A method for preparing a perovskite solar cell

Abstract

The application relates to the technical field of solar cell preparation, in particular to a preparation method of a perovskite solar cell. The method comprises the following steps: pretreating a conductive substrate; preparing an electron transport layer or a hole transport layer on the conductive substrate; preparing a perovskite precursor solution; attaching the perovskite precursor solution to the surface of a sample; placing the sample on a carrier disc, increasing the temperature of the carrier disc to 60-80 DEG C, increasing the temperature of a source bottle to 90-110 DEG C; starting a vacuum pump, purging a chamber with nitrogen, reducing the air pressure in the chamber to 1 Kpa, loading lactic acid in the source bottle into the chamber, closing the source bottle and the nitrogen; circulating for 5 times; reducing the air pressure in the chamber to 0 pa, closing the vacuum pump, increasing the temperature of the carrier disc to 90-110 DEG C; recovering normal pressure by passing nitrogen; covering the perovskite layer with a hole transport layer or an electron transport layer; and preparing a back electrode. The method has the advantages that no anti-solvent is used; lactic acid is used to control the crystallization process, and hydrophobic polylactic acid is generated in situ, thereby improving the stability of the device.

Description

Technical Field

[0001] This invention relates to the field of solar cell fabrication technology, and in particular to a method for fabricating perovskite solar cells. Background Technology

[0002] Perovskite solar cells (PSCs) have attracted widespread attention due to their excellent photoelectric properties, solution-based fabrication capabilities, and low cost. As an emerging photovoltaic technology, they play a positive role in national economic and social development.

[0003] However, the commercial application of PSCs still faces the following problems: (1) In order to promote the nucleation process of perovskite thin films, toxic chlorobenzene is usually used as an antisolvent, which is not conducive to building an environmentally friendly society. (2) The crystallization rate of perovskite is too fast and difficult to control, which will result in small perovskite grains, disordered crystal orientation, and high defect state density, affecting the performance and stability of PSCs devices. (3) Currently, high-efficiency PSCs devices contain the toxic heavy metal element lead, and the problem of lead leakage caused by damage during use has also attracted the attention of researchers.

[0004] The following is a brief description of the technical solutions proposed by researchers to address the above problems. (1) Perovskite thin films are prepared by developing green and non-toxic antisolvents or by direct vapor deposition. (2) To address the problem of excessively fast perovskite crystallization, materials containing lone pairs of electrons are usually added to the precursor solution or antisolvent to chelate uncoordinated lead ions, thereby increasing the crystallization energy barrier and slowing down the crystallization rate and passivating defects. (3) Potential lead leakage problems can be addressed by introducing hydrophobic materials into the fabrication process of PSCs devices or by implementing reliable encapsulation. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing perovskite solar cells.

[0006] The present invention aims to provide a method for fabricating a perovskite solar cell, wherein the perovskite solar cell has a structure of mesoporous upright, planar upright, or inverted type, and includes a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode; the fabrication method specifically includes the following steps:

[0007] S1, Pre-treated conductive substrate;

[0008] S2. Prepare an electron transport layer or hole transport layer on the treated conductive substrate and place it in a plasma-ozone generator for 10-20 minutes.

[0009] S3. Process the perovskite layer using molecular layer deposition (MLD); specifically including the following sub-steps:

[0010] S301. Prepare perovskite precursor solution;

[0011] S302. The perovskite precursor solution is attached to the surface of the sample treated in step S2 to form a perovskite film.

[0012] S303. Place the sample on the carrier tray in the chamber of the molecular layer deposition equipment, raise the temperature of the carrier tray to 60-80°C, raise the temperature of the source bottle to 90-110°C and maintain the temperature.

[0013] S304. Start the vacuum pump and purge the chamber with nitrogen. After 25-35 seconds, turn off the nitrogen. Use the vacuum pump to reduce the pressure in the chamber to 1 kPa and then turn off the vacuum pump. Then, use nitrogen as a carrier gas to load the lactic acid in the source bottle into the chamber. After 3-6 seconds, turn off the source bottle and nitrogen and maintain this for 20-40 seconds. Repeat this step 5 times.

[0014] S305. After the cycle, reduce the pressure in the chamber to 0 Pa, turn off the vacuum pump, raise the temperature of the loading tray to 90-110°C and maintain it for 8-15 minutes; then introduce nitrogen into the chamber to restore it to normal pressure, and the perovskite layer preparation is complete.

[0015] S4. Cover the perovskite layer with a hole transport layer or an electron transport layer;

[0016] S5. Prepare a back electrode on the sample surface obtained in step S4 to complete the fabrication of the perovskite solar cell.

[0017] Preferably, in step S305, the temperature of the tray is raised to 100°C and maintained for 10 minutes.

[0018] Preferably, in step S303, the temperature of the carrier plate is raised to 70°C and the temperature of the source bottle is raised to 100°C.

[0019] Preferably, the perovskite thin film preparation method in step S302 includes spin coating, vapor deposition, inkjet printing, doctor blade coating, or screen printing.

[0020] Preferably, the perovskite layer has a two-dimensional crystal structure, a three-dimensional crystal structure, or a two-dimensional / three-dimensional hybrid crystal structure.

[0021] Preferably, the methods for preparing the electron transport layer and the hole transport layer include spin coating, chemical bath method, atomic layer deposition or vapor deposition.

[0022] Preferably, the electron transport layer is titanium dioxide, zinc oxide, tin oxide, or fullerene and its derivatives.

[0023] Preferably, the hole transport layer is Spiro-OMeTAD, P3HT, PTAA, CuI, or NiOx.

[0024] Preferably, the back electrode is prepared by spin coating, vapor deposition, inkjet printing, doctor blade coating, screen printing or atomic layer deposition; the back electrode material is gold, silver or carbon paste.

[0025] Preferably, the conductive substrate is an ITO substrate; step S1 includes: cleaning the ITO substrate by ultrasonically cleaning it in acetone, ethanol, and deionized water for 10-20 minutes; drying the cleaned ITO substrate with nitrogen gas and drying it at 95-105°C for 2 hours; taking it out and letting it cool to room temperature before placing it in a plasma-ozone generator for 10-20 minutes.

[0026] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0027] (1) The vacuum pump draws the chamber into a low vacuum and heats the tray at the same time, which promotes solvent evaporation and eliminates the need for anti-solvent.

[0028] (2) After the temperature of the carrier disk is raised to a certain temperature by the molecular layer deposition equipment, the perovskite film annealing process is carried out; at the same time, lactic acid molecules are sprayed into the chamber, and the lactic acid will diffuse into the perovskite film that has just been spin-coated; since the carbonyl group in the lactic acid molecule contains lone pair electrons, it will chelate with lead ions, increase the crystallization energy barrier of perovskite, slow down the crystallization rate of perovskite, thereby regulating the crystallization process of perovskite, and at the same time passivating the defects in the perovskite film;

[0029] (3) Lactic acid molecules spontaneously polymerize in the high temperature and low vacuum environment of the chamber to generate hydrophobic polylactic acid, which improves the stability of PSCs devices and reduces lead leakage that may occur during device operation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a molecular layer deposition apparatus provided according to an embodiment of the present invention.

[0031] Figure 2 The results are efficiency test results of the perovskite solar cell device provided in the embodiments of the present invention. Detailed Implementation

[0032] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0034] The present invention aims to provide a method for fabricating a perovskite solar cell. The perovskite solar cell has a structure of mesoporous upright, planar upright, or planar inverted type, including a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode. The mesoporous upright and planar upright types include a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode stacked sequentially; the planar inverted type includes a conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer, and a back electrode stacked sequentially.

[0035] The preparation method specifically includes the following steps:

[0036] S1, Pre-treated conductive substrate;

[0037] S2. Prepare an electron transport layer or hole transport layer on the treated conductive substrate and place it in a plasma-ozone generator for 10-20 minutes.

[0038] S3. Process the perovskite layer using molecular layer deposition (MLD); specifically including the following sub-steps:

[0039] S301. Prepare perovskite precursor solution;

[0040] S302. The perovskite precursor solution is attached to the surface of the sample treated in step S2 to form a perovskite film.

[0041] S303. Place the sample on the carrier tray in the chamber of the molecular layer deposition equipment, raise the temperature of the carrier tray to 60-80°C, raise the temperature of the source bottle to 90-110°C and maintain the temperature.

[0042] S304. Start the vacuum pump and purge the chamber with nitrogen. After 25-35 seconds, turn off the nitrogen. Use the vacuum pump to reduce the pressure in the chamber to 1 kPa and then turn off the vacuum pump. Then, use nitrogen as a carrier gas to load the lactic acid in the source bottle into the chamber. After 3-6 seconds, turn off the source bottle and nitrogen and maintain this for 20-40 seconds. Repeat this step 5 times.

[0043] S305. After the cycle, reduce the pressure in the chamber to 0 Pa, turn off the vacuum pump, raise the temperature of the loading tray to 90-110°C and maintain it for 8-15 minutes; then introduce nitrogen into the chamber to restore it to normal pressure, and the perovskite layer preparation is complete.

[0044] S4. Cover the perovskite layer with a hole transport layer or an electron transport layer;

[0045] S5. Prepare a back electrode on the sample surface obtained in step S4 to complete the fabrication of the perovskite solar cell.

[0046] Molecular layer deposition equipment such as Figure 1 As shown, the system includes a vacuum pump, a chamber, a loading tray, a source bottle, and a working gas cylinder. The vacuum pump is used to extract gas from the chamber to create a low-vacuum environment. The chamber is used to maintain the environment required during the molecular layer deposition process. The loading tray is used to place and heat the sample. The source bottle is used to load the precursor, which is lactic acid in this embodiment. The working gas cylinder is used to load the working gas, load the precursor into the chamber, and also purge the chamber. The working gas is an inert gas, such as nitrogen or argon.

[0047] In specific embodiments, the perovskite solar cells prepared are mesoporous upright type, planar upright type, or inverted type.

[0048] In a specific embodiment, the conductive substrate is an ITO substrate; step S1 includes: cleaning the ITO substrate by ultrasonically cleaning it in acetone, ethanol, and deionized water for 10-20 minutes; drying the cleaned ITO substrate with nitrogen gas and drying it at 95-105°C for 2 hours; taking it out and letting it cool to room temperature before placing it in a plasma-ozone generator for 10-20 minutes.

[0049] In specific embodiments, the electron transport layer is an inorganic material such as titanium dioxide (TiO2), zinc oxide (ZnO), or tin oxide (SnO2), or an electron transport material such as fullerene and its derivatives; the preparation methods include spin coating, chemical bath method, atomic layer deposition, vapor deposition and other preparation methods.

[0050] In specific embodiments, the perovskite material can be a two-dimensional, three-dimensional crystal structure or a two-dimensional / three-dimensional mixed crystal structure.

[0051] In specific embodiments, the hole transport layer is an organic material such as Spiro-OMeTAD, P3HT, or PTAA, or an inorganic material such as CuI or NiOx; the preparation methods include spin coating, chemical bath method, atomic layer deposition, and vapor deposition.

[0052] In specific embodiments, methods for preparing perovskite thin films include spin coating, vapor deposition, inkjet printing, doctor blade coating, or screen printing.

[0053] In specific embodiments, the back electrode material is a metallic material such as gold or silver, or a non-metallic material such as carbon paste, or other stacked electrodes; the preparation methods include spin coating, vapor deposition, inkjet printing, doctor blade coating, screen printing, atomic layer deposition, and other preparation methods.

[0054] Example 1

[0055] A method for fabricating a perovskite solar cell, wherein the perovskite solar cell is a planar upright type, comprising a conductive substrate (in this embodiment, an ITO substrate), an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode stacked sequentially; the fabrication method specifically includes the following steps:

[0056] S1. Pretreatment of conductive substrate: First, clean the indium doped tin oxide (ITO) substrate by ultrasonic cleaning in acetone, ethanol, and deionized water for 15 minutes respectively. After cleaning, dry the ITO substrate with nitrogen gas and place it in an oven at 100°C for 2 hours. After removing it and letting it cool to room temperature, place it in a plasma-ozone generator for 15 minutes to enhance the hydrophilicity of its surface.

[0057] S2. Fabricating an electron transport layer (ETL) on the treated conductive substrate, specifically including:

[0058] S201. Preparation of electron transport layer precursor solution: Take 200 μL of commercial tin oxide aqueous solution (Alfaesa, 15 wt%) and mix with 1200 μL of deionized water, shake and mix for 5 min; filter with a 0.22 μm aqueous filter to obtain electron transport layer precursor solution (tin oxide precursor solution);

[0059] S202. Preparation of the electron transport layer: The electron transport layer precursor solution (tin oxide precursor solution) is prepared by spin coating. 60 μL of the electron transport layer precursor solution (tin oxide precursor solution) is uniformly coated onto the ITO substrate. The spin coater speed is set to 3000-6000 rpm, the spin coating time is 30-60 seconds, and the acceleration is 1500-3000 rpm. After spin coating, it is placed on a hot plate at 150°C for 30 minutes, then removed and allowed to cool to room temperature to obtain the electron transport layer (tin oxide ETL).

[0060] S203. Place the device in a plasma-ozone generator for 10-20 minutes.

[0061] S3. Process the perovskite layer using molecular layer deposition (MLD); specifically including the following sub-steps:

[0062] S301. Preparation of perovskite precursor solution (taking MAPbI3 as an example): Weigh 190.8 mg of methylamine iodide (MAI) and 553.2 mg of lead iodide (PbI2), and dissolve them in a mixed solution of 700 μL of γ-butyrolactone (GBL) and 300 μL of dimethyl sulfoxide (DMSO); place the resulting solution on a magnetic stirrer at 70°C and stir for more than 2 hours, then filter using a 0.22 μm organic filter to obtain the perovskite precursor solution;

[0063] S302. Preparation of perovskite thin film: The perovskite precursor solution is prepared by spin coating. Take 60 μL of perovskite precursor solution and coat it uniformly on the surface of the device after treatment in step S2. The spin coater speed is 3000-9000 rpm, the spin coating time is 30-90 seconds, and the acceleration is 1500-4500 rpm.

[0064] S303. Place the spin-coated perovskite film sample onto the carrier tray in the chamber of the molecular layer deposition equipment, raise the temperature of the carrier tray to 70°C, raise the temperature of the source bottle to 100°C and maintain the temperature.

[0065] S304. Start the vacuum pump and purge the chamber with nitrogen as the working gas to create a nitrogen environment. After 30 seconds, turn off the nitrogen and continue using the vacuum pump until the pressure in the chamber drops to 1 kPa. Then, turn off the vacuum pump and use nitrogen as the carrier gas to load the lactic acid from the source bottle into the chamber. After 5 seconds, turn off the source bottle and the nitrogen and maintain the environment in the chamber for 30 seconds to promote solvent evaporation and the diffusion of lactic acid molecules into the perovskite film. Repeat this step 5 times.

[0066] S305. After the cycle, use a vacuum pump to reduce the air pressure in the chamber to 0 Pa, turn off the vacuum pump, raise the temperature of the tray to 100°C and maintain it for 10 minutes to complete the annealing process of the perovskite film and allow lactic acid molecules to polymerize to form polylactic acid; then introduce nitrogen into the chamber to restore it to normal pressure, and the perovskite layer preparation is complete.

[0067] S4. Preparation of the hole transport layer:

[0068] S401. Preparation of hole transport layer precursor solution (taking Spiro-OMeTAD as an example): Weigh 520 mg of lithium salt (Li-TFSI) and dissolve it in 1 mL of acetonitrile. Stir on a magnetic stirrer for at least 8 hours to obtain a lithium salt solution. Weigh 90 mg of Spiro-OMeTAD and dissolve it in 1 mL of chlorobenzene. Add 22.5 μL of lithium salt solution and 36 μL of 4-tert-butylpyridine (t-BP) solution to the solution. Stir on a magnetic stirrer for 2 hours. Filter the solution using a 0.22 μm organic filter to obtain the hole transport layer precursor solution.

[0069] S402. Preparation of hole transport layer: Prepared by spin coating. Take 60 μL of hole transport layer precursor solution and coat it evenly on the perovskite layer. Set the spin coater speed to 3000-9000 rpm, the spin coating time to 30-90 seconds, and the acceleration to 1500-4500 rpm.

[0070] S5. Preparation of back electrode: Transfer the sample obtained in step S4 to the vapor deposition chamber, use a vacuum pump to evaporate the vapor deposition chamber pressure to below 10 Pa, and then use a molecular pump to evaporate the vapor deposition chamber pressure to below 5 × 10-4 Pa, and start electrode vapor deposition at a rate of 2 Å / s; a silver back electrode with a thickness of 80-100 nm is prepared.

[0071] Experiments show that this method is practical and effective, increasing the efficiency of the fabricated PSCs devices from 18.91% to 19.78%. Figure 2 As shown.

[0072] Example 2

[0073] A method for fabricating a perovskite solar cell, wherein the perovskite solar cell is a planar inverted type, comprising a conductive substrate (in this embodiment, an ITO substrate), a hole transport layer, a perovskite layer, an electron transport layer, and a back electrode stacked sequentially; the fabrication method specifically includes the following steps:

[0074] Step S1 is the same as in Example 1;

[0075] S2. Fabricating a hole transport layer on the treated conductive substrate, specifically including:

[0076] S201. Preparation of hole transport layer precursor solution (taking PTAA as an example): Weigh 20 mg of PTAA and dissolve it in 1 mL of chlorobenzene. Stir on a magnetic stirrer for 2 hours and filter using a 0.22 micron organic filter to obtain the hole transport layer precursor solution.

[0077] S202. Preparation of hole transport layer: The hole transport layer precursor solution was prepared by spin coating. 20 μL of the hole transport layer precursor solution was uniformly coated on a conductive substrate. The spin coater speed was set to 3000-9000 rpm, the spin coating time was 30-90 seconds, and the acceleration was 1500-4500 rpm. After spin coating, the substrate was placed on a hot plate at 100℃ for 5 minutes, then removed and cooled to room temperature to obtain the hole transport layer.

[0078] Step S3 is the same as in Example 1;

[0079] S4. Fabrication of the electron transport layer (taking PCBM as an example), specifically including:

[0080] S401. Preparation of electron transport layer precursor solution: Weigh 20 mg of PCBM and dissolve it in 1 mL of chlorobenzene. Stir on a magnetic stirrer for 2 hours and filter with a 0.22 micron organic filter to obtain the electron transport layer precursor solution.

[0081] S402, Preparation of electron transport layer: Prepared by spin coating. Take 20 μL of electron transport layer precursor solution and coat it evenly on the sample obtained in S3. Set the spin coater speed to 3000-6000 rpm, the spin coating time to 30-60 seconds, and the acceleration to 1500-3000 rpm.

[0082] S5. The back electrode is prepared by vapor deposition, with the same steps as in Example 1. The back electrode material is gold.

[0083] Example 3

[0084] A method for fabricating a perovskite solar cell, wherein the perovskite solar cell is a planar upright type, comprising a conductive substrate (in this embodiment, an ITO substrate), an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode stacked sequentially.

[0085] The electron transport layer is made of titanium dioxide and prepared by atomic layer deposition; the hole transport layer is made of P3HT and prepared by spin coating.

[0086] The remaining preparation steps are the same as in Example 1; the structure of the prepared perovskite layer is a two-dimensional / three-dimensional mixed crystal structure.

[0087] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0088] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for fabricating a perovskite solar cell, wherein the perovskite solar cell has a structure of mesoporous upright, planar upright, or planar inverted, comprising a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode, characterized in that: The preparation method specifically includes the following steps: S1, Pre-treated conductive substrate; S2. Prepare an electron transport layer or hole transport layer on the treated conductive substrate and place it in a plasma-ozone generator for 10-20 minutes. S3. Process the perovskite layer using molecular layer deposition (MLD); specifically including the following sub-steps: S301. Prepare perovskite precursor solution; S302. The perovskite precursor solution is attached to the surface of the sample treated in step S2 to form a perovskite film. S303. Place the sample on the carrier tray in the chamber of the molecular layer deposition equipment, raise the temperature of the carrier tray to 60-80°C, raise the temperature of the source bottle to 90-110°C and maintain the temperature. S304. Start the vacuum pump and purge the chamber with nitrogen. After 25-35 seconds, turn off the nitrogen. Use the vacuum pump to reduce the pressure in the chamber to 1 kPa and then turn off the vacuum pump. Then, use nitrogen as a carrier gas to load the lactic acid in the source bottle into the chamber. After 3-6 seconds, turn off the source bottle and nitrogen and maintain this for 20-40 seconds. Repeat this step 5 times. S305. After the cycle, reduce the pressure in the chamber to 0 Pa, turn off the vacuum pump, raise the temperature of the loading tray to 90-110°C and maintain it for 8-15 minutes; then introduce nitrogen into the chamber to restore it to normal pressure, and the perovskite layer preparation is complete. S4. Cover the perovskite layer with a hole transport layer or an electron transport layer; S5. Prepare a back electrode on the sample surface obtained in step S4 to complete the fabrication of the perovskite solar cell.

2. The method for preparing a perovskite solar cell according to claim 1, characterized in that: In step S305, the temperature of the loading tray is raised to 100°C and maintained for 10 minutes.

3. The method for preparing a perovskite solar cell according to claim 2, characterized in that: In step S303, the temperature of the carrier plate is raised to 70°C and the temperature of the source bottle is raised to 100°C.

4. The method for preparing a perovskite solar cell according to claim 3, characterized in that: The perovskite thin film preparation methods in step S302 include spin coating, vapor deposition, inkjet printing, doctor blade coating, or screen printing.

5. A method for preparing a perovskite solar cell according to any one of claims 1-4, characterized in that: The perovskite layer has a structure including a two-dimensional crystal structure, a three-dimensional crystal structure, or a two-dimensional / three-dimensional mixed crystal structure.

6. The method for preparing a perovskite solar cell according to claim 5, characterized in that: The methods for preparing the electron transport layer and hole transport layer include spin coating, chemical bath method, atomic layer deposition or vapor deposition.

7. The method for preparing a perovskite solar cell according to claim 6, characterized in that: The electron transport layer is titanium dioxide, zinc oxide, tin oxide, or fullerene and its derivatives.

8. The method for preparing a perovskite solar cell according to claim 7, characterized in that: The hole transport layer is Spiro-OMeTAD, P3HT, PTAA, CuI, or NiOx.

9. The method for preparing a perovskite solar cell according to claim 8, characterized in that: The back electrode is prepared by methods including spin coating, vapor deposition, inkjet printing, doctor blade coating, screen printing, or atomic layer deposition; the back electrode material is gold, silver, or carbon paste.

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that: The conductive substrate is an ITO substrate; step S1 includes: cleaning the ITO substrate by ultrasonically cleaning it in acetone, ethanol, and deionized water for 10-20 minutes; drying the cleaned ITO substrate with nitrogen gas and drying it at 95-105°C for 2 hours; taking it out and letting it cool to room temperature before placing it in a plasma-ozone generator for 10-20 minutes.

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