickel oxide thin film manufactured by a method according to any one of claims 1 to 10, and A nickel oxide thin film in which the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the thin film.

12. In Paragraph 11, The above nickel oxide thin film is a nickel oxide thin film for use as a hole transport layer in a perovskite solar cell.

13. First electrode; A hole transport layer located on the first electrode; and A photoactive layer located on the hole transport layer and containing a perovskite compound; comprising A perovskite solar cell in which the hole transport layer comprises a nickel oxide thin film in which the (111) plane of the nickel oxide is oriented perpendicular to the plane direction of the first electrode.

14. In Paragraph 13, A perovskite solar cell in which the hole transport layer satisfies the following Equation 2 in the Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) spectrum. [Equation 2] I1> I2 (In Equation 2 above, I1 is q=2.65±0.2 Å -1 It refers to the first peak intensity at, and I2 is q=3.0±0.2 Å. -1 (refers to the second peak intensity at) 15. In Paragraph 13, A perovskite solar cell having a hole transport layer thickness of 1 to 40 nm.

16. In Paragraph 13, The above first electrode is a transparent electrode, a perovskite solar cell.

17. In Paragraph 13, An electron transport layer located on the above photoactive layer; and A perovskite solar cell further comprising a second electrode located on the electron transport layer.

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