A C-based 60 Hysteresis-free flexible perovskite solar cells with SnO2 composite electron transport layer and their fabrication method

Abstract

The application discloses a kind of based on C 60 SnO2 composite electron transport layer's non-hysteresis flexible perovskite solar cell and preparation method thereof belong to the technical field of semiconductor optoelectronic device preparation field.The application adopts low-temperature atomic layer deposition technology, in C 60 Surface in situ deposition SnO2 Film, through spin coating process constructs C 60 SnO2 composite electron transport layer for flexible perovskite solar cell.The application utilizes SnO2 to bridge C 60 Electronic transport layer and perovskite layer, its special structure and surface functional group effectively enhance the chemical interaction between C 60 Perovskite, passivates interface defect.Meanwhile the hydrophobicity of C 60 Heterogeneous nucleation process of perovskite film is inhibited, and high-quality perovskite grain with larger and more uniform size is generated, realizing bulk defect passivation of perovskite, hysteresis phenomenon is obviously inhibited, and good stability is shown, and the performance and stability of solar cell are synergistically improved.

Description

Technical Field

[0001] This invention relates to a C-based 60 The invention relates to a hysteresis-free flexible perovskite solar cell with a SnO2 composite electron transport layer and its fabrication method, belonging to the field of semiconductor optoelectronic device fabrication technology. Background Technology

[0002] Solar energy is considered the most important renewable energy source due to its numerous advantages, including being clean, environmentally friendly, pollution-free, highly valuable, and not facing energy depletion. In the utilization of solar energy, solar cells, which convert solar energy into electricity, have attracted widespread attention. Currently, solar cells mainly include silicon-based solar cells, compound semiconductor thin-film batteries, organic solar cells, dye-sensitized solar cells, and perovskite solar cells. Among them, perovskite solar cells, due to their simple fabrication methods and high photoelectric conversion efficiency (currently exceeding 25%), have seen their development speed far surpass that of other traditional batteries.

[0003] Compared to rigid perovskite solar cells, flexible perovskite solar cells offer a range of advantages, including lightweight, bendability, and compatibility with roll-to-roll (R2R) mass production, demonstrating significant application potential in wearable electronic devices, mobile power supply, and smart photovoltaics. The biggest factor hindering the development of flexible perovskite solar cells is their mechanical bending stability. Poor ductility and flexibility of inorganic and electrode materials, significant differences in interlayer stress distribution during bending, mismatched stretching, and intergranular frictional fracture all contribute to the rapid decline in efficiency of flexible devices with increasing bending cycles. Therefore, improving bending stability while maintaining high conversion efficiency is a crucial challenge that urgently needs to be addressed for the application of flexible perovskite solar cells.

[0004] Flexible perovskite solar cells are heterogeneous structures composed of a flexible substrate, an electron transport layer, a light absorption layer, a hole transport layer, and metal electrodes. Currently, they are mostly constructed layer by layer. Therefore, the strength of the interlayer bonding directly affects the photoelectric conversion efficiency of the device. A good interlayer interface structure will facilitate the growth and nucleation of materials in each layer, improve the electron transport rate, and is a key factor that facilitates stress release during the bending process of the cell, which can greatly improve the bending stability of the device.

[0005] Traditional electron transport layer material TiO2 has low electron mobility, high trapped state density, and requires high-temperature processing, making it difficult to meet the development requirements of flexible perovskite solar cells. Metal oxides such as ZnO and SnO2 have much higher electron mobility than TiO2, better match with perovskite, and are easier to prepare at low temperatures. However, perovskite solar cells based on a single inorganic electron transport layer exhibit some hysteresis, limiting the photoelectric conversion efficiency of the device. Furthermore, the single inorganic electron transport layer is brittle and prone to cracking, resulting in poor bending stability of the prepared flexible perovskite solar cells. In addition, existing methods for improving the photoelectric conversion efficiency of flexible perovskite solar cells have many drawbacks; for example, while low-temperature solution methods can produce metal oxides, they cannot achieve large-area fabrication.

[0006] Fullerenes and their derivatives possess advantages such as low-temperature solution processing, excellent bending resistance, good electron transport performance, and reduced hysteresis effects, and have been widely used in flexible perovskite solar cells. However, the poor energy level matching between fullerenes and other organic materials and perovskites hinders further improvements in solar cell performance. Therefore, combining the advantages of inorganic metal oxides and organic materials to provide a novel composite electron transport layer material is of great significance for improving the overall performance of the battery. Summary of the Invention

[0007] To address the aforementioned technical problems in the prior art, this invention provides a C-based... 60 Hysteresis-free flexible perovskite solar cells with a SnO2 composite electron transport layer and their fabrication method.

[0008] The technical solution of the present invention:

[0009] One of the objectives of this invention is to provide a C 60 - A method for preparing a SnO2 composite electron transport layer, the method comprising the following steps:

[0010] S1, for C 60 Powder undergoes atomic layer deposition (ALD) treatment at C 60 SnO2 is deposited on the surface of the powder to obtain C 60 -SnO2 powder;

[0011] S2, C 60 -SnO2 powder is dissolved in chlorobenzene to obtain a solution;

[0012] S3, the solution obtained in S2 is spin-coated onto the pretreated substrate, and C is obtained on the substrate surface after annealing. 60 -The dense SnO2 layer is the composite electron transport layer.

[0013] Further specifying, the atomic layer deposition process in step S1 is as follows:

[0014] (1) C 60 The powder was placed in the deposition chamber of the atomic layer deposition instrument, and the pressure inside the deposition chamber was evacuated to 1×10⁻⁶. -3 ~2×10 -3 Pa, then introduce carrier gas until the cavity pressure is 0.1-0.2 Pa, and set the temperature inside the deposition cavity to 70-110℃;

[0015] (2) In C 60 Atomic layer deposition was performed on the powder surface, and this process was repeated for 300–500 growth and deposition cycles to obtain C. 60 -SnO2 powder.

[0016] To further define it, the process of each growth and deposition cycle is as follows:

[0017] ① A tin source is injected into the deposition chamber of the atomic layer deposition instrument in a pulsed manner, with a pulse time t1 of 0.07–0.09 s;

[0018] ②The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t2 of 1 to 5 seconds;

[0019] ③ Open the intake and exhaust valves and purge with nitrogen. The purging time t3 is 30-60 seconds.

[0020] ④ Inject oxygen into the deposition chamber in a pulsed manner. The oxygen source temperature is room temperature, and the pulse time t4 is 0.01 to 0.03 s.

[0021] ⑤ The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t5 of 1 to 5 seconds;

[0022] ⑥ Open the intake and exhaust valves and purge with nitrogen for 30-60 seconds.

[0023] To further specify, the tin source is tetra(dimethylamino)tin.

[0024] Furthermore, the oxygen source is deionized water.

[0025] Further specifying, the solution concentration in step S2 is 10–30 mg / mL.

[0026] Further specifying, the spin coating operation in step S3 is as follows:

[0027] Spin-coat the solution onto the pretreated substrate at a speed of 3000-5000 rpm for 30-50 seconds.

[0028] Further specified, the annealing temperature in step S3 is 70-100℃, and the annealing time is 5-10 min.

[0029] The second objective of this invention is to provide a C prepared by the above method. 60 -SnO2 composite electron transport layer.

[0030] The third objective of this invention is to provide a hysteresis-free flexible perovskite solar cell, the structure of which, from bottom to top, consists of a flexible substrate, an electron transport layer, a light absorption layer, a hole transport layer, and a metal electrode.

[0031] Among them, the electron transport layer is the aforementioned C 60 -SnO2 composite electron transport layer.

[0032] The fourth objective of this invention is to provide a method for fabricating the above-mentioned hysteresis-free flexible perovskite solar cell, the method comprising the following steps:

[0033] I. Pretreatment of flexible substrate materials:

[0034] Cut the ITO / PEN substrate to the required size using a cutter, and then clean it.

[0035] II. Fabrication of the electron transport layer:

[0036] C is prepared on the surface of the pretreated flexible substrate material. 60 -SnO2 composite electron transport layer:

[0037] III. Preparation of the perovskite absorber layer:

[0038] Using PbI2, HC(NH2)2I, CH3NH3Br, PbBr2, and CsI as raw materials, a one-step antisolvent method was employed to achieve the desired effect in C... 60 - A CsFAMA ternary cationic perovskite film was prepared on a SnO2 composite electron transport layer;

[0039] IV. Preparation of the hole transport layer:

[0040] Spiro-OMeTAD hole transport layer was prepared on perovskite absorber layer by spin-coating oxidation.

[0041] V, Preparation of metal electrodes:

[0042] An Au electrode layer was deposited on the hole transport layer using a vacuum evaporation coating apparatus.

[0043] To further define it, the specific operation process of step I is as follows:

[0044] First, use a cutter to cut ITO / PEN into squares with sides of 1-3cm to serve as flexible base material;

[0045] Then, the flexible substrate material is placed on a cleaning rack and ultrasonically cleaned with a cleaning agent aqueous solution for 0.5 to 2 hours. The residual detergent on the flexible substrate material is then washed away with deionized water.

[0046] Then, the material is ultrasonically cleaned with deionized water, ethanol, and isopropanol in sequence for 0.5 to 2 hours. After ultrasonic cleaning, nitrogen gas is used to blow dry the surface of the flexible substrate material to remove any residual isopropanol.

[0047] Finally, blow away any remaining dust, place the material in a clean petri dish, and clean it in a UV ozone cleaner for 10–30 minutes. After cleaning, remove the material to complete the pretreatment of the flexible substrate material, and set it aside for later use.

[0048] Furthermore, the cleaning agent aqueous solution is Opivet cleaning agent with a volume fraction of 5%.

[0049] Furthermore, the purity of nitrogen is specified to be 99.99%.

[0050] To further specify, the purpose of using an ultraviolet ozone cleaner is to improve the surface wettability of flexible substrate materials.

[0051] Further specifying, the specific operation process of step II is as follows:

[0052] S1, for C 60 Powder undergoes atomic layer deposition (ALD) treatment at C 60 SnO2 is deposited on the surface of the powder to obtain C 60 -SnO2 powder;

[0053] The atomic layer deposition process in step S1 is as follows:

[0054] (1) C 60 The powder was placed in the deposition chamber of the atomic layer deposition instrument, and the pressure inside the deposition chamber was evacuated to 1×10⁻⁶. -3 ~2×10 -3 Pa, then introduce carrier gas until the cavity pressure is 0.1-0.2 Pa, and set the temperature inside the deposition cavity to 70-110℃;

[0055] (2) In C 60 Atomic layer deposition was performed on the powder surface, and this process was repeated for 300–500 growth and deposition cycles to obtain C. 60 -SnO2 powder;

[0056] The process of each growth and deposition cycle is as follows:

[0057] ① A tin source is injected into the deposition chamber of the atomic layer deposition instrument in a pulsed manner, with a pulse time t1 of 0.07–0.09 s;

[0058] ②The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t2 of 1 to 5 seconds;

[0059] ③ Open the intake and exhaust valves and purge with nitrogen. The purging time t3 is 30-60 seconds.

[0060] ④ Inject oxygen into the reaction chamber in a pulsed manner. The oxygen source temperature is room temperature, and the pulse time t4 is 0.01 to 0.03 s.

[0061] ⑤ The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t5 of 1 to 5 seconds;

[0062] ⑥ Open the intake and exhaust valves and purge with nitrogen. The purging time t6 is 30-60 seconds.

[0063] S2, C 60 -SnO2 powder is dissolved in chlorobenzene to prepare a solution with a concentration of 10-30 mg / mL;

[0064] S3, the solution obtained in S2 is spin-coated onto the pretreated substrate at a speed of 3000-5000 rpm for 30-50 seconds. After spin-coating, the substrate is placed on a heating table for annealing at a temperature of 70-100℃ for 5-10 minutes. After annealing, C is obtained on the surface of the flexible substrate material. 60 -SnO2 dense layer, completing the preparation of electron transport layer.

[0065] To further define the specific operation process of step III, it is as follows:

[0066] Weigh PbI2, PbBr2, HC(NH2)2I and CH3NH3Br in an analytical balance in a glove box and place them in a reagent bottle. Add a mixed solution of DMF and DMSO with a volume ratio of 4:1 to obtain a reaction solution. Place the solution in a magnetic stirrer and stir at 30-40°C for 8-12 hours. Then add CsI solution and continue stirring for 2-4 hours.

[0067] After the reaction is complete, the solution is filtered and the filtrate is spin-coated onto the electron transport layer. Before the spin coating is complete, the antisolvent chlorobenzene is added dropwise. After the spin coating is complete, the solution is placed on a hot stage and heated at 100–140°C for 30–80 min to obtain a perovskite absorption layer on the electron transport layer.

[0068] Furthermore, the concentration of Pb source (PbI2 and PbBr2) in the reaction solution is 1.4 mol / L, and the concentration of organic salt source (HC(NH2)2I and CH3NH3Br) is 1.3 mol / L.

[0069] Furthermore, the molar ratio of PbI2 to PbBr2 in the Pb source is 85:15.

[0070] Furthermore, the molar ratio of HC(NH2)2I to CH3NH3Br in the organic salt source is 85:15.

[0071] Furthermore, the preparation process of the CsI solution is as follows: 208 mg of CsI is dissolved in 400 μL of DMSO and stirred for 8–14 h.

[0072] To further specify, the spin coating process is as follows:

[0073] First, spin-coat the filtrate onto the electron transport layer at a speed of 1000-1400 rpm for 5-15 seconds.

[0074] Then, increase the rotation speed to 4000-6000 rpm and spin coat for 40-60 seconds.

[0075] To further specify, the anti-solvent chlorobenzene is added 15–16 seconds before spin coating is completed.

[0076] To further define it, the specific operation process of step IV is as follows:

[0077] First, Spiro-OMeTAD was weighed and dissolved in chlorobenzene and stirred for 1.5–3 hours to obtain a Spiro-OMeTAD / chlorobenzene solution for later use; Li-TFSI was weighed and dissolved in acetonitrile and stirred for 1.5–3 hours to obtain a Li-TFSI / acetonitrile solution for later use.

[0078] Then, 4-tert-butylpyridine and Li-TFSI / acetonitrile solution were added to the Spiro-OMeTAD / chlorobenzene solution and stirred for 2-4 hours to obtain the precursor solution;

[0079] Next, take the precursor solution and spin-coat it onto the perovskite absorber layer at a speed of 3000-5000 rpm for 30-50 seconds.

[0080] Finally, the material is placed in a drying oven with a humidity of <20% for 8–12 hours to oxidize, thereby obtaining a hole transport layer on the perovskite absorber layer.

[0081] Further specifying, the thickness of the Au electrode layer in step V is 60-100 nm.

[0082] This invention employs low-temperature atomic layer deposition technology, in C 60 SnO2 is deposited on the surface, and C is constructed by spin coating. 60 -A SnO2 composite electron transport layer is applied to flexible perovskite solar cells. Compared with existing technologies, this application has the following advantages:

[0083] (1) This invention employs low-temperature atomic layer deposition technology to achieve C at the atomic / molecular level and nanoscale.60 The controllable fabrication of SnO2 composite electron transport layers enables atomically controlled growth of monomolecular thin films. This method features low substrate temperature, precise and controllable morphology, abundant surface functional groups, and good film uniformity, achieving full compatibility with flexible substrates.

[0084] (2) C prepared by the present invention 60 The SnO2 composite electron transport layer structure exhibits stronger electron extraction capability and lower interface defect state density compared to a single-layer electron transport layer. It also combines the properties of SnO2 and C. 60 Their respective performance advantages can effectively improve the carrier lifetime and photoelectric conversion efficiency of perovskite solar cells.

[0085] (3) In the process of solar cell fabrication, this invention utilizes SnO2 to bridge C 60 The electron transport layer and perovskite layer, with their unique structure and surface functional groups, effectively enhance C 60 The chemical interaction with the perovskite passivates interface defects. Meanwhile, C... 60 The hydrophobicity of the material inhibits the heterogeneous nucleation process of the perovskite film, promotes the generation of larger and more uniform high-quality perovskite grains, achieves passivation of bulk defects in perovskite, significantly suppresses hysteresis, and demonstrates good stability, thus achieving a synergistic improvement in device performance and stability.

[0086] (4) This invention uses C 60 - Flexible perovskite solar cells based on SnO2 composite electron transport layers exhibit C during bending. 60 It can disperse stress, effectively suppressing the occurrence of cracks in the electron transport layer and perovskite layer caused by stress accumulation, and greatly improving the bending stability of flexible perovskite solar cells. Attached Figure Description

[0087] Figure 1 A photograph of the flexible perovskite solar cell prepared in Example 1;

[0088] Figure 2 An atomic force microscope (AFM) image of the perovskite absorbing layer prepared for Comparative Example 1;

[0089] Figure 3 An atomic force microscope (AFM) image of the perovskite absorbing layer prepared for Comparative Example 2;

[0090] Figure 4 An atomic force microscope (AFM) image of the perovskite absorbing layer prepared in Example 1;

[0091] Figure 5The photoelectric density-voltage (JV) curve of the solar cell prepared in Example 1;

[0092] Figure 6 Photovoltaic density-voltage (JV) curves of the solar cell prepared for Comparative Example 1;

[0093] Figure 7 Photovoltaic density-voltage (JV) curves of the solar cell prepared for Comparative Example 2;

[0094] Figure 8 The graph shows the test results of the bending stability of the solar cells prepared in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0095] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0096] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0097] Example 1:

[0098] The specific process for fabricating flexible perovskite solar cells in this embodiment is carried out according to the following steps:

[0099] Step 1, Pretreatment of flexible substrate material

[0100] (1) Use a cutter to cut the ITO / PEN into squares with a side length of 2cm, which will serve as the flexible substrate material (hereinafter referred to as ITO-PEN). The reason for using a cutter in this step is that the presence of shear force will cause the ITO-PEN to crack in the part subjected to shear stress, and in order to make the edges and corners of the flexible substrate material more even, a cutter is chosen for cutting.

[0101] (2) Place the ITO-PEN on the cleaning rack and first use an aqueous cleaning solution (Opivit cleaning agent, 5% volume fraction) for 1 hour of ultrasonic treatment. Then wash away the residual detergent on the ITO-PEN with deionized water. Next, use deionized water, ethanol, and isopropanol in sequence for 0.5 hours of ultrasonic treatment. After ultrasonic treatment, blow the remaining isopropanol on the ITO-PEN with nitrogen (purity 99.99%).

[0102] (3) Blow away the residual dust, place it in a clean petri dish, and clean it in an ultraviolet ozone cleaner for 20 minutes. After cleaning, take it out for use.

[0103] Step 2, prepare C on a flexible substrate material 60 -SnO2 composite electron transport layer

[0104] (1) C 60 The powder was placed in the deposition chamber of the atomic layer deposition instrument, and the pressure inside the deposition chamber was evacuated to 1×10⁻⁶. -3 Pa, then carrier gas is introduced until the cavity pressure is 0.2 Pa, the temperature inside the deposition cavity is set to 110℃, and this process is repeated for 300 growth and deposition cycles to obtain C. 60 -SnO2 powder.

[0105] The process of each growth and deposition cycle is as follows:

[0106] ① Tin source tetra(dimethylamino)tin was injected into the deposition chamber of the atomic layer deposition instrument in a pulsed manner, with a pulse time t1 of 0.07s;

[0107] ②The intake valve and exhaust valve are shut off to allow for a reaction, and the reaction time t2 is 5s;

[0108] ③ Open the intake and exhaust valves and purge with nitrogen. The purging time t3 is 60s.

[0109] ④ Inject oxygen-sourced deionized water into the reaction chamber in a pulsed manner. The oxygen source temperature is room temperature, and the pulse time t4 is 0.03s.

[0110] ⑤ The intake valve and exhaust valve are shut off to allow for a reaction, and the reaction time t5 is 5 seconds.

[0111] ⑥ Open the intake and exhaust valves and purge with nitrogen for 60 seconds.

[0112] (2) The C obtained above 60 SnO2 powder was dissolved in chlorobenzene to prepare a solution with a concentration of 20 mg / mL. The solution was then spin-coated onto a pretreated ITO-PEN substrate at 3000 rpm for 30 seconds.

[0113] (3) The spin-coated substrate was placed on a heating stage, and the annealing temperature was 80℃ for 5 min. After annealing, a 50 nm thick C layer was obtained on the ITO-PEN surface. 60 -SnO2 dense layer, serving as an electron transport layer.

[0114] Step 3: Fabricate a perovskite absorber layer on the electron transport layer.

[0115] (1) Weigh 548.6 mg PbI2, 77.07 mg PbBr2, 190.12 mg HC(NH2)2I and 21.84 mg CH3NH3Br into a reagent bottle using an analytical balance in a glove box. Add 1 mL of a 4:1 mixture of DMF and DMSO to obtain the reaction solution. Stir the solution in a magnetic stirrer at 35 °C for 10 h. Then add 34 μL of CsI solution and continue stirring for 2 h. The CsI solution was prepared by dissolving 208 mg of CsI in 400 μL of DMSO and stirring for 10 h.

[0116] After the reaction was completed, the solution was filtered, and the filtrate was spin-coated onto the electron transport layer. The specific operation process was as follows: spin-coating at 1300 rpm for 15 seconds; then, the speed was increased to 5000 rpm and spin-coated for 45 seconds. 15 seconds before the spin-coating was completed, 200 μL of the anti-solvent chlorobenzene was added dropwise. After spin-coating, the solution was placed on a hot stage and heated at 110 °C for 60 minutes to obtain a perovskite absorption layer with a thickness of 400 nm on the electron transport layer.

[0117] Step 4: Fabricate a hole transport layer on the perovskite absorber layer.

[0118] (1) Weigh 72.3 mg Spiro-OMeTAD and dissolve it in 1 mL of chlorobenzene and stir for 2 h to obtain a Spiro-OMeTAD / chlorobenzene solution for later use; weigh 260 mg Li-TFSI and dissolve it in 500 μL of acetonitrile and stir for 2 h to obtain a Li-TFSI / acetonitrile solution for later use.

[0119] (2) Add 28.8 μL of 4-tert-butylpyridine and 18 μL of Li-TFSI / acetonitrile solution to Spiro-OMeTAD / chlorobenzene solution and stir for 2 h to obtain the precursor solution.

[0120] (3) Take 90 μL of precursor solution and spin-coat it onto the perovskite absorber layer at a speed of 3000 rpm for 30 s.

[0121] (4) Place it in a drying oven with a humidity of <20% for 8 hours to obtain a hole transport layer with a thickness of 200nm on the perovskite absorption layer.

[0122] The final product obtained in this step was characterized by its microstructure, and atomic force microscopy (AFM) images are shown below. Figure 4 As shown, its root mean square roughness is 7.23 nm.

[0123] Step 5: Fabricate metal electrodes on the hole transport layer.

[0124] A flexible perovskite solar cell was fabricated by depositing an Au electrode layer with a thickness of approximately 80 nm on the hole transport layer using a vacuum evaporation deposition apparatus. The resulting flexible perovskite solar cell is shown in the figure. Figure 1 As shown.

[0125] The photoelectric conversion efficiency of the obtained flexible perovskite solar cells was characterized, and the photoelectric density-voltage (JV) curves are shown below. Figure 5 As shown, the performance parameters are detailed in Table 1 below:

[0126] PCE (%) <![CDATA[J sc (mA / cm 2 )]]> <![CDATA[V oc (V)]]> FF (%) Forward 20.74 23.12 1.05 78.5 Reverse 20.78 23.08 1.04 79.4

[0127] Depend on Figure 5 As shown in Table 1, the solar cell prepared in this embodiment has a high photoelectric conversion efficiency and the hysteresis effect can be ignored.

[0128] The bending stability of the obtained flexible perovskite solar cells was tested, and the results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the solar cell obtained in this embodiment has good bending stability. After 1000 bending cycles at a curvature radius of 9mm, the photoelectric conversion efficiency still remains above 80% of the original efficiency.

[0129] Comparative Example 1:

[0130] The difference between this comparative example and Example 1 is that a single SnO2 dense layer is used as the electron transport layer. The specific process for fabricating the flexible perovskite solar cell in this comparative example is as follows:

[0131] Step 1, Pretreatment of flexible substrate material

[0132] (1) Use a cutter to cut the ITO / PEN into squares with a side length of 1 to 3 cm, which will serve as the flexible substrate material (hereinafter referred to as ITO-PEN). The reason for using a cutter in this step is that the presence of shear force will cause the ITO-PEN to crack in the part subjected to shear stress, and in order to make the edges and corners of the flexible substrate material more even, a cutter is selected for cutting.

[0133] (2) Place the ITO-PEN on the cleaning rack and first use an aqueous cleaning solution (Opivit cleaning agent, 5% volume fraction) for 1 hour of ultrasonic treatment. Then wash away the residual detergent on the ITO-PEN with deionized water. Next, use deionized water, ethanol, and isopropanol in sequence for 0.5 hours of ultrasonic treatment. After ultrasonic treatment, blow the remaining isopropanol on the ITO-PEN with nitrogen (purity 99.99%).

[0134] (3) Blow away the residual dust, place it in a clean petri dish, and clean it in an ultraviolet ozone cleaner for 20 minutes. After cleaning, take it out for use.

[0135] Step 2: Prepare a SnO2 composite electron transport layer on a flexible substrate material.

[0136] (1) SnO2 (15% aqueous dispersion) and deionized water were mixed at a volume ratio of 1:4 to prepare an aqueous SnO2 solution. Then, the solution was spin-coated onto the pretreated ITO-PEN substrate at a speed of 3000 rpm for 30 s.

[0137] (2) The spin-coated substrate was placed on a heating stage. The annealing temperature was 80°C and the annealing time was 5 min. After annealing, a SnO2 dense layer with a thickness of 50 nm was obtained on the ITO-PEN surface as an electron transport layer.

[0138] Step 3: Fabricate a perovskite absorber layer on the electron transport layer.

[0139] (1) Weigh 548.6 mg PbI2, 77.07 mg PbBr2, 190.12 mg HC(NH2)2I and 21.84 mg CH3NH3Br into a reagent bottle using an analytical balance in a glove box. Add 1 mL of a 4:1 mixture of DMF and DMSO to obtain the reaction solution. Stir the solution in a magnetic stirrer at 35 °C for 10 h. Then add 34 μL of CsI solution and continue stirring for 2 h. The CsI solution was prepared by dissolving 208 mg of CsI in 400 μL of DMSO and stirring for 10 h.

[0140] After the reaction was completed, the solution was filtered, and the filtrate was spin-coated onto the electron transport layer. The specific operation process was as follows: spin-coating at 1300 rpm for 15 seconds; then, the speed was increased to 5000 rpm and spin-coated for 45 seconds. 15 seconds before the spin-coating was completed, 200 μL of the anti-solvent chlorobenzene was added dropwise. After spin-coating, the solution was placed on a hot stage and heated at 110 °C for 60 minutes to obtain a perovskite absorption layer with a thickness of 400 nm on the electron transport layer.

[0141] Step 4: Fabricate a hole transport layer on the perovskite absorber layer.

[0142] (1) Weigh 72.3 mg Spiro-OMeTAD and dissolve it in 1 mL of chlorobenzene and stir for 2 h to obtain a Spiro-OMeTAD / chlorobenzene solution for later use; weigh 260 mg Li-TFSI and dissolve it in 500 μL of acetonitrile and stir for 2 h to obtain a Li-TFSI / acetonitrile solution for later use.

[0143] (2) Add 28.8 μL of 4-tert-butylpyridine and 18 μL of Li-TFSI / acetonitrile solution to Spiro-OMeTAD / chlorobenzene solution and stir for 2 h to obtain the precursor solution.

[0144] (3) Take 90 μL of precursor solution and spin-coat it onto the perovskite absorber layer at a speed of 3000 rpm for 30 s.

[0145] (4) Place it in a drying oven with a humidity of <20% for 8 hours to obtain a hole transport layer with a thickness of 200nm on the perovskite absorption layer.

[0146] The final product obtained in this step was characterized by its microstructure, and atomic force microscopy (AFM) images are shown below. Figure 2 As shown, its root mean square roughness is 13 nm.

[0147] Step 5: Fabricate metal electrodes on the hole transport layer.

[0148] A flexible perovskite solar cell was fabricated by depositing an Au electrode layer with a thickness of approximately 80 nm on the hole transport layer using a vacuum evaporation coating apparatus.

[0149] The photoelectric conversion efficiency of the flexible perovskite solar cell obtained in this comparative example was characterized, and the photoelectric density-voltage (JV) curve is shown below. Figure 6 As shown, the performance parameters are detailed in Table 2 below:

[0150] PCE (%) <![CDATA[J sc (mA / cm 2 )]]> <![CDATA[V oc (V)]]> FF (%) Forward 18.37 22.34 1.05 75.44 Reverse 17.93 21.84 1.00 74.35

[0151] The bending stability of the obtained flexible perovskite solar cells was tested, and the results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the bending stability of the solar cell obtained in this comparative example is lower than that of the solar cell obtained in Example 1.

[0152] Comparative Example 2:

[0153] The difference between this comparative example and Example 1 is that it uses a single C 60 The dense layer serves as the electron transport layer. The specific process for fabricating this comparative example of a flexible perovskite solar cell is as follows:

[0154] Step 1, Pretreatment of flexible substrate material

[0155] (1) Use a cutter to cut the ITO / PEN into squares with a side length of 1 to 3 cm, which will serve as the flexible substrate material (hereinafter referred to as ITO-PEN). The reason for using a cutter in this step is that the presence of shear force will cause the ITO-PEN to crack in the part subjected to shear stress, and in order to make the edges and corners of the flexible substrate material more even, a cutter is selected for cutting.

[0156] (2) Place the ITO-PEN on the cleaning rack and first use an aqueous cleaning solution (Opivit cleaning agent, 5% volume fraction) for 1 hour of ultrasonic treatment. Then wash away the residual detergent on the ITO-PEN with deionized water. Next, use deionized water, ethanol, and isopropanol in sequence for 0.5 hours of ultrasonic treatment. After ultrasonic treatment, blow the remaining isopropanol on the ITO-PEN with nitrogen (purity 99.99%).

[0157] (3) Blow away the residual dust, place it in a clean petri dish, and clean it in an ultraviolet ozone cleaner for 20 minutes. After cleaning, take it out for use.

[0158] Step 2, prepare C on a flexible substrate material 60 Electron transport layer

[0159] (1) C 60 The powder was dissolved in chlorobenzene to prepare a solution with a concentration of 20 mg / mL, and then spin-coated onto the pretreated ITO-PEN substrate at a speed of 3000 rpm for 30 s.

[0160] (3) The spin-coated substrate was placed on a heating stage, and the annealing temperature was 80℃ for 5 min. After annealing, a 50 nm thick C layer was obtained on the ITO-PEN surface. 60 The dense layer serves as an electron transport layer.

[0161] Step 3: Fabricate a perovskite absorber layer on the electron transport layer.

[0162] (1) Weigh 548.6 mg PbI2, 77.07 mg PbBr2, 190.12 mg HC(NH2)2I and 21.84 mg CH3NH3Br into a reagent bottle using an analytical balance in a glove box. Add 1 mL of a 4:1 mixture of DMF and DMSO to obtain the reaction solution. Stir the solution in a magnetic stirrer at 35 °C for 10 h. Then add 34 μL of CsI solution and continue stirring for 2 h. The CsI solution was prepared by dissolving 208 mg of CsI in 400 μL of DMSO and stirring for 10 h.

[0163] After the reaction was completed, the solution was filtered, and the filtrate was spin-coated onto the electron transport layer. The specific operation process was as follows: spin-coating at 1300 rpm for 15 seconds; then, the speed was increased to 5000 rpm and spin-coated for 45 seconds. 15 seconds before the spin-coating was completed, 200 μL of the anti-solvent chlorobenzene was added dropwise. After spin-coating, the solution was placed on a hot stage and heated at 110 °C for 60 minutes to obtain a perovskite absorption layer with a thickness of 400 nm on the electron transport layer.

[0164] Step 4: Fabricate a hole transport layer on the perovskite absorber layer.

[0165] (1) Weigh 72.3 mg Spiro-OMeTAD and dissolve it in 1 mL of chlorobenzene and stir for 2 h to obtain a Spiro-OMeTAD / chlorobenzene solution for later use; weigh 260 mg Li-TFSI and dissolve it in 500 μL of acetonitrile and stir for 2 h to obtain a Li-TFSI / acetonitrile solution for later use.

[0166] (2) Add 28.8 μL of 4-tert-butylpyridine and 18 μL of Li-TFSI / acetonitrile solution to Spiro-OMeTAD / chlorobenzene solution and stir for 2 h to obtain the precursor solution.

[0167] (3) Take 90 μL of precursor solution and spin-coat it onto the perovskite absorber layer at a speed of 3000 rpm for 30 s.

[0168] (4) Place it in a drying oven with a humidity of <20% for 8 hours to obtain a hole transport layer with a thickness of 200nm on the perovskite absorption layer.

[0169] The final product obtained in this step was characterized by its microstructure, and atomic force microscopy (AFM) images are shown below. Figure 3 As shown, its root mean square roughness is 8.45 nm, compared to... Figures 1-3 It can be seen that the C prepared in Example 1 60 Compared to the perovskite film with a single SnO2 electron transport layer prepared in Comparative Example 1 and the perovskite film with a single C electron transport layer prepared in Comparative Example 2, the perovskite film with a SnO2 composite electron transport layer is a different material. 60 The perovskite film of the electron transport layer is smoother, which proves that the composite electron transport layer prepared in Example 1 is more conducive to the deposition of perovskite film.

[0170] Step 5: Fabricate metal electrodes on the hole transport layer.

[0171] A flexible perovskite solar cell was fabricated by depositing an Au electrode layer with a thickness of approximately 80 nm on the hole transport layer using a vacuum evaporation coating apparatus.

[0172] The photoelectric conversion efficiency of the flexible perovskite solar cell obtained in this comparative example was characterized, and the photoelectric density-voltage (JV) curve is shown below. Figure 7 As shown, the performance parameters are detailed in Table 3 below:

[0173] PCE (%) <![CDATA[J sc (mA / cm 2 )]]> <![CDATA[V oc (V)]]> FF (%) Forward 17.35 19.7 1.02 67.86 Reverse 16.48 19.6 1.01 67.61

[0174] The bending stability of the obtained flexible perovskite solar cells was tested, and the results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the bending stability of the solar cell obtained in this comparative example is lower than that of the solar cell obtained in Example 1.

[0175] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A type of C 60 The method for preparing a SnO2 composite electron transport layer is characterized by... Includes the following steps: S1, for C 60 Powder undergoes atomic layer deposition (ALD) treatment at C 60 SnO2 is deposited on the surface of the powder to obtain C 60 -SnO2 powder; S2, C 60 -SnO2 powder is dissolved in chlorobenzene to obtain a solution; S3, spin-coating the solution obtained in S2 onto the pretreated substrate, followed by annealing, to obtain C on the substrate surface. 60 -The dense SnO2 layer is the composite electron transport layer.

2. The C according to claim 1 60 The method for preparing a SnO2 composite electron transport layer is characterized by... The atomic layer deposition process in S1 is as follows: (1) C 60 The powder was placed in the deposition chamber of the atomic layer deposition instrument, and the pressure inside the deposition chamber was evacuated to 1×10⁻⁶. -3 ~2×10 -3 Pa, then introduce carrier gas until the cavity pressure is 0.1~0.2 Pa, and set the temperature inside the deposition cavity to 70~110℃; (2) In C 60 Atomic layer deposition was performed on the powder surface, and this process was repeated for 300-500 growth and deposition cycles to obtain C. 60 -SnO2 powder.

3. The C according to claim 2 60 The method for preparing a SnO2 composite electron transport layer is characterized by... Each of the aforementioned growth and deposition cycles is: ①Inject tin source into the deposition chamber of the atomic layer deposition instrument in a pulsed manner, with a pulse time t1 of 0.07~0.09s; ②The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t2 of 1~5s; ③ Open the intake and exhaust valves and purge with nitrogen. The purging time t3 is 30~60s. ④ Inject oxygen into the deposition chamber in a pulsed manner. The oxygen source temperature is room temperature, and the pulse time t4 is 0.01~0.03s. ⑤ The intake valve and exhaust valve are shut off to allow for a reaction, with a reaction time t5 of 1~5s; ⑥ Open the intake and exhaust valves and purge with nitrogen for 30-60 seconds.

4. The C according to claim 3 60 The method for preparing a SnO2 composite electron transport layer is characterized by... The tin source is tetra(dimethylamino)tin.

5. The C according to claim 3 60 The method for preparing a SnO2 composite electron transport layer is characterized by... The oxygen source is deionized water.

6. The C according to claim 1 60 The method for preparing a SnO2 composite electron transport layer is characterized by... The concentration of the solution in S2 is 10~30 mg / mL.

7. C according to claim 1 60 The method for preparing a SnO2 composite electron transport layer is characterized by... The annealing temperature in S3 is 70~100℃, and the time is 5~10min.

8. A C prepared by the method of claim 1 60 -SnO2 composite electron transport layer.

9. A hysteresis-free flexible perovskite solar cell, characterized in that, The solar cell structure consists of, from bottom to top, a flexible substrate, an electron transport layer, a light absorption layer, a hole transport layer, and a metal electrode. Wherein, the electron transport layer is the C as described in claim 8. 60 -SnO2 composite electron transport layer.

10. A method for fabricating a hysteresis-free flexible perovskite solar cell according to claim 9, characterized in that, The method includes the following steps: I. Pretreatment of flexible substrate materials: Cut the ITO / PEN substrate to the required size using a cutter, and then clean it. II. Fabrication of the electron transport layer: C is prepared on the surface of the pretreated flexible substrate material. 60 -SnO2 composite electron transport layer; III. Preparation of the perovskite absorber layer: Using PbI2, HC(NH2)2I, CH3NH3Br, PbBr2, and CsI as raw materials, a one-step antisolvent method was employed to achieve the desired effect in C 60 - A CsFAMA ternary cationic perovskite film was prepared on a SnO2 composite electron transport layer; IV. Preparation of the hole transport layer: Spiro-OMeTAD hole transport layer was prepared on perovskite absorber layer by spin-coating oxidation. V, Preparation of metal electrodes: An Au electrode layer was deposited on the hole transport layer using a vacuum evaporation coating apparatus.

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