WO2023132259A1

WO2023132259A1 - Method for treating surface of metal oxide, method for manufacturing perovskite solar cell, and metal oxide surface treatment device

Info

Publication number: WO2023132259A1
Application number: PCT/JP2022/047340
Authority: WO
Inventors: 晃平山本; 拓郎村上; 郵司吉田
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2022-01-06
Filing date: 2022-12-22
Publication date: 2023-07-13

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 P_O, and a metal oxide surface modification step for irradiating the surface of the metal oxide 30 with oxygen ions I_O in the oxygen plasma P_O to modify the surface of the metal oxide 30.

Description

Metal oxide surface treatment method, perovskite solar cell manufacturing method, and metal oxide surface treatment apparatus

This application relates to a method of treating the surface of metal oxides used in the electron transport layer of perovskite solar cells, etc., using oxygen ions in oxygen plasma. The present application also relates to a method of manufacturing a perovskite solar cell, including a method of treating the surface of this metal oxide. The present application also relates to a metal oxide surface treatment apparatus suitable for carrying out this method of treating the surface of metal oxides.

In recent years, attention has been paid to perovskite solar cells that comprise a transparent electrode layer, an electron transport layer, a perovskite crystal layer, a hole transport layer, and an electrode layer in this order. In order to improve the adhesion between the metal oxide and the perovskite crystal layer that constitute the electron transport layer of the perovskite solar cell and to reduce the interfacial resistance, the surface of the metal oxide is subjected to modification treatment. Patent Document 1 describes a method of modifying the surface of an ITO substrate using mixed gas plasma of argon gas and oxygen gas.

In Patent Document 1, the ITO substrate surface is modified for 2 minutes. On the other hand, there is also known a method of modifying the surface of the metal oxide that constitutes the electron transport layer of the perovskite solar cell by UV irradiation of ozone, which does not require a plasma treatment apparatus. However, even with this UV irradiation of ozone, it takes about 20 minutes to modify the surface of the metal oxide. In order to reduce the cost of mass-producing perovskite solar cells, it is necessary to improve the surface treatment speed of metal oxides.

Japanese Patent Application Laid-Open No. 2001-284059

The present application has been made in view of such circumstances, and the object of the present application is to treat the surface of metal oxides used as the electron transport layer of perovskite solar cells in a short period of time.

The metal oxide surface treatment method of the present application comprises an oxygen plasma generation step of supplying high-frequency power with a frequency of 1 kHz or more and 40 kHz or less to generate oxygen plasma, and irradiating the surface of the metal oxide with oxygen ions in the oxygen plasma. and a metal oxide surface modification step of modifying the surface of the metal oxide.

A method for producing a perovskite solar cell of the present application comprises: a transparent electrode layer, a metal oxide layer that is an electron transport layer or a hole transport layer; a perovskite crystal layer that is a power generation layer; a hole transport layer or an electron transport layer; and an electrode layer in this order, and a perovskite crystal layer is formed on the surface of the metal oxide layer, wherein high-frequency power with a frequency of 1 kHz or more and 40 kHz or less is applied to generate oxygen plasma. and irradiating oxygen ions in the oxygen plasma to the surface of the metal oxide layer of the object to be treated, which includes the transparent electrode layer and the metal oxide layer, to modify the surface of the metal oxide layer. and a perovskite crystal layer forming step of forming a perovskite crystal layer on the surface of the metal oxide layer modified by the metal oxide layer surface modification step.

A metal oxide surface treatment apparatus according to one aspect of the present application includes a processing container, an upper electrode provided in the processing container, and a transparent electrode layer and a metal oxide layer provided in the processing container so as to be grounded. a lower electrode on which the object to be processed is placed so as to expose the metal oxide layer of the object to be processed, a gas supply unit for introducing oxygen gas into the processing container, and the upper electrode and the lower electrode from the gas supply unit a high-frequency power source with a frequency of 1 kHz or more and 40 kHz or less for supplying power between the upper electrode and the lower electrode so that oxygen plasma is generated from the oxygen gas introduced between.

A metal oxide surface treatment apparatus according to another aspect of the present application includes a dielectric processing container, an induction coil provided around the dielectric processing container, and a transparent electrode layer and a metal oxide provided in the dielectric processing container. An electrode on which the object to be processed is installed so that the metal oxide layer of the object to be processed on which layers are laminated is exposed, a gas supply unit for introducing oxygen gas into the dielectric processing container, and a dielectric from the gas supply unit a high-frequency power supply with a frequency of 1 kHz or more and 40 kHz or less for supplying power to the induction coil so as to generate oxygen plasma from the oxygen gas introduced into the body treatment container.

In the metal oxide surface treatment method of the present application, the surface of the metal oxide is irradiated with oxygen ions of oxygen plasma generated by high-frequency power with a frequency of 1 kHz or more and 40 kHz or less. Therefore, according to the metal oxide surface treatment method of the present application, the surface of the metal oxide can be treated in a short time. Further, the method of manufacturing a perovskite solar cell of the present application includes a step of irradiating the surface of the metal oxide layer with oxygen ions of oxygen plasma generated by high-frequency power having a frequency of 1 kHz or more and 40 kHz or less. Therefore, according to the method for manufacturing a perovskite solar cell of the present application, a perovskite solar cell can be manufactured in a short time. The metal oxide surface treatment apparatus of the present application is configured to irradiate the surface of the metal oxide layer with oxygen ions of oxygen plasma generated by high-frequency power having a frequency of 1 kHz to 40 kHz. Therefore, according to the metal oxide surface treatment apparatus of the present application, the surface of the metal oxide layer can be treated in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS The cross-sectional schematic diagram of the metal oxide surface treatment apparatus of embodiment. 1 is a schematic cross-sectional view of a perovskite solar cell according to an embodiment; FIG. An emission spectroscopic analysis chart of oxygen plasma of a reference example. An atomic force microscope image of Example 2. 4 is a graph showing the relationship between the light irradiation time and the photoelectric conversion efficiency of the perovskite solar cell of Example 2. FIG. 4 is a schematic cross-sectional view of the perovskite solar cell of Example 2. FIG.

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 apparatus of the present application will be described based on embodiments and examples with reference to the drawings as appropriate. The metal oxide surface treatment method of the present application will be described as part of the method of manufacturing the perovskite solar cell of the present application. Also, since the metal oxide surface treatment apparatus and perovskite solar cell in the drawings are schematic representations of their configurations, they do not match the dimensional ratios of the actual metal oxide surface treatment apparatus and perovskite solar cell. . The same reference numerals may be given to the same members, and repeated explanations will be omitted as appropriate.

FIG. 1 schematically shows a 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 application. The surface treatment apparatus 10 includes a processing vessel 12, an upper electrode 14, a lower electrode 16, a gas supply section 18, a high frequency power source 20, an exhaust port 22, an observation window 24, an emission detection section 26, and a recording section. 28. The surface treatment apparatus 10 treats the surface of the metal oxide 30 forming the electron transport layer of the object S to be treated with oxygen ions in oxygen plasma, which will be described later. In this application, the metals of the metal oxides are Al, Si, Sc with atomic number 21 to As with atomic number 33, Y with atomic number 38 to Sb with atomic number 51, and La with atomic number 57 to atomic number Up to Po of 84.

The processing container 12 is made of a conductor material, such as an aluminum alloy, and is grounded. The upper electrode 14 is provided inside the processing container 12 and is made of a conductive material such as carbon. The lower electrode 16 is provided inside the processing container 12 so as to face the upper electrode 14 . The bottom electrode 16 is made of a conductive material such as carbon and is grounded. An object S to be processed is placed on the lower electrode 16 . The object S to be processed includes a transparent electrode layer 32 which is a constituent member of the perovskite solar cell C, and a layer of metal oxide 30 which is an electron transport layer formed on the transparent electrode layer 32 . In this embodiment, a transparent electrode layer 32 and a layer of metal oxide 30 are laminated on a substrate 34 made of glass. Then, the object S to be processed is placed on the lower electrode 16 so that the layer of the metal oxide 30 is exposed.

The gas supply unit 18 is connected to the processing container 12 and introduces oxygen gas G into the processing container 12 . A 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 having a frequency of 1 kHz or more and 40 kHz or less between the upper electrode 14 and the lower electrode 16, that is, supplies electric power. When electric power is supplied between the upper electrode 14 and the lower electrode 16 from the high-frequency power source 20, the oxygen gas G introduced between the upper electrode 14 and the lower electrode 16 from the gas supply section 18 is plasmatized to generate oxygen. Plasma _PO is generated.

By setting the frequency of the high-frequency power to 40 kHz or less, oxygen plasma P ₀ , that is, oxygen radicals R _{2 O} and oxygen ions I 2 _O can be efficiently generated. Further, by setting the frequency of the high-frequency power to 1 kHz or higher, the oxygen gas G can be turned 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 a plasma generated from a gas containing 95 vol% or more of oxygen gas, more preferably a plasma generated from a gas containing 99 vol% or more of oxygen gas, and substantially composed of only oxygen gas. More preferably, the plasma is generated from a gas that

Oxygen gas composed substantially only of oxygen is oxygen gas that does not contain impurities other than unavoidable impurities. For example, oxygen gas supplied from a commercially available oxygen gas cylinder is oxygen gas substantially composed only of oxygen. Since the lower electrode 16 is grounded in the surface treatment apparatus 10, the oxygen ions _I.sub.2O in the oxygen plasma _P.sub.2O reach the surface of the metal oxide 30 considerably faster than the oxygen radicals _R.sub.2O . The surface of the metal oxide 30 is modified by the oxygen ions I 2 _O that have reached the surface of the metal oxide 30 .

The exhaust port 22 discharges substances and oxygen radicals generated when the surface of the metal oxide 30 is treated with oxygen ions to the outside of the processing container 12 by an exhaust pump (not shown). Exhaust pumps include, for example, dry pumps, rotary pumps, or turbomolecular pumps that produce a high vacuum. In general, high vacuum increases the mean free path of plasma and improves plasma generation efficiency, so use of a turbo-molecular pump is preferred.

The observation window 24 is a window for observing the inside of the processing container 12 from the outside, and is made of quartz, for example. The luminescence detector 26 detects luminescence within the processing container 12 . In this embodiment, the light emission detector 26 is an optical fiber. The recording unit 28 is connected to the luminescence detection unit 26 to analyze and record luminescence within the processing container 12 . In this embodiment, the recording unit 28 is a computer equipped with software for analyzing the type and intensity of light.

In this embodiment, the metal oxide surface treatment apparatus is a capacitively coupled plasma type metal oxide surface treatment apparatus, but instead of this, an inductively coupled plasma type metal oxide surface treatment apparatus is used. good too. An inductively coupled plasma type metal oxide surface treatment apparatus comprises: a dielectric processing container; an induction coil provided around the dielectric processing container; An electrode on which the object to be processed is installed so that the metal oxide layer of the object to be processed on which layers are laminated is exposed, a gas supply unit for introducing oxygen gas into the dielectric processing container, and a dielectric from the gas supply unit a high-frequency power supply having a frequency of 1 kHz or more and 40 kHz or less for supplying power to the induction coil so as to generate oxygen plasma from the oxygen gas introduced into the body treatment container.

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

In the perovskite solar cell C, in addition to these constituent members, a diffusion prevention film provided on the light incident side of the substrate 34 and an interface between the metal oxide 30 layer as the electron transport layer and the perovskite crystal layer 36 are provided. An interface modification film or auxiliary layer, 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 sealing material and moisture for protecting the perovskite solar cell C from atmospheric moisture A getter material may be provided. Moreover, the perovskite solar cell may be an inverted structure solar cell in which the electron transport layer and the hole transport layer in the perovskite solar cell C are exchanged. In this inverted structure solar cell, a structure in which the hole transport layer is a layer of metal oxide 30 and a perovskite crystal layer 36 is formed on the layer of metal oxide 30 can be adopted.

In this embodiment, the substrate 34 is a glass substrate, the transparent electrode layer 32 is an FTO (fluorine-doped tin oxide) layer, and the metal oxide 30 layer is a tin oxide (SnO ₂ ) layer composed of nanoparticles. and the perovskite crystal layer 36 is Cs _0.05 (FA _0.89 MA _0.11 ) _0.95 Pb(I _0.89 Br _0.11 ) _three layers (FA is formidinium, MA is methylamine (hereinafter the same) ), the hole-transporting layer 38 is a Spiro-OMeTAD (2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene) layer, The upper electrode layer 40 is a gold layer.

A method for manufacturing a perovskite solar cell C according to an embodiment of the present application includes a transparent electrode layer, a metal oxide layer as an electron transport layer, a perovskite crystal layer as a power generation layer, a hole transport layer, and an upper electrode layer. , in this order, and the perovskite crystal layer is formed on the surface of the metal oxide layer. A method for manufacturing a perovskite solar cell according to another embodiment of the present application includes a transparent electrode layer, a metal oxide layer that is a hole transport layer, a perovskite crystal layer that is a power generation layer, an electron transport layer, and an upper electrode layer. are provided in this order, and the perovskite crystal layer is formed on the surface of the metal oxide layer.

A method for manufacturing a perovskite solar cell according to 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 titanium oxide and nickel oxide, in addition to tin oxide. As perovskite crystals forming _the

perovskite crystal

_layer 36, in addition to _Cs0.05 ₍ _FA0.89MA0.11 ) _0.95Pb ( _I0.89Br0.11 ) ₃ _, _CH3NH3PbI3 and CH(NH ₂ ) ₂ PbI ₃ and the like. In addition, in the method for manufacturing a perovskite solar cell according to each embodiment, the surface treatment apparatus 10 may be used, or another plasma treatment apparatus may be used.

In the oxygen plasma generation step, high-frequency power with a frequency of 1 kHz or more and 40 kHz or less is applied to generate oxygen plasma. More specifically, after cleaning the inside of the processing chamber 12 in advance with oxygen plasma, the object S to be processed is placed on the lower electrode 16, and the upper electrode 14 and the lower electrode are supplied from an oxygen tank connected to the gas supply unit 18. 16, the pressure in the processing container 12 is set to 50 Pa or more and 1200 Pa or less, and the power of 10 W is applied from the high frequency power supply 20 between the upper electrode 14 and the lower electrode 16 at a frequency of 1 kHz or more and 40 kHz or less. A high frequency power of 1000 W or more is supplied. Oxygen ions are efficiently generated by setting the power to 100 W or more and 1000 W or less.

The supply of this high-frequency power converts the oxygen gas G into plasma, generating oxygen plasma _PO . The pressure in the processing container 12 where the oxygen plasma P 2 _O is generated is maintained at 1 Pa or more and 200 Pa or less, and the metal oxide layer surface modification step is performed. Oxygen ions are efficiently generated by setting the pressure to 1 Pa or more and 200 Pa or less. In Examples described later, oxygen plasma P 2 _O containing oxygen ions I _{2 O} was generated when the pressure in the processing container 12 was 500 Pa or less. However, this upper limit pressure varies depending on the surface treatment apparatus, the object to be treated, the concentration of the oxygen gas supplied into the treatment container, and the like. Therefore, as long as oxygen plasma P 2 _O containing oxygen ions I 2 _O can be generated, the pressure inside the processing container 12 is not particularly limited.

In the metal oxide layer surface modification step, the surface of the metal oxide 30 layer of the object S to be processed is irradiated with oxygen ions I 2 _O in the oxygen plasma P 2 _O to modify the surface of the metal oxide 30 layer. question. Since the oxygen radicals R 2 _O are not charged, they float between the upper electrode 14 and the lower electrode 16, and the surface of the metal oxide 30 is hardly irradiated. The surface of the metal oxide 30 after modification has substantially the same shape and a larger work function than the surface of the metal oxide 30 before modification.

In addition, since the surface of the metal oxide 30 is modified by the oxygen ions I 2 _O , the surface of the metal oxide 30 is generated by plasma generated from a mixed gas of oxygen gas containing less than 90 vol % of oxygen gas and other gases. Processing time can be shortened compared to reforming. For example, in the metal oxide layer surface modification step of the present embodiment using plasma generated from a gas containing 90 vol % or more of oxygen gas, the surface modification can be performed in less than 40 seconds, whereas the treatment time is It takes 2 minutes or more for metal oxide surface modification using plasma of a mixed gas containing equal amounts of oxygen gas and argon gas, and 20 minutes or more for metal oxide surface modification by UV irradiation of ozone.

The metal oxide surface treatment method of the embodiment of the present application includes the above oxygen plasma generation step and the above metal oxide surface modification step. In the metal oxide surface modification step, the surface of the metal oxide is irradiated with oxygen ions in oxygen plasma to modify the surface of the metal oxide. This method for surface treatment of metal oxides is also a method for producing metal oxides whose surfaces have been modified. In the perovskite crystal layer forming 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.

Other processes for manufacturing the perovskite solar cell C can be performed, for example, as follows. A transparent electrode layer 32 is formed on a glass substrate 34 using a spin coating method, a sputtering method, a vacuum deposition method, a spray film forming method, a die coating method, a gravure printing method, a screen printing method, or the like. A metal oxide 30 is formed on the substrate, a hole transport layer 38 is formed on the perovskite crystal layer 36, and an upper electrode layer 40 is formed on the hole transport layer 38, respectively. These methods can also be employed when forming the perovskite crystal layer 36 on the layer of metal oxide 30 . The same is true for the reverse structure solar cell. Using these methods, a transparent electrode layer 32 is formed on a substrate 34 made of glass, and a metal oxide layer 30, which is a hole transport layer, is formed on the transparent electrode layer 32. , the perovskite crystal layer 36 on the metal oxide 30 layer, the electron transport layer on the perovskite crystal layer 36, and the upper electrode layer 40 on the electron transport layer.

Reference Example As a metal oxide surface treatment apparatus, a plasma treatment apparatus (FEMTO (high-frequency power source frequency: 40 kHz, maximum power: 100 W), manufactured by Diener) having a structure as shown in FIG. 1 was used. A dry pump (ISP-50, manufactured by Anest Iwata Co., Ltd.) 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, respectively. Oxygen gas G was introduced into the processing container 12, and oxygen plasma P 2 _O was generated so that the pressure in the processing container 12 was 10 different values ranging from 100 Pa to 1000 Pa. FIG. 3 shows an emission spectroscopic analysis chart at this time.

As shown in FIG. 3, at pressures of 100 Pa and 200 Pa, luminescence derived from oxygen ions (O ₂ ⁺ and O ⁺ ) and oxygen radicals (O ₂ ^* ) was observed, and at pressures of 300 Pa, 400 Pa, and 500 Pa. Occasionally, luminescence derived from oxygen ions (O ₂ ⁺ ) and oxygen radicals (O ₂ ^* ) was observed, and when the pressure was 600 Pa or higher, luminescence derived from oxygen ions (O ₂ ⁺ and O ⁺ ) was not observed. , only luminescence originating from oxygen radicals (O ₂ ^* ) was observed. That is, it was found that the lower the pressure, more specifically, the pressure of 200 Pa or less, the more efficiently oxygen ions are generated. Oxygen plasma is generated when the pressure is 1 Pa or more.

Example 1 Surface Treatment of Tin Oxide with Oxygen Ions Surface treatment of tin oxide was performed using the plasma treatment apparatus of Reference Example. First, the FTO surface of glass with FTO (Nippon Sheet Glass Co., Ltd., NSG TEC 10) was dripped and spin-coated with a 15% by mass aqueous dispersion of tin (IV) oxide (Alfa Aesar) and dried at 150° C. for 1 hour. Thus, an object to be processed was obtained in which a glass substrate, an FTO layer as a transparent electrode layer, and a tin oxide layer as an electron transport layer were laminated in this order.

Next, this object to be processed was placed on the lower electrode so that the tin oxide faced the upper electrode. In order to remove moisture and nitrogen in the atmosphere, the pressure inside the processing container was reduced to 20 Pa or less by evacuation. In order to generate plasma, oxygen gas was introduced into the processing chamber, the pressure in the processing chamber was maintained at 100 Pa, and high frequency power of 100 W was supplied between the upper electrode and the lower electrode to perform plasma cleaning for 30 seconds. rice field.

Then, in order to remove the solvent contained in the object to be processed, the object to be processed was heated at 150°C for 1 hour. Next, oxygen gas is introduced into the processing chamber, the pressure in the processing chamber is maintained at 100 Pa, high-frequency power of 100 W is supplied between the upper electrode and the lower electrode, and the oxygen gas is turned into plasma to generate oxygen plasma. let me This oxygen plasma contains oxygen radicals and oxygen ions as compared with the reference example. Then, the tin oxide was surface-treated for 30 seconds using oxygen ions in the oxygen plasma.

Comparative Example 1: Surface Treatment of Tin Oxide with Ozone The surface treatment of tin oxide on the same object to be treated as in Example 1 was performed using a tabletop surface treatment apparatus (SSP16-110, Sen Special Light Source Co., Ltd.). First, this object to be processed was heated at 150° C. for 1 hour. Next, this object to be treated was placed in a desktop surface treatment apparatus. Then, the power of the UV light source was turned on, and the surface treatment of the tin oxide was performed for 20 minutes with ozone generated by the UV irradiation.

Comparative Example 2: Surface Treatment of Tin Oxide with Oxygen Radicals Oxidation was carried out in the same manner as in Example 1, except that the pressure during oxygen plasma generation in Example 1 was changed to 1000 Pa and the surface treatment time was changed to 50 seconds. Tin surface treatment was performed. Oxygen plasma at a pressure of 1000 Pa contains only oxygen radicals compared to the reference example. Since the pressure inside the processing vessel is higher than in Example 1, the oxygen radicals descend quickly due to gravity, irradiate the object to be processed, and modify the surface of the tin oxide.

Example 2: Evaluation of surface treatment of tin oxide (1) Work function of tin oxide By UPS (ultraviolet photoelectron spectroscopy), before surface treatment (untreated), Example 1, Comparative Example 1, and Comparative Example 2 The work function of the tin oxide surface after the surface treatment was calculated. The work functions of the tin oxide surfaces 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. rice field. The surface treatment increased the work function of the tin oxide surface. Moreover, in Example 1, the work function of the tin oxide surface after the surface treatment was larger than in Comparative Examples 1 and 2. This is the effect of efficiently repairing oxygen defects in tin oxide with oxygen ions.

The level of the conduction band of the perovskite crystal layer used in perovskite solar cells is generally between 3.5 eV and 4.5 eV, although it depends on the perovskite material. In order to reduce the interfacial resistance between the perovskite crystal and the metal oxide and improve the electron extraction efficiency, the work function of the metal oxide should be brought close to the level of the conduction band of the perovskite crystal layer, or the work function of the metal oxide is higher than the conduction band level of the perovskite crystal layer by about 0.2 eV. Since the work function of the tin oxide after the surface treatment of Example 1 was 4.12 eV, the electron extraction efficiency from this tin oxide to the perovskite crystal is high.

(2) Surface Roughness of Tin Oxide The surface of tin oxide was observed with an AFM (atomic force microscope) (SII Nanotechnology Co., Ltd., E-sweep) for plasma damage to the surface shape of tin oxide. , RMS (root mean square roughness) was evaluated. Atomic force microscope images of the surface of tin oxide before the surface treatment and after the surface treatments of Example 1, Comparative Example 1, and Comparative Example 2 are shown in FIG. As shown in FIG. 4, the shape of the tin oxide surface was almost unchanged before and after the surface treatment. In addition, the RMS 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 13.71 nm, 13.63 nm, 14.32 nm, and 12.72 nm, respectively. there were. From these similar RMS, it was found that the surface treatment did not cause damage that would change the surface shape of the tin oxide.

(3) Solar cell characteristics In a mixture of 560 µL of DMF and 140 µL of DMSO, 123 mg of FAI, 382 mg _of PbI ₂ , 14 mg of MABr, 36 mg of PbBr ₂ , and ₂₉ µL of a DMSO solution (1.5 M) of CsI were dissolved, respectively. _A precursor solution _of _.89MA0.11 ) _0.95Pb ( _I0.89Br0.11 ) ₃ was prepared. This precursor solution was spin-coated on the tin oxide surface of the object to be treated obtained in Example 1, Comparative Example 1, and Comparative Example 2 at 1000 rpm for 10 seconds, and then a small amount of chlorobenzene was further spin-coated at 6000 rpm for 20 seconds. Coated to obtain a uniform perovskite precursor thin film. Next, it was heated at 100° C. for 1 hour on a hot plate to form Cs _0.05 (FA _0.89 MA _0.11 ) _0.95 Pb(I _0.89 Br _0.11 ) ₃ layers.

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. This Spiro-OMeTAD precursor solution was applied to the surface of each of the Cs _0.05 (FA _0.89 MA _0.11 ) _0.95 Pb(I _0.89 Br _0.11 ) _three layers obtained above at 3000 rpm. Spin coated for 30 seconds. Then, it was dried at 65° C. for 10 minutes to form a Spiro-OMeTAD layer. A gold layer having a thickness of 50 nm was deposited on the surface of these Spiro-OMeTAD layers using a vacuum deposition machine to obtain a solar cell member.

Calcium oxide 52 is supported in the center of the surface of the glass plate 50, and an ultraviolet curable adhesive 54 containing glass spheres with a diameter of 10 μm is applied to the periphery as a spacer with a thickness of 0.05 mm and a width of 0.2 mm to form a sealing member. got In a nitrogen atmosphere, this sealing member is placed on this solar cell member, and the adhesive 54 is cured by irradiating with ultraviolet rays. Each battery was manufactured. FIG. 6 schematically shows a cross section of these perovskite solar cells.

The properties of these perovskite solar cells were evaluated. These perovskite solar cells were irradiated with simulated AM 1.5 sunlight (intensity 1000 W/m ² ) using a solar simulator (OTENTO-SUN, manufactured by Spectroscopic Instruments Co., Ltd.). A short-circuit current density, an open-circuit voltage, a fill factor, and a photoelectric conversion efficiency were obtained from a curve plotting a current-voltage relationship using a source meter (Keithley 2400, manufactured by Keithley Instruments (hereinafter the same)). Table 1 shows the results.

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

In addition, the light durability of the perovskite solar cells produced from the objects to be treated obtained in Example 1, Comparative Example 1, and Comparative Example 2 was evaluated. Using a compact light irradiation environment test system (manufactured by ESPEC), these perovskite solar cells were continuously irradiated with AM1.5 simulated sunlight (intensity 1000 W/m ² ) at 25° C. and 30% humidity. The photoelectric conversion efficiency was obtained from a curve obtained by plotting the current-voltage relationship with a source meter at predetermined time intervals, and the ratio between the obtained photoelectric conversion efficiency and the initial photoelectric conversion efficiency was calculated. The results are shown in FIG. As shown in FIG. 5, the perovskite solar cell manufactured from the object to be processed obtained in Example 1 had higher light durability than other perovskite solar cells. This is because the oxygen deficiency on the surface of the tin oxide was repaired by the surface treatment of the tin oxide in Example 1, and the light durability centering on the visible light region was improved.

Example 3: Surface Treatment of Titanium Oxide with Oxygen Ions A titanium diisopropoxide acetylacetonate solution (Aldrich Co.) was diluted with ethanol so that the concentration of this titanium compound was 6% by mass to prepare a titanium oxide precursor solution. got In an environment of 400° C., this titanium oxide precursor liquid was sprayed onto the FTO surface of a glass with FTO (NSG TEC 10, Nippon Sheet Glass Co., Ltd.) using an air brush, and dried at 500° C. for 10 minutes to form a glass substrate, An object to be treated was obtained in which an FTO layer and a titanium oxide layer used as an electron transport layer of a regular structure perovskite solar cell were laminated in this order. In the same manner as in Example 1, the titanium oxide surface of this object to be treated was treated with oxygen ions.

Comparative Example 3 Surface Treatment of Titanium Oxide with Ozone An object to be treated having a layer of titanium oxide was obtained in the same manner as in Example 3, and the surface of the titanium oxide of the object to be treated was treated with ozone in the same manner as in Comparative Example 1. processed.

Comparative Example 4 Surface Treatment of Titanium Oxide with Oxygen Radicals An object to be treated having a layer of titanium oxide was obtained in the same manner as in Example 3, and the titanium oxide surface of the object to be treated was treated in the same manner as in Comparative Example 2. Oxygen radical treatment.

Example 4: Evaluation of surface treatment of titanium oxide In the same manner as in Example 2 (1), titanium oxide before surface treatment (untreated) and after surface treatment of Example 3, Comparative Example 3, and Comparative Example 4 We calculated the work function of the surface of The work functions of the titanium oxide surfaces before the surface treatment and after the surface treatments of Example 2, Comparative Example 3, and Comparative Example 4 were 3.87 eV, 4.12 eV, 4.27 eV, and 4.34 eV, respectively. rice field. The surface treatment increased the work function of the titanium oxide surface. Moreover, in Example 3, the work function of the titanium oxide surface after the surface treatment was larger than in Comparative Examples 3 and 4. This is the effect of efficiently repairing oxygen defects in titanium oxide with oxygen ions. For the same reason as in Example 2(1), the work function of the titanium oxide after the surface treatment in Example 3 was 4.12 eV, so the electron extraction efficiency from this titanium oxide to the perovskite crystal is high.

Example 5 Surface Treatment of Nickel Oxide with Oxygen Ions Surface treatment of nickel oxide used as a hole-transporting layer for an inverse structure perovskite solar cell was performed. First, the FTO surface of glass with FTO (Nippon Sheet Glass Co., Ltd., NSG TEC 10) was dropped and spin-coated with a 2.5 mass% ethanol dispersion of nickel (II) oxide (AVANTAMA), and dried at 150 ° C. for 1 hour. Then, an object to be processed in which the glass substrate, the FTO layer, and the nickel oxide layer were laminated in this order was obtained.

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 nickel oxide surface of the object to be treated was treated with ozone in the same manner as in Comparative Example 1. processed.

Comparative Example 6 Surface Treatment of Nickel Oxide with Oxygen Radicals An object to be treated having a layer of nickel oxide was obtained in the same manner as in Example 5, and the nickel oxide surface of the object to be treated was treated in the same manner as in Comparative Example 2. Oxygen radical treatment.

Example 6: Evaluation of surface treatment of nickel oxide In the same manner as in Example 2 (1), nickel oxide before surface treatment (untreated) and after surface treatment of Example 5, Comparative Example 5, and Comparative Example 6 We calculated the work function of the surface of The work functions of the nickel oxide surfaces 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. rice field. The surface treatment increased the work function of the nickel oxide surface.

The valence band level of the perovskite crystal layer used in perovskite solar cells depends on the perovskite material, but is generally between 4.5 eV and 6.0 eV. be. 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 level of the valence band of the perovskite crystal layer. Since the work function of the nickel oxide after the surface treatment of Example 5 was 5.43 eV, the hole extraction efficiency from this nickel oxide to the perovskite crystal is high.

10 Surface treatment apparatus 12 Processing container 14 Upper electrode 16 Lower electrode 18 Gas supply unit 20 High frequency power supply 22 Exhaust port 24 Observation window 26 Light emission detection unit 28 Recording unit 30 Metal oxide 32 Transparent electrode layer 34 Substrate 36 Perovskite crystal layer 38 Holes Transport layer 40 Upper electrode layer 50 Glass plate 52 Calcium oxide 54 Ultraviolet curable adhesive C Perovskite solar cell S Object to be processed P _O oxygen plasma R _O oxygen radicals I _O oxygen ions G Oxygen gas

Claims

an oxygen plasma generation step of generating oxygen plasma by supplying high-frequency power with a frequency of 1 kHz or more and 40 kHz or less;
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;
A method for surface treatment of a metal oxide having
In the method for surface treatment of metal oxide according to claim 1,
A method for surface treatment of a metal oxide, wherein the metal oxide is tin oxide, titanium oxide, or nickel oxide.
In the metal oxide surface treatment method according to claim 1 or 2,
A metal oxide surface treatment method, wherein the oxygen plasma generation step and the metal oxide surface modification step are performed in a pressure atmosphere of 1 Pa or more and 200 Pa or less.
In the metal oxide surface treatment method according to any one of claims 1 to 3,
A surface treatment method for a metal oxide, wherein the high-frequency power is 50 W or more and 1000 W or less.
A transparent electrode layer, a metal oxide layer that is an electron transport layer, a perovskite crystal layer that is a power generation layer, a hole transport layer, and an upper electrode layer are provided in this order. A method for manufacturing a perovskite solar cell in which a perovskite crystal layer is formed,
an oxygen plasma generation step of generating oxygen plasma by applying high-frequency power with a frequency of 1 kHz or more and 40 kHz or less;
Metal oxidation of modifying the surface of the metal oxide layer by irradiating the surface of the metal oxide layer of the object to be treated comprising the transparent electrode layer and the metal oxide layer with oxygen ions in the oxygen plasma. a material layer surface modification 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 modification step;
A method for manufacturing a perovskite solar cell having
A transparent electrode layer, a metal oxide layer as a hole transport layer, a perovskite crystal layer as a power generation layer, an electron transport layer, and an upper electrode layer are provided in this order, and the perovskite layer is provided on the surface of the metal oxide layer. A method for producing a perovskite solar cell having a crystal layer, comprising:
an oxygen plasma generation step of generating oxygen plasma by applying high-frequency power with a frequency of 1 kHz or more and 40 kHz or less;
Metal oxidation of modifying the surface of the metal oxide layer by irradiating the surface of the metal oxide layer of the object to be treated comprising the transparent electrode layer and the metal oxide layer with oxygen ions in the oxygen plasma. a material layer surface modification 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 modification step;
A method for manufacturing a perovskite solar cell having
a processing vessel;
an upper electrode provided in the processing container;
a lower electrode provided in the processing vessel so as to be grounded, and on which the object to be processed is placed so as to expose the metal oxide layer of the object to be processed in which the transparent electrode layer and the metal oxide layer are laminated; and,
a gas supply unit for introducing oxygen gas into the processing container;
a frequency of 1 kHz or more and 40 kHz or less for supplying electric 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; a high-frequency power supply of
A metal oxide surface treatment apparatus having
a dielectric processing container;
an induction coil provided around the dielectric processing container;
an electrode provided in the dielectric processing vessel, on which the object to be processed is placed so as to expose the metal oxide layer of the object to be processed on which the transparent electrode layer and the metal oxide layer are laminated;
a gas supply unit for introducing oxygen gas into the dielectric processing container;
a high frequency power supply having a frequency of 1 kHz or more and 40 kHz or less for supplying power to the induction coil so as to generate oxygen plasma from the oxygen gas introduced into the dielectric processing container from the gas supply unit;
A metal oxide surface treatment apparatus having