Preparation of MA3Bi2I9 perovskite solar cells by controlling BiI3 thin film orientation via solvent evaporation

Abstract

The present invention proposes a method for preparing high-efficiency MA3Bi2I9 perovskite solar cells by controlling the orientation of BiI3 thin films by solvent evaporation induction. First, a BiI3 thin film is prepared by spin-coating a DMF precursor solution of BiI3 onto a fluorine-doped tin oxide (FTO) substrate on which TiO2 has been deposited. Subsequently, the prepared BiI3 wet film is placed in a sealed container at room temperature in a glove box. Due to the sealing conditions in the container, DMF evaporated from the wet film generates a DMF atmosphere, thereby greatly reducing its evaporation rate. By slowing down the evaporation of DMF, a BiI3 thin film with (113) and (300) preferred orientations and a weakened (003) crystal plane is successfully prepared. Subsequently, the prepared BiI3 thin film reacts with MAI to form an MBI thin film. Since the growth of the BiI3 (003) crystal plane is restricted, the (006) crystal plane of MBI is also effectively restricted, which is more conducive to carrier transport than devices prepared from MBI thin films with a (006) preferred orientation.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing high-efficiency MA3Bi2I9 perovskite solar cells by controlling the orientation of BiI3 thin films through solvent evaporation induction. Background Art

[0002] In recent years, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has rapidly increased from 3.9% to 25.7% based on the improvement of the optoelectronic properties and device structure of perovskite materials. However, due to the easy tilt of PbI6 octahedron in perovskite and the 2+ The presence of PbI6 and its toxicity greatly limits its market application prospects. Therefore, the development of non-toxic / low-toxic non-lead perovskite materials has very important scientific and application value. Among the many non-lead elements, Sn 2+ and Bi 3+ Replace Pb 2 + It has attracted widespread attention as an effective way to prepare environmentally friendly perovskite solar cells. Currently, tin-based perovskites have achieved an efficiency of 14.6%. However, the Sn content in tin-based perovskites is 2+ Easily oxidized to Sn 4+, which ultimately leads to its low photoelectric efficiency. Recently, bismuth-based perovskite MA3Bi2I9 (MBI) has attracted much attention due to its particularly excellent photoelectric properties and high stability in the environment. A large number of related studies have reported MBI perovskite solar cells, and their highest efficiency has reached 3.17%. The preparation method of MBI perovskite films was originally evolved from the lead-containing perovskite system, mainly one-step or two-step solvent method. Park.BW et al. first prepared MBI films with grain interdigitation by a one-step solution method and achieved an efficiency of 0.12%. Shin.SS et al. prepared MBI films with uniform surface and few holes by forming a Bi-DMF complex with Bi and DMF. However, the rapid crystallization of MBI films prepared by the solution method leads to the formation of a morphology with a large number of poorly interdigitated grains, which inhibits the transport of carriers in the perovskite film. In order to solve the problem of rapid crystallization of MBI films, the vapor-assisted solution method (VASP) was applied to the preparation of MBI films. Compared with traditional solution processes, vapor deposition can reduce the excessively fast intercalation reaction rate between BiI3 and CH3NH3I (MAI), avoid undesirable structural transformations during the solution process, and thus optimize the surface morphology of the perovskite. Ran et al. developed a two-step method to prepare uniform and pinhole-free MBI films by thermally evaporating BiI3 and then spin-coating MAI solution. The resulting device had a PCE of 0.39% and an open-circuit voltage of up to 0.83V. Zhang et al. obtained highly dense and uniform MBI films through a solvent-free contact method of vacuum deposition of BiI3 and MAI, ultimately achieving an efficiency of 1.64%. Jain et al. used BiI3 grains as nucleation centers to react with CH3NH2(MA) and HI vapor and prepared MBI perovskite films with uniform surface coverage, achieving a record-breaking maximum efficiency of 3.17%.

[0003] Studies have shown that the crystal structure and surface morphology of BiI3 thin films have a strong influence on the performance of MBI perovskite solar cells. Williamson.BW experimentally proved that the (003) crystal plane of BiI3 thin films is usually oriented parallel to the substrate. Generally speaking, after reacting with MAI, BiI3 thin films with (003) orientation can easily form (006) oriented MBI perovskite thin films, which is not conducive to carrier transport and collection to the electron / hole transport layer. On the other hand, previous studies have shown that BiI3 and MBI can form a (BiI3) when they coexist in thin films. 1-x (MBI) xThe energy level of the BiI3 film can be well matched with the energy level of TiO2, thereby improving the electron injection from the light absorption layer to the TiO2 layer. Therefore, the growth of the (003) crystal plane of the BiI3 film is suppressed and the BiI3 content in the MBI film is adjusted to effectively promote the carrier transport in the MBI solar cell. In response to the above problems, the present invention weakens the (003) preferential orientation of the BiI3 film by a DMF solvent evaporation induction method, and successfully prepares a BiI3 and MBI coexistence film that promotes carrier transport performance. By slowing down the evaporation of DMF, a BiI3 film with (113) and (300) preferential orientations and accompanied by the weakening of the (003) crystal plane is successfully prepared. Subsequently, the prepared BiI3 film reacts with MAI to form an MBI film. Since the growth of the BiI3 (003) crystal plane is restricted, the (006) crystal plane of MBI can also be effectively restricted, which is more conducive to carrier transport than the device prepared from the (006) oriented MBI film. In addition, by adjusting the reaction time to control the ratio of MBI to BiI3 in the film, a (BiI3) 1-x (MBI) x The energy level of the composite is better matched with that of TiO2, thereby improving the electron injection from the light absorbing layer to the TiO2 layer and thus improving the device performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of existing preparation technologies and provide a method for preparing MBI perovskite solar cells that is easy to operate, highly repeatable, has good crystal plane preferential orientation, and is conducive to carrier transport.

[0005] To solve the above technical problems, the present invention provides a method for preparing high-efficiency MBI perovskite solar cells by controlling the orientation of BiI3 thin films by solvent evaporation induction, which comprises:

[0006] The first step is to prepare BiI3 solution: weigh BiI3 solid powder, dissolve it in an organic solvent, stir it thoroughly at room temperature, filter it and set it aside;

[0007] The second step is spin coating, in which the solution prepared in the first step is spin-coated on a FTO substrate covered with an electron transport layer (TiO2) to form a uniform BiI3 film;

[0008] The third step is to let the film stand for different periods of time after the spin coating in the second step is completed.

[0009] The fourth step is annealing, placing the BiI3 film on a heating table for heating and annealing;

[0010] The fifth step is to prepare the MBI perovskite film. The BiI3 film prepared in the fourth step is placed in a culture dish with CH3NH3I (MAI) powder evenly dispersed around the substrate. The culture dish is placed in a vacuum drying oven and MBI is prepared by low-pressure heating and deposition of MAI for different times.

[0011] Step 6: Prepare a hole transport layer by spin-coating a hole transport layer solution on the prepared MBI perovskite film to obtain a hole transport layer;

[0012] The seventh step is vacuum evaporation of electrodes. A gold electrode layer is prepared on the surface of the hole transport layer prepared in the sixth step using a vacuum evaporation method.

[0013] Wherein, in the first step, the organic solvent required for preparing the solution is DMF, the concentration of the solution is 0.5 to 2 mmol / mL, and the stirring time is 5 to 15 hours.

[0014] Wherein, in the second step, the amount of the spin coating solution is 30-50 uL, the spin coating speed is 2000-5000 rpm, and the spin coating time is 20-50 s.

[0015] Wherein, in the third step, the sealed standing time is 0-10 hours.

[0016] Wherein, in the fourth step, the heating temperature is 80-150° C., and the heating time is 5-30 minutes.

[0017] Wherein, in the fifth step, the low pressure of the vacuum oven is 1-100 KPa, the set temperature is 100-200° C., and the reaction time is 1-60 min.

[0018] Wherein, in the sixth step, the concentration of the hole transport layer is 72.3-90 mg / mL.

[0019] Beneficial effects of the present invention

[0020] The present invention has developed a method for preparing high-efficiency MA3Bi2I9 perovskite solar cells by controlling the orientation of BiI3 thin films by solvent evaporation induction. The BiI3 thin film is placed in a sealed container for different time periods to control the evaporation rate of the solvent, thereby adjusting the orientation of the BiI3 thin film. Compared with the BiI3 thin film obtained by direct annealing (003) orientation, the growth of the BiI3 (003) crystal plane is restricted by this method ( Figure 1 ), the (006) crystal plane of MBI can also be effectively restricted, which is more conducive to carrier transport compared with the device prepared by the (006) oriented MBI film. At the same time, the reaction time of BiI3 and MAI was optimized to obtain a film with better surface morphology ( Figure 2 ), and finally achieved the preparation of high-efficiency lead-free bismuth-based perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD patterns of the BiI3 precursor solution after spin coating on the FTO substrate covered with the electron transport layer TiO2 and then annealing in a sealed container for different times, where “*” represents FTO;

[0022] Figure 2 The SEM image of the MA3Bi2I9 perovskite film prepared by the reaction of BiI3 film annealed in a closed container with MAI vapor;

[0023] Figure 3 The IV test diagrams of the solar cell reacting with BiI3 thin film annealed after standing in a sealed container for different time periods and MAI vapor respectively;

[0024] Figure 4 Schematic diagram of MBI perovskite preparation. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing a high-efficiency MA3Bi2I9 perovskite solar cell by controlling the orientation of a BiI3 thin film by induction of solvent evaporation. First, a BiI3 thin film is prepared by spin-coating a DMF precursor solution of BiI3 onto a fluorine-doped tin oxide (FTO) substrate on which TiO2 has been deposited. Subsequently, the prepared BiI3 wet film is placed in a sealed container at room temperature in a glove box. Due to the sealing conditions in the container, DMF evaporated from the wet film generates a DMF atmosphere, thereby greatly reducing its evaporation rate. Since the binding energy of DMF molecules with the BiI3 (113) and (300) crystal planes is greater than the binding energy with the (003) crystal plane, the crystal plane with smaller binding energy grows rapidly and eventually disappears. By slowing down the evaporation of DMF, a BiI3 thin film with (113) and (300) preferred orientations and a weakened (003) crystal plane is successfully prepared. Subsequently, the prepared BiI3 thin film reacts with MAI to form an MBI thin film. Since the growth of BiI3(003) crystal plane is restricted, the (006) crystal plane of MBI is also effectively restricted, which is more conducive to carrier transport compared with the device prepared by MBI film with (006) preferred orientation. In addition, by adjusting the reaction time of BiI3 film and MAI to control the ratio of MBI to BiI3 in the film, a (BiI3) 1-x (MBI) x The coexistence of MBI and BiI3 achieves a better match between the energy levels of the light absorption layer and the TiO2 layer, thereby improving the electron injection from the light absorption layer to the TiO2 layer and thus improving the device performance.

[0026] Specifically, the present invention provides a method for preparing high-efficiency MBI perovskite solar cells by controlling the orientation of BiI3 thin films by solvent evaporation induction, which comprises:

[0027] The first step is to prepare BiI3 solution: weigh BiI3 solid powder, dissolve it in an organic solvent, stir it thoroughly at room temperature, filter it and set it aside;

[0028] The second step is spin coating, where the solution prepared in the first step is spin-coated on a FTO substrate covered with an electron transport layer (TiO2);

[0029] The third step is to let the film stand for different periods of time after the spin coating in the second step is completed.

[0030] The fourth step is annealing, placing the BiI3 film on a heating table for heating and annealing;

[0031] The fifth step is to prepare the MBI perovskite film. The BiI3 film prepared in the fourth step is placed in a culture dish with CH3NH3I (MAI) powder evenly dispersed around the substrate. The culture dish is placed in a vacuum drying oven and MBI is prepared by low-pressure heating and deposition of MAI for different times.

[0032] Step 6: Prepare a hole transport layer by spin-coating a hole transport layer solution on the prepared MBI perovskite film to obtain a hole transport layer;

[0033] The seventh step is vacuum evaporation of electrodes. A gold electrode layer is prepared on the surface of the hole transport layer prepared in the sixth step using a vacuum evaporation method.

[0034] Wherein, in the first step, the organic solvent required for preparing the solution is preferably N,N-dimethylformamide (DMF), the concentration of the solution is preferably 0.5 to 2 mmol / mL, and the stirring time is preferably 5 to 15 hours.

[0035] Wherein, in the second step, the amount of the spin coating solution is preferably 30-50 uL, the spin coating speed is preferably 2000-5000 rpm, and the spin coating time is preferably 20-50 s.

[0036] Wherein, in the third step, the sealed standing time is preferably 0-10 hours.

[0037] Wherein, in the fourth step, the heating temperature is preferably 80-150° C., and the heating time is preferably 5-30 minutes.

[0038] In the fifth step, the low pressure of the vacuum oven is preferably 1-100 KPa, the set temperature is preferably 100-200°C, and the reaction time is preferably 1-60 min.

[0039] Wherein, in the sixth step, the concentration of the hole transport layer is preferably 72.3 mg / mL.

[0040] The hole transport layer solution is specifically prepared as follows: 10 to 28.8 μL of tributyl phosphate (TBP), 15 to 17.5 μL of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and 3 to 8 μL of bis(trifluoromethanesulfonyl)imide salt (FK209Co(III)) are dissolved in 1 to 1.5 mL of chlorobenzene solvent.

[0041] The following examples and drawings are used to describe the embodiments of the present invention in detail, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0042] Example 1:

[0043] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0044] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container in a glove box and allowed to stand for 0 hours;

[0045] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0046] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 thin film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum drying oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0047] 5) Preparation of hole transport layer:

[0048] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0049] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0050] Example 2:

[0051] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0052] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, and the solution was spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 1 hour;

[0053] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0054] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0055] 5) Preparation of hole transport layer:

[0056] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0057] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0058] Example 3:

[0059] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0060] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, and the solution was spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 2 hours;

[0061] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0062] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0063] 5) Preparation of hole transport layer:

[0064] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0065] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0066] Example 4:

[0067] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0068] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, and the solution was spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 3 hours;

[0069] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0070] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0071] 5) Preparation of hole transport layer:

[0072] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0073] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0074] Example 5:

[0075] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0076] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 4 hours;

[0077] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0078] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0079] 5) Preparation of hole transport layer:

[0080] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0081] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0082] Example 6:

[0083] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0084] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, and the solution was spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 5 hours;

[0085] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0086] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0087] 5) Preparation of hole transport layer:

[0088] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0089] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0090] Example 7:

[0091] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0092] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 4 hours;

[0093] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 30 minutes of annealing.

[0094] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0095] 5) Preparation of hole transport layer:

[0096] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0097] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0098] Example 8:

[0099] 1) Preparation of BiI3 precursor solution: Weigh 1 mmol of bismuth iodide (BiI3) and dissolve it in 1 mL of DMF. Then stir at room temperature for 12 hours to prepare a 1 mmol / mL solution.

[0100] 2) BiI3 film pre-preparation: The precursor solution was coated on the FTO substrate with the electron transport layer, spun at 3000 rpm for 30 seconds using a spinner, and then placed in a sealed container and allowed to stand for 4 hours;

[0101] 3) Annealing of BiI3 film: The BiI3 film after standing was placed on a heating platform at 120°C for 20 minutes for annealing.

[0102] 4) Preparation of BiI3 and MBI Coexistence Thin Films: The annealed BiI3 film was placed in a covered glass Petri dish, and MAI powder was evenly dispersed around it. The glass Petri dish was then placed in a vacuum oven and heated at 100°C under 10 kPa to deposit MAI for 30 minutes.

[0103] 5) Preparation of hole transport layer:

[0104] Preparation of the spiro hole transport layer: Two hours before use, prepare a spiro precursor solution containing 1 mL of chlorobenzene, 72.3 mg of spiro powder, 28.8 μL of TBP, 17.5 μL of LiTFSI, and 8 μL of Co(III)TFSI. After the sample cools to room temperature, 30 μL of the precursor solution is dropped onto the sample and spin-coated (3500 rpm for 20 s).

[0105] 6) Evaporation electrode: using vacuum coating machine on 1×10 -5 65nm gold was evaporated at pa as the electrode.

[0106] All of the above are intended to be primary implementations of this intellectual property and do not constitute limitations on other implementations of such new products and / or methods. Those skilled in the art will utilize this important information and modify the above to achieve similar implementations. However, all modifications or adaptations based on this invention to new products are reserved.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing MBI perovskite solar cells by controlling the orientation of BiI3 thin films by solvent evaporation induction, characterized in that: include: The first step is to prepare BiI3 solution: weigh BiI3 solid powder, dissolve it in an organic solvent, stir it thoroughly at room temperature, filter it and set it aside; The second step is spin coating, where the solution prepared in the first step is spin-coated on the FTO substrate covered with the electron transport layer TiO2; The third step is to let the film stand for different periods of time after the spin coating in the second step is completed. The fourth step is annealing, placing the BiI3 film on a heating table for heating and annealing; The fifth step is to prepare the MBI perovskite film. The BiI3 film prepared in the fourth step is placed in a culture dish with CH3NH3I (MAI) powder evenly dispersed around the substrate. The culture dish is placed in a vacuum drying oven and MBI is prepared by low-pressure heating and deposition of MAI for different times. Step 6: Prepare a hole transport layer by spin-coating a hole transport layer solution on the prepared MBI perovskite film to obtain a hole transport layer; Step 7: vacuum evaporation electrode, a gold electrode layer is prepared on the surface of the hole transport layer prepared in step 6 by vacuum evaporation method; In the first step, the organic solvent required for preparing the solution is N,N-dimethylformamide, and the concentration of the solution is 0.5-2 mmol / mL; In the third step, the sealed standing time is 1-5 hours.

2. The method for preparing MBI perovskite solar cells by controlling BiI3 thin film orientation by solvent evaporation induction according to claim 1, characterized in that: In the first step, the stirring time is 5 to 15 hours.

3. The method for preparing MBI perovskite solar cells by controlling BiI3 thin film orientation by solvent evaporation induction according to claim 1, characterized in that: In the second step, the amount of the spin coating solution is 30-50 uL, the spin coating speed is 2000-5000 rpm, and the spin coating time is 20-50 s.

4. The method for preparing MBI perovskite solar cells by controlling BiI3 thin film orientation by solvent evaporation induction according to claim 1, characterized in that: In the fourth step, the heating temperature is 80-150° C., and the heating time is 5-30 minutes.

5. The method for preparing MBI perovskite solar cells by controlling BiI3 thin film orientation by solvent evaporation induction according to claim 1, characterized in that: In the fifth step, the low pressure of the vacuum drying oven is 1-100 KPa, the set temperature is 100-200° C., and the reaction time is 1-60 min.

6. The method for preparing MBI perovskite solar cells by controlling BiI3 thin film orientation by solvent evaporation induction according to claim 1, characterized in that: In the sixth step, the concentration of the prepared hole transport layer is 72.3-90 mg / mL.

7. An MBI perovskite solar cell prepared by the method according to any one of claims 1 to 6.

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