Perovskite solar cell, manufacturing method thereof, nickel oxide film with reduced defects at interface, and interface treatment method for nickel oxide film

Abstract

To provide a perovskite solar cell with high photoelectric conversion efficiency.SOLUTION: In a perovskite solar cell, a transparent conductive layer, a hole transport layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode are sequentially formed. The hole transport layer is made of inorganic nickel oxide (NiOx), and at least a part of the surface of the hole transport layer on the perovskite layer side is covered with the substance X-nPACz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to perovskite solar cells and interfacial treatment of nickel oxide films, and more specifically to perovskite solar cells with high photoelectric conversion efficiency and a method for manufacturing the same, as well as nickel oxide films with reduced defects at the interface and interfacial treatment methods for nickel oxide films. [Background technology]

[0002] In recent years, solar cells, which can convert solar energy into electrical energy, have attracted attention as a clean energy source to replace fossil fuels, in light of global environmental issues such as global warming.

[0003] Solar cells that can efficiently convert sunlight into electricity include monocrystalline silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide. Challenges with these inorganic solar cells include the requirement for extremely high purity in silicon-based solar cells, which involves a complex and multi-step refining process and high manufacturing costs.

[0004] In response to this, perovskite solar cells are attracting attention as a new type of solar cell. Perovskite solar cells are expected to be inexpensive and highly efficient because the perovskite, which is the photoelectric conversion component, can be manufactured by coating (see Patent Document 1).

[0005] A perovskite solar cell, for example, consists of a transparent electrode layer, a hole transport layer (electron blocking layer), a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode, all formed on a transparent substrate. Perovskite solar cells using NiO (nickel oxide) as the hole transport layer are disclosed in Patent Document 1, but Patent Document 2 describes NiO deposited by sputtering as the hole transport layer. xIt has been disclosed that by using this method, it is possible to provide a perovskite solar cell in which the light irradiation resistance, which has been a drawback of solar cells using organic materials, is significantly improved.

[0006] Perovskite solar cells have seen significant performance improvements through such enhancements, but NiO x The photoelectric conversion efficiency using the hall transport layer was only 13%, which did not necessarily meet the demands of the market, and there was a need for even higher photoelectric conversion efficiency.

[0007] Furthermore, looking at nickel oxide films deposited by sputtering, although a vacuum process is required, these nickel oxide films can be deposited as uniform and dense thin films at high speed and at relatively low temperatures of room temperature or below 100°C. They are also less prone to physical peeling or detachment, resulting in excellent long-term stability and reliability. On the other hand, nickel oxide films deposited by sputtering have the problem of being difficult to remove or control impurity sites. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-22354 [Patent Document 2] Japanese Patent Publication No. 2018-190028 [Patent Document 3] Japanese Patent Publication No. 2007-242646 [Non-patent literature]

[0009] [Non-Patent Document 1] Japanese Journal of Applied Physics 2018,vol.57,08RE06 [Non-Patent Document 2] Applied Physics Express 2020,vol.13,025505 [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to solve the above problems and provide a perovskite solar cell with high photoelectric conversion efficiency and a method for manufacturing the perovskite solar cell. Furthermore, the objective is to provide a nickel oxide film with a low defect interface and a method for treating that interface. [Means for solving the problem]

[0011] The inventors of this invention investigated in detail the factors that greatly affect the photoelectric conversion efficiency of perovskite solar cells and found that the NiO of the inorganic film used as a hole transport layer with high light irradiation resistance was a major factor. x We discovered that impurity sites, which are defects present at the interface, were having a negative impact. We then solved the problem related to the photoelectric conversion efficiency described below.

[0012] (Composition 1) A transparent conductive layer, a hole transport layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode are formed sequentially. The aforementioned hole transport layer is made of inorganic nickel oxide, A perovskite solar cell in which at least a portion of the surface of the hole transport layer on the perovskite layer side is covered with a material (X-nPACz) described by the following formula (1). [ka] [In formula (1), X is OR or R, where O is oxygen, R is a linear hydrocarbon group with 1 to 12 carbon atoms, and n is an integer between 2 and 12.] (Configuration 2) The perovskite solar cell according to configuration 1, wherein n is 2 or 4. (Composition 3) The perovskite solar cell according to configuration 1, wherein X is OCH3 and n is 2. (Composition 4) A perovskite solar cell according to any one of configurations 1 to 3, wherein the thickness of the hole transport layer is 4 nm or more and 50 nm or less. (Composition 5) The perovskite solar cell according to configuration 4, wherein the thickness of the hole transport layer is 4 nm or more and 18 nm or less. (Composition 6) The perovskite solar cell according to configuration 5, wherein the thickness of the hole transport layer is 15 nm or more and 18 nm or less. (Composition 7) The electron transport layer is [6,6]-phenyl-C 61 - Methyl butyrate (PCBM) film, fullerene C 60 The film, or PCBM film and C 60 A perovskite solar cell according to any one of configurations 1 to 6, wherein the laminated film with the film, the hole blocking layer, consists of an aluminum zinc oxide film, a LiF film, or a bathocuproine (BCP) film. (Composition 8) A method for manufacturing a perovskite solar cell, comprising the steps of sequentially forming a transparent conductive layer on a transparent support, forming a hole transport layer, forming a surface compensation zone, forming a perovskite layer, forming an electron transport layer, forming a hole blocking layer, and forming a back electrode, The transparent conductive layer is made of ITO, the hole transport layer is made of inorganic nickel oxide, and the surface compensation band is made of the substance (X-nPACz) described in the following formula (1). The hole transport layer formation step is performed by sputtering, which is a method for manufacturing a perovskite solar cell. [ka] [In formula (1), X is OR or R, where O is oxygen, R is a linear hydrocarbon group with 1 to 12 carbon atoms, and n is an integer between 2 and 12.] (Composition 9) A method for manufacturing a perovskite solar cell according to configuration 8, wherein n is 2 or 4. (Composition 10) A method for manufacturing a perovskite solar cell according to configuration 8, wherein X is OCH3 and n is 2. (Composition 11) A method for manufacturing a perovskite solar cell according to any one of configurations 8 to 10, wherein the step for forming the surface compensation zone is one selected from the group consisting of spin coating, dip coating, spray coating, and vapor deposition. (Composition 12) A method for manufacturing a perovskite solar cell according to any one of configurations 8 to 11, wherein the surface compensation band is deposited on the hole transport layer and then subjected to heat treatment. (Composition 13) A method for manufacturing a perovskite solar cell according to configuration 12, wherein the temperature of the heat treatment is 20°C or more and 150°C or less. (Composition 14) A method for manufacturing a perovskite solar cell according to any one of configurations 8 to 13, wherein the thickness of the hole transport layer is 4 nm or more and 50 nm or less. (Composition 15) A method for manufacturing a perovskite solar cell according to any one of configurations 8 to 14, wherein the perovskite layer consists of a chlorine-containing perovskite. (Composition 16) The electron transport layer is a PCBM film, fullerene C 60 The film, or PCBM film and C 60 A method for manufacturing a perovskite solar cell according to any one of configurations 8 to 15, wherein the laminated film with the film and the hole blocking layer consist of an aluminum zinc oxide film, a LiF film, or a BCP film. (Composition 17) An inorganic nickel oxide film formed on the first main surface, the substance (X-nPACz) described in formula (1) below. [ka] [In formula (1), X is OR or R, where O is oxygen, R is a linear hydrocarbon group with 1 to 12 carbon atoms, and n is an integer between 2 and 12.] (Composition 18) Forming an inorganic nickel oxide film by sputtering, A method for treating the interface of a nickel oxide film, comprising forming a substance (X-nPACz) described in formula (1) below on the first main surface of the nickel oxide film. [ka] [In formula (1), X is OR or R, where O is oxygen, R is a linear hydrocarbon group with 1 to 12 carbon atoms, and n is an integer between 2 and 12.] (Composition 19) The method for treating the interface of a nickel oxide film according to configuration 18, wherein the method for forming the X-nPACz is a coating method. [Effects of the Invention]

[0013] The present invention provides a perovskite solar cell with high photoelectric conversion efficiency and a method for manufacturing the perovskite solar cell. Furthermore, a nickel oxide film with a low defect interface and a method for treating that interface are also provided. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing the structure of the perovskite solar cell of the present invention. [Figure 2] This is a schematic diagram showing the layer configuration of the perovskite solar cell of the present invention. [Figure 3] This is a schematic diagram illustrating the effect of X-nPACz. [Figure 4] This is a flowchart illustrating the manufacturing process of the solar cell of the present invention. [Figure 5] This is a flowchart illustrating the interface treatment method for nickel oxide films according to the present invention. [Figure 6] These are planar SEM images before and after X-nPACz deposition; (a) shows NiOx before deposition, and (b) shows NiOx after X-nPACz deposition. [Figure 7] This characteristic diagram compares the light transmission characteristics of NiOx with and without X-nPACz deposition. [Figure 8]These are SEM images of the perovskite film of the sample. (a) is a plan view image of the perovskite film formed on NiOx, and (b) is a plan view image of the perovskite film formed after X-nPACz was deposited on NiOx. [Figure 9] This is a characteristic diagram showing the difference between the presence and absence of MeO-2PACz in PL (photoluminescent) material. [Figure 10] This is a characteristic diagram showing the results of photothermal deflection spectroscopy (PDS) measurements. [Figure 11] This characteristic graph compares the dependence of photoelectric conversion efficiency on NiOx film thickness with and without the MeO-2PACz surface compensation band. [Figure 12] This characteristic graph compares the dependence of the internal quantum yield (IQE) on the NiOx film thickness with and without the MeO-2PACz surface compensation band. [Figure 13] This is a characteristic graph comparing the dependence of the internal quantum yield on NiOx film thickness with and without the MeO-2PACz surface compensation band. [Figure 14] This is a schematic diagram showing the layer configuration of the perovskite solar cell of Example 2. [Modes for carrying out the invention]

[0015] (Embodiment 1) Embodiment 1 describes the perovskite solar cell and its manufacturing method according to the present invention.

[0016] <Structure> As shown in Figure 1, the perovskite solar cell 102 of the present invention (Embodiment 1) includes at least a transparent substrate 11, a transparent conductive layer 12, a hole transport layer 13, an X-PACz layer 14, a perovskite layer 15, an electron transport layer 16, a hole blocking layer 17, a back electrode 18, and a metal film (wiring layer) 19. The configuration is such that light 20 is irradiated from the transparent substrate 11 side. In addition, when showing its configuration with representative materials, as shown in FIG. 2, the perovskite solar cell 101 of the present invention includes a transparent conductive layer / transparent substrate 1 made of ITO / glass, and an inorganic nickel oxide film (hereinafter, also referred to as NiO film) formed by sputtering. Here, 0 < x ≦ 4) and a hole transport layer 2, an X-nPACz layer 3, a perovskite (CH3NH3PbI3) layer 4, an electron transport layer 5 made of a PCBM film, a hole blocking layer 6 made of an AZO film, and a back electrode 7 made of a silver (Ag) film. x The perovskite solar cells 101 and 102 of the present invention are characterized in that X-nPACz layers 3 and 14 are formed on inorganic NiO films 2 and 13 formed by sputtering. With this configuration, the interface of the NiO films 2 and 13 and the vacancy of the perovskite layers 4 and 15 are suppressed, and the photoelectric conversion efficiency of the perovskite solar cells 101 and 102 is improved.

[0017] Here, the perovskite solar cells 101 and 102 of the present invention are characterized in that X-nPACz layers 3 and 14 are formed on inorganic NiO films 2 and 13 formed by sputtering. x The perovskite solar cells 101 and 102 of the present invention are characterized in that X-nPACz layers 3 and 14 are formed on inorganic NiO films 2 and 13 formed by sputtering. With this configuration, the interface of the NiO films 2 and 13 and the vacancy of the perovskite layers 4 and 15 are suppressed, and the photoelectric conversion efficiency of the perovskite solar cells 101 and 102 is improved. x The perovskite solar cells 101 and 102 of the present invention are characterized in that X-nPACz layers 3 and 14 are formed on inorganic NiO films 2 and 13 formed by sputtering. With this configuration, the interface of the NiO films 2 and 13 and the vacancy of the perovskite layers 4 and 15 are suppressed, and the photoelectric conversion efficiency of the perovskite solar cells 101 and 102 is improved. As disclosed in Patent Document 2, the hole transport layers 2 and 13 made of an inorganic NiO film formed by a PVD (Physical Vapor Deposition) method such as sputtering have high light irradiation resistance. x The hole transport layers 2 and 13 made of an inorganic NiO film formed by a PVD (Physical Vapor Deposition) method such as sputtering have high light irradiation resistance.

[0018] Next, each layer constituting the perovskite solar cell of the present invention will be described.

[0019] The transparent substrate 11 (and a part of 1) is not particularly limited as long as it transmits sunlight and has rigidity of a predetermined value or more. Various glasses such as quartz glass, flint glass, and soda lime float glass can be preferably used, but transparent plastics such as acrylic and polycarbonate can also be used. Glass has the characteristics of high transparency (high transmittance) to sunlight, sufficient rigidity, and excellent light resistance and weather resistance. Plastic is preferable for producing a curved solar cell or using a solar cell by bending it flexibly because it can be easily processed into a free shape and can be given flexibility.

[0020] The material of the transparent electrode 12 (and part of 1) is indium tin oxide (ITO). This film is preferably deposited by sputtering from the viewpoint of improving light resistance. Specifically, RF sputtering with ITO as the target and a noble gas such as argon (Ar) or krypton (Kr) as the sputtering gas is preferred. The substrate temperature can be room temperature, but is not limited to room temperature. Furthermore, applying heat treatment to 150°C or higher after ITO deposition is preferable because it improves sunlight transmittance and reduces electrical resistance. On the other hand, heat treatment exceeding 300°C is undesirable because it increases electrical resistance. ITO has high transparency and relatively low electrical resistivity for a transparent conductive film. Furthermore, because indium (In) and tin (Sn) are oxidized and immobilized, these metals do not easily diffuse, providing the mutual diffusion prevention function necessary for improving light resistance. The film thickness of the ITO on the transparent electrode 12 is preferably 150 nm or less. The film resistance of the ITO should be as low as possible, preferably 15 Ω / sq or less.

[0021] To reduce the resistance of the transparent electrode 12, a metal lead wire may be added between the ITO film and the transparent substrate 1. Examples of materials for the metal lead wire include platinum (Pt), gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), and titanium (Ti). It is preferable to form the metal lead wire on the transparent substrate 1 by sputtering or vapor deposition, and then form the ITO film on top of it. However, since the presence of the metal lead wire reduces the amount of incident light, it is preferable that the thickness of the metal lead wire be between 0.01 mm and 3 mm.

[0022] The hole transport layers 2 and 13 are inorganic NiO formed by PVD (Physical Vapor Deposition) methods such as sputtering, as described above. x It is a membrane. Hole transport layers 2,13 are transported by inorganic NiO xBy constructing it as a film, it is possible to form a large-area layer with fewer pinholes and cracks, and also improve resistance to light irradiation. The thickness of the hole transport layer 2,13 is preferably 4 nm to 50 nm, and more preferably 4 nm to 18 nm. Setting the thickness of the hole transport layer 2,13 within this range makes it possible to obtain high photoelectric conversion efficiency. Furthermore, setting the thickness of the hole transport layer 2,13 to 15 nm to 18 nm makes it possible to achieve high long-term reliability. This is because NiO x This is due to the suppression of pinholes in the thin film.

[0023] To improve the conductivity of the hole transport layers 2 and 13, NiO x It is also preferable to dope the film with metal ions other than Ni. Examples of metal ions include alkali metals, alkaline earth metals, and transition metals. A specific metal ion is Li + kaNa + , K + Mg 2+ Cu 2+ Fe 2+ Mn 2+ , and Zn 2+ At least one selected from, and more preferably Li + and Mg 2+ It is at least one of the following. + and Mg 2+ These may be used simultaneously. The doping concentration is preferably 0.5 mol% to 50 mol%, and more preferably 2 mol% to 30 mol%. These metal ions can be introduced into the hole transport layer 3, for example, by incorporating them into the target material when sputtering.

[0024] The X-nPACz layers 3 and 14 are layers made of the substance described in formula (1). Here, in formula (1), X is OR or R, O is oxygen, R is a straight-chain hydrocarbon group having 1 to 12 carbon atoms, and n is an integer between 2 and 12. Due to the presence of this layer, as shown in Figure 3, NiO xVacancy is suppressed at the interface of films 2 and 13 and at the perovskite layers 4 and 15, improving the photoelectric conversion efficiency of the perovskite solar cells 101 and 102. Here, vacancy refers to the depletion of halide ions such as iodine (I), chlorine (Cl), or bromine (Br). Figure 3 shows the sputtering formation of NiO that constitutes the hole transport layers 3 and 14. x (sp-NiO x This diagram schematically shows the perovskite layer formed on the film, and as shown in Figure 3(a), the perovskite layer is sp-NiO x When formed directly on a film, sp-NiO x Vaccines are formed at the film interface and within the perovskite layer, but as shown in Figure 3(b), vacancy formation is suppressed when the perovskite layer is formed via an X-nPACz layer.

[0025] In formula (1), n ​​is more preferably 2 or 4, and it is even more preferable that X in formula (1) is OCH3 and n is 2, i.e., MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid) shown in formula (2), because vacancy formation is more suppressed and photoelectric conversion efficiency is higher.

[0026] [ka]

[0027] Note that X-nPACz is NiO x By applying it on top and then heat-treating it, NiO x The surface is modified. A heat treatment temperature of 20°C to 150°C is suitable for promoting surface modification, and heat treatment within this temperature range can be preferred. X-nPACz is NiO x By coating with this, a uniform hole transport layer is formed. In other words, X-nPACz functions as a surface compensation band. Furthermore, even if there are local defects in some areas of the surface modification, it will not affect NiO xThere is no adverse effect as long as it is not near the interface of the film 2,13 and the vacancy of the halide ions in the perovskite layer 4,15.

[0028] The material constituting the perovskite layer 4,15 is not particularly limited, and examples include CH3NH3PbI3, CH(NH2)2PbI3, CsPbI3, CH3NH3SnI3, CH3NH3Sn x Pb (1-x) I3, CH(NH2)2SnI3, etc., and preferably CH3NH3PbI3 and CH(NH2)2PbI3 can be mentioned. Furthermore, a material in which a part of iodine (I) in these materials is replaced by chlorine (Cl), for example, CH3NH3PbI 3―x Cl x is more preferable because the photoelectric conversion efficiency and the light irradiation resistance are improved, and the change with time during storage is reduced. Here, as the reaction for replacing a part of iodine with chlorine, the chlorine-mediated interdiffusion method can be mentioned.

[0029] The perovskite layer 4,15 may be a single-layer film or a laminated film composed of a plurality of layers. In the case of a single-layer film, it has the characteristics that the manufacturing process is less, it is rich in mass productivity as a solar cell, and the cost can be reduced. On the other hand, in the case of a laminated film, by forming a tandem structure in which a plurality of perovskites having different light absorption bands are laminated, light in a wide wavelength band can be efficiently absorbed, and the photoelectric conversion efficiency of the entire solar cell can be increased. Examples of the laminated film include, for example, FA having a wide band gap a Cs b Rb 1-a-b Pb(I x Br 1-x )3 (FA = (I x Br 1-x )3 (FA = formamidinium (H2NCHNH2), 0 < a ≤ 1, 0 < b ≤ 1, 0 < x ≤ 1), and a structure in which a perovskite is laminated on a Sn-based perovskite having a narrow band gap can be mentioned.

[0030] The perovskite layers 4 and 15 can be formed by coating methods such as spin coating. For example, a perovskite precursor dissolved in a solvent can be prepared, and the perovskite layers 4 and 15 can be formed by spin coating and then applying heat treatment. As a specific example of perovskite layer formation 4,15, CH3NH3PbI3 is used. A perovskite precursor solution is prepared by dissolving methylammonium iodide (CH3NH3I, abbreviated as "MAI") and lead iodide (PbI2) in a solvent, and this solution is then spin-coated. Dimethyl sulfoxide (DMSO) can be used as the solvent. During spin-coating, it is preferable to dropwise add a small amount of toluene as a volatile preparation to reduce striations and ensure uniform film thickness. The heat treatment temperature is preferably between 50°C and 120°C.

[0031] The materials constituting the electron transport layers 5 and 16 are not particularly limited, and examples include n-type conductive polymers, n-type low molecular weight organic semiconductors, graphene materials, and n-type metal oxides. Preferably, [6,6]-phenyl-C 61 - Methyl butyrate (PCBM) is used. PCBM can be formed by a coating method and is preferred from the viewpoint of throughput and manufacturing cost.

[0032] The hole blocking layers 6,17 are at least one metal ion-doped oxide film selected from, for example, zinc oxide, titanium oxide, and tin oxide. The doped metal ions are, for example, W 6+ Nb 5+ Sb 5+ Ta 5+ , Al 3+ , Y 3+ , Ga 3+ It is at least one selected from the following. The doping concentration is 0.5 mol% to 50 mol%, preferably 0.5 mol% to 20 mol%. For example, a zinc oxide film (AZO) doped with 1.6 mol% aluminum can be preferably used as the hole blocking layer 6,17. The thickness of the hole blocking layers 6 and 17 is preferably 30 nm to 150 nm, and more preferably 40 nm to 100 nm, considering electrical resistance and uniformity of layer thickness.

[0033] The back electrodes 7 and 18 are metal films such as silver or composite films of indium tin oxide (ITO) and a metal such as silver. These films are preferably deposited by sputtering. When ITO is also used, it can be utilized as an optical interference film to increase the back surface light reflectivity and thereby improve the overall photoelectric conversion efficiency of the solar cell. For forming ITO, RF sputtering is preferred, using ITO as the target and a noble gas such as argon (Ar) or krypton (Kr) as the sputtering gas. The substrate temperature can be room temperature, but is not limited to room temperature. Furthermore, applying heat treatment after ITO film formation is effective, but if heat treatment is applied, it should be at 140°C or lower, preferably 120°C or lower, to avoid damaging the perovskite layer 4, etc. The material for the wiring 19 can be a metal such as silver, aluminum (Al), tungsten (W), copper (Cu), or gold (Au), or an alloy such as Al-Si. The wiring 19 may also be fabricated in the form of lead wires from the back electrodes 7 and 18.

[0034] <Manufacturing method> The manufacturing method for the perovskite solar cell 102 shown in Embodiment 1 will be explained with reference to Figure 1 and Figure 4, which shows the manufacturing process as a flowchart. The perovskite solar cell 102 is manufactured by sequentially performing the following steps on a transparent support 11: forming a transparent conductive layer 12 made of ITO (S11), forming a hole transport layer 13 (S12), forming a surface compensation band 14 made of an X-nPACz layer (S13), forming a perovskite layer 15 (S14), forming an electron transport layer 16 (S15), forming a hole blocking layer 17 (S16), and forming a back electrode 18 (S17).

[0035] The hole transport layer 13 is an inorganic nickel oxide film (NiO x The material consists of a film deposited by a PVD method such as sputtering. Here, the sputtering method is preferred because it is highly productive and has high manufacturing stability among PVD methods. Due to its productivity, a method of depositing the hole transport layer 13 using an RF magnetron sputtering apparatus with NiO as the target is preferred, but a method of sputtering in the presence of oxygen with Ni as the target can also be used.

[0036] The surface compensation zone (X-nPACz layer) 14 is a layer made of the substance described in formula (1). Here, in formula (1), X is OR or R, O is oxygen, R is a straight-chain hydrocarbon group having 1 to 12 carbon atoms, and n is an integer between 2 and 12. More preferably, n in formula (1) is 2 or 4, and even more preferably, X in formula (1) is OCH3 and n is 2, i.e., MeO-2PACz shown in formula (2). As a method for forming the surface compensation zone 14, one method can be selected from the group consisting of spin coating, dip coating, spray coating, and vapor deposition. Among these, the spin coating method and the dip coating method, which have fewer defects and high mass production potential, can be preferred. X-nPACz is NiO x After formation, it is preferable to perform a heat treatment at a temperature between 20°C and 150°C. This treatment causes X-nPACz to act as a surface compensation band, resulting in a dense hole transport layer with high in-plane uniformity.

[0037] The thickness of the hole transport layer 13 is preferably 4 nm to 50 nm, and more preferably 10 nm to 50 nm, considering electrical resistance and uniformity of layer thickness. The perovskite layer 15 is preferably formed by a coating method from the viewpoint of mass production and defect reduction, and the perovskite layer 15 is preferably a chlorine-containing perovskite. Furthermore, it is preferable to perform heat treatment at 60°C to 150°C after coating from the viewpoint of ensuring long-term stability as a solar cell and improving photoelectric conversion efficiency.

[0038] The electron transport layer 16 can be a PCBM film or fullerene C 60 The film, or PCBM film and C 60 Examples include laminated films. These films can be formed by methods such as coating and vacuum deposition. The hole blocking layer 17 is preferably made of an aluminum zinc oxide (AZO), a LiF film, or a BCP film. These films can be formed by methods such as coating or vacuum deposition. Examples of back-side electrodes include single-layer films made of metals such as Ag or alloys such as Al-Si, and multilayer films of ITO and metals or alloys. Methods for forming these films include sputtering, vapor deposition, CVD, and coating.

[0039] When a perovskite solar cell is manufactured in the manner described above, the resulting solar cell 102 will have high photoelectric conversion efficiency.

[0040] Embodiment 2 describes the nickel oxide film and its interface treatment method according to the present invention.

[0041] The nickel oxide film of Embodiment 2 is an inorganic nickel oxide film (NiO x The present invention is characterized by having a surface compensation band formed on its surface, consisting of the X-nPACz layer described in Embodiment 1. The material of the X-nPACz layer and the method for forming it are the same as those described in Embodiment 1. Therefore, the method for manufacturing a nickel oxide film in Embodiment 2, as shown in Figure 5, consists of a step of forming an inorganic nickel oxide film by sputtering (S21) and a step of depositing X-nPACz, shown in formula (1) above, onto the first main surface of the nickel oxide film (S22). Here, it is preferable that the method for forming X-nPACz is a coating method, and it is also effective to perform a heat treatment at 20°C to 159°C after coating, as in Embodiment 1.

[0042] The surface compensation band consisting of X-nPACz deposited on the nickel oxide film in this manner is a hole transport layer (NiO x The layer that transports holes, including X-nPACz, is made into an ultrathin film that is dense and has high in-plane uniformity. This surface compensation zone then becomes a nickel oxide film with reduced defects at its interface and at the interface in contact with the surface, which has the function of reducing vacancies in the film. Therefore, applying the nickel oxide film of Embodiment 2 to other organic thin-film solar cells or CIGS solar cells can improve photoelectric conversion efficiency, and applying it to semiconductor devices such as light-emitting elements and FETs can improve luminous efficiency and suppress recombination. [Examples]

[0043] (Example 1) The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0044] 1. Manufacturing of solar cells 1-1. Preparation of a transparent substrate with a transparent electrode layer A transparent substrate 1 (see Figure 2) was prepared, which had a transparent electrode layer on its first main surface consisting of a commercially available ITO film patterned into a transparent electrode shape. The thickness of the ITO film was 150 nm, and the film resistance was approximately 15 Ω / sq.

[0045] 1-2. Formation of the Hole Transport Layer NiO3 is used as the hole transport layer 3 on top of the ITO film. x A film was deposited to a thickness of 20 nm using the sputtering method. An RF magnetron sputtering system (SVC-700 RFINA, manufactured by Sanyu Electronics Co., Ltd.) was used for this deposition. The target was 99.9% pure NiO (manufactured by Kojunka Kagaku Kenkyusho Co., Ltd.). Argon (Ar) gas was used as the sputtering gas, and the vacuum level of the sputtering chamber was set to <2 × 10⁻⁶. -3After setting the temperature to Pa, argon gas was introduced into the chamber at a flow rate of 20 sccm, and sputtering was performed at room temperature with a power of 50 W. The argon gas pressure at this time was 3.5 Pa. Immediately before this sputtering, the transparent substrate 1, to which the ITO film 2 was deposited, was UV-ozone cleaned for 20 minutes.

[0046] 1-3. Formation of surface compensation zone In a glove box filled with nitrogen, 6 mg of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid) was dissolved in 18 mL of ethanol and filtered through a 0.22 μm syringe filter to obtain a MeO-2PACz solution. This solution was dropped onto NiOx and spin-coated at 300 rpm for 30 seconds, followed by heat treatment on a hot plate at 100°C for 10 minutes to form a surface compensation zone 3 consisting of MeO-2PACz.

[0047] 1-4. Formation of the perovskite layer (two-step method) Next, on the surface compensation band 3, lead halide perovskite (CH3NH3PbI 3-x Cl x A perovskite layer 4 consisting of ) was formed with a film thickness of 280 nm by coating. Specifically, a solution was prepared consisting of 6.3 mg of 5-AVAl, 1260 mg of PbI2 (Kanto Chemical, 98% purity), 5 mg of methylammonium chloride (MACl, Wako Chemicals, battery grade), and 95 mg of methylammonium iodide (MAI, Wako Chemicals) in a DMF-DMDO mixture consisting of 2.85 mL of DMF and 0.15 mL of DMSO. This solution was then used to prepare NiO2. xThe film was spin-coated. Here, the solution was dissolved in ethanol and stirred overnight at 300 rpm at 70°C to obtain a homogeneous solution. The spin-coating conditions were as follows: first, PbI2 was coated onto the surface compensation band 3 at 3000 rpm for 30 seconds and then heat-treated at 100°C for 3 minutes; next, MAI was coated onto the PbI2 at 4000 rpm for 30 seconds; and then treated with methylammonium chloride (MACl). The MACl treatment conditions were 100°C for 20 minutes. A perovskite layer 4 was formed through the above process.

[0048] 1-5. Formation of the electron transport layer An electron transport layer 5 made of PCBM was fabricated using the following procedure. 99% pure PC 61 A solution of BM (SIGMA-ALDRICH) dissolved in anhydrous chlorobenzene at a ratio of 2% by weight was dropped onto the perovskite layer 4, and then spin-coated at 700 rpm for 7 seconds, followed by 3000 rpm for 30 seconds. A heat treatment was then applied at 105°C for 15 minutes to form an electron transport layer 5 with a thickness of 50 nm.

[0049] 1-6. Formation of the Hole Blocking Layer Nanograde N-21X (Nanograde Inc.), an ink containing zinc oxide nanoparticles (AZO nanoparticles) doped with AvantamaAG, was dropped onto the surface. A hole-blocking layer 6 consisting of a 100 nm thick AZO film was then fabricated by spin-coating at 1500 rpm for 5.5 seconds, followed by 4000 rpm for 20 seconds. After coating with the ink, a heat treatment was performed at 105°C for 10 minutes.

[0050] 1-7. Formation of the back electrode A 150 nm thick layer of silver (Ag) was deposited using thermal deposition to form the back surface electrode 7.

[0051] 1-8. Sealing The resulting cells were fitted with cover glass and sealed using UVRESIN XNR5516Z (manufactured by NagaseChemteX), an ultraviolet-curable resin (not shown), to encapsulate them and evaluate their electrical properties.

[0052] 2. Material Evaluation 2-1. Surface shape evaluation Figure 6(a) shows NiO x Planar SEM image, Figure 6(b) shows NiO x The image above shows an SEM photograph of a sample coated with MeO-2PACz as X-nPACz. A Hitachi High-Tech S4800 SEM was used for the observation under an acceleration voltage of 10kV. In terms of surface morphology, no significant difference was observed due to the application of MeO-2PACz, partly because the MeO-2PACz layer was thin.

[0053] 2-2. Evaluation of Transmittance Characteristics The effect of the presence or absence of X-nPACz on the light transmittance characteristics was measured using MeO-2PACz as the X-nPACz. The results are shown in Figure 7. A 7200 spectrometer (manufactured by V-JASCO) was used as the measurement device. Note that NiO was used in this measurement. x They are using the same thing. Figure 7 shows that the presence of MeO-2PACz reduces light transmittance by approximately 2% in the wavelength range of 400 nm to 900 nm. In this wavelength range, the light absorption of MeO-2PACz is extremely small, so this is thought to be due to the effect of thin-film optical interference. Therefore, it is considered that the influence of MeO-2PACz on the amount of light reaching the perovskite layer responsible for photoelectric conversion is small.

[0054] 2-3. Perovskite Evaluation We investigated the effect of the presence or absence of a MeO-2PACz layer on the perovskite formed on top of it. Figure 8 is an SEM image showing the grain structure of the perovskite. Figure 8(a) shows NiO x This is an example where a perovskite is formed on top, and Figure 8(a) shows NiO x This is an example of forming a perovskite after forming a MeO-2PACz layer on top. The formation conditions are the same as those described in the section on solar cell fabrication. An S4800 (manufactured by Hitachi High-Tech Corporation) was used as the apparatus, and observations were made under an acceleration voltage of 10kV. Figure 8 shows that the perovskite grains are larger and more closely spaced in the area where the MeO-2PACz layer is formed.

[0055] Figure 9 shows the effect of the presence or absence of a MeO-2PACz layer on the photoluminescence (PL) of a perovskite, investigated using a spectrofluorometer FP8500 (JASCO). It can be seen that the PL intensity improves when a MeO-2PACz layer is formed. This means that the MeO-2PACz layer suppresses recombination and produces a passivation effect.

[0056] 2-4. Passivation Evaluation The passivation effect of the MeO-2PACz layer was investigated using photothermal deflection spectroscopy (PDF). The results are shown in Figure 10. Figure 10(a) shows NiO x Figure 10(b) shows a comparison with and without the upper MeO-2PACz layer, and further comparison when a perovskite layer is formed on top of that. By forming a MeO-2PACz layer, NiO x As can be seen above, even when further perovskite is formed, the PDS value is significantly reduced. This is because the MeO-2PACz layer is NiO x This means that defects in the interface and perovskite are reduced.

[0057] 3. Evaluation of Photoelectric Conversion Characteristics The joint voltage (JV) and external quantum effect (EQE) characteristics of perovskite solar cells 102 fabricated using the above method were investigated in comparison with samples fabricated in the same manner except for the formation of the MeO-2PACz layer. There, measurements were taken using an AM1.5G spectral filter under 1-SUN standard conditions, and EQE characteristics were measured using an SM-250IQE (manufactured by Spectrometer). From that data, the short-circuit current (J) was calculated. sc ), open-circuit voltage (V oc ), fill factor (FF), series resistance (R s), parallel resistance (R sh The results for calculating the power (θ) and conversion efficiency (η) are shown in Table 1. Note that the values ​​are the average values ​​of data obtained using a minimum of 20 perovskite solar cells.

[0058] [Table 1]

[0059] By using a MeO-2PACz layer, the conversion efficiency η improved by approximately 25%, from 13.01% to 16.31%. Although the open-circuit voltage Voc remained unchanged, the short-circuit current J sc , curve factor FF and parallel resistance R sh A clear improvement was observed. External quantum effect EQE was improved across the entire wavelength range from 300 nm to 800 nm by using a MeO-2PACz layer. From the above, the hole transport layer is NiO x By forming a MeO-2PACz layer on top, it was confirmed that the perovskite solar cell showed an improvement in photoelectric conversion efficiency of approximately 25% and an improvement in EQE across the entire wavelength range.

[0060] (Example 2) In Example 2, when MeO-2PACz was used as the surface compensation bands 3 and 14, NiO x The film thickness dependence was investigated by comparing it with the case without using MeO-2PACz. Here, NiO x All conditions other than the film thickness are the same as in Example 1. Table 2 shows the results when using MeO-2PACz for NiO x Table 3 shows the film thickness dependence when NiO is not used with MeO-2PACz. x This depends on the film thickness. Figure 11 shows this data graphically.

[0061] [Table 2]

[0062] [Table 3]

[0063] Looking at these data, when MeO-2PACz is present, the conversion efficiency η is 14.95% or more when the film thickness of NiO x ranges from 4 nm to 53 nm, and it can be seen that high conversion efficiency η can be obtained at all NiO x film thicknesses compared to the case where MeO-2PACz is absent. <www.wipo.int / patentscope / en / help / glossary.html# Also, when MeO-2PACz is absent, the conversion efficiency η tends to decrease as the film thickness of NiO x decreases. However, when MeO-2PACz is present, the conversion efficiency η tends to increase as the film thickness of NiO x decreases, and it can be seen that the conversion efficiency η is extremely high at 17% or more when the film thickness of NiO x ranges from 4 nm to 18 nm. NiO x film is prone to pinholes when it becomes a thin film with a thickness of 18 nm or less, which is also related to the film formation method being sputtering. The MeO-2PACz film has a function to remedy such pinhole defects, and it is considered that high conversion efficiency η can be obtained even for such thin films of NiO x film thickness.

[0064] Figures 12 and 13 are characteristic diagrams showing the film thickness dependence of the internal quantum efficiency (IQE) when irradiated with light of wavelengths 360 nm and 500 nm, respectively, for NiO x film. When MeO-2PACz is absent, the IQE decreases rapidly as the NiO x film becomes thinner when the film thickness is 18 nm or less. This is considered to be affected by the pinholes in the NiO x film. On the other hand, when MeO-2PACz is present, the variation in IQE becomes large when the film thickness of NiO x is 18 nm or less. However, when the incident light wavelength is 500 nm, even when the film thickness of NiO x is 4 nm, the decrease in the average value of IQE remains slight. This variation in IQE is due to NiO xThis is thought to be due to the effects of pinholes in the film. Initial characteristics include NiO x Although a high conversion efficiency η can be obtained even with a film thickness of 4 nm, from the perspective of characteristic variations and changes over time with long-term use, NiO x The film thickness is preferably 15 nm to 18 nm.

[0065] (Example 3) In Example 3, the properties when Me-4PACz, shown in formula (3), was used as the surface compensation bands 3 and 14 were compared with those when MeO-2PACz was used as the surface compensation band. The results are shown in Table 4. Here, the conditions were the same as in Example 1, except for the Me-4PACz material.

[0066] [ka]

[0067] [Table 4]

[0068] The conversion efficiency η when Me-4PACz is used as surface compensation bands 3 and 14 is 14.41%. This value is lower than that when MeO-2PACz is used, but it is higher than the η of 13.01% (see Table 1) when no surface compensation bands are formed, confirming the effect of surface compensation bands provided by Me-4PACz.

[0069] (Reference example) In the example, surface compensation zones 3 and 14 are used. [1] 11-AUPA (11-Aminoundeylphosphonic acid, Dojin Chemical Co., Ltd.) shown in formula (4) [2] Glutanic acid (Aldrich) shown in formula (5) [3] 4-aminobutylic acid (Aldrich) shown in formula (6) [4] PTAA shown in formula (7) (Poly[bis(4-phenyl)(2,4,6-Trimethylphenyl)amine] Aldrich) Using the above, solar cells were fabricated in accordance with Example 1, and their conversion efficiency η was measured. As a result, the respective η values ​​were 9.89% for [1], 8.70% for [2], 9.88% for [3], and 6.47% for [4], which were lower than the η of 13.01% (see Table 1) when no surface compensation band was formed, indicating that no effect of surface compensation band formation on improving conversion efficiency was observed. Note that 11-AUPA is NiO x It had excellent adhesion to the hall transport layer, which was composed of [the material].

[0070] [ka] [ka] [ka] [ka]

[0071] (Example 2) In Example 2, the effect on photoelectric conversion characteristics was investigated when pentafluorophenylhydrazine (5F-PHZ) was formed as a passivation layer on the perovskite layer on the electron transport layer side.

[0072] 1. Manufacturing of solar cells The fabrication of the solar cell in Example 2 will be explained with reference to Figure 14.

[0073] 1-1. Preparation of a transparent substrate with a transparent electrode layer A transparent substrate 1 was prepared in the same manner as in Example 1. 1-2. Formation of the Hole Transport Layer The hole transport layer 2 was also formed in accordance with Example 1. 1-3. Formation of surface compensation zone A surface compensation zone 3 consisting of MeO-2PACz was also formed in accordance with Example 1.

[0074] 1-4. Formation of the perovskite layer (one-step method) A perovskite layer 24 made of halogenated perovskite (FACsRbPbI3) was formed on the surface protection zone 3 with a film thickness of approximately 500 nm by coating. Specifically, a coating solution was prepared by dissolving 0.84 M formamidinium iodide (FAI, GreatCells), 0.12 M CsI (TCI), 0.04 M RbI (Sigma-Aldrich), 1.0 M PbI2 (Kanto Chemical, 98% purity), and 1 mM 5-AVAI (TCI) in a DMF:DMSO (4:1) solvent. This coating solution was then spin-coated onto a NiOx film, which served as the hole transport layer 2. The spin coating conditions were as follows: first, maintain a spin rate of 1000 rpm for 10 seconds, then accelerate to 5000 rpm in 2 seconds and maintain at 5000 rpm for 40 seconds. At this time, 34 seconds after the start of spinning, 0.8 mL of chlorobenzene solution was applied to promote the crystallization of the perovskite layer. After spin coating was completed, the perovskite layer 24 was formed by heat treatment at 60°C for 1 minute and then at 100°C for 45 minutes.

[0075] 1-5. Formation of the perovskite passivation layer 5F-PHZ(25), which is responsible for passivation and surface protection of the perovskite layer, was applied and formed on the perovskite (24). Here, the coating solution was prepared by mixing 5F-PHZ (manufactured by TCI) shown in formula (8) with IPA solvent at a concentration of 0.5–10 mol% / mL, followed by stirring at 60°C for 2 hours. The spin coating speed was 5000 rpm.

[0076] [ka]

[0077] 1-6. Formation of the electron transport layer As an electron transport layer, a layer of C approximately 26 nm thick is used.60 An electron transport layer made of BCP with a thickness of approximately 6 nm was formed by thermal deposition.

[0078] 1-7. Formation of the back electrode In the same manner as in Example 1, a 150 nm thick layer of silver (Ag) was deposited by thermal deposition to form the back surface electrode 7.

[0079] 2. Evaluation of Photoelectric Conversion Characteristics Table 5 shows the effect of forming a passivation layer consisting of 5F-PHZ(25) on the photoelectric conversion characteristics compared to the case where 5F-PHZ is not formed. The conversion efficiency η when 5F-PHZ was formed was 22.0%, which is approximately 25% higher than when 5F-PHZ was not formed, confirming the effect of 5F-PHZ in forming a passivation layer.

[0080] [Table 5] [Industrial applicability]

[0081] The present invention provides a perovskite solar cell with high conversion efficiency and a method for manufacturing the perovskite solar cell, and is therefore expected to greatly contribute to the development of industry. [Explanation of symbols]

[0082] 1. Transparent conductive layer / transparent substrate (ITO / glass) 2 Hole transport layer (NiO x film) 3. Surface compensation band, X-nPACz layer 4 Perovskite layer 5 Electron transport layer (PCBM film) 6. Hole blocking layer (AZO film) 7 Back electrode (Ag film) 11 Transparent substrate (transparent support) 12 Transparent conductive layer (ITO film) 13 Hole transport layer (NiO xfilm) 14. Surface compensation band, X-nPACz layer 15 Perovskite layer 16 Electron transport layer (PCBM film) 17 Hole blocking layer (AZO film) 18 Back electrode (ITO film) 19 Metal film, wiring layer 20 light 24 Perovskite 25 5F-PHZ 26 C 60 27 BCP 101, 102, 201 Perovskite Solar Cells

Claims

1. A perovskite solar cell, in which a transparent conductive layer, a hole transport layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode are sequentially formed, wherein the hole transport layer is made of an inorganic nickel oxide, and at least a part of the surface of the hole transport layer on the perovskite layer side is covered with a substance (X-nPACz) represented by the following formula (1). [In formula (1), X is OR or R, O is oxygen, R is a linear hydrocarbon group having 1 or more and 12 or less carbon atoms, and n represents an integer of 2 or more and 12 or less.]

2. 【Chemical 1】 The perovskite solar cell according to claim 1, wherein n is 2 or 4.

3.

4. The perovskite solar cell according to any one of claims 1 to 3, wherein the thickness of the hole transport layer is 4 nm or more and 50 nm or less.

5. wherein X is OCH ３ and n is 2, the perovskite solar cell according to claim 1. The perovskite solar cell according to claim 4, wherein the thickness of the hole transport layer is 4 nm or more and 18 nm or less.

6. The perovskite solar cell according to claim 5, wherein the thickness of the hole transport layer is 15 nm or more and 18 nm or less.

7.

8. A method for manufacturing a perovskite solar cell, comprising sequentially performing a step of forming a transparent conductive layer on a transparent support, a step of forming a hole transport layer, a step of forming a surface compensation band, a step of forming a perovskite layer, a step of forming an electron transport layer, a step of forming a hole blocking layer, and a step of forming a back electrode, wherein the transparent conductive layer is ITO, the hole transport layer is an inorganic nickel oxide, the surface compensation band is made of a substance (X-nPACz) represented by the following formula (1), The electron transport layer is [6,6]-phenyl-C ６１ -methyl butyrate (PCBM) film, fullerene C ６０ film, or a laminated film of a PCBM film and a C ６０ film, and the hole blocking layer is made of an aluminum zinc oxide film, a LiF film, or a bathocuproine (BCP) film. The perovskite solar cell according to claim 1. and the step of forming the hole transport layer is by a sputtering method.

9. The method for manufacturing a perovskite solar cell according to claim 8, wherein n is 2 or 4.

10. [Chemical 2]

11. The method for manufacturing a perovskite solar cell according to any one of claims 8 to 10, wherein the step of forming the surface compensation band uses one selected from the group consisting of a spin coating method, a dip method, a spray coating method, and a vapor deposition method.

12. The method for manufacturing a perovskite solar cell according to claim 8, wherein heat treatment is performed after the surface compensation band is deposited on the hole transport layer. wherein X is OCH ３ and n is 2. The method for manufacturing a perovskite solar cell according to claim 8.

13. ​ ​ ​ ​ The manufacturing method of the perovskite solar cell according to claim 12, wherein the temperature of the heat treatment is 20°C or higher and 150°C or lower.

14. The manufacturing method of the perovskite solar cell according to claim 8, wherein the thickness of the hole transport layer is 4 nm or more and 50 nm or less.

15. The manufacturing method of the perovskite solar cell according to claim 8, wherein the perovskite layer is composed of a perovskite containing chlorine.

16. The electron transport layer is a PCBM film, a fullerene C ６０ film, or a laminated film of a PCBM film and a C ６０ film, and the hole blocking layer is made of an aluminum zinc oxide film, a LiF film, or a CP film. The method for manufacturing a perovskite solar cell according to claim 8.

17. An inorganic nickel oxide film formed with a substance (X-nPACz) described in the following formula (1) on the first main surface. 【Chemical 3】 [In formula (1), X is OR or R, O is oxygen, R is a linear hydrocarbon group having 1 or more and 12 or less carbon atoms, and n represents an integer of 2 or more and 12 or less. ]

18. Forming an inorganic nickel oxide film by a sputtering method, and An interface treatment method for a nickel oxide film, comprising forming a substance (X-nPACz) described in the following formula (1) on the first main surface of the nickel oxide film. 【Chemical Formula 4】 [In formula (1), X is OR or R, O is oxygen, R is a linear hydrocarbon group having 1 or more and 12 or less carbon atoms, and n represents an integer of 2 or more and 12 or less. ]

19. The interface treatment method for a nickel oxide film according to claim 18, wherein the method for forming the X-nPACz is a coating formation method.

Images