A surface treatment method for improving the photoelectric performance of perovskite

Abstract

The present invention provides a surface treatment method for improving the photoelectric performance of perovskite, the method comprising the steps of: S1, applying a 2-(1-cyclohexenyl)ethylammonium salt solution to the surface of a perovskite film, and performing surface treatment; S2, after removing the perovskite film surface solvent, annealing. The present invention treats the film surface using a solution of 2-(1-cyclohexenyl)ethylammonium salt, converts a thin layer with multiple surface defects into a more stable low-dimensional covering layer, and then achieves repair and passivation of film surface defects, so that the stability and photoelectric performance of perovskite are improved. The perovskite film obtained after the method is treated has a low surface defect density and good stability, and the treated film has significantly enhanced photoelectric conversion performance.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite photovoltaics and relates to a surface treatment method for improving the photoelectric performance of perovskite. Specifically, a method for improving the photoelectric performance of a perovskite film by repairing and passivating surface defects of the perovskite film is designed. Background Art

[0002] Metal halide perovskites possess nearly all the properties required for photoelectric conversion applications, such as high absorption coefficients, long carrier diffusion lengths, and high defect tolerance. Therefore, they are considered promising candidates for next-generation solar cells, LEDs, and other applications. However, the intrinsic sensitivity of three-dimensional perovskites to light, heat, water, and oxygen limits their commercial application. In contrast, low-dimensional perovskites, while exhibiting inferior photoelectric performance, offer superior stability. Researchers have discovered that forming a low-dimensional (two-dimensional, one-dimensional) capping layer on the surface of a three-dimensional perovskite not only improves the perovskite's stability to light, heat, water, and oxygen, but also passivates surface defects, enhancing the perovskite's photoelectric performance. Despite this, currently used methods still face certain limitations. For example, treating the perovskite surface with n-octylamine hydroiodide (OAI), one of the most commonly used treatment materials, improves stability and photoelectric performance. However, the long organic alkane chain presents new challenges in the preparation of the subsequent hole transport layer. Therefore, exploring a method that can improve the stability and photoelectric properties of perovskite without introducing new problems is particularly important for promoting the commercial application of perovskite. Summary of the Invention

[0003] In response to the defects of the prior art, the present invention relates to a surface treatment method for improving the photoelectric performance of perovskite. The method is a method for repairing and passivating defects on the surface of a perovskite film. The film surface is treated with a solution of 2-(1-cyclohexenyl)ethylammonium salt, and a thin layer with many surface defects is converted into a more stable low-dimensional covering layer, thereby achieving repair and passivation of the film surface defects, thereby improving the stability and photoelectric performance of the perovskite.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a surface treatment method for improving the photoelectric performance of perovskite, the method comprising the following steps:

[0006] S1, applying a 2-(1-cyclohexenyl)ethylammonium salt solution on the surface of the perovskite film for surface treatment;

[0007] S2. After removing the solvent from the surface of the perovskite film, annealing is performed.

[0008] As an embodiment of the present invention, in step S1, the solvent in the 2-(1-cyclohexenyl)ethylammonium salt solution includes at least one of chloroform and isopropanol.

[0009] As an embodiment of the present invention, in step S1, the 2-(1-cyclohexenyl)ethylammonium salt includes at least one of 2-(1-cyclohexenyl)ethylammonium iodide (CHEAI), 2-(1-cyclohexenyl)ethylammonium bromide (CHEABr), CHEA2PbI4, and CHEA2PbBr4.

[0010] Furthermore, CHEA2PbI4 and CHEA2PbBr4 are two-dimensional perovskites generated by halogen salts of 2-(1-cyclohexenyl)ethylamine and lead halides (PbI2, PbBr2).

[0011] As an embodiment of the present invention, in step S1, the concentration of 2-(1-cyclohexenyl)ethylammonium salt in the 2-(1-cyclohexenyl)ethylammonium salt solution is 0.5-10 g / L.

[0012] As an embodiment of the present invention, in step S1, the coating amount of the 2-(1-cyclohexenyl)ethylammonium salt solution is 0.01-0.03 mL / cm 2 .

[0013] In some embodiments, the coating amount of the 2-(1-cyclohexenyl)ethylammonium salt solution is 0.02-0.025 mL / cm 2 .

[0014] As an embodiment of the present invention, in step S1, the perovskite film includes an organic-inorganic hybrid lead halide perovskite film and an all-inorganic cesium lead halide perovskite film.

[0015] In some embodiments, the perovskite film is a formamidinium lead iodide (FAPbI 3 ) perovskite film.

[0016] As an embodiment of the present invention, in step S1, the coating method includes at least one of a spin coating method and a coating method.

[0017] As an embodiment of the present invention, when the spin coating method is used, the rotation speed is 1000-6000 rpm and the time is 5-60 s; when the coating method is used, the airflow used to assist the coating includes at least one of dry air and inert gas.

[0018] In the present invention, the auxiliary gas flow includes at least one of nitrogen and argon.

[0019] As an embodiment of the present invention, in step S2, when the coating method is adopted, air flow can be used to assist in removing the surface solvent; when the spin coating method is adopted, the film will rotate at high speed, and the excess solvent will be directly thrown off the film during the rotation process, and the remaining solvent will be dried by air convection during the spin coating process.

[0020] As an embodiment of the present invention, in step S2, the annealing temperature is 60-120° C., and the time is 0.5-10 min.

[0021] In some embodiments, the annealing temperature is 100° C. and the annealing time is 0.5-2 min.

[0022] The present invention uses 2-(1-cyclohexenyl)ethylammonium salt to post-treat the surface of a perovskite film, uses 2-(1-cyclohexenyl)ethylammonium salt to chemically react with the perovskite surface to repair and passivate defects on the film surface, forms a passivation layer on the film surface and at the grain boundaries, improves the stability of the perovskite by inhibiting ion migration in the perovskite and blocking water and oxygen, and improves the photoelectric performance of the perovskite by promoting the separation and extraction of carriers.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Since the impurity phase in the perovskite film will become the recombination center of the carriers and the site for inducing phase separation of the perovskite, it is crucial to eliminate the impurity phase remaining on the surface of the film during the preparation process to improve the photoelectric conversion performance and stability of the perovskite. The 2-(1-cyclohexenyl)ethylammonium salt used in the present invention can not only react with the uncoordinated lead halide and residual lead halide on the surface of the film to form a low-dimensional perovskite, but also react with the impurity phase (yellow phase) to convert the impurity phase into a low-dimensional perovskite, thereby achieving comprehensive defect repair of the film and improving its photoelectric conversion performance and stability.

[0025] 2. Using the method of the present invention to treat the perovskite film can not only repair and passivate the surface defects of the film, but the 2-(1-cyclohexenyl)ethylammonium salt in the present invention can also convert the residual lead halide at the grain boundary into a low-dimensional perovskite that grows vertically on the substrate, thereby achieving deep defect repair of the film; and the vertically grown low-dimensional perovskite provides a channel for the extraction of carriers (the in-plane mobility of carriers in the low-dimensional perovskite is much higher than the mobility between layers), thereby promoting the extraction of carriers in the bulk of the film and greatly improving the filling of the device.

[0026] 3. The present invention uses 2-(1-cyclohexenyl)ethylammonium salt to treat the perovskite film, so that the wettability of the treated film to chlorobenzene is almost unchanged, which is conducive to the large-area preparation of high-quality carrier transport layers.

[0027] 4. The perovskite treated by the method of the present invention has good wet and hot stability and can be widely used in solar cells, detectors, LEDs and other fields.

[0028] 5. The processing method of the present invention is conducive to the preparation of the subsequent hole transport layer of the perovskite film, so that the perovskite solar cell module prepared using the perovskite film has a higher fill factor and exhibits better performance.

[0029] 6. The raw material cost of the perovskite processed by the method of the present invention is low, which is conducive to large-scale commercial application.

[0030] 7. The present invention has low requirements on equipment, is simple to operate, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0032] Figure 1 is the XRD pattern of CHEAI;

[0033] Figure 2 Characteristic diagram of CHEA2PbI4; Figure A is a physical diagram of CHEA2PbI4, and Figure B is the XRD and single crystal XRD diffraction pattern of CHEA2PbI4;

[0034] Figure 3 is a SEM image of the perovskite film obtained in Example 1;

[0035] Figure 4 is the X-ray diffraction pattern of the perovskite film obtained in Example 1;

[0036] Figure 5 is the contact angle of the perovskite film surface to water obtained in Example 1;

[0037] Figure 6 The JV curve of the solar cell device prepared by the perovskite thin film obtained in Example 1;

[0038] Figure 7 Comparison diagrams of the yellow phase perovskite film before and after treatment in Example 1; Figure A is the UV-visible absorption spectrum of the yellow phase perovskite film and the film after the yellow phase is treated with CHEAI, and Figure B is the XRD of the yellow phase perovskite film and the film after the yellow phase is treated with CHEAI;

[0039] Figure 8 This is a JV curve diagram of a solar cell module prepared using the perovskite film obtained in Example 2;

[0040] Figure 9This is a photo of a solar cell module prepared using the perovskite film obtained in Example 2;

[0041] Figure 10 This is a graph of the electroluminescent efficiency of an LED device prepared using the perovskite film obtained in Example 3;

[0042] Figure 11 The contact angles of the perovskite film surfaces obtained by the control sample in Comparative Example 1, OAI treatment, and 2-(1-cyclohexenyl)ethylammonium iodide (CHEAI) treatment to a commonly used hole transport layer solution;

[0043] Figure 12 JV curves of solar cell modules prepared from the control sample in Comparative Example 1, perovskite thin films obtained by OAI treatment, and perovskite thin films obtained by 2-(1-cyclohexenyl)ethylammonium iodide treatment;

[0044] Figure 13 It is a comparison diagram of the yellow phase perovskite film before and after treatment in Comparative Example 1; wherein, Figure A is the UV-visible absorption spectrum of the yellow phase perovskite film and the yellow phase film after CHEAI treatment, and Figure B is the XRD of the yellow phase perovskite film and the yellow phase film after CHEAI treatment. DETAILED DESCRIPTION

[0045] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, provide detailed implementation methods and specific operating procedures, and will help those skilled in the art to further understand the present invention. It should be pointed out that the scope of protection of the present invention is not limited to the following embodiments, and a number of adjustments and improvements made under the premise of the concept of the present invention all fall within the scope of protection of the present invention.

[0046] The preparation method of 2-(1-cyclohexenyl)ethylammonium salt (i.e., CHEAI, CHEABr, CHEA2PbI4, CHEA2PbBr4) in the present invention is as follows:

[0047] Synthesis of CHEAI: Add 9.5 mL (55–58 wt%) of HI solution to 4 mL of ethanol and 1 mL of isopropanol. Stir thoroughly, then slowly add 5 mL of 2-(1-cyclohexenyl)ethylamine in an ice-water bath (this reaction is exothermic; the ice-water bath is to prevent overheating). Heat to 75°C to dissolve the solution. Once completely dissolved, cool to –20°C to allow crystallization. Wash the resulting crystals five times with diethyl ether or ethyl acetate. Figure 1 This is the XRD pattern of CHEAI.

[0048] Synthesis of CHEABr: The synthesis of CHEABr is the same as that of CHEAI, except that HI acid solution is replaced with HBr solution.

[0049] Synthesis of CHEA2PbI4: Dissolve 0.56 mmol of CHEA1 in 4 mL of ethanol to obtain solution A. Dissolve 0.28 mmol of PbI2 in 4 mL of 55–58 wt% HI solution. Once completely dissolved, add 3 mL of ethanol and mix thoroughly to obtain solution B. After heating solutions A and B to ~60°C, add solution A to solution B to obtain solution C. Slowly cool solution C to obtain CHEA2PbI4 single crystals. Figure 2 The physical picture and XRD pattern of CHEA2PbI4.

[0050] Synthesis of CHEA2PbBr4: The synthesis of CHEA2PbBr4 is the same as that of CHEA2PbI4, except that lead iodide and hydroiodic acid are replaced by lead bromide and hydrobromic acid respectively.

[0051] Note that among the preparation methods of the above reagents, the present invention only provides a preparation method with simple operation.

[0052] It should be noted that the comparative sample referred to in the present invention is a perovskite film sample obtained without any treatment on the surface of the perovskite film or a device prepared based on the film.

[0053] Example 1

[0054] Example 1 Taking a 3 g / L 2-(1-cyclohexenyl)ethylammonium iodide (CHEAI) chloroform solution as an example, a formamidinium lead iodide (FAPbI3) perovskite film is treated by spin coating. The method includes the following steps:

[0055] S1. Dissolve 3 mg of 2-(1-cyclohexenyl)ethylammonium iodide in 1 mL of chloroform to obtain solution A.

[0056] S2. Drop 0.1 mL of solution A onto a 2×2 cm 2 The perovskite film surface was then subjected to 5000 rpm for 20 seconds;

[0057] S3. Anneal the spin-coated perovskite film at 100° C. for 1 minute.

[0058] Figure 3 The SEM images of the formamidinium lead iodide perovskite film obtained in Example 1 and the comparative sample show that vertically grown two-dimensional perovskite exists at the grain boundaries after CHEAI treatment. Figure 4 The X-ray diffraction patterns of the formamidinium lead iodide perovskite film obtained in Example 1 and the comparative sample show that the FAPbI3 obtained in Example 1 retains its original crystal structure, and the diffraction peak belonging to lead iodide disappears, while the diffraction peak of the two-dimensional perovskite appears at 5.19°. Figure 5 The contact angle test results of the formamidinium lead iodide perovskite film surface obtained in Example 1 on water show that the contact angle increases significantly after CHEAI treatment, which is beneficial to improving the wet stability of the perovskite. Figure 6 Table 1 and Table 2 are the JV curves and corresponding parameters of the formamidinium lead iodide perovskite solar cell obtained in Example 1. It can be seen that after treatment, the photoelectric conversion performance of the device is significantly improved.

[0059] Table 1. Photoelectric conversion parameters of devices prepared before and after CHEAI treatment of perovskite films

[0060] PCE (%) FF(%) <![CDATA[J SC (mA cm -2 )]]> <![CDATA[V OC (V)]]> Comparison sample 22.87 82.70 25.83 1.07 CHEAI treatment 25.20 86.18 25.87 1.13

[0061] Yellow phase perovskite conversion to 2D experiment

[0062] The CHEAI solution used in Example 1 to treat the perovskite film was used to treat the yellow phase perovskite film in the same manner.

[0063] Figure 7 Figure A shows the UV-visible absorption spectra of the yellow phase and the yellow phase film after CHEAI treatment. As can be seen from the figure, the light absorption properties of the yellow phase film undergo significant changes after CHEAI treatment. The yellow phase absorption peak at 385nm almost disappears, while new absorption peaks attributed to the 2D perovskite appear at 509nm and 580nm, indicating that the yellow phase perovskite is converted into a 2D perovskite after CHEAI treatment. Figure 7 B is the XRD pattern of the yellow phase and the film after the yellow phase was treated with CHEAI, which further proves that the yellow phase film is almost completely converted into 2D perovskite after CHEAI treatment.

[0064] Example 2

[0065] Example 2 Taking a 2 g / L isopropanol solution of 2-(1-cyclohexenyl)ethylammonium iodide as an example, a method for preparing a large-area component by treating a formamidine lead iodide perovskite film with a spin coating method includes the following steps:

[0066] S1. Dissolve 2 mg of 2-(1-cyclohexenyl)ethylammonium iodide in 1 mL of chloroform to obtain solution A.

[0067] S2. Drop 0.5 mL of solution A onto a 5×5 cm 2 The perovskite film surface was then subjected to 5000 rpm for 20 seconds;

[0068] S3. Anneal the spin-coated perovskite film at 100° C. for 2 minutes.

[0069] Figure 8Table 2 and Table 3 are the JV curves and corresponding parameters of the solar cell module prepared from the formamidinium lead iodide perovskite film obtained in Example 2. It can be seen that after surface treatment with 2-(1-cyclohexenyl)ethylammonium iodide, the photoelectric conversion performance of the module is significantly improved. Figure 9 This is a physical picture of a perovskite solar cell module prepared based on the perovskite film obtained in Example 2.

[0070] Table 2. 12.25 cm2 perovskite films prepared before and after CHEAI treatment 2 Photoelectric conversion parameter table of components

[0071] PCE (%) FF(%) <![CDATA[J SC (mA cm -2 )]]> <![CDATA[V OC (V)]]> Comparison sample 17.86 73.67 3.73 6.49 CHEAI treatment 20.77 84.06 3.73 6.62

[0072] Example 3

[0073] The method of this embodiment is the same as that of embodiment 1, except that the annealing time in step 3 is 30 seconds.

[0074] Figure 10 This is a graph of the electroluminescent efficiency of the LED device prepared with the formamidinium lead iodide perovskite film obtained in Example 3 at different voltages. It can be seen that the LED device prepared with the perovskite film treated with 2-(1-cyclohexenyl)ethylammonium iodide has significantly improved efficiency at the same voltage.

[0075] Comparative Example 1

[0076] The method of this comparative example is the same as that of Example 1, except that the formamidinium lead iodide perovskite film is treated with n-octyl hydroiodide (OAI) in the same manner as in Example 1. Figure 11 The contact angles of the perovskite film surfaces obtained by the control sample in the comparative example, treatment with OAI, and treatment with 2-(1-cyclohexenyl)ethylammonium iodide to the commonly used hole transport layer solution are shown. It can be seen that the contact angle of the perovskite film surface obtained by treatment with 2-(1-cyclohexenyl)ethylammonium iodide has almost no change, while the contact angle after OAI treatment increases from 9.9° to 43.6°. Good wettability is conducive to building a good interface contact. Figure 12 Table 3 shows the JV curves and corresponding parameters of the perovskite solar cell modules prepared from the control sample in Comparative Example 1, the perovskite thin film obtained by OAI treatment and the perovskite thin film obtained by 2-(1-cyclohexenyl)ethylammonium iodide treatment. The solar cell module obtained by 2-(1-cyclohexenyl)ethylammonium iodide treatment shows better performance, with a fill factor (FF) exceeding 84%, which is much higher than the fill factor obtained by the control sample and OAI treatment.

[0077] Similarly, the method of treating the yellow phase with the CHEAI solution in Example 1 was adopted, but the CHEAI was replaced with the commonly used post-treatment amine salt OAI, and the yellow phase film was treated with OAI. Figure 13 Figure A shows the UV-visible absorption spectra of the yellow phase film before and after OAI treatment. The absorption spectrum remains dominated by the yellow phase before and after treatment, indicating that the main component of the yellow phase perovskite remains unchanged. A very weak absorption peak at 570 nm, attributed to low-dimensional perovskites, appears primarily due to the reaction of a small amount of uncoordinated lead iodide (PI) on the yellow phase surface with the OAI to form a small amount of 2D perovskite. Figure 13 XRD patterns of the yellow phase film (B) before and after OAI treatment further demonstrate that after OAI treatment, the film remains primarily yellow, with only a weak 2D diffraction peak appearing near 3.8°, consistent with the conclusions from the UV-Vis absorption spectrum. This suggests that the commonly used OAI salt post-treatment can only convert residual and uncoordinated lead iodide into low-dimensional perovskite.

[0078] Table 3. 12.25 cm2 perovskite films prepared before and after different salt treatments 2 Photoelectric conversion parameter table of components

[0079] PCE (%) FF(%) <![CDATA[J SC (mA cm -2 )]]> <![CDATA[V OC (V)]]> Comparison sample 17.86 73.67 3.73 6.49 CHEAI treatment 20.77 84.06 3.73 6.62 OAI processing 19.45 79.68 3.74 6.53

[0080] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A surface treatment method for improving the photoelectric performance of perovskite, characterized in that: The surface treatment method comprises the following steps: S1, applying a 2-(1-cyclohexenyl)ethylammonium salt solution on the surface of the perovskite film for surface treatment; The 2-(1-cyclohexenyl)ethylammonium salt includes at least one of CHEAI, CHEABr, CHEA2PbI4, and CHEA2PbBr4; S2. After removing the solvent from the surface of the perovskite film, annealing is performed.

2. The surface treatment method according to claim 1, characterized in that In step S1, the solvent in the 2-(1-cyclohexenyl)ethylammonium salt solution includes at least one of chloroform and isopropanol.

3. The surface treatment method according to claim 1, wherein: In step S1, the concentration of 2-(1-cyclohexenyl)ethylammonium salt in the 2-(1-cyclohexenyl)ethylammonium salt solution is 0.5-10 g / L.

4. The surface treatment method according to claim 1, characterized in that In step S1, the coating amount of the 2-(1-cyclohexenyl)ethylammonium salt solution is 0.01-0.03 mL / cm 2 .

5. The surface treatment method according to claim 1, characterized in that: In step S1, the perovskite film includes an organic-inorganic hybrid lead halide perovskite film and an all-inorganic cesium lead halide perovskite film.

6. The surface treatment method according to claim 1, characterized in that: In step S1, the coating method includes spin coating. When the spin coating method is used, the spin coating speed is 1000-6000 rpm and the time is 5-60 s.

7. The surface treatment method according to claim 1, characterized in that: In step S1, the coating method includes a coating method; when the coating method is used, the airflow used to assist the coating includes at least one of dry air and inert gas.

8. The surface treatment method according to claim 1, characterized in that: In step S2, the annealing temperature is 60-120° C., and the time is 0.5-10 min.

9. A perovskite film prepared by the surface treatment method according to any one of claims 1 to 8.

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