Perovskite crystal deposition method and deposition apparatus

Abstract

The present invention quickly deposits perovskite crystals while suppressing decreases in the smoothness of a perovskite crystalline film.　A perovskite crystal deposition apparatus 10 comprises: a base body stage 12 on which a base body 20 is placed; a blade 26 that, when the base body 20 is placed on the base body stage 12, is disposed so as to face the surface of the base body 20 such that a gap is formed therebetween; and a gas supply member 18 that, when the base body 20 is placed on the base body stage 12, sprays a gas at a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min onto the surface of the base body 20, that is capable of moving at a speed of 0.6 m / min to 4 m / min with respect to the base body, and that is fixed to the blade 26.

Description

Perovskite crystal film formation method and film formation device

[0001] The present application relates to a method and apparatus for depositing perovskite crystals for perovskite solar cells.

[0002] In recent years, perovskite solar cells, in which the power generation layer is a perovskite crystal layer, have been attracting attention. However, when forming a perovskite crystal layer using spin coating, it is difficult to achieve a large area. Furthermore, spin coating cannot be applied to the roll-to-roll method. Furthermore, spin coating requires the addition of a poor solvent during spin coating of the perovskite crystal precursor liquid to control crystal growth. This results in problems of reduced yield and in-plane uniformity of film thickness (film smoothness).

[0003] In contrast, in Non-Patent Document 1, a perovskite crystal precursor liquid is applied to a substrate using a slot die method, and then immediately thereafter, nitrogen gas is sprayed onto the substrate to dry it, thereby forming a perovskite crystal film. However, the method of Non-Patent Document 1 uses a poor solvent in the precursor liquid, which may affect reproducibility and may result in a reduced yield. Furthermore, the method of Non-Patent Document 1 has a film formation speed of 7 mm / sec (0.42 m / min), and further improvement in the film formation speed is required for mass production.

[0004] Adv. Mater., 2015, 27, 1241-1247.

[0005] The present application has been made in view of the above circumstances, and aims to rapidly form a perovskite crystal film while suppressing a decrease in the smoothness of the perovskite crystal film.

[0006] The method for forming a perovskite crystal film of the present application comprises a coating step of spreading a precursor liquid of a perovskite crystal on a substrate to obtain a precursor film, and a drying step of spraying a gas having a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min onto the precursor film from above the surface of the precursor film while moving the precursor film at a speed of 0.6 m / min to 4 m / min in a direction along the surface of the precursor film to obtain a perovskite crystal layer.

[0007] The perovskite crystal film forming apparatus of the present application comprises a substrate stage on which a substrate is placed, a blade arranged opposite to the substrate stage so as to form a gap with the surface of the substrate when the substrate is placed on the substrate stage, and a gas supply member fixed to the blade that blows gas onto the surface of the substrate when the substrate is placed on the substrate stage at a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min, and that can move relative to the substrate at a speed of 0.6 m / min to 4 m / min, and obtains a perovskite crystal layer by blowing gas from the gas supply member onto the precursor film obtained by spreading a perovskite crystal precursor liquid on the substrate with the blade.

[0008] In the film formation method of the present application, gas is sprayed onto the precursor film at a predetermined pressure, temperature, and flow rate while moving at a speed of 0.6 m / min to 4 m / min. Furthermore, in the film formation apparatus of the present application, gas is sprayed onto the precursor film on the substrate at a predetermined pressure, temperature, and flow rate while moving relative to the substrate at a speed of 0.6 m / min to 4 m / min. The perovskite crystal film obtained by the film formation method and film formation apparatus of the present application exhibits reduced deterioration in smoothness. Therefore, the perovskite crystal film formation method and perovskite crystal film formation apparatus of the present application enable rapid film formation of perovskite crystals while reducing deterioration in the smoothness of the perovskite crystal film.

[0009] 1 is a schematic cross-sectional view of a film-forming apparatus according to an embodiment; 2 is a schematic top view of a film-forming apparatus according to an embodiment; 3 is a schematic cross-sectional view of a film-forming apparatus used in Examples; 4 is a schematic cross-sectional view of a perovskite solar cell according to Examples.

[0010] Hereinafter, the perovskite crystal film formation method and perovskite crystal film formation apparatus of the present application will be described based on embodiments and examples, with appropriate reference to the drawings. Note that the perovskite crystal film formation apparatus in the drawings is a schematic representation of its configuration, and therefore does not match the dimensional ratio of the actual film formation apparatus. Furthermore, identical components may be assigned the same reference numerals, and duplicate explanations will be omitted where appropriate.

[0011] FIG. 1 schematically illustrates a cross section of a perovskite crystal film formation apparatus 10 according to an embodiment of the present application (hereinafter, the "perovskite crystal film formation apparatus 10" may be simply referred to as the "film formation apparatus 10"). FIG. 2 also schematically illustrates the top surface of the film formation apparatus 10. The film formation apparatus 10 includes a substrate stage 12, a dripping member 14, a coating member 16, and a gas supply member 18. A substrate 20 is placed on the substrate stage 12. The film formation apparatus 10 is a roll-to-roll film formation apparatus. The substrate stage 12 can move in the direction indicated by the arrow at a speed of 0.6 m / min to 4 m / min. As the substrate stage 12 moves in the direction indicated by the arrow, the substrate 20 also moves in the direction indicated by the arrow, and the top surface of the substrate 20 is processed by the fixed dripping member 14, coating member 16, and gas supply member 18. Specific processing details will be described later.

[0012] The dripping member 14 drips a precursor liquid 22 of a perovskite crystal onto the substrate 20. In this embodiment, the precursor liquid 22 supplied to the dripping member 14 from a tank (not shown) or the like is dripped onto the substrate 20 through a slit 24 provided on the lower surface. The dripping member may have any structure as long as it can drip the precursor liquid 22 onto the substrate 20. For example, the dripping member may be a device that sprays the precursor liquid 22 onto the substrate 20.

[0013] The application member 16 is provided with a blade 26 on its underside. The blade 26 spreads the precursor liquid 22 of the perovskite crystal on the substrate 20 to form a precursor film 28. In other words, the precursor film 28 is a thin film of the precursor liquid 22, contains moisture, and has not crystallized into perovskite. The blade 26 is made of a metal such as stainless steel. There are no particular restrictions on the material of the blade 26 as long as it can spread the precursor liquid 22 and form the precursor film 28. In addition to metal, examples of materials for the blade 26 include resin, rubber, and glass.

[0014] The blade 26 is a rectangular plate having a protruding shape on one side thereof, and is placed with this protruding surface facing downwards. In this embodiment, the lower surface of the blade 26 has a flat tip that narrows toward the flat surface. The blades 26 are also arranged opposite each other so as to form a gap between them and the surface, i.e., the upper surface, of the substrate 20 when the substrate 20 is placed on the substrate stand 12. From the viewpoint of forming a good perovskite crystal film, the gap between the surface of the substrate 20 and the tip of the blade 26 is preferably 25 μm or more and 500 μm or less, and more preferably 25 μm or more and 130 μm or less.

[0015] The gas supply member 18 blows gas 30, which is supplied via a cylinder, piping, a compressor (none of which are shown), in the direction of the substrate stage 12. When the substrate 20 is placed on the substrate stage 12, the gas supply member 18 blows gas onto the surface of the substrate 20 at a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min. A perovskite crystal layer 32 is obtained by blowing the gas 30 from the gas supply member 18 onto the precursor film 28. As the perovskite crystal, Cs ｘ (FA ｙ MA １－ｙ ) １－ｘ Pb(I ｙ Br １－ｙ ) ３ , Cs ｘ FA １－ｘ PbI ３ , C.H. ３ NH ３ PbI ３ , and CH(NH ２ ) ２ PbI ３ Here, 0<x<1, 0<y<1, FA is formamidinium, and MA is methylamine.

[0016] In this embodiment, nitrogen gas is sprayed through slits 34 provided in the lower surface of the gas supply member 18. There are no limitations on the type of gas 30, as long as a perovskite crystal layer 32 can be obtained by spraying the gas onto the precursor film 28. From the viewpoint of forming a good perovskite crystal film, preferred gases 30 include dry air containing only enough moisture to give a dew point below freezing, nitrogen, rare gases such as argon, and mixtures of these.

[0017] Furthermore, the gas supply member 18 is fixed to the application member 16, i.e., to the blade 26, via a bonding member 36. This makes it possible to maintain a constant time between the formation of the precursor film 28 and the spraying of the gas 30 onto the precursor film 28, thereby obtaining a homogeneous perovskite crystal layer 32. The dripping member 14 and application member 16 are also fixed to each other via a bonding member 36. Furthermore, the gas supply member 18 can move relative to the substrate 20 at a speed of 0.6 m / min or more and 4 m / min or less. Because the gas supply member 18 can move at such a speed, the perovskite crystal layer 32 can be produced quickly.

[0018] In this embodiment, the gas supply member 18 is stationary and the base table 12 is moved at a speed of 0.6 m / min to 4 m / min, thereby moving the gas supply member 18 relative to the base 20 at a speed of 0.6 m / min to 4 m / min. The base table may be stationary and the gas supply member may be moved at a speed of 0.6 m / min to 4 m / min, thereby moving the gas supply member relative to the base at a speed of 0.6 m / min to 4 m / min. The movement is more preferably at a speed of 0.6 m / min to 3 m / min, and even more preferably at a speed of 0.6 m / min to 2 m / min.

[0019] The perovskite crystal film formation method according to an embodiment of the present application (hereinafter, the "perovskite crystal film formation method" may be simply referred to as the "film formation method") comprises a dropping step, a coating step, and a drying step. The film formation method according to the present application may be carried out using the film formation apparatus 10, or may be carried out using other apparatus. Below, a film formation method using the film formation apparatus 10 will be described as an example.

[0020] In the dropping step, a perovskite crystal precursor liquid 22 is dropped onto the substrate 20 from a dropping member 14. In the coating step following the dropping step, the precursor liquid 22 on the substrate 20 is spread using a blade 26 to obtain a precursor film 28. From the viewpoint of forming a good perovskite crystal film, the thickness of the precursor film 28 is preferably 25 μm to 500 μm, and more preferably 25 μm to 130 μm. In the drying step following the coating step, a gas 30 at a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25° C. to 200° C., and a flow rate of 80 L / min to 120 L / min is sprayed onto the precursor film 28 from the gas supply member 18, i.e., from above the surface of the precursor film 28, to obtain a perovskite crystal layer 32.

[0021] Because the pressure of the gas 30 is not high, at 0.1 MPa or more and 0.2 MPa or less, smoothness of the precursor film 28 is easily maintained when drying. The pressure of the gas 30 is more preferably 0.1 MPa or more and 0.15 MPa or less, and even more preferably 0.1 MPa or more and 0.13 MPa or less. Because the flow rate of the gas 30 is fast, at 80 L / min or more and 120 L / min or less, the precursor film 28 dries quickly. The flow rate of the gas 30 is more preferably 90 L / min or more and 110 L / min or less, and even more preferably 100 L / min or more and 105 L / min or less. The gas 30 can be used at a wide range of temperatures from room temperature (25°C) to 200°C, but a range of 50°C to 150°C is more preferable, and a range of 120°C to 130°C is even more preferable.

[0022] At this time, the gas supply member 18 is moved so that the speed in the direction along the surface of the precursor film 28 is 0.6 m / min or more and 4 m / min or less. However, this movement depends on the relative relationship between the precursor film 28 and the gas supply member 18, and in this embodiment, the gas supply member 18 is stationary, and the precursor film 28, i.e., the base stage 12, moves. Note that it is preferable to spread the precursor liquid 22 while moving the blade 26 so that the speed in the direction along the surface of the precursor film 28 is 0.6 m / min or more and 4 m / min or less. This is because a good perovskite crystal layer 32 can be formed quickly.

[0023] Furthermore, it is preferable to spray the gas 30 onto the precursor film 28 while moving synchronously with the blade 26, as this allows for a homogeneous perovskite crystal layer 32 to be obtained. In the film formation apparatus 10, the dropping member 14, the coating member 16, and the gas supply member 18 are fixed at a predetermined interval. Therefore, in the film formation method using the film formation apparatus 10, a homogeneous perovskite crystal layer 32 can be rapidly formed.

[0024] Using the film-forming apparatus 40 shown in FIG. 3, a Cs perovskite crystal layer 62 was formed on a glass plate 50 in the following procedure. ０．０５ (FA ０．８９ MA ０．１１ ) ０．９５ Pb(I ０．８９ Br ０．１１ ) ３ (hereinafter sometimes referred to as "CsFAMAPbIBr") layer or Cs ０．０５ FA ０．９５ PbI ３ (hereinafter, sometimes referred to as "CsFAPbI") layer was formed. In the film formation apparatus 40, the substrate stage 12 and the glass plate 50 are stationary, and the coating member 16, i.e., the blade 26 and the gas supply member 18, move synchronously in the direction indicated by the arrows along guide rails (not shown) provided on both sides of the coating member 16 and the gas supply member 18. The gas supply member 18 can blow out gas at a pressure of 0.6 MPa or less.

[0025] 3 corresponds to the vertical direction of the glass plate 50 and the vertical direction in which the components of the film forming apparatus 40 move, and the direction perpendicular to the vertical direction on the plane of the glass plate 50 corresponds to the horizontal direction of the glass plate 50. The blade 26 was a stainless steel plate measuring 30 mm in length, 120 mm in width, and 0.5 mm in thickness, with one side surface processed to have a flat, acute-angled tip. The blade 26 was positioned so that the gap between the flat tip and the upper surface of the glass plate 50 was 130 μm.

[0026] Example 1: Formation of CsFAMAPbIBr film In a mixture of 885 μL of DMF and 15 μL of DMSO, 189 mg of FAI and PbI ２ 640mg, MABr22mg, PbBr ２A CsFAMAPbIBr precursor solution, a precursor solution for perovskite crystals, was prepared by dissolving 55 mg of CsFAMAPbIBr in 50 μL of a DMSO solution (1.5 M) of CsI. A glass plate 50 measuring 50 mm in length, 70 mm in width, and 1.6 mm in thickness was placed on a base stage 12. 40 μL of this CsFAMAPbIBr precursor solution was dropped onto the upper surface of the edge of the glass plate 50 in a linear pattern measuring 50 mm in width and 2 mm in length along the horizontal direction.

[0027] Blade 26 was moved at 0.6 m / min in the vertical direction indicated by the arrow, and this CsFAMAPbIBr precursor liquid was spread on glass plate 50 to form a CsFAMAPbIBr precursor film, which was precursor film 28. At this time, nitrogen gas 60 at a pressure of 0.1 MPa, a temperature of 50°C to 150°C, and a flow rate of 100 L / min was sprayed onto this CsFAMAPbIBr precursor film from a horizontally long slit (0.3 mm long x 120 mm wide) that moved synchronously with blade 26 and faced the upper surface of glass plate 50. The CsFAMAPbIBr precursor film above which the slit passed was immediately crystallized, and a CsFAMAPbIBr layer was formed.

[0028] Comparative Example 1: Formation of CsFAMAPbIBr Film A CsFAMAPbIBr precursor liquid, which is a precursor liquid for perovskite crystals, was prepared in the same manner as in Example 1. 40 μL of this CsFAMAPbIBr precursor liquid was dropped onto the upper surface of the edge of the glass plate 50, and the blade 26 was moved at 0.6 m / min in the vertical direction indicated by the arrow. The CsFAMAPbIBr precursor liquid was spread on the glass plate 50 to form a CsFAMAPbIBr precursor film, which is the precursor film 28. At this time, nitrogen gas 60 at a pressure of 0.1 MPa, a temperature of 25°C, and a flow rate of 100 L / min was blown onto the CsFAMAPbIBr precursor film from a slit similar to that in Example 1, moving in synchronization with the blade 26. The CsFAMAPbIBr precursor film immediately crystallized as the slit passed above it, forming a CsFAMAPbIBr layer.

[0029] Example 2: Formation of CsFAPbI film A CsFAPbI precursor solution was prepared by dissolving 215 mg of FAI and 18 mg of CsI in a mixture of 935 μL of DMF and 65 μL of DMSO. In the same manner as in Example 1, a glass plate 50 was placed on the substrate stage 12, and 40 μL of this CsFAPbI precursor solution was dropped onto the upper surface of the edge of the glass plate 50 in a linear pattern measuring 50 mm in width and 2 mm in length along the horizontal direction. A CsFAPbI layer was then formed in the same manner as in Example 1, except that the temperature of the nitrogen gas 60 was changed to 50°C to 200°C.

[0030] Comparative Example 2: Formation of CsFAPbI Film A CsFAPbI precursor solution was prepared by dissolving 215 mg of FAI and 18 mg of CsI in a mixture of 935 μL of DMF and 65 μL of DMSO. As in Example 1, a glass plate 50 was placed on the substrate stage 12, and 40 μL of this CsFAPbI precursor solution was dropped onto the upper surface of the edge of the glass plate 50 in a linear pattern measuring 50 mm wide and 2 mm long along the horizontal direction. A CsFAPbI layer was then formed in the same manner as in Example 1, except that the temperature of the nitrogen gas 60 was changed to 25°C.

[0031] Example 3: Evaluation of in-plane uniformity of CsFAMAPbIBr layer The CsFAMAPbIBr layer (nitrogen gas temperature 120°C) on the glass plate 50 of Example 1 was divided into four 25 mm squares, excluding a central 20 mm-wide region, and the surface roughness (RMS) of each section was calculated from the profile obtained when a stylus was tipped over a 5 mm width with a contact pressure of 1 mg using a Dektak XT (manufactured by Bruker). The RMS measurements of the CsFAMAPbIBr layer in each section on the glass plate 50 were 21.2 nm, 25.6 nm, 30.5 nm, and 30.6 nm, respectively, in ascending order, and the average RMS value was 27.0 nm.

[0032] Comparative Example 3: Evaluation of In-Plane Uniformity of the CsFAMAPbIBr Layer The CsFAMAPbIBr layer (nitrogen gas temperature 25°C) on the glass plate 50 of Example 1 was divided into four 25 mm squares, excluding a central 20 mm-wide region, and the surface roughness (RMS) of each section was calculated from the profile obtained when a stylus was tipped over a 5 mm width with a contact pressure of 1 mg using a Dektak XT (manufactured by Bruker). The RMS measurements of the CsFAMAPbIBr layer in each section on the glass plate 50 were 19.4 nm, 24.6 nm, 27.5 nm, and 29 nm, respectively, in ascending order, with the average RMS value being 25.1 nm.

[0033] Example 4: Evaluation of in-plane uniformity of CsFAPbI layer The surface roughness (RMS) of four sections of the CsFAPbI layer (nitrogen gas temperature 125°C) on the glass plate 50 of Example 2 was evaluated in the same manner as in Example 3. The RMS measurements of the CsFAPbI layer in each section on the glass plate 50 were 17.8 nm, 18.9 nm, 21.6 nm, and 22.7 nm, respectively, in ascending order, and the average RMS value was 20.3 nm.

[0034] Comparative Example 4: Evaluation of in-plane uniformity of CsFAPbI layer The surface roughness (RMS) of four sections of the CsFAPbI layer (nitrogen gas temperature 25°C) on the glass plate 50 of Example 2 was evaluated in the same manner as in Example 3. The RMS measurement values ​​of the CsFAPbI layer in each section on the glass plate 50 were 12.6 nm, 20.7 nm, 30.6 nm, and 33.7 nm, respectively, in order from smallest to largest, and the average RMS value was 24.4 nm.

[0035] From the results of Example 3 and Comparative Example 3, the average RMS value of the CsFAMAPbIBr layer was 25.1 nm when the nitrogen gas temperature was 25° C., whereas it was 27.0 nm when the nitrogen gas temperature was 120° C. From the results of Example 4 and Comparative Example 4, the average RMS value of the CsFAPbI layer was 24.4 nm when the nitrogen gas temperature was 25° C., whereas it was an extremely small 20.3 nm when the nitrogen gas temperature was 125° C.

[0036] The above results demonstrate that the film formation method of the present invention can produce a perovskite crystal layer with extremely excellent smoothness. Therefore, the film formation method of the present invention enables the production of larger glass plates 50, i.e., the mass production of perovskite crystal layers.

[0037] Example 5: Evaluation of photoelectric conversion efficiency of CsFAMAPbIBr layer To evaluate the photoelectric conversion efficiency of the CsFAMAPbIBr layer, a perovskite solar cell 70 shown in FIG. 4 was fabricated using the following procedure. A 15% by mass aqueous dispersion of tin(IV) oxide (Alfa Aesar) was dropped and spin-coated onto the FTO surface of FTO-attached glass (NSG TEC 10, Nippon Sheet Glass Co., Ltd.), and the resulting substrate was dried at 150°C for 1 hour to obtain a substrate comprising a glass substrate (substrate 70), an FTO layer (transparent electrode layer 74), and a tin oxide layer (electron transport layer 76) stacked in this order. The tin oxide surface of this substrate was treated with oxygen ions in oxygen plasma.

[0038] That is, in the processing chamber of a plasma processing apparatus (Diener, FEMTO (high frequency power supply frequency 40 kHz, maximum power 100 W)), the substrate was placed on the lower electrode so that the tin oxide layer 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.

[0039] To remove the solvent contained in the substrate, the substrate was heated at 150°C for 1 hour. Oxygen gas was 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 and generate oxygen plasma. This oxygen plasma contained oxygen radicals and oxygen ions. The oxygen ions in this oxygen plasma were used to perform surface treatment of the tin oxide layer for 30 seconds.

[0040] A CsFAMAPbIBr layer, which is a perovskite crystal layer 78, was formed on the surface-treated tin oxide layer by adjusting the nitrogen gas pressure, temperature, and flow rate to the same conditions as in Example 1. Then, 61 mg of Spiro-OMeTAD (2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene) and 10 mg of LiTFSI (TFS: trifluoromethanesulfonate) were dissolved in 0.7 mL of chlorobenzene, and 22 μL of 4-tert-butylpyridine was added to obtain a Spiro-OMeTAD precursor solution, which is a hole transport layer precursor solution. This Spiro-OMeTAD precursor solution was spin-coated on the surface of the CsFAMAPbIBr layer at 3000 rpm for 30 seconds.

[0041] The spin-coated Spiro-OMeTAD precursor solution was dried at 65°C for 10 minutes to form a Spiro-OMeTAD layer, which served as a hole transport layer 80. A 50-nm-thick gold layer, which served as an upper electrode layer 82, was deposited on the surface of this Spiro-OMeTAD layer using a vacuum deposition machine, yielding a solar cell component. Calcium oxide 52 was supported on the center of the surface of a glass plate 50, and a 0.05 mm-thick, 0.2 mm-wide ultraviolet-curable adhesive 54 containing glass spheres with a diameter of 10 μm was applied to the periphery as spacers, yielding a sealing member. In a nitrogen atmosphere, this sealing member was layered on top of the solar cell component, and the adhesive 54 was cured by ultraviolet irradiation, yielding a perovskite solar cell 70.

[0042] Using a solar simulator (OTENTO-SUN, manufactured by Bunkoukeiki Co., Ltd.), the perovskite solar cell was exposed to simulated sunlight of AM 1.5 (intensity 1000 W / m ２) was irradiated. The photoelectric conversion efficiency was determined from a curve plotting the current-voltage relationship using a source meter (Keithley 2400 manufactured by Keithley Instruments, Inc. (hereinafter the same)). As a result, the photoelectric conversion efficiencies of perovskite solar cells fabricated under conditions of nitrogen gas temperatures of 50°C, 100°C, 110°C, 120°C, and 150°C were 15.9%, 17.8%, 18.1%, 19.0%, and 18.8%, respectively. When the nitrogen gas temperature was 100°C to 150°C, the photoelectric conversion efficiency of the perovskite solar cell was high, ranging from 17.8% to 19.0%. Furthermore, when the nitrogen gas temperature was 120°C, the photoelectric conversion efficiency of the resulting perovskite solar cell was an extremely high 19.0%.

[0043] Comparative Example 5: Evaluation of photoelectric conversion efficiency of CsFAMAPbIBr layer A perovskite solar cell 70 was obtained in the same manner as in Example 5, except that the pressure, temperature, and flow rate of the nitrogen gas were adjusted to the conditions of Comparative Example 1. Using a solar simulator (OTENTO-SUN, manufactured by Bunkoukeiki Co., Ltd.), the perovskite solar cell was exposed to simulated sunlight of AM 1.5 (intensity 1000 W / m ２ The photoelectric conversion efficiency was determined from a curve plotting the current-voltage relationship using a source meter (Keithley 2400 manufactured by Keithley Instruments (hereinafter the same)). As a result, the photoelectric conversion efficiency of the perovskite solar cell fabricated under the condition of a nitrogen gas temperature of 25°C was 17.2%.

[0044] Example 6: Evaluation of photoelectric conversion efficiency of CsFAPbI layer Fabrication of perovskite solar cells and evaluation of photoelectric conversion efficiency were performed in the same manner as in Example 5, except that the formation of the perovskite crystal layer 78 was changed to the method of Example 2. As a result, the photoelectric conversion efficiencies of perovskite solar cells fabricated under conditions where the nitrogen gas temperatures were 50°C, 100°C, 120°C, 125°C, 130°C, 150°C, 175°C, and 200°C were 17.9%, 15.1%, 20.1%, 20.7%, 20.5%, 16.9%, 15.7%, and 16.1%, respectively.

[0045] Comparative Example 6: Evaluation of photoelectric conversion efficiency of CsFAPbI layer A perovskite solar cell was fabricated and its photoelectric conversion efficiency was evaluated in the same manner as in Example 5, except that the formation of the perovskite crystal layer 78 was changed to the method in Example 2. As a result, the photoelectric conversion efficiency of the perovskite solar cell fabricated under the condition of a nitrogen gas temperature of 25°C was 18.8%.

[0046] When the nitrogen gas temperature was between 25°C and 50°C, the photoelectric conversion efficiency of the perovskite solar cell was high, at 17.9% to 18.8%. Furthermore, when the nitrogen gas temperature was between 120°C and 130°C, the photoelectric conversion efficiency of the perovskite solar cell was extremely high, at over 20%. When the nitrogen gas temperature was 125°C, the photoelectric conversion efficiency of the perovskite solar cell was the highest, at 20.7%.

[0047] The results of Examples 5 and 6 demonstrate that the film formation method of the present application can produce perovskite solar cells with high photoelectric conversion efficiency. Furthermore, the perovskite solar cell with a CsFAPbI layer fabricated under conditions where the nitrogen gas temperature was 125°C had the highest photoelectric conversion efficiency and the smallest RMS of this CsFAPbI layer. This suggests that the smooth perovskite crystals obtained by the film formation method of the present application contributed to the high photoelectric conversion efficiency of the perovskite solar cell.

[0048] 10, 40 Film forming apparatus 12 Substrate stage 14 Dropping member 16 Coating member 18 Gas supply member 20 Substrate 22 Precursor liquid 24, 34 Slit 26 Blade 28 Precursor film 30 Gas 32, 62, 78 Perovskite crystal layer 36 Bonding member 50 Glass plate 60 Nitrogen gas 70 Perovskite solar cell 72 Substrate 74 Transparent electrode layer 76 Electron transport layer 80 Hole transport layer 82 Upper electrode layer

Claims

1. A method for forming a perovskite crystal film, comprising: a coating step of spreading a precursor liquid of a perovskite crystal on a substrate to obtain a precursor film; and a drying step of spraying a gas having a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min onto the precursor film from above the surface of the precursor film while moving at a speed of 0.6 m / min to 4 m / min in a direction along the surface of the precursor film to obtain a perovskite crystal layer.

2. A method for forming a perovskite crystal film according to claim 1, further comprising a dripping step of dripping a precursor liquid of the perovskite crystal onto the substrate prior to the coating step.

3. A method for forming a perovskite crystal film according to claim 1 or 2, wherein in the coating step, the precursor liquid is spread by a blade.

4. A method for forming a perovskite crystal film according to claim 3, wherein the precursor liquid is spread while moving the blade so that the speed in the direction along the surface of the precursor film is 0.6 m / min or more and 4 m / min or less.

5. A method for forming a perovskite crystal film according to claim 4, wherein the gas is sprayed onto the precursor film while moving in synchronism with the blade.

6. A film forming apparatus for perovskite crystals comprising: a substrate stage for placing a substrate; a blade disposed opposite to the substrate stage so as to form a gap between the substrate and a surface of the substrate when the substrate is placed on the substrate stage; and a gas supply member fixed to the blade which can blow gas at a pressure of 0.1 MPa to 0.2 MPa, a temperature of 25°C to 200°C, and a flow rate of 80 L / min to 120 L / min onto the surface of the substrate when the substrate is placed on the substrate stage, and which can move at a speed of 0.6 m / min to 4 m / min relative to the substrate, wherein a perovskite crystal layer is obtained by blowing the gas from the gas supply member onto a precursor film obtained by spreading a precursor liquid of perovskite crystals on the substrate with the blade.

7. A film forming apparatus for perovskite crystals according to claim 6, further comprising a dripping member for dripping a precursor liquid of the perovskite crystals onto the substrate.

8. A perovskite crystal film forming apparatus according to claim 6 or 7, wherein the substrate stage can move at a speed of 0.6 m / min or more and 4 m / min or less.