METHOD FOR SURFACE TREATMENT OF METAL OXIDE, METHOD FOR PRODUCING PEROVSKITE SOLAR CELL, AND METAL OXIDE SURFACE TREATMENT DEVICE

Abstract

In order to treat, in a short time, the surface of a metal oxide used in an electron transport layer or the like of a Perovskite solar cell, this method for treating the surface of a metal oxide 30 is provided with an oxygen plasma generation step for supplying high-frequency electric power having a frequency of 1-40 kHz to generate an oxygen plasma PO, and a metal oxide surface modification step for irradiating the surface of the metal oxide 30 with oxygen ions IO in the oxygen plasma PO to modify the surface of the metal oxide 30.

Description

[Technical Field]

[0001] The present application relates to a method for treating the surface of a metal oxide used in an electron transport layer or the like of a perovskite solar cell using oxygen ions in oxygen plasma. The present application also relates to a method for manufacturing a perovskite solar cell that includes the method for treating the surface of a metal oxide. The present application also relates to a metal oxide surface treatment device suitable for performing the method for treating the surface of a metal oxide. [Background technology]

[0002] In recent years, perovskite solar cells, which include a transparent electrode layer, an electron transport layer, a perovskite crystal layer, a hole transport layer, and an electrode layer in this order, have been attracting attention. In order to improve the adhesion between the metal oxide constituting the electron transport layer of perovskite solar cells and the perovskite crystal layer, and to reduce the interface resistance, the surface of the metal oxide is modified. Patent Document 1 describes a method for modifying the surface of an ITO substrate using a mixed gas plasma of argon gas and oxygen gas.

[0003] In Patent Document 1, the ITO substrate surface is modified over a period of two minutes. Meanwhile, a method for modifying the surface of a metal oxide constituting the electron transport layer of a perovskite solar cell by UV irradiation with ozone, which does not require a plasma treatment device, is also known. However, even with this UV irradiation with ozone, it takes approximately 20 minutes to modify the metal oxide surface. To reduce the cost of mass-producing perovskite solar cells, there is a need to improve the speed of metal oxide surface treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-284059 Summary of the Invention [Problem to be solved by the invention]

[0005] The present application has been made in view of the above circumstances, and aims to treat the surface of a metal oxide used as an electron transport layer in a perovskite solar cell, etc., in a short period of time. [Means for solving the problem]

[0006] The method for treating a metal oxide surface of the present application includes an oxygen plasma generation step of generating oxygen plasma by supplying high-frequency power having a frequency of 1 kHz or more and 40 kHz or less, and a metal oxide surface modification step of irradiating the surface of the metal oxide with oxygen ions in the oxygen plasma to modify the surface of the metal oxide.

[0007] The method for manufacturing a perovskite solar cell of the present application is a method for manufacturing a perovskite solar cell comprising, in this order, a transparent electrode layer, a metal oxide layer which is an electron transport layer or a hole transport layer, a power generation layer which is a perovskite crystal layer, a hole transport layer or an electron transport layer, and an upper electrode layer, with the perovskite crystal layer being formed on the surface of the metal oxide layer, and comprises the following steps: an oxygen plasma generation step of applying high-frequency power with a frequency of 1 kHz to 40 kHz to generate oxygen plasma; a metal oxide layer surface modification step of irradiating the surface of the metal oxide layer of a treatment object which comprises the transparent electrode layer and the metal oxide layer with oxygen ions in the oxygen plasma to modify the surface of the metal oxide layer; and a perovskite crystal layer formation step of forming a perovskite crystal layer on the surface of the metal oxide layer modified in the metal oxide layer surface modification step.

[0008] A metal oxide surface treatment device according to one embodiment of the present application includes a treatment vessel, an upper electrode provided within the treatment vessel, a lower electrode provided within the treatment vessel so as to be grounded and on which a treatment object having a transparent electrode layer and a metal oxide layer laminated thereon is placed so that the metal oxide layer of the treatment object is exposed, a gas supply unit that introduces oxygen gas into the treatment vessel, and a high-frequency power source having a frequency of 1 kHz to 40 kHz that supplies power between the upper electrode and the lower electrode so as to generate oxygen plasma from the oxygen gas introduced between the upper electrode and the lower electrode from the gas supply unit.

[0009] Another embodiment of the metal oxide surface treatment device of the present application includes a dielectric treatment container, an induction coil arranged around the dielectric treatment container, an electrode arranged within the dielectric treatment container on which an object to be treated, having a transparent electrode layer and a metal oxide layer laminated thereon, is placed so that the metal oxide layer of the object to be treated is exposed, a gas supply unit that introduces oxygen gas into the dielectric treatment container, and a high-frequency power source having a frequency of 1 kHz to 40 kHz that supplies power to the induction coil so that oxygen plasma is generated from the oxygen gas introduced from the gas supply unit into the dielectric treatment container. [Effects of the Invention]

[0010] The metal oxide surface treatment method of the present application irradiates the surface of the metal oxide with oxygen ions from oxygen plasma generated by high-frequency power having a frequency of 1 kHz to 40 kHz. Therefore, the metal oxide surface treatment method of the present application can treat the surface of the metal oxide in a short time. Furthermore, the perovskite solar cell manufacturing method of the present application includes a step of irradiating the surface of the metal oxide layer with oxygen ions from oxygen plasma generated by high-frequency power having a frequency of 1 kHz to 40 kHz. Therefore, the perovskite solar cell manufacturing method of the present application can manufacture perovskite solar cells in a short time. The metal oxide surface treatment device of the present application is configured to irradiate the surface of the metal oxide layer with oxygen ions from oxygen plasma generated by high-frequency power having a frequency of 1 kHz to 40 kHz. Therefore, the metal oxide surface treatment device of the present application can treat the surface of the metal oxide layer in a short time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a metal oxide surface treatment apparatus according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional schematic diagram of a perovskite solar cell according to an embodiment. [Figure 3] 10 is an optical emission spectroscopy chart of oxygen plasma as a reference example. [Figure 4] 1 is an atomic force microscope image of Example 2. [Figure 5] 1 is a graph showing the relationship between light irradiation time and photoelectric conversion efficiency of the perovskite solar cell of Example 2. [Figure 6] FIG. 1 is a cross-sectional view of a perovskite solar cell according to Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the metal oxide surface treatment method of the present application, the perovskite solar cell manufacturing method of the present application, and the metal oxide surface treatment device of the present application will be described based on embodiments and examples, with appropriate reference to the drawings. The metal oxide surface treatment method of the present application will be described as part of the perovskite solar cell manufacturing method of the present application. Furthermore, the metal oxide surface treatment device and perovskite solar cell in the drawings are schematic representations of their configurations, and therefore do not match the dimensional ratios of the actual metal oxide surface treatment device and perovskite solar cell. The same components may be assigned the same reference numerals, and redundant explanations will be omitted where appropriate.

[0013] FIG. 1 shows a schematic cross section of a metal oxide surface treatment apparatus 10 (hereinafter sometimes simply referred to as "surface treatment apparatus 10") according to an embodiment of the present invention. Surface treatment apparatus 10 includes a treatment vessel 12, an upper electrode 14, a lower electrode 16, a gas supply unit 18, a high-frequency power supply 20, an exhaust port 22, an observation window 24, an emission detection unit 26, and a recording unit 28. Surface treatment apparatus 10 treats the surface of metal oxide 30 constituting the electron transport layer of a treatment target object S with oxygen ions in oxygen plasma, as described below. In the present application, the metals of metal oxides refer to Al, Si, Sc (atomic number 21) to As (atomic number 33), Y (atomic number 38) to Sb (atomic number 51), and La (atomic number 57) to Po (atomic number 84).

[0014] The processing vessel 12 is made of a conductive material, such as an aluminum alloy, and is grounded. The upper electrode 14 is provided within the processing vessel 12 and is made of a conductive material, such as carbon. The lower electrode 16 is provided within the processing vessel 12 so as to face the upper electrode 14. The lower electrode 16 is made of a conductive material, such as carbon, and is grounded. The processing target S is placed on the lower electrode 16. The processing target S includes a transparent electrode layer 32, a component of a perovskite solar cell C, and a layer of metal oxide 30, which serves as an electron transport layer, formed on the transparent electrode layer 32. In this embodiment, the transparent electrode layer 32 and the layer of metal oxide 30 are stacked on a substrate 34 made of glass. The processing target S is then placed on the lower electrode 16 so that the layer of metal oxide 30 is exposed.

[0015] The gas supply unit 18 is connected to the processing chamber 12 and introduces oxygen gas G into the processing chamber 12. The high-frequency power supply 20 is electrically connected to the upper electrode 14 and the lower electrode 16. The high-frequency power supply 20 applies a voltage with a frequency of 1 kHz to 40 kHz between the upper electrode 14 and the lower electrode 16, i.e., supplies power. When power is supplied from the high-frequency power supply 20 between the upper electrode 14 and the lower electrode 16, the oxygen gas G introduced from the gas supply unit 18 between the upper electrode 14 and the lower electrode 16 is converted into plasma, and oxygen plasma P O is generated.

[0016] By setting the frequency of the high frequency power to 40 kHz or less, oxygen plasma P O , i.e., oxygen radical R O and oxygen ions I O can be efficiently generated. Furthermore, by setting the frequency of the high frequency power to 1 kHz or higher, it is possible to convert the oxygen gas G into plasma. Note that oxygen plasma is plasma generated from a gas containing 90 vol% or more of oxygen gas. The oxygen plasma is preferably plasma generated from a gas containing 95 vol% or more of oxygen gas, more preferably plasma generated from a gas containing 99 vol% or more of oxygen gas, and even more preferably plasma generated from a gas consisting essentially of oxygen gas only.

[0017] The oxygen gas substantially composed of only oxygen is an oxygen gas that does not contain impurities other than unavoidable impurities. For example, the oxygen gas supplied from a commercially available oxygen gas cylinder is an oxygen gas that substantially consists of only oxygen. In the surface treatment device 10, the lower electrode 16 is grounded, so that the oxygen plasma P O Oxygen ions in I O is the oxygen radical R O The oxygen ions I reach the surface of the metal oxide 30 much faster than the oxygen ions I O The surface of the metal oxide 30 is modified by this.

[0018] The exhaust port 22 uses an exhaust pump (not shown) to exhaust substances and oxygen radicals generated when the surface of the metal oxide 30 is treated with oxygen ions to the outside of the processing chamber 12. Examples of the exhaust pump include a dry pump, a rotary pump, and a turbomolecular pump that generates a high vacuum. Generally, a high vacuum increases the mean free path of the plasma, improving plasma generation efficiency, so it is preferable to use a turbomolecular pump.

[0019] Observation window 24 is a window for observing the inside of treatment vessel 12 from the outside, and is made of, for example, quartz. Light emission detection unit 26 detects light emission inside treatment vessel 12. In this embodiment, light emission detection unit 26 is an optical fiber. Recording unit 28 is connected to light emission detection unit 26, and analyzes and records the light emission inside treatment vessel 12. In this embodiment, recording unit 28 is a computer equipped with software that analyzes the type and intensity of light, etc.

[0020] In this embodiment, the metal oxide surface treatment apparatus is a capacitively coupled plasma type metal oxide surface treatment apparatus, but it may instead be an inductively coupled plasma type metal oxide surface treatment apparatus. The inductively coupled plasma type metal oxide surface treatment apparatus includes a dielectric treatment vessel, an induction coil provided around the dielectric treatment vessel, an electrode provided in the dielectric treatment vessel on which an object to be treated, which has a transparent electrode layer and a metal oxide layer stacked thereon, is placed so that the metal oxide layer of the object to be treated is exposed, a gas supply unit that introduces oxygen gas into the dielectric treatment vessel, and a high-frequency power source with a frequency of 1 kHz to 40 kHz that supplies power to the induction coil so that oxygen plasma is generated from the oxygen gas introduced from the gas supply unit into the dielectric treatment vessel.

[0021] A method for manufacturing a perovskite solar cell C using the surface treatment device 10 will be described below. FIG. 2 shows a schematic cross section of the perovskite solar cell C. The perovskite solar cell C comprises, in this order, a substrate 34, a transparent electrode layer 32, a layer of metal oxide 30 serving as an electron transport layer, a perovskite crystal layer 36 serving as a power generation layer, a hole transport layer 38, and an upper electrode layer 40. The perovskite crystal layer 36 is formed on the surface of the metal oxide 30 layer.

[0022] In addition to these components, the perovskite solar cell C may also include a diffusion prevention film provided on the light-incident side of the substrate 34, an interface modification film or auxiliary layer provided at the interface between the metal oxide 30 layer serving as the electron transport layer and the perovskite crystal layer 36, an interface modification film or auxiliary layer provided at the interface between the perovskite crystal layer 36 and the hole transport layer 38, or a sealant and moisture getter material that protect the perovskite solar cell C from atmospheric moisture. The perovskite solar cell may also be an inverted solar cell in which the electron transport layer and hole transport layer of the perovskite solar cell C are reversed. This inverted solar cell may employ a structure in which the hole transport layer is a layer of metal oxide 30 and the perovskite crystal layer 36 is formed on this metal oxide 30 layer.

[0023] In this embodiment, the substrate 34 is a glass substrate, the transparent electrode layer 32 is a fluorine-doped tin oxide (FTO) layer, the metal oxide layer 30 is a tin oxide (SnO2) layer composed of nanoparticles, and the perovskite crystal layer 36 is a Cs 0.05 (FA 0.89 MA 0.11 ) 0.95 Pb(I 0.89 Br 0.11 ) three layers (FA is formamidinium, MA is methylamine (same below)), the hole transport layer 38 is a Spiro-OMeTAD (2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene) layer, and the upper electrode layer 40 is a gold layer.

[0024] The method for manufacturing perovskite solar cell C of an embodiment of the present application is a method for manufacturing a perovskite solar cell comprising, in this order, a transparent electrode layer, a metal oxide layer serving as an electron transport layer, a perovskite crystal layer serving as a power generation layer, a hole transport layer, and an upper electrode layer, with the perovskite crystal layer being formed on the surface of the metal oxide layer.The method for manufacturing a perovskite solar cell of another embodiment of the present application is a method for manufacturing a perovskite solar cell comprising, in this order, a transparent electrode layer, a metal oxide layer serving as a hole transport layer, a perovskite crystal layer serving as a power generation layer, an electron transport layer, and an upper electrode layer, with the perovskite crystal layer being formed on the surface of the metal oxide layer.

[0025] The manufacturing method of the perovskite solar cell of each embodiment includes an oxygen plasma generation step, a metal oxide layer surface modification step, and a perovskite crystal layer formation step. Examples of the metal oxide 30 include tin oxide, titanium oxide, nickel oxide, and the like. Examples of the perovskite crystals that make up the perovskite crystal layer 36 include Cs 0.05 (FA 0.89 MA 0.11 ) 0.95 Pb(I 0.89 Br 0.11In addition to )3, examples include CH3NH3PbI3 and CH(NH2)2PbI3. In the method for manufacturing a perovskite solar cell of each embodiment, surface treatment device 10 may be used, or other plasma treatment devices may be used.

[0026] In the oxygen plasma generation process, high-frequency power with a frequency of 1 kHz to 40 kHz is applied to generate oxygen plasma. More specifically, after the interior of the processing vessel 12 is cleaned with oxygen plasma in advance, the workpiece S is placed on the lower electrode 16. Oxygen gas G is introduced between the upper electrode 14 and the lower electrode 16 from an oxygen cylinder connected to the gas supply unit 18. The pressure inside the processing vessel 12 is adjusted to 50 Pa to 1200 Pa, and high-frequency power with a frequency of 1 kHz to 40 kHz and a power of 10 W to 1000 W is supplied from the high-frequency power source 20 between the upper electrode 14 and the lower electrode 16. By setting the power to 100 W to 1000 W, oxygen ions are efficiently generated.

[0027] By supplying this high frequency power, the oxygen gas G is converted into plasma, and oxygen plasma P O is generated. Oxygen plasma P O The pressure inside the processing vessel 12 where oxygen ions are generated is maintained at 1 Pa or more and 200 Pa or less to perform the metal oxide layer surface modification process. By maintaining the pressure at 1 Pa or more and 200 Pa or less, oxygen ions are efficiently generated. In the example described later, when the pressure inside the processing vessel 12 is 500 Pa or less, oxygen ions I O Oxygen plasma containing P O However, this upper limit pressure varies depending on the concentration of oxygen gas supplied to the surface treatment device, the object to be treated, and the treatment vessel. O Oxygen plasma containing P O As long as the pressure inside the processing vessel 12 can be generated, there is no particular limitation.

[0028] In the metal oxide layer surface modification step, oxygen plasma P is applied to the surface of the metal oxide layer 30 of the treatment object S. O Oxygen ions in I O The surface of the metal oxide layer 30 is modified by irradiating the oxygen radicals RO Since the electrons are not charged, they float between the upper electrode 14 and the lower electrode 16 and are hardly irradiated onto the surface of the metal oxide 30. The surface of the metal oxide 30 after modification has almost the same shape as the surface of the metal oxide 30 before modification and has a larger work function.

[0029] Also, oxygen ions I O Since the surface of the metal oxide 30 is modified by plasma, the processing time can be shortened compared to surface modification of the metal oxide 30 using plasma generated from a mixed gas of oxygen gas containing less than 90 vol% oxygen and other gases. For example, in the metal oxide layer surface modification step of this embodiment, which uses plasma generated from a gas containing 90 vol% or more oxygen gas, surface modification can be completed in less than 40 seconds, whereas metal oxide surface modification using plasma of a mixed gas containing equal amounts of oxygen gas and argon gas requires processing time of 2 minutes or more, and metal oxide surface modification by UV irradiation of ozone requires processing time of 20 minutes or more.

[0030] The metal oxide surface treatment method of the present embodiment includes the oxygen plasma generation step and the metal oxide surface modification step. In the metal oxide surface modification step, the surface of the metal oxide is modified by irradiating the surface of the metal oxide with oxygen ions in the oxygen plasma. This metal oxide surface treatment method also serves as a method for producing a surface-modified metal oxide. In the perovskite crystal layer formation step, a perovskite crystal layer is formed on the surface of the metal oxide layer modified in the metal oxide layer surface modification step. For example, a perovskite crystal layer can be formed on the surface of the modified metal oxide layer by applying a perovskite crystal precursor to the surface of the modified metal oxide layer and drying it.

[0031] Other steps for manufacturing the perovskite solar cell C can be performed, for example, as follows. Using methods such as spin coating, sputtering, vacuum deposition, spray coating, die coating, gravure printing, or screen printing, a transparent electrode layer 32 is formed on a glass substrate 34, a metal oxide 30 is formed on the transparent electrode layer 32, a hole transport layer 38 is formed on a perovskite crystal layer 36, and an upper electrode layer 40 is formed on the hole transport layer 38. These methods can also be used to form the perovskite crystal layer 36 on the metal oxide 30 layer. The same applies to inverted structure solar cells, where these methods are used to form a transparent electrode layer 32 on a glass substrate 34, a metal oxide 30 layer (hole transport layer) on the transparent electrode layer 32, a perovskite crystal layer 36 on the metal oxide 30 layer, an electron transport layer on the perovskite crystal layer 36, and an upper electrode layer 40 on the electron transport layer. [Example]

[0032] Reference example As the metal oxide surface treatment device, a plasma treatment device (Diener, FEMTO (frequency of high frequency power supply: 40 kHz, maximum power: 100 W)) having the structure shown in FIG. 1 was used. A dry pump (Anest Iwata, ISP-50) was connected to the exhaust port 22, and an oxygen cylinder (oxygen gas concentration: 99.5 vol%) was connected to the gas supply unit 18. Oxygen gas G was introduced into the treatment container 12, and oxygen plasma P was generated so that the pressure inside the treatment container 12 was set to 10 levels from 100 Pa to 1000 Pa. O The emission spectroscopic analysis chart at this time is shown in Figure 3.

[0033] As shown in Figure 3, when the pressure is 100 Pa and 200 Pa, oxygen ions (O2 + and O + ) and oxygen radicals (O2 * ) was observed, and at pressures of 300 Pa, 400 Pa, and 500 Pa, oxygen ions (O2 + ) and oxygen radicals (O2 * ) was observed, and when the pressure was above 600 Pa, oxygen ions (O2+ and O + ) was not observed, and the emission from oxygen radicals (O2 * ) was observed. In other words, oxygen ions were generated more efficiently at lower pressures, specifically at pressures of 200 Pa or less. However, oxygen plasma was generated at pressures of 1 Pa or more.

[0034] Example 1: Surface treatment of tin oxide with oxygen ions A tin oxide surface treatment was performed using the plasma treatment device of the reference example. First, a 15% by mass aqueous dispersion of tin (IV) oxide (Alfa Aesar) was dropped and spin-coated onto the FTO surface of an FTO-attached glass (Nippon Sheet Glass Co., Ltd., NSG TEC 10), and the resulting substrate was dried at 150°C for 1 hour to obtain a substrate having a glass substrate, an FTO layer serving as a transparent electrode layer, and a tin oxide layer serving as an electron transport layer stacked in this order.

[0035] Next, the workpiece was placed on the lower electrode so that the tin oxide faced the upper electrode. To remove moisture and nitrogen from the atmosphere, the pressure inside the processing chamber was reduced to 20 Pa or less by evacuation. To generate plasma, oxygen gas was introduced into the processing chamber, the pressure inside the processing chamber was maintained at 100 Pa, and 100 W of high-frequency power was supplied between the upper and lower electrodes to perform plasma cleaning for 30 seconds.

[0036] The object was then heated at 150°C for 1 hour to remove the solvent contained therein. Oxygen gas was then introduced into the treatment vessel, and the pressure inside the treatment vessel was maintained at 100 Pa. High-frequency power of 100 W was supplied between the upper and lower electrodes to convert the oxygen gas into plasma, generating oxygen plasma. This oxygen plasma contained more oxygen radicals and oxygen ions than the reference example. The oxygen ions in the oxygen plasma were then used to perform surface treatment of tin oxide for 30 seconds.

[0037] Comparative Example 1: Surface treatment of tin oxide with ozone Using a tabletop surface treatment device (Sen Special Light Sources Co., Ltd., SSP16-110), the same tin oxide surface treatment was performed on the same object to be treated as in Example 1. First, the object to be treated was heated at 150°C for 1 hour. Next, the object to be treated was placed in the tabletop surface treatment device. Then, the UV light source was turned on, and the tin oxide surface treatment was performed for 20 minutes using ozone generated by UV irradiation.

[0038] Comparative Example 2: Surface treatment of tin oxide with oxygen radicals Surface treatment of tin oxide was carried out in the same manner as in Example 1, except that the pressure during oxygen plasma generation was changed to 1000 Pa and the surface treatment time was changed to 50 seconds. The oxygen plasma at a pressure of 1000 Pa contains only oxygen radicals, as compared to the reference example. Because the pressure inside the treatment vessel is higher than in Example 1, the oxygen radicals fall quickly due to gravity and are irradiated onto the workpiece, modifying the surface of the tin oxide.

[0039] Example 2: Evaluation of tin oxide surface treatment (1) Work function of tin oxide The work function of the tin oxide surface before the surface treatment (untreated) and after the surface treatments of Example 1, Comparative Example 1, and Comparative Example 2 was calculated using UPS (ultraviolet photoelectron spectroscopy). The work functions of the tin oxide surface before the surface treatment and after the surface treatments of Example 1, Comparative Example 1, and Comparative Example 2 were 3.79 eV, 4.12 eV, 4.06 eV, and 4.04 eV, respectively. The surface treatment increased the work function of the tin oxide surface. Furthermore, in Example 1, the work function of the tin oxide surface after the surface treatment was higher than in Comparative Examples 1 and 2. This is the effect of efficiently repairing oxygen defects in the tin oxide by oxygen ions.

[0040] The conduction band level of the perovskite crystal layer used in perovskite solar cells is generally between 3.5 eV and 4.5 eV, depending on the perovskite material. To reduce the interfacial resistance between the perovskite crystal and the metal oxide and improve electron extraction efficiency, it is preferable to bring the work function of the metal oxide closer to the conduction band level of the perovskite crystal layer, or to make the work function of the metal oxide approximately 0.2 eV higher than the conduction band level of the perovskite crystal layer. Since the work function of the tin oxide after the surface treatment in Example 1 was 4.12 eV, the efficiency of electron extraction from this tin oxide to the perovskite crystal was high.

[0041] (2) Surface roughness of tin oxide To determine whether the tin oxide surface was damaged by plasma, the tin oxide surface was observed using an atomic force microscope (AFM) (SII NanoTechnology, Inc., E-sweep) and the root mean square roughness (RMS) was evaluated. Figure 4 shows atomic force microscope images of the tin oxide surface before and after the surface treatments of Example 1, Comparative Example 1, and Comparative Example 2. As shown in Figure 4, the tin oxide surface shape remained almost unchanged before and after the surface treatment. Furthermore, the RMS values ​​of the tin oxide surface before and after the surface treatments of Example 1, Comparative Example 1, and Comparative Example 2 were 13.71 nm, 13.63 nm, 14.32 nm, and 12.72 nm, respectively. These similar RMS values ​​indicated that the surface treatment did not cause any damage that would change the tin oxide surface shape.

[0042] (3) Solar cell characteristics Dissolve 123 mg of FAI, 382 mg of PbI, 14 mg of MABr, 36 mg of PbBr, and 29 μL of a 1.5 M DMSO solution of CsI in a mixture of 560 μL of DMF and 140 μL of DMSO. 0.05 (FA 0.89 MA 0.11 ) 0.95 Pb(I 0.89 Br 0.11A precursor solution of 3 was prepared. This precursor solution was spin-coated at 1000 rpm for 10 seconds onto the tin oxide surface of the workpieces obtained in Example 1, Comparative Example 1, and Comparative Example 2, and then a small amount of chlorobenzene was further spin-coated at 6000 rpm for 20 seconds to obtain a uniform perovskite precursor thin film. Next, the solution was heated on a hot plate at 100°C for 1 hour to obtain a Cs 0.05 (FA 0.89 MA 0.11 ) 0.95 Pb(I 0.89 Br 0.11 ) Three layers were formed.

[0043] 61 mg of Spiro-OMeTAD and 10 mg of LiTFSI were dissolved in 0.7 mL of chlorobenzene, and 22 μL of 4-tert-butylpyridine was added to obtain a Spiro-OMeTAD precursor solution. 0.05 (FA 0.89 MA 0.11 ) 0.95 Pb(I 0.89 Br 0.11 The Spiro-OMeTAD precursor solution was spin-coated on the surfaces of the three layers at 3000 rpm for 30 seconds. The resulting solution was then dried at 65°C for 10 minutes to form a Spiro-OMeTAD layer. A 50-nm-thick gold layer was then deposited on the surface of the Spiro-OMeTAD layer using a vacuum deposition machine to obtain a solar cell component.

[0044] A sealing member was obtained by carrying calcium oxide 52 in the center of the surface of a glass plate 50 and applying a 0.05 mm thick, 0.2 mm wide ultraviolet-curing adhesive 54 containing glass spheres with a diameter of 10 μm around the periphery as spacers. The sealing member was then placed on top of this solar cell member in a nitrogen atmosphere, and ultraviolet light was applied to cure the adhesive 54, producing perovskite solar cells from the treated bodies obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 6 shows a schematic cross-section of these perovskite solar cells.

[0045] The characteristics of these perovskite solar cells were evaluated. Using a solar simulator (OTENTO-SUN, manufactured by Bunkoukeiki Co., Ltd.), these perovskite solar cells were exposed to simulated sunlight of AM1.5 (intensity 1000 W / m 2 The short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency were determined from the current-voltage curves plotted using a source meter (Keithley 2400, manufactured by Keithley Instruments, Inc.). The results are shown in Table 1.

[0046] [Table 1]

[0047] As shown in Table 1, the perovskite solar cell manufactured from the treated body obtained in Example 1 had a higher open-circuit voltage than the perovskite solar cell manufactured from the treated body obtained in Comparative Example 1. This is due to the effect of increasing the work function of the tin oxide surface by surface treatment of the tin oxide with oxygen ions.

[0048] The light durability of the perovskite solar cells manufactured from the treated bodies obtained in Example 1, Comparative Example 1, and Comparative Example 2 was evaluated. Using a small light irradiation environment testing system (manufactured by ESPEC), these perovskite solar cells were exposed to simulated sunlight of AM1.5 (intensity 1000 W / m) at 25°C and humidity 30%. 2 ) was continuously irradiated. The photoelectric conversion efficiency was determined from a curve plotting the current-voltage relationship using a source meter at predetermined time intervals, and the ratio of the determined photoelectric conversion efficiency to the initial photoelectric conversion efficiency was calculated. The results are shown in Figure 5. As shown in Figure 5, the perovskite solar cell manufactured from the treated body obtained in Example 1 had higher light durability than other perovskite solar cells. This is because the oxygen vacancies on the tin oxide surface were repaired by the tin oxide surface treatment in Example 1, improving light durability mainly in the visible light region.

[0049] Example 3: Surface treatment of titanium oxide with oxygen ions A titanium diisopropoxide acetylacetonate solution (Aldrich) was diluted with ethanol to a titanium compound concentration of 6% by mass to obtain a titanium oxide precursor liquid. This titanium oxide precursor liquid was sprayed onto the FTO surface of FTO-attached glass (Nippon Sheet Glass Co., Ltd., NSG TEC 10) using an airbrush in a 400°C environment, and then dried at 500°C for 10 minutes to obtain a treated object consisting of a glass substrate, an FTO layer, and a titanium oxide layer used as an electron transport layer in a normal structure perovskite solar cell, stacked in this order. The titanium oxide surface of this treated object was treated with oxygen ions in the same manner as in Example 1.

[0050] Comparative Example 3: Surface treatment of titanium oxide with ozone An object to be treated having a titanium oxide layer was obtained in the same manner as in Example 3, and the surface of the titanium oxide of this object to be treated was treated with ozone in the same manner as in Comparative Example 1.

[0051] Comparative Example 4: Surface treatment of titanium oxide with oxygen radicals An object to be treated having a titanium oxide layer was obtained in the same manner as in Example 3, and the surface of the titanium oxide of this object to be treated was subjected to oxygen radical treatment in the same manner as in Comparative Example 2.

[0052] Example 4: Evaluation of surface treatment of titanium oxide The surface work function of titanium oxide before surface treatment (untreated) and after surface treatment in Example 3, Comparative Example 3, and Comparative Example 4 was calculated in the same manner as in Example 2(1). The surface work functions of titanium oxide before surface treatment and after surface treatment in Example 2, Comparative Example 3, and Comparative Example 4 were 3.87 eV, 4.12 eV, 4.27 eV, and 4.34 eV, respectively. The surface work function of titanium oxide increased due to the surface treatment. Furthermore, the surface work function of titanium oxide after surface treatment in Example 3 was higher than that in Comparative Examples 3 and 4. This is due to the effect of oxygen ions efficiently repairing oxygen defects in titanium oxide. For the same reasons as in Example 2(1), the work function of titanium oxide after surface treatment in Example 3 was 4.12 eV, indicating high electron extraction efficiency from this titanium oxide to the perovskite crystal.

[0053] Example 5: Surface treatment of nickel oxide with oxygen ions We performed surface treatment on nickel oxide, which is used as a hole transport layer in inverted perovskite solar cells. First, a 2.5% by mass ethanol dispersion of nickel(II) oxide (AVANTAMA) was dropped and spin-coated onto the FTO surface of a glass substrate (NSG TEC 10, Nippon Sheet Glass Co., Ltd.), and the substrate was dried at 150°C for 1 hour to obtain a treated object consisting of a glass substrate, an FTO layer, and a nickel oxide layer stacked in that order.

[0054] Comparative Example 5: Surface treatment of nickel oxide with ozone An object to be treated having a nickel oxide layer was obtained in the same manner as in Example 5, and the surface of the nickel oxide of this object to be treated was treated with ozone in the same manner as in Comparative Example 1.

[0055] Comparative Example 6: Surface treatment of nickel oxide with oxygen radicals An object to be treated having a nickel oxide layer was obtained in the same manner as in Example 5, and the surface of the nickel oxide of this object to be treated was subjected to oxygen radical treatment in the same manner as in Comparative Example 2.

[0056] Example 6: Evaluation of nickel oxide surface treatment In the same manner as in Example 2(1), the work function of the surface of nickel oxide was calculated before the surface treatment (untreated) and after the surface treatments of Example 5, Comparative Example 5, and Comparative Example 6. The work functions of the surface of nickel oxide before the surface treatment and after the surface treatments of Example 5, Comparative Example 5, and Comparative Example 6 were 5.16 eV, 5.43 eV, 5.59 eV, and 5.52 eV, respectively. The surface treatment increased the work function of the surface of nickel oxide.

[0057] The valence band level of the perovskite crystal layer used in perovskite solar cells is generally between 4.5 eV and 6.0 eV, depending on the perovskite material, and is around 5.5 eV for commonly used perovskite crystals. In order to reduce the interfacial resistance between the perovskite crystal and the metal oxide and improve the hole extraction efficiency, it is preferable to bring the work function of the metal oxide closer to the valence band level of the perovskite crystal layer. The work function of the nickel oxide after the surface treatment in Example 5 was 5.43 eV, so the hole extraction efficiency from this nickel oxide to the perovskite crystal was high. [Explanation of symbols]

[0058] 10 Surface treatment equipment 12 Processing container 14 Upper electrode 16 Lower electrode 18 Gas supply section 20 High frequency power supply 22 Exhaust port 24 Observation window 26 Luminescence detection unit 28 Recording Section 30 Metal Oxides 32 Transparent electrode layer 34 PCB 36 Perovskite crystal layer 38 Hole transport layer 40 Upper electrode layer 50 Glass Plate 52 Calcium oxide 54 UV-curing adhesive C Perovskite Solar Cell S: Object to be treated P O oxygen plasma R O oxygen radicals I O oxygen ions G. Oxygen gas

Claims

1. A method for manufacturing a perovskite solar cell comprising, in this order, a transparent electrode layer, a metal oxide layer serving as an electron transport layer, a perovskite crystal layer serving as a power generation layer, a hole transport layer, and an upper electrode layer, wherein the perovskite crystal layer is formed on a surface of the metal oxide layer, comprising: an oxygen plasma generating step of applying power having a frequency of 1 kHz to 40 kHz to generate oxygen plasma; a metal oxide layer surface modification step of modifying a surface of the metal oxide layer of a treatment object including the transparent electrode layer and the metal oxide layer by the oxygen plasma generated in the oxygen plasma generation step; a perovskite crystal layer forming step of forming the perovskite crystal layer on the surface of the metal oxide layer modified by the metal oxide layer surface modifying step; and the metal oxide layer surface modification step is a step of irradiating the surface of the metal oxide layer with oxygen ions in the oxygen plasma.

2. A method for manufacturing a perovskite solar cell comprising, in this order, a transparent electrode layer, a metal oxide layer serving as a hole transport layer, a perovskite crystal layer serving as a power generation layer, an electron transport layer, and an upper electrode layer, wherein the perovskite crystal layer is formed on a surface of the metal oxide layer, comprising: an oxygen plasma generating step of applying power having a frequency of 1 kHz to 40 kHz to generate oxygen plasma; a metal oxide layer surface modification step of modifying a surface of the metal oxide layer of a treatment object including the transparent electrode layer and the metal oxide layer by the oxygen plasma generated in the oxygen plasma generation step; a perovskite crystal layer forming step of forming the perovskite crystal layer on the surface of the metal oxide layer modified by the metal oxide layer surface modifying step; and the metal oxide layer surface modification step is a step of irradiating the surface of the metal oxide layer with oxygen ions in the oxygen plasma.

3. A method for manufacturing a perovskite solar cell according to claim 1 or 2, A method for producing a perovskite solar cell, wherein the metal oxide of the metal oxide layer is tin oxide, titanium oxide, or nickel oxide.

4. A method for manufacturing a perovskite solar cell according to claim 1 or 2, The method for manufacturing a perovskite solar cell, wherein the oxygen plasma generating step and the metal oxide layer surface modifying step are carried out in an atmosphere with a pressure of 1 Pa or more and 200 Pa or less.

5. A method for manufacturing a perovskite solar cell according to claim 1 or 2, The method for manufacturing a perovskite solar cell, wherein the power is 50 W or more and 1000 W or less.

6. A processing vessel; an upper electrode provided in the processing chamber; a lower electrode that is provided in the processing vessel so as to be grounded, and on which a perovskite solar cell having a transparent electrode layer, a metal oxide layer, and a perovskite crystal layer stacked thereon is placed so that the metal oxide layer of the perovskite solar cell is exposed; a gas supply unit that introduces oxygen gas into the processing vessel; a power supply that supplies power between the upper electrode and the lower electrode so that oxygen plasma is generated from the oxygen gas introduced between the upper electrode and the lower electrode from the gas supply unit; an exhaust port; The power supply supplies power at a frequency of 1 kHz to 40 kHz and 100 W to 1000 W, and generates the oxygen plasma from a gas containing 90 vol % or more of oxygen gas introduced from the gas supply unit in the processing chamber at a pressure of 1 Pa to 200 Pa, irradiating the surface of the metal oxide layer with charged oxygen ions in the oxygen plasma, and floating uncharged oxygen radicals in the oxygen plasma between the upper electrode and the lower electrode, and exhausting them through the exhaust port; a metal oxide surface treatment device for forming the perovskite crystal layer on the metal oxide layer irradiated with the oxygen ions;

7. A dielectric processing vessel; an induction coil provided around the dielectric processing vessel; an electrode provided in the dielectric treatment vessel, on which a perovskite solar cell having a transparent electrode layer, a metal oxide layer, and a perovskite crystal layer stacked thereon is placed so that the metal oxide layer of the perovskite solar cell is exposed; a gas supply unit that introduces oxygen gas into the dielectric processing chamber; a power supply that supplies power to the induction coil so that oxygen plasma is generated from the oxygen gas introduced into the dielectric processing vessel from the gas supply unit; an exhaust port; the power supply supplies power at a frequency of 1 kHz to 40 kHz and 100 W to 1000 W, and generates the oxygen plasma from a gas containing 90 vol % or more of oxygen gas introduced from the gas supply unit in the dielectric processing chamber at a pressure of 1 Pa to 200 Pa; irradiating the surface of the metal oxide layer with charged oxygen ions in the oxygen plasma and discharging uncharged oxygen radicals in the oxygen plasma through the exhaust port; a metal oxide surface treatment device for forming the perovskite crystal layer on the metal oxide layer irradiated with the oxygen ions;

Images