Perovskite surface sequential post-processing method based on two-dimensional ligand modification materials with different polarities

Abstract

The invention provides a perovskite surface sequential post-processing method based on different-polarity two-dimensional ligand modification materials, and relates to the technical field of semiconductor materials. The method comprises the following steps: step 1, processing the surface of three-dimensional perovskite by using a material x dissolved in an organic solvent to prepare a perovskite heterojunction sample; step 2, carrying out secondary treatment on the sample in the step 1 by adopting a material y dissolved in an organic solvent to obtain a perovskite heterojunction thin film sample of which the surface is finally modified; the polarity of the material x is smaller than that of the material y, and the dipole moment of molecules or ions of the material y is not lower than 4 Debye; the organic solvent is a liquid phase at normal temperature and normal pressure. According to the modification method, the problem that transportation of surface and interface carriers of perovskite is blocked due to a traditional 2D processing method can be weakened, so that the charge transportation capacity is improved, and the efficiency of a perovskite solar cell device is improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor materials, and in particular to a novel perovskite surface sequential post-treatment method based on two-dimensional ligands modified with different polarities. Background Art

[0002] Perovskite materials have attracted much attention due to their excellent photovoltaic properties, especially in the application of solar cells. This type of material has characteristics such as high absorption coefficient, long carrier diffusion length and tunable band gap, which makes it show great potential in terms of photoelectric conversion efficiency. In recent years, perovskite solar cells have developed rapidly, and the photoelectric conversion efficiency of perovskite solar cells on a laboratory scale has been comparable to that of traditional silicon-based solar cells, and even surpassed the latter in some cases. This marks a major advancement in perovskite solar cell technology and lays the foundation for its commercial application. However, despite these advances, further industrial development still depends on the improvement of perovskite photovoltaic performance.

[0003] The existing strategy for improving photovoltaic performance is mainly to use 2D ligand-modified materials for post-treatment to passivate surface defects of perovskite films. This method is widely considered to be an effective strategy to simultaneously improve the efficiency and stability of perovskite solar cells (PSCs). This method aims to improve the charge collection efficiency by optimizing the surface properties of the material to reduce the non-radiative recombination of carriers, thereby improving the overall performance of solar cells. However, most post-treatment strategies are single-step post-treatment methods, which are usually limited to a single post-treatment material or process, and may lead to the problem of blocked carrier transport at the perovskite surface interface, which hinders the transport of charges and thus reduces device performance, restricting the further development of perovskite photovoltaic industrialization.

[0004] Therefore, it is urgent to develop a new method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities, so as to improve the problem of obstructed carrier transport at the perovskite surface interface caused by traditional 2D processing methods, thereby improving the charge transport capacity, and further improving device performance and promoting the development of related industries. Summary of the invention

[0005] The present invention proposes a method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand modified materials with different polarities. The two-step sequential treatment of two-dimensional ligand modified materials with different polarities can effectively change the surface morphology of the perovskite film and passivate the surface defects of the film. At the same time, the phenomenon of obstructed carrier transport and reduced charge transport capacity on the perovskite surface caused by traditional 2D treatment methods can be improved, so as to improve the performance of solar cell devices.

[0006] The present invention provides a method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand modified materials with different polarities, the method comprising the following steps:

[0007] Step 1: using material x dissolved in an organic solvent to treat the surface of a three-dimensional perovskite to prepare a 2D / 3D perovskite heterojunction sample;

[0008] Step 2: using material y dissolved in an organic solvent to perform secondary treatment on the sample of step 1 to obtain a 2D / 3D perovskite heterojunction thin film sample with a final surface modification;

[0009] The polarity of the material x is smaller than that of the material y, and the dipole moment of the molecules or ions of the material y is not less than 4 Debye; the organic solvent is in liquid phase at normal temperature and pressure.

[0010] By adopting the above technical scheme, sequential post-treatment of the perovskite surface of materials modified with two-dimensional ligands of different polarities can improve the problem of obstructed carrier transport at the perovskite surface interface caused by traditional 2D treatment methods, thereby improving the charge transport capacity.

[0011] On the basis of the above technical solution, preferably, the material x is selected from benzylamine halide and / or phenethylamine halide; the material y is selected from 4-trifluoromethylbenzylamine halide and / or 4-trifluoromethylphenethylamine halide.

[0012] On the basis of the above technical scheme, preferably, the material x is selected from one or more of phenethylamine hydroiodide (PEAI), phenethylamine hydrochloride, phenethylamine hydrobromide, benzylamine hydrochloride, benzylamine hydrobromide or benzylamine hydroiodide; the material y is selected from one or more of 4-trifluoromethylphenethylamine hydroiodide (CF3PEAI), 4-trifluoromethylphenethylamine hydrobromide, 4-trifluoromethylphenethylamine hydrochloride, 4-trifluoromethylbenzylamine hydroiodide, 4-trifluoromethylbenzylamine hydrobromide or 4-trifluoromethylbenzylamine hydrochloride.

[0013] On the basis of the above technical solution, preferably, the organic solvent is selected from a non-polar solvent or a solvent with a weaker polarity, and cannot dissolve the perovskite film.

[0014] More preferably, the organic solvent is selected from isopropyl alcohol (IPA) and / or chlorobenzene.

[0015] Based on the above technical solution, preferably, the concentrations of the material x and the material y are both no higher than 50 mM.

[0016] By adopting the above technical solution, excessively high concentrations of reagent a and reagent b will lead to the presence of a thicker 2D / 3D perovskite heterojunction structure on the surface of the perovskite film, hindering charge transfer.

[0017] On the basis of the above technical solution, preferably, the perovskite heterojunction sample includes two-dimensional perovskite and three-dimensional perovskite;

[0018] The chemical composition of the three-dimensional perovskite is shown in formula (I): ABX3; the two-dimensional perovskite includes RP type and / or DJ type, and the chemical composition of the RP type two-dimensional perovskite is shown in formula (II): R2A n-1 B n X 3n+1 The chemical composition of the DJ-type two-dimensional perovskite is shown in formula (III): DA n-1 B n X 3n+1 ;

[0019] In formulas (I) to (III), A is a monovalent cation, B is a divalent cation, X is a monovalent anion, n is a positive integer, R is a monovalent two-dimensional ligand cation, and D is a divalent two-dimensional ligand cation.

[0020] On the basis of the above technical solution, preferably, the A is selected from the group consisting of formamidinium ion (FA + ), methylamine ion (MA + ), dimethylamine ion (DMA + ) or cesium ion (Cs + ) at least one; wherein B is selected from lead ions (Pb 2+ ) and / or tin ions (Sn 2+ ); wherein X is selected from bromide ion (Br - ), iodide ion (I - ), thiocyanate ion (SCN - ), chloride ion (Cl - ) or at least one of formate ions.

[0021] On the basis of the above technical solution, preferably, the post-treatment method is selected from one or more of spin coating, blade coating, slit coating, spray coating, and immersion.

[0022] On the basis of the above technical solutions, preferably, the control method is selected from one or more of spin coating, blade coating, slit coating, spray coating, and immersion.

[0023] The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities provided by the present invention has the following beneficial effects compared with the prior art:

[0024] (1) The post-treatment method of the present invention can change the surface morphology of the perovskite film and improve the quality of the film.

[0025] (2) The post-treatment method of the present invention can effectively improve the problem of blocked carrier transport at the perovskite surface interface caused by the traditional 2D treatment method, thereby improving the charge transport capacity and further improving the efficiency of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of a method for sequential post-treatment of a perovskite surface based on two-dimensional ligand-modified materials with different polarities according to the present invention;

[0028] Figure 2 is a scanning electron microscope image of the perovskite sample of Example 1 of the present invention;

[0029] Figure 3 This is a scanning electron microscope image of the perovskite sample of Comparative Example 1 of the present invention;

[0030] Figure 4 This is a scanning electron microscope image of the perovskite sample of Comparative Example 2 of the present invention;

[0031] Figure 5 The fluorescence spectra of the glass / perovskite samples of Comparative Examples 1-2 and Example 1 of the present invention;

[0032] Figure 6 The glass / perovskite / C of Comparative Examples 1-2 and Example 1 of the present invention 60 Fluorescence spectra of samples;

[0033] Figure 7 is a JV curve diagram of the inverted perovskite solar cell according to Example 1 of the present invention;

[0034] Figure 8 is a JV curve diagram of the inverted perovskite solar cell according to Example 2 of the present invention;

[0035] Fig. 9 is a JV curve diagram of the inverted perovskite solar cell according to Example 3 of the present invention;

[0036] Fig.10 is a JV curve diagram of the inverted perovskite solar cell according to Example 4 of the present invention;

[0037] Fig.11 is a JV curve diagram of the inverted perovskite solar cell according to Example 5 of the present invention;

[0038] Fig.12 is a JV curve diagram of the inverse perovskite solar cell of Comparative Example 1 of the present invention;

[0039] Fig.13is a JV curve diagram of the inverse perovskite solar cell of Comparative Example 2 of the present invention;

[0040] Fig.14 is a JV curve diagram of the inverse perovskite solar cell of Comparative Example 3 of the present invention;

[0041] Fig.15 is a JV curve diagram of the inverted perovskite solar cell of Comparative Example 4 of the present invention;

[0042] Fig.16 is a JV curve diagram of the inverted perovskite solar cell of Comparative Example 5 of the present invention;

[0043] Fig.17 is a JV curve diagram of the inverted perovskite solar cell of Comparative Example 6 of the present invention;

[0044] Fig.18 is a JV curve diagram of the inverse perovskite solar cell of Comparative Example 7 of the present invention;

[0045] Fig.19 This is a JV curve diagram of the inverted perovskite solar cell of Comparative Example 8 of the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] The currently reported perovskite post-treatment strategy, i.e., using PEAI IPA solution to post-treat the perovskite precursor solution once, often has the problem of blocked carrier transport at the perovskite surface interface, which affects the charge transport capacity and severely limits the device performance and the development of related industries. Based on this, the inventor made the present invention through further research.

[0048] The present invention has developed a method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand modified materials with different polarities. Figure 1 By sequentially post-treating the perovskite precursor solution, the surface defects of the perovskite film can be effectively passivated, the surface morphology of the film can be changed, and the interface charge transfer can be improved. The specific steps include:

[0049] Step 1: using material x dissolved in an organic solvent to treat the surface of a three-dimensional perovskite to prepare a 2D / 3D perovskite heterojunction sample;

[0050] Step 2: using material y dissolved in an organic solvent to perform secondary treatment on the sample of step 1 to obtain a 2D / 3D perovskite heterojunction thin film sample with a final surface modification;

[0051] The polarity of the material x is smaller than that of the material y, and the dipole moment of the molecules or ions of the material y is not less than 4 Debye; the organic solvent is in liquid phase at normal temperature and pressure.

[0052] In the embodiment of the present invention, the dipole moment of the molecule or ion of material x is lower than 4 Debye mainly because it is easier to form a 2D / 3D heterojunction structure on the surface of 3D perovskite. The dipole moment of the molecule or ion of material y is not lower than 4 Debye mainly because the material can form a local electric field on the surface and inside of the perovskite film, so as to effectively improve the problem of blocked carrier transport at the perovskite surface interface caused by the first step of the traditional 2D processing method, thereby improving the charge transport capacity. The organic solvent is liquid at room temperature and pressure, and can dissolve material x and material y without damaging the perovskite film itself, ensuring the mildness and controllability of the processing process.

[0053] In the present invention, step one uses a low-polarity modification material with a dipole moment lower than 4 Debye to preliminarily passivate the surface defects of the perovskite film, which is used to preliminarily improve the charge transport capacity. However, the 2D / 3D heterojunction structure formed by this type of material often still has problems such as uneven distribution of lead iodide, and the passivation effect is limited, which leads to the obstruction of carrier transport on the perovskite surface interface, limiting the improvement of device performance. Therefore, the present invention additionally proposes a second step of high-polarity 2D ligand modification material post-processing step, that is, using a high-polarity modification material with a dipole moment higher than 4 Debye and a strong interaction with the perovskite surface structure to further passivate defects and improve the uneven distribution of lead iodide on the surface of the sample obtained in step one, thereby optimizing the carrier transport effect and ultimately achieving a substantial improvement in device performance. It is worth noting that the order of this processing step is crucial to obtaining the best effect. Only one material treatment or simply swapping the order of these two steps cannot achieve the same improvement effect. First of all, the effect of single-step passivation is limited by the properties of the modification material itself, and it is difficult to achieve the effect of passivation of two materials. Secondly, if the high polarity material is used for treatment first and then the low polarity material is used for treatment, the improvement effect is weak due to the weak interaction between the low polarity material and the sample, and it is still difficult to solve the problem of blocked carrier transport, which affects charge transport and device performance. Therefore, using these two materials to treat the surface of the perovskite film in the specific treatment sequence proposed by the present invention can maximize their respective advantages and achieve a qualitative leap in the performance of the perovskite film.

[0054] The present invention is further described below in conjunction with specific examples, and the protection scope of the present invention is not limited by the following examples. The sources of materials mainly involved in the examples are all conventional commercial products unless otherwise specified.

[0055] Example 1

[0056] This embodiment provides a method for sequential post-treatment of the perovskite surface based on two-dimensional ligand modified materials with different polarities.

[0057] The method for preparing the perovskite film provided in this embodiment comprises the following steps:

[0058] A1. Prepare a transparent substrate made of indium tin oxide (ITO), pre-treat the substrate by ultrasonic cleaning with ultrapure water for 20 minutes, and then treat it with UV-ozone for 20 minutes after drying;

[0059] A2. Preparation of self-assembled molecular layers on transparent substrates:

[0060] A3. Preparation of perovskite light-absorbing layer on the self-assembled monolayer: Prepare a DMF and DMSO mixed solvent (the volume ratio of DMF to DMSO is 5:1) with a concentration of 1.67 mmol mL -1 Cs 0.05 MA 0.1 FA 0.85 PbI3 perovskite precursor solution, under nitrogen protection, the perovskite precursor solution was spin-coated on the HTL at 1000 rpm and 5000 rpm for 10 seconds and 35 seconds respectively. 10 seconds after the start of the second step, 150 μl CB was added to the center of the sample, followed by annealing at 100 °C for 30 minutes and then cooling;

[0061] A4. Performing sequential post-treatment of the perovskite surface based on two-dimensional ligand modified materials with different polarities on the perovskite light absorbing layer, comprising the following steps:

[0062] Step 1: Preparation of 2D / 3D perovskite heterojunction samples using low-polarity 2D ligand-modified materials

[0063] A 10 mM PEAI IPA solution was prepared, and the spin coating method was used (spin coating at 5000 rpm for 30 seconds, and after the spin coating started, the 10 mM PEAI IPA solution was dropped onto the surface of the perovskite light-absorbing layer prepared by A3), and then annealed at 100 ° C for 5 minutes to prepare a 2D / 3D perovskite heterojunction sample with random distribution of lead iodide on the surface, wherein the 2D perovskite structure formula is PEA2FAPb2I7 (n = 2), PEA2PbI4 (n = 1);

[0064] Step 2: Use high-polarity 2D ligand modified materials to perform secondary treatment on the sample in step 1 to obtain a 2D / 3D perovskite heterojunction thin film sample with final surface modification.

[0065] For the 2D / 3D perovskite heterojunction sample prepared in step 1, 5 mmol L-1 The surface impurity phase structure was rearranged by using the IPA solution of CF3PEAI: the perovskite film was rotated at an acceleration of 5000 rpm for 40 seconds, and 50 μL of CF3PEAI solution was added to the perovskite film about 5 seconds after the start of rotation. After the spin coating, the perovskite film sample was annealed at 100°C for 5 minutes to obtain a 2D / 3D perovskite heterojunction film sample with final surface modification.

[0066] Based on the 2D / 3D perovskite heterojunction thin film sample with the final surface modification obtained by the second post-treatment, preparing a related solar cell device also includes the following steps:

[0067] Prepare the electron transport layer on the perovskite light absorbing layer, and sequentially evaporate and prepare 25nm C 60 and 2nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer; a top electrode is prepared on the electron transport layer, and 100nm Ag is prepared by thermal evaporation as the top electrode of the device.

[0068] Example 2

[0069] The difference between this embodiment and embodiment 1 is that when performing sequential treatment, step 1 uses an IPA solution of PEAI with a concentration of 5 mM, and the other steps remain unchanged.

[0070] Example 3

[0071] The difference between this embodiment and embodiment 1 is that: when performing sequential treatment, step 2 uses an IPA solution of CF3PEAI with a concentration of 10 mM, and the other steps remain unchanged.

[0072] Example 4

[0073] The difference between this embodiment and embodiment 1 is that: in step 1, 10 mM PEABr IPA solution is used to replace the 10 mM PEAI IPA solution in the original step, and the other steps remain unchanged.

[0074] Example 5

[0075] The difference between this embodiment and embodiment 1 is that when preparing the perovskite film, the perovskite light absorbing layer in A3 is prepared with a mixed solvent of DMF and DMSO (wherein the volume ratio of DMF to DMSO is 4:1) with a concentration of 1.5 mmol mL -1 Cs 0.05 MA 0.22 FA 0.73 Pb(I 0.77 Br 0.23)3 Perovskite precursor solution, under nitrogen protection, the perovskite precursor solution was spin-coated on the HTL at a speed of 1000rpm and 5000rpm for 10 seconds and 30 seconds respectively. 20 seconds after the start of the second step, 150μL of ethyl acetate was added to the center of the sample, and then annealed at 100℃ for 50 minutes; when preparing the electron transport layer on the perovskite light absorbing layer in A4, 1nm lithium fluoride (LiF), 25nm C 60 and 2nm of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as an electron transport layer; a top electrode is prepared on the electron transport layer, and 100nm Ag is prepared as the top electrode of the device by thermal evaporation, and the other steps remain unchanged.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that step 1 and step 2 are not performed, and the remaining steps are the same as Example 1.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that when performing sequential processing, the operation of step 2 is omitted, and the remaining steps are the same as Example 1.

[0080] Comparative Example 3

[0081] The difference between this comparative example and Example 1 is that: when the sequential treatment is performed, step 1 uses 10 mmol L -1 The CF3PEAI IPA solution was used to replace the 10 mM PEAI IPA solution in the original step, and step 2 was omitted.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 is that: when the sequential treatment is performed, step 1 uses 10 mmol L -1 Step 1 is carried out with a 5 mM PEAI solution in IPA. Step 2 uses a 5 mM PEAI solution in IPA.

[0084] Comparative Example 5

[0085] The difference between this comparative example and Example 1 is that when performing sequential treatment, step 2 uses an IPA solution of 5 mM PEAI.

[0086] Comparative Example 6

[0087] The difference between this comparative example and Example 4 is that when performing sequential processing, the operation of step 2 is omitted, and the remaining steps are the same as Example 4.

[0088] Comparative Example 7

[0089] The difference between this comparative example and Example 5 is that step 1 and step 2 are not performed, and the remaining steps are the same as Example 5.

[0090] Comparative Example 8

[0091] The difference between this comparative example and Example 5 is that when performing sequential processing, the operation of step 2 is omitted, and the remaining steps are the same as Example 5.

[0092] Taking Example 1 and Comparative Examples 1-2 as examples, the prepared perovskite thin film materials were tested by scanning electron microscope (SEM). The test results are as follows: Figures 2 to 4 shown.

[0093] Combined with Example 1, Comparative Examples 1 to 2 and Figures 2 to 4 It can be seen that there is a large amount of unevenly distributed lead iodide on the surface of the perovskite prepared by the traditional method. However, through a sequential post-treatment method of the perovskite surface based on two-dimensional ligand-modified materials with different polarities, the lead iodide on the accumulated perovskite surface can be effectively and evenly rearranged to the grain boundary position, thereby improving the quality of the film.

[0094] On the basis of the above, the perovskite films prepared in Example 1 and Comparative Examples 1-2 were further tested for fluorescence spectrum. The test results are as follows: Figure 5 and Figure 6 shown.

[0095] Depend on Figure 5 It can be seen that: the left figure shows the fluorescence spectrum of the entire band. The results show that although the traditional method can suppress the non-radiative recombination of carriers, the improvement effect of the method proposed in the present invention is more superior. The right figure shows that after conventional treatment, the sample has low-dimensional characteristics, while after sequential treatment, the sample still retains the characteristics of the low-dimensional phase. This shows that the sequential post-treatment method of the perovskite surface based on two-dimensional ligand modified materials with different polarities proposed in the present invention can further suppress the non-radiative recombination of carriers while retaining the low-dimensional structural characteristics. Figure 6 The experimental results show that compared with the traditional one-step passivation method, the sequential processing strategy proposed in the present invention can significantly improve the carrier transport characteristics.

[0096] In order to more intuitively demonstrate the practical application value of the additional post-treatment method for the perovskite surface based on the high-polarity modified material proposed in the present invention, the inventors conducted performance tests of the corresponding solar cells. The tests were all conducted under the illumination conditions of a solar simulator (illumination intensity of 100 mW cm -2 ), and the test results can be used to characterize the device structure that is common in the field (ITO / 4PADCB / perovskite / C 60 / BCP / Ag or ITO / 4PADCB / Perovskite / LiF / C 60 / BCP / Ag). In particular, the device described herein is only used to evaluate the practical effect of the technology of the present invention and is not used to limit the scope of use of the technology.

[0097] Combination Figures 7 to 9 and Figures 12-13 By comparing Examples 1 to 3 and Comparative Examples 1 to 2, it can be seen that even for different 2D / 3D perovskite heterojunctions or different concentrations of post-processing technologies, the method proposed in the present invention also has the effect of improving device performance.

[0098] Combination Figure 7 and Figures 14 to 16 By comparing Example 1 with Comparative Examples 3 to 5, it can be seen that: comparing different treatment sequences, first using PEAI to surface treat the perovskite film and then using CF3PEAI to treat the device has the best performance improvement effect.

[0099] Combination Figures 10-11 and Figures 17 to 19 By comparing Examples 4 to 5 and Comparative Examples 6 to 8, it can be seen that compared with conventional passivation strategies, even with different perovskite compositions, the device optimized by the technology proposed in the present invention has the best performance.

[0100] In summary, the present invention proposes a method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand modified materials with different polarities. This method can passivate perovskite surface defects, regulate the surface structure and morphology of perovskite, effectively improve the problem of obstructed carrier transport at the perovskite surface interface caused by traditional single-step 2D treatment methods, improve the charge transport capacity, and thus effectively improve device performance.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities, characterized in that: The following steps are involved: Step 1: using material x dissolved in an organic solvent to treat the surface of a three-dimensional perovskite to prepare a perovskite heterojunction sample; Step 2: using material y dissolved in an organic solvent to perform secondary treatment on the sample of step 1 to obtain a perovskite heterojunction thin film sample with a final surface modification; The polarity of the material x is smaller than that of the material y, and the dipole moment of the molecules or ions of the material y is not less than 4 Debye; the organic solvent is in liquid phase at normal temperature and pressure.

2. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities according to claim 1, characterized in that: The material x is selected from benzylamine halide and / or phenethylamine halide; the material y is selected from 4-trifluoromethylbenzylamine halide and / or 4-trifluoromethylphenethylamine halide.

3. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities according to claim 2, characterized in that: The material x is selected from one or more of phenethylamine hydroiodide, phenethylamine hydrochloride, phenethylamine hydrobromide, benzylamine hydrochloride, benzylamine hydrobromide, and benzylamine hydroiodide; The material y is selected from one or more of 4-trifluoromethylphenethylamine hydroiodide, 4-trifluoromethylphenethylamine hydrobromide, 4-trifluoromethylphenethylamine hydrochloride, 4-trifluoromethylbenzylamine hydroiodide, 4-trifluoromethylbenzylamine hydrobromide or 4-trifluoromethylbenzylamine hydrochloride.

4. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities according to claim 1, characterized in that: The organic solvent is selected from isopropanol and / or chlorobenzene.

5. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities according to claim 4, characterized in that: The concentrations of the material x and the material y are both no higher than 50 mM.

6. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligand-modified materials with different polarities according to claim 1, characterized in that: The perovskite heterojunction sample includes two-dimensional perovskite and three-dimensional perovskite; The chemical composition of the three-dimensional perovskite is shown in formula (I): ABX3; The two-dimensional perovskite includes RP type and / or DJ type. The chemical composition of the RP type two-dimensional perovskite is as shown in formula (II): R2A n-1 B n X 3n+1 The chemical composition of the DJ-type two-dimensional perovskite is shown in formula (III): DA n-1 B n X 3n+1 ; In formulas (I) to (III), A is a monovalent cation, B is a divalent cation, X is a monovalent anion, n is a positive integer, R is a monovalent two-dimensional ligand cation, and D is a divalent two-dimensional ligand cation.

7. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligands modified with different polarities according to claim 6, characterized in that: The A is selected from at least one of formamidine ion, methylamine ion and cesium ion; the B is selected from lead ion and / or tin ion; and the X is selected from at least one of bromide ion, iodide ion, thiocyanate ion, chloride ion and formate ion.

8. The method for sequential post-treatment of perovskite surfaces based on two-dimensional ligands modified with different polarities according to claim 1, characterized in that: The post-treatment method is selected from one or more of spin coating, blade coating, slit coating, spray coating, and immersion.

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