Perovskite solar cell and method for manufacturing the same

Abstract

An object of the present invention is to provide a perovskite solar cell having a large total power generation amount.SOLUTION: In the perovskite solar cell, an additive layer containing one or more selected from the group consisting of 1 - (2,3,4 - trimethoxybenzyl) piperazine dihydrochloride and 1 - (2-furoyl) piperazine hydrochloride is formed on the surface of a perovskite semiconductor layer, and an electron transport layer is formed on the additive layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a perovskite solar cell, and more particularly to a perovskite solar cell with a high total power generation capacity and a method for manufacturing the same. [Background technology]

[0002] BACKGROUND ART In recent years, solar cells capable of converting solar energy into electrical energy have been attracting attention as a clean energy source that can replace fossil fuels in light of global environmental issues such as global warming.

[0003] Solar cells that can efficiently convert sunlight into electricity and that are currently in practical use include monocrystalline silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and copper indium selenide. One of the challenges with these inorganic solar cells is that silicon requires extremely high purity, and the refining process requires high temperatures, such as the Czochralski (CZ) method for producing silicon ingots, which requires a high-temperature process of approximately 1400°C. For this reason, mass production of silicon solar cells could result in the emission of large amounts of greenhouse gases.

[0004] In response to this, perovskite solar cells have been attracting attention as a new type of solar cell that is inexpensive and highly efficient (see Patent Document 1).

[0005] Perovskite solar cells are typically composed of a transparent electrode layer formed on a transparent substrate, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode. Alternatively, they may further comprise an electron blocking layer and / or a buffer layer. The hole transport layer and electron transport layer transport holes and electrons, respectively, while preventing reverse transport of electrons in the hole transport layer and holes in the electron transport layer, thereby ensuring a constant current flow.

[0006] The reason why perovskite solar cells are inexpensive is that the perovskite layer is made of organic material that can be applied by coating, and can be produced using a low-temperature process at around 100°C. Perovskite solar cells can be manufactured using a coating method, making them suitable for large-scale cell production and also have the excellent applicability of being able to be manufactured on flexible substrates. Furthermore, because they can be manufactured using a low-temperature process, they have excellent potential for development, such as being combined in tandem with other solar cells, such as silicon solar cells.

[0007] In addition to these advantages, perovskites also possess high charge transport properties and a long diffusion length of over 1 μm for photogenerated electrons and holes before they recombine, which means that perovskite solar cells have the potential to achieve high photoelectric conversion efficiencies.

[0008] If solar cells cannot generate more electricity than the amount of energy required to manufacture them, they will not be a sustainable technology and will lose their marketability. However, current perovskite solar cells have a problem in that they do not meet the total power generation requirements over the expected period of use, due in part to the fact that they are subject to significant changes over time and are difficult to maintain their initial characteristics. One indicator of total power generation is ISOS2-L-1, for example.

[0009] Against this background, as disclosed in Non-Patent Documents 1-3, for example, active research has been conducted into the control of the interface between the perovskite layer and the electron transport layer using additives. However, the research is still in the development stage and has not yet reached the required level for total power generation, etc. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2017-22354 [Patent Document 2] Japanese Patent Publication No. 2023-036564 [Non-patent literature]

[0011] [Non-Patent Document 1] Nature,2019,571,245 [Non-patent document 2] Adv.Energy Mater.,2020,1902492 [Non-patent document 3] Adv.Energy Mater.,2020,1902579 [Non-patent document 4] NATURE ENERGY,Vol.5,JANUARY 2020,35-49 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a perovskite solar cell with a large total power generation capacity and a method for manufacturing the perovskite solar cell. [Means for solving the problem]

[0013] The present inventors have searched for an additive that controls the interface between the perovskite layer and the electron transport layer in order to significantly increase the total power generation of perovskite solar cells. As a result, the following configuration has been found to solve the above-mentioned problems related to total power generation.

[0014] (Configuration 1) an additive layer containing one or more selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride is formed on the surface of a perovskite semiconductor layer; A perovskite solar cell, wherein an electron transport layer is formed on the additive layer. (Configuration 2) 2. The perovskite solar cell according to claim 1, wherein the additive layer comprises a material selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride. (Configuration 3) 3. The perovskite solar cell according to claim 1, wherein the perovskite layer is made of a three-dimensional (3D) perovskite. (Configuration 4) 4. The perovskite solar cell of any one of Aspects 1 to 3, wherein the perovskite solar cell comprises a transparent electrode layer, a hole transport layer, the perovskite semiconductor layer, the electron transport layer, a buffer layer, and a back electrode layer. (Configuration 5) preparing a transparent substrate that transmits sunlight and has a transparent electrode formed thereon; forming a hole transport layer and a perovskite layer in this order on the transparent electrode; modifying the surface of the perovskite layer with an additive; After the surface modification treatment, an electron transport layer, a buffer layer, and a back electrode are sequentially formed; The method for producing a perovskite solar cell, wherein the additive comprises at least one selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride. (Configuration 6) 6. The method for producing a perovskite solar cell according to claim 5, wherein the additive is one selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride. (Configuration 7) 7. The method for producing a perovskite solar cell according to aspect 5 or 6, wherein the perovskite layer is made of a 3D perovskite. (Configuration 8) 8. The method for producing a perovskite solar cell according to any one of Aspects 5 to 7, wherein the surface modification treatment is performed by one method selected from the group consisting of spin coating, dipping, spray coating, and vapor deposition. (Configuration 9) 9. The method for producing a perovskite solar cell according to any one of Configurations 5 to 8, wherein a heat treatment is performed after the surface modification treatment and before the electron transport layer is formed. (Configuration 10) 10. The method for producing a perovskite solar cell according to claim 9, wherein the temperature of the heat treatment is 90°C or higher and 110°C or lower. [Effects of the Invention]

[0015] The present invention provides a perovskite solar cell with a large total power generation capacity and a method for manufacturing the perovskite solar cell. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing the structure of a perovskite solar cell of the present invention. [Figure 2] FIG. 1 is a schematic diagram for explaining the mechanism of the effect of the present invention. [Figure 3] FIG. 1 is a flowchart showing the steps of manufacturing a solar cell of the present invention. [Figure 4] FIG. 1 is an explanatory diagram showing a list of chemical formulas and structures of additives. [Figure 5] FIG. 10 is a characteristic diagram showing the change over time in photoelectric conversion efficiency. [Figure 6] FIG. 1 is a characteristic diagram showing the effect of the additive used in the examples in the form of a map of integral retention rate and integrated power generation amount over 100 hours. [Figure 7] FIG. 1 is a characteristic diagram showing the effect of an additive used in an example in the form of a map of integral retention rate and initial photoelectric conversion efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Embodiment 1) In the first embodiment, a perovskite solar cell and a method for manufacturing the same of the present invention will be described.

[0018] <Concept> First, the concept of the present invention will be explained.

[0019] Metal halide perovskite (perovskite) solar cells consist of, from the sunlight incident side, a transparent conductive oxide film such as ITO (indium tin oxide) or FTO (F-doped tin oxide), a hole transport layer, a perovskite layer, an electron transport layer, and a metal electrode. The hole transport layer and electron transport layer transport holes and electrons, respectively, while the hole transport layer prevents the reverse transport of electrons, and the electron transport layer prevents the reverse transport of holes, allowing current to flow in a certain direction.

[0020] However, in reality, charge recombination occurs, where electrons and holes separated by light recombine via defect levels that arise at the interface between the charge transport layer and the perovskite layer in the hole transport layer and electron transport layer. Furthermore, during power generation under continuous light irradiation (maximum power point tracking (MPPT)), halide ions from the perovskite layer migrate across the interface to the charge transport layer, or oxygen and water molecules that have penetrated the charge transport layer migrate to the perovskite layer, causing the perovskite layer to decompose and reducing the photoelectric conversion efficiency of the solar cell over time. This condition makes accurate solar cell evaluation impossible and impairs long-term reliability. The charge transport layer, which is a cause of such deterioration, has little interaction with the perovskite layer, and the interface between the perovskite layer and the charge transport layer is vulnerable to physical movement of ions and molecules, heat, and other factors.

[0021] In view of the above, in the present invention, we have searched for an interfacial interaction additive (formed between the perovskite layer and the charge transport layer) that can maintain high photoelectric conversion efficiency for a long period of time under continuous light irradiation, and confirmed the effects of this additive. Here, the evaluation standard for long-term, highly efficient power generation was the integrated power generation (total power generation over 100 hours). There is an international agreement on the evaluation standard for stability evaluation in perovskite solar cell power generation, and the gist of this agreement is disclosed in Non-Patent Document 4.

[0022] The following is considered to be the function of the interface interaction additive having a substituent that interacts with both the perovskite layer and the charge transport layer. (1) The effect of facilitating the movement of electrons and holes from the perovskite layer to each charge transport layer. (2) Passivating defects in the perovskite and charge transport layer due to X-site deficiencies at the interface. (3) Preventing the migration of halide ions from the perovskite layer across the perovskite / charge transport layer interface to the charge transport layer. (4) Prevents the migration of oxygen and water molecules from the charge transport layer side across the perovskite / charge transport layer interface to the perovskite layer. (5) The function of firmly connecting the charge transport layer and the perovskite layer.

[0023] Here, the focus of the search for the additive in this invention was on an interfacial interaction additive that could be expected to have the effects (1) to (5) above and that had a site that interacted not only with the perovskite layer but also with the fullerene material in the electron transport layer. A total of 82 types of materials were evaluated and examined, and 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride were selected as the additive.

[0024] <Device structure> As shown in FIG. 1, the perovskite solar cell 101 of the first embodiment includes a transparent substrate 11, a transparent conductive layer 12, a hole transport layer 13, an X-PACz layer (surface compensation layer) 13a, a perovskite layer 14, an additive layer 15, an electron transport layer 16, a buffer layer 17, a back electrode 18, and a metal film (wiring layer) 19. The solar cell is configured to receive light 20 from the transparent substrate 11 side. The X-PACz layer (surface compensation layer) 13a is a layer introduced to improve photoelectric conversion efficiency. Its effects are disclosed in Patent Document 2, but it can be omitted. The buffer layer 17 can also be omitted depending on the material of the electron transport layer 16. The transparent electrode layer 12 is electrically connected to a first terminal electrode (not shown), and the back electrode 18 is electrically connected to a wiring layer 19 that forms a second terminal electrode.

[0025] A feature of the first embodiment is that, as shown in FIG. 2, an additive layer 15 is formed on the surface of the perovskite layer 14 on the electron transport layer 16 side.

[0026] The Coulomb repulsion of this additive material inhibits the migration of halide ions (anions) across the interface between the perovskite layer 14 and the electron transport layer 16 . Furthermore, the mismatch in energy levels occurring at the interface between the perovskite layer 14 and the electron transport layer 16 is suppressed, allowing electrons generated by light irradiation to move smoothly to the electron transport layer. Furthermore, the recombination of electrons and holes generated by light irradiation via defect levels occurring at the interface between the perovskite layer 14 and the charge transport layer 16 is suppressed by the passivation effect. The above effects improve the photoelectric conversion efficiency of perovskite solar cells and suppress deterioration over time, making it possible to increase the total amount of power generated over the long term.

[0027] Next, each layer constituting the perovskite solar cell 101 of the present invention will be described.

[0028] The transparent substrate 11 is a base that transmits sunlight and has a rigidity equal to or greater than a predetermined value. Various types of glass, 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 is characterized by its high transparency (high transmittance) to sunlight, sufficient rigidity, and excellent light resistance and weather resistance. Plastic can be easily processed into any shape and can be made flexible, making it suitable for applications such as producing curved solar cells and for flexibly bending solar cells for use.

[0029] Indium tin oxide (ITO) can be used as the material for the transparent conductive layer (transparent electrode) 12. Fluorine-doped tin oxide (FTO) can also be used. To improve light resistance, ITO is preferably deposited by sputtering. Specifically, 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. Heat treatment at 150°C or higher after ITO deposition is preferred, as it improves solar transmittance and reduces electrical resistance. Heat treatment at temperatures above 300°C is undesirable, as it increases electrical resistance. ITO is highly transparent and has a relatively low electrical resistivity for a transparent conductive film. Furthermore, because indium (In) and tin (Sn) are oxidized and fixed, these metals are less likely to diffuse, providing the interdiffusion prevention function necessary for improving light resistance. The ITO film thickness of the transparent electrode 12 is preferably 150 nm or less. On the other hand, to ensure the necessary conductivity, the ITO film thickness is preferably 100 nm or more. The lower the ITO film resistance, the better, and it is preferably more than 0 Ω / sq and 15 Ω / sq or less.

[0030] To reduce the resistance of the transparent electrode 12, a metal lead wire may be added between the ITO film and the transparent substrate 11. Examples of materials for the metal lead wire include platinum (Pt), gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), and titanium (Ti). The metal lead wire is preferably formed on the transparent substrate 11 by a sputtering method or a vapor deposition method, and the ITO film is then formed thereon. However, since providing the metal lead wire reduces the amount of incident light, the thickness of the metal lead wire is preferably 0.01 mm or more and 3 mm or less.

[0031] The hole transport layer 13 is made of inorganic NiO xExamples include membranes, Spiro-OMeTAD (2,2',7,7-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirofluorene), PTAA (Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), and MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid). In particular, the hole transport layer 13 is made of inorganic NiO formed by a PVD (Physical Vapor Deposition) method such as a sputtering method. x When the hole transport layer 13 is formed from a film, a layer with a large area and few pinholes or cracks can be formed, and the light irradiation resistance can be further increased. Other methods for forming the hole transport layer 13 include a coating method and a casting method. The thickness of the hole transport layer 13 is preferably 4 nm to 50 nm, more preferably 4 nm to 18 nm. Setting the thickness of the hole transport layer 13 within this range makes it possible to obtain high photoelectric conversion efficiency. Furthermore, setting the thickness of the hole transport layer 13 to 15 nm to 18 nm makes it possible to achieve high long-term reliability. This is due to the suppression of pinholes in the hole transport layer 13.

[0032] NiO as the hole transport layer 13 x When a film is used, NiO is used to improve the conductivity of the hole transport layer 13. x It is also preferable to dope the film with metal ions other than Ni. Examples of metal ions include ions of alkali metals, alkaline earth metals, and transition metals. Specific metal ions include Li + , Na + , K. + , Mg 2+ , Cu 2+ , Fe 2+ , Mn 2+ , and Zn 2+ and more preferably Li + and Mg 2+ At least one selected from Li + and Mg2+ The doping concentration is preferably 0.5 mol % or more and 50 mol % or less, and more preferably 2 mol % or more and 30 mol % or less. These metal ions can be introduced into the hole transport layer 13 by, for example, incorporating them into the target material used in sputtering.

[0033] The X-nPACz layer 13a is a layer made of a substance represented by chemical formula (1), where X is OR or R, O is oxygen, R is a linear hydrocarbon group having 1 to 12 carbon atoms, and n is an integer of 2 to 12. The presence of this layer allows NiO x Vacancy at the interface of the film 13 and in the perovskite layer 14 is suppressed, improving the photoelectric conversion efficiency of the perovskite solar cell 101. Here, vacancy refers to the depletion of halide ions such as iodine (I), chlorine (Cl), or bromine (Br).

[0034] In formula (1), n ​​is preferably 2 or 4, and it is even more preferable that X in chemical formula (1) is OCH3 and n is 2, i.e., MeO-2PACz shown in chemical formula (2), because this further suppresses the formation of vacancy and further increases the photoelectric conversion efficiency.

[0035] [ka]

[0036] X-nPACz is a NiO x By applying it on top and heat treating it, NiO x The temperature for this heat treatment is preferably 20° C. or higher and 150° C. or lower to promote the surface modification, and heat treatment within this temperature range can be preferably used. X-nPACz is NiO x By coating the NiO film, a uniform hole transport layer is formed. In other words, the X-nPACz functions as a surface compensation layer. xThere is no adverse effect unless it is near the interface of the film 13 and the vacancy of the halide ions in the perovskite layer 14 .

[0037] The material constituting the perovskite layer 14 is not particularly limited, and examples thereof include CH3NH3PbI3, CH(NH2)2PbI3, CsPbI3, CH3NH3SnI3, CH3NH3Sn x Pb (1-x) I3, CH(NH2)2SnI3, FA 0.84 Cs 0.12 Rb 0.04 PbI3, etc., and preferably CH3NH3PbI3, CH(NH2)2PbI3, and FA 0.84 Cs 0.12 Rb 0.04 PbI3 can be mentioned. Furthermore, materials in which part of the iodine (I) in these materials is replaced by chlorine (Cl), such as CH3NH3PbI 3―x Cl x This is more preferable because it improves the photoelectric conversion efficiency and light irradiation resistance and reduces deterioration over time when left unattended. Here, the reaction of substituting a portion of the iodine with chlorine can be carried out by the chlorine-mediated interdiffusion method.

[0038] The perovskite layer 14 may be a single layer film or a laminated film made up of multiple layers. The single-layer film has the advantage that it requires fewer manufacturing steps, is suitable for mass production as a solar cell, and can reduce costs. On the other hand, in the case of a laminated film, by forming a tandem structure in which multiple perovskites with different light absorption bands are laminated, it is possible to efficiently absorb light in a wide wavelength range and increase the photoelectric conversion efficiency of the entire solar cell. 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 stacked on a Sn-based perovskite having a narrow bandgap can be mentioned.

[0039] The perovskite layer 14 can be formed by a coating method such as spin coating. For example, a perovskite precursor dissolved in a solvent is prepared, and after spin coating, heat treatment is applied to form the perovskite layer 14. As a specific example of forming the perovskite layer 14, when CH3NH3PbI3 is mentioned, a perovskite precursor solution in which methylammonium iodide CH3NH3I (abbreviated as "MAI") and lead iodide PbI2 are dissolved in a solvent is prepared and spin-coated. As the solvent, for example, dimethyl sulfoxide (DMSO) can be used. At the time of spin coating, it is preferable to also drop a small amount of toluene or the like as a volatility preparation for the purpose of reducing striation and film thickness uniformity. The heat treatment temperature is preferably 50°C or higher and 120°C or lower.

[0040] The additive layer 15 consists of one or more selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride selected by performance evaluation exploration. For reference, 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride are shown in Chemical Formulas (3) and (4) respectively. Also, in FIG. 4, the chemical formulas and structures are listed and displayed. Here, the large dark gray circles (●) in the structure of FIG. 4 represent carbon, the small dark gray circles (●) represent nitrogen, the small black circles (●) represent oxygen, and the light small gray circles (〇) represent hydrogen.

[0041]

Chemical formula

[0042] The additive layer 15 provides the perovskite solar cell 101 with a stable, high photoelectric conversion efficiency and high stability over time, resulting in a large integrated power generation amount (per 100 hours).

[0043] The material for the electron transport layer 16 is not particularly limited, but examples thereof include n-type conductive polymers, n-type small molecule organic semiconductors, graphene materials, and n-type metal oxides. 61 Polybutylene methyl ester (PCBM) can be formed by a coating method, and is preferably used as the electron transport layer 16 from the viewpoints of throughput and manufacturing costs.

[0044] The buffer layer 17 may be an oxide film doped with metal ions, such as at least one selected from zinc oxide, titanium oxide, and tin oxide. The doped metal ions may be, for example, W 6+ , Nb 5+ , Sb 5+ , Ta 5+ , Al 3+ , Y 3+ , Ga 3+ The doping concentration is 0.5 mol % or more and 50 mol % or less, preferably 0.5 mol % or more and 20 mol % or less. For example, a zinc oxide film (AZO) doped with 1.6 mol % aluminum can be preferably used as the buffer layer 17. The thickness of the buffer layer 17 is preferably 30 nm or more and 150 nm or less, and more preferably 40 nm or more and 100 nm or less, taking into consideration the electrical resistance and the uniformity of the layer thickness.

[0045] The back electrode 18 is a metal film such as silver or a composite film of indium tin oxide (ITO) and a metal such as silver. This film is preferably formed by sputtering. When ITO is also used, it can be used as an optical interference film to increase the back surface light reflectance and improve the photoelectric conversion efficiency of the solar cell as a whole. The preferred method for forming ITO is RF sputtering 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, but is not limited to, room temperature. It is also effective to apply a heat treatment after ITO deposition. However, if heat treatment is applied, the temperature should be 140°C or less, preferably 120°C or less, to avoid damaging the perovskite layer 4. Examples of materials for the wiring 19 include metals such as silver, aluminum (Al), tungsten (W), copper (Cu), and gold (Au), and alloys such as Al-Si. The wiring 19 may be formed as an extraction line of the back electrode 18 by utilizing the back electrode 18.

[0046] The perovskite solar cell 101 having the structure of the first embodiment provides a perovskite solar cell that has a stable and high photoelectric conversion efficiency, high stability over time, and a large 100-hour integrated power generation amount.

[0047] <Manufacturing method> The method for manufacturing the perovskite solar cell 101 will be described with reference to FIG. 3, which shows a flowchart of the manufacturing steps. A perovskite solar cell 101 is manufactured by sequentially performing the following steps: step (S11) of forming a transparent conductive layer 12 made of ITO on a transparent substrate 11, step (S12) of forming a hole transport layer 13, step (S12a) of forming a surface compensation layer 13a made of an X-nPACz layer, step (S13) of forming a perovskite layer 14, step (S14) of forming an additive layer 15, step (S15) of forming an electron transport layer 16, step (S16) of forming a buffer layer 17, step (S17) of forming a back electrode 18, and step (S18) of forming wiring. Here, step S12 can be omitted, and step S16 can also be omitted depending on the material of the electron transport layer 16.

[0048] The hole transport layer 13 is made of Spiro-OMeTAD (2,2´,7,7-Tetrakis(N,N-di-p-methoxyphenylamino)-9,9´-spirofluorene), PTTA(Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), MeO-2PACz and nickel oxide film (NiO x ) and the like. Examples of the forming method include a coating method, a casting method, and a PVD method such as sputtering. Among these, inorganic nickel oxide films (NiO x ) is suitable for the hole transport layer 13 in order to obtain high photoelectric conversion efficiency. Among the PVD methods, the sputtering method is preferred because it is suitable for mass production and has high manufacturing stability. In view of its productivity, a method of forming the hole transport layer 13 using a NiO target with an RF magnetron sputtering device is preferred, but a method of sputtering using Ni as a target in the presence of oxygen can also be used. The thickness of the hole transport layer 13 is preferably 4 nm or more and 50 nm or less, and more preferably 10 nm or more and 50 nm or less, taking into consideration the electrical resistance and the uniformity of the layer thickness.

[0049] The surface compensation layer (X-nPACz layer) 13a is a layer made of a material represented by the formula (1). In formula (1), X represents OR or R, O represents oxygen, R represents a linear hydrocarbon group having 1 to 12 carbon atoms, and n represents an integer of 2 to 12. n in formula (1) is preferably 2 or 4, and even more preferably, X in formula (1) is OCH3 and n is 2, i.e., MeO-2PACz represented by formula (2). The surface compensation band 13a can be formed by a method selected from the group consisting of spin coating, dipping, spray coating, and vapor deposition. Among these, spin coating and dipping are preferred because they have fewer defects and are suitable for mass production. X-nPACz is NiO xAfter forming the hole transport layer on the substrate, it is preferable to perform a heat treatment at a temperature of 20° C. to 150° C. This treatment allows the X-nPACz to act as a surface compensation layer, making the hole transport layer dense and improving in-plane uniformity.

[0050] From the viewpoints of mass productivity and defect reduction, it is preferable to form the perovskite layer 14 by a coating method, and a chlorine-containing perovskite is preferable for the perovskite layer 14. Furthermore, from the viewpoints of ensuring long-term stability as a solar cell and improving photoelectric conversion efficiency, it is preferable to subject the layer to a heat treatment at a temperature of 60°C to 150°C after coating formation.

[0051] The additive layer 15 is formed by applying a solution containing the additive to the surface of the perovskite layer 14 by spin coating, dipping or spray coating, or by vapor deposition. The solvent may be one or more selected from the group consisting of 2-propanol (isopropanol), toluene, xylene, chloroform, chlorobenzene, 1,2-dichlorobenzene, and diethyl ether. The concentration of the solution is 0.05 mM (mmol L -1 ) to 10 mM is preferred.

[0052] After forming the additive layer 15, it is preferable to perform a heat treatment before forming the electron transport layer 16. The temperature for the heat treatment can be 90° C. or higher and 110° C. or lower. This heat treatment has the effect of fixing the additive in the perovskite crystal, on the surface, and at the grain boundaries.

[0053] The electron transport layer 16 may be a PCBM film, a fullerene C 60 membrane, or PCBM membrane and C 60 These films can be formed by coating methods, vacuum deposition methods, etc. The buffer layer 17 is preferably made of an aluminum zinc oxide (AZO) film, a LiF film, or a bathocuproine (BCP) film. These films can be formed by a coating method, a vacuum deposition method, or the like.

[0054] Examples of the back electrode 18 include a single layer film made of a metal such as Ag or an alloy such as Al-Si, and a laminated film of ITO and a metal or alloy. Methods for forming these films include sputtering, evaporation, CVD (Chemical Vapor Deposition), and coating methods. Examples of the wiring 19 include a single layer film made of a metal such as Al, W, or Cu, or an alloy such as Poly-Si or Al-Si, and a laminated film with a metal or alloy. Methods for forming these films include sputtering, vapor deposition, CVD, and coating methods.

[0055] When a perovskite solar cell is manufactured in the above manner, the solar cell 101 becomes a solar cell with a stable, high photoelectric conversion efficiency, high temporal stability, and a large 100-hour integrated power generation amount. [Example]

[0056] Example 1 The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0057] 1. Solar Cell Fabrication 1-1. Preparation of a transparent substrate with a transparent electrode layer A transparent substrate 11 was prepared, having on its first main surface a transparent electrode layer 12 made of an ITO film patterned into the shape of a commercially available transparent electrode. The ITO film had a thickness of 150 nm and a film resistance of approximately 15 Ω / sq.

[0058] 1-2. Formation of hole transport layer On the ITO film, a hole transport layer 13 was formed using NiO. x The film was deposited to a thickness of 20 nm by sputtering. An RF magnetron sputtering device (SVC-700 RFINA, manufactured by Sanyu Electronics Co., Ltd.) was used for this deposition. The target was 99.9% pure NiO (manufactured by Kojundo Chemical Laboratory Co., Ltd.). Argon (Ar) gas was used as the sputtering gas, and the vacuum level in the sputtering chamber was 2 × 10-3 After the pressure was reduced to less than Pa, argon gas was introduced into the chamber at a flow rate of 20 sccm, and sputtering was carried out 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 coated with the ITO film 2 was subjected to UV ozone cleaning for 20 minutes.

[0059] 1-3. Formation of surface compensation zone In a nitrogen-filled glove box, 6 mg of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-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 then 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 13a composed of MeO-2PACz.

[0060] 1-4. Formation of perovskite layer (two-step method) Next, lead halide perovskite (FA) is deposited on the surface compensation layer 13a. 0.84 Cs 0.12 Rb 0.04 A perovskite layer 14 made of PbI3) was formed to a thickness of 500 nm by a coating method.

[0061] Specifically, 9 mg of 5-AVAl, 1383 mg of PbI2 (Kanto Chemical, purity 98%), 433.4 mg of formamidinium (FA) in DMF-DMDO consisting of 2.4 mL of DMF and 0.6 mL of DMSO were dissolved. + A solution of iodide salt (FAI), 93.6 mg of CsI, and 25.5 mg of RbI was prepared and spin-coated onto a NiOx film 13 with a surface compensation band. After annealing at 105°C for 30 minutes, 0.5-10 mol% / mL of 5F-PHZ in 2-propanol (IPA) solvent was spin-coated to passivate the perovskite layer 14. The perovskite layer 14 was formed through the above process.

[0062] 1-5. Formation of additive layer (perovskite surface treatment with additive) A solution prepared by dissolving 6 mmol of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride additives in 6 mL of IPA solvent was dropped onto the perovskite layer 14, spin-coated at 5000 rpm for 50 seconds, and then annealed at 100°C for 5-10 minutes to form the additive layer 15. As a comparative example, a sample without an additive layer was also prepared, which was produced in the same manner except that no additive was applied.

[0063] 1-6. Formation of electron transport layer An electron transport layer 16 made of PCBM was prepared by the following procedure. A solution of 99% pure PCBM (SIGMA-ALDRICH) dissolved in anhydrous chlorobenzene at a ratio of 2% by weight was dropped onto the perovskite layer 14, and then spin-coated at 700 rpm for 7 seconds, followed by 3000 rpm for 30 seconds. A heat treatment was then performed at 105°C for 15 minutes to form an electron transport layer 16 with a thickness of 50 nm.

[0064] 1-7. Formation of buffer layer Nanograde N-21X (Nanograde Co., Ltd.), an ink containing suspended (aluminum-doped) zinc oxide nanoparticles (AZO nanoparticles) containing Avantama AG, was dropped onto the substrate, followed by spin coating at 1500 rpm for 5.5 seconds and then at 4000 rpm for 20 seconds to form a buffer layer 17 made of an AZO film with a thickness of 100 nm. After applying the ink, the substrate was subjected to a heat treatment at 105°C for 10 minutes.

[0065] 1-8. Formation of rear electrode A back electrode 18 was formed by depositing silver (Ag) to a thickness of 150 nm by thermal evaporation.

[0066] 1-9.Sealing A cover glass was placed on the obtained cell, and the cell was sealed (not shown) with UVRESIN XNR5516Z (manufactured by NagaseChemteX), which is an ultraviolet-curable resin, to encapsulate the cell and evaluate its electrical properties.

[0067] 2. Photoelectric conversion characteristics evaluation The JV characteristics, external quantum yield (EQE) characteristics, and internal quantum yield (IQE) characteristics of the perovskite solar cell 101 fabricated by the above fabrication method were investigated. There, measurements were made using an AM1.5G spectral filter under the conditions of the 1-SUN standard, and the EQE and IQE characteristics were measured using an SM-250IQE (manufactured by Bunkoukeiki).

[0068] Figure 5 shows the change over time in photoelectric conversion efficiency (PCE) evaluated by MPPT. When no additives were added, the initial PCE value was low at 17.28%, dropping to 13% in about 5 hours, hitting bottom at about 20 hours, and then stabilizing at about 14%. In contrast, when 1-(2-furoyl)piperazine hydrochloride was used as an additive, the initial value was high at approximately 18.41%, and although the PCE decreased slowly and linearly over time, it was still approximately 17% even after 130 hours, demonstrating good aging characteristics. When 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride was used as the additive, the initial PCE value was high at approximately 18.47%. It was found that the PCE value decreased to approximately 14% over 40 hours, and then gradually decreased thereafter. From the above, it was shown that by providing an additive layer consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride or 1-(2-furoyl)piperazine hydrochloride, a high initial PCE value can be obtained and the change in PCE over time can be suppressed.

[0069] We also investigated the relationship between the amount of power consumed and the integral holding rate, and the relationship between the initial efficiency and the integral holding rate after a 100-hour evaluation in a 70°C accelerated evaluation environment. The results are shown in the form of maps in Figure 6 and Figure 7, respectively. Here, the integral holding rate is defined by the following (Equation 1).

[0070]

number

[0071] As a result, it was visualized that the samples in which the additive layer 15 was formed using 1-(2-furoyl)piperazine hydrochloride and 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride as additives had excellent power consumption and initial PCE values.

[0072] Next, from the measurement data, the short circuit current (J sc ), open circuit voltage (V oc ), fill factor (FF), series resistance (R s ), parallel resistance (R sh The PVD performance and conversion efficiency (PCE) were measured and are summarized in Table 1. Three types of samples were used: #1, which used 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride as the additive; #2, which used 1-(2-furoyl)piperazine hydrochloride as the additive; and #Ref., which was prepared in the same manner but without any additives. The values ​​shown are the highest values ​​obtained from data obtained using at least eight perovskite solar cells.

[0073] [Table 1]

[0074] It can be seen that #1 and #2, which use additives, have higher 100-hour power generation and initial photoelectric conversion efficiency than #Ref., which does not use additives. [Industrial Applicability]

[0075] The present invention provides a perovskite solar cell with a large total power generation capacity and a method for manufacturing such a perovskite solar cell, and is expected to greatly contribute to the development of the industry. [Explanation of symbols]

[0076] 11 Transparent substrate (transparent support) 12 Transparent conductive layer (ITO film) 13 Hole transport layer (NiO x film) 13a Surface compensation zone, X-nPACz layer 14 Perovskite layer 15 Additive layer 16 Electron transport layer (PCBM film) 17 Buffer layer (AZO film, LiF film, or BCP film) 18 Back electrode (ITO film, metal film) 19 Wiring 20 light 101 Perovskite solar cells

Claims

1. an additive layer containing one or more selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride is formed on the surface of a perovskite semiconductor layer; A perovskite solar cell, wherein an electron transport layer is formed on the additive layer.

2. 2. The perovskite solar cell in accordance with claim 1, wherein the additive layer comprises one selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride.

3. The perovskite solar cell according to claim 1 or 2, wherein the perovskite layer is made of a three-dimensional (3D) perovskite.

4. 4. The perovskite solar cell according to claim 1, comprising a transparent electrode layer, a hole transport layer, the perovskite semiconductor layer, the electron transport layer, a buffer layer, and a back electrode layer.

5. providing a sunlight-transmitting transparent substrate having a transparent electrode formed on a first main surface thereof; forming a hole transport layer and a perovskite layer in this order on the transparent electrode; modifying the surface of the perovskite layer with an additive; After the surface modification treatment, an electron transport layer, a buffer layer, and a back electrode are sequentially formed; The method for producing a perovskite solar cell, wherein the additive contains at least one selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride.

6. 6. The method for producing a perovskite solar cell according to claim 5, wherein the additive is one selected from the group consisting of 1-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride and 1-(2-furoyl)piperazine hydrochloride.

7. The method for producing a perovskite solar cell according to claim 5 or 6, wherein the perovskite layer is made of a 3D perovskite.

8. 8. The method for producing a perovskite solar cell according to claim 5, wherein the surface modification treatment is performed by one method selected from the group consisting of spin coating, dipping, spray coating, and vapor deposition.

9. The method for producing a perovskite solar cell according to claim 5 , wherein a heat treatment is performed after the surface modification treatment and before the electron transport layer is formed.

10. The method for producing a perovskite solar cell according to claim 9 , wherein the temperature of the heat treatment is 90° C. or higher and 110° C. or lower.

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