Perovskite solar cell with Van der Waals interface structure and preparation method

Abstract

The invention discloses a perovskite solar cell with a Van der Waals interface structure and a preparation method thereof, a two-dimensional sheet material with a Van der Waals surface is introduced between a perovskite absorption layer and a substrate to construct a Van der Waals interface, CsPbI3 perovskite is prepared through epitaxial growth, controllable preparation of a CsPbI3 film with low defects is realized, and the perovskite solar cell with the Van der Waals interface structure is obtained. The phase change problem caused by defects is effectively inhibited; according to the CsPbI3 perovskite solar cell, tensile stress generated by thermal mismatch in CsPbI3 is effectively released through interface weak Van der Waals interaction, and the problem that residual stress induces yellow phase generation is solved; comprising a transparent electrode, an electron transport layer, a Van der Waals interface layer constructed by a two-dimensional material sheet, a perovskite active layer, a hole transport layer and a metal electrode which are sequentially laminated from bottom to top. According to the invention, the efficient and stable inorganic perovskite cell can be prepared, the development of the perovskite technology is promoted, and the method plays a certain role in promoting the national strategy of clean energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite solar cells, and in particular relates to a perovskite solar cell with a van der Waals interface structure and a preparation method thereof. Background Art

[0002] Perovskite solar cells (PSCs) have attracted extensive attention from scientists working on photovoltaic technology in recent years due to their high efficiency, low cost and solution processability. Due to the interesting optoelectronic properties of perovskite materials such as high light absorption coefficient, ideal / tunable band gap and long charge diffusion length, the highest certified power conversion efficiency (PCE) of PSCs based on rigid glass substrates has been improved to 26.7%.

[0003] The efficiency of PSCs is close to the commercial standard, but its long-term instability (short life) is one of the main obstacles to the practical application of this technology. Its poor stability mainly comes from the fact that perovskite materials contain organic components with low boiling points and are easily decomposed. Replacing its organic cations with inorganic cesium ions to construct inorganic perovskites can avoid the instability caused by organic cations. For example, inorganic CsPbI3 perovskite materials can exist stably at high temperatures above 400°C. In addition to its superior chemical and thermal stability, CsPbI3 perovskite also has the advantages of high carrier mobility, long diffusion distance and high absorption coefficient. Its band gap is wide at around 1.7eV, which is suitable for combining with silicon-based batteries to prepare stacked batteries to break through the SQ efficiency limit. The theoretical efficiency of its single-junction battery can also reach 28% (band gap width is 1.73eV). Therefore, actively carrying out research on inorganic CsPbI3 perovskite batteries with high thermal stability is expected to break through the bottleneck of perovskite battery stability and promote its industrialization process.

[0004] Regarding the source of the phase instability of CsPbI3 perovskite film, in addition to the intrinsic factor of the material caused by the mismatch of ion radius, it is mainly affected by two factors. First, the crystallization speed of CsPbI3 film is fast, and the surface morphology and chemical properties of the substrate interface are very different, resulting in a large number of vacancy defects in the film. Vacancy defects can cause lattice distortion, aggravate internal stress, and induce the formation of yellow phase. In addition, the tensile strain generated in CsPbI3 by external high-temperature heat treatment also seriously affects its phase stability. The tensile stress in CsPbI3 film can accelerate the transformation of black phase to yellow phase by reducing the formation energy of vacancy defects, the activation energy of ion migration and the formation energy of yellow phase. The difference in thermal expansion coefficient between the perovskite layer and the substrate layer, the heat treatment temperature and the contact interface are the main factors that produce tensile stress. The tensile strain can be reduced by lowering the heating temperature, but low-temperature treatment often leads to low crystallinity of perovskite and loss of its photoelectric conversion efficiency; it can also be selected by selecting a substrate material with a thermal expansion coefficient equivalent to that of perovskite, but the existing materials that meet the conditions often cannot withstand high-temperature treatment. In addition, experiments show that the yellow phase of CsPbI3 often starts near the contact interface.

[0005] In summary, in the existing preparation methods, the interface between the perovskite and the substrate interacts through strong chemical bonds. This interface prevents the perovskite layer from shrinking, resulting in considerable tensile strain in the perovskite layer, making the perovskite black phase unstable and easily converted into a more stable yellow phase. The yellow phase without photovoltaic response seriously affects the optical response of the battery and the carrier transport efficiency, greatly limiting the conversion efficiency and stability of the device. Therefore, there are great limitations in the preparation of inorganic perovskite films with high crystalline quality and low residual stress. Therefore, regulating the interaction of the contact interface is an important breakthrough in alleviating the damage to the stability of the CsPbI3 phase caused by heat treatment. Summary of the invention

[0006] In order to solve the problem that the growth of CsPbI3 perovskite thin films based on chemical bond interfaces is adversely affected by the lattice mismatch of the growth substrate, large differences in surface morphology and chemical properties, and to improve the efficiency and stability of the device, the present invention provides a perovskite solar cell with a van der Waals interface structure and a preparation method thereof.

[0007] A method for preparing a perovskite solar cell having a van der Waals interface structure of the present invention comprises the following steps:

[0008] Step 1: Clean the FTO glass with detergent, deionized water, ethanol, and isopropanol in an ultrasonic machine for 20 minutes each; then blow dry the FTO glass with nitrogen and put it in an oven to dry.

[0009] Step 2: The cleaned and dried FTO glass substrate surface is subjected to UV plasma treatment for 20 minutes to clean the organic matter remaining on the FTO surface, thereby improving the surface work function of the FTO and the surface wettability of the FTO glass.

[0010] Step 3: Spin-coat the SnO2 solution on the surface of the FTO glass substrate treated in step 2; the SnO2 solution is spin-coated at 2000 rpm, 40 s, and an acceleration of 1000 rpm / s 2 The substrate was spin-coated onto the treated FTO glass substrate surface; the spin-coated substrate was annealed at 120° C. for 25 minutes.

[0011] Step 4: Spin-coat a two-dimensional thin sheet material with a van der Waals surface on the surface of a SnO2 substrate, and then spin-coat a perovskite precursor solution. The perovskite absorption layer is prepared from a CsPbI3 precursor solution, which is prepared from a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1, and the molar ratio of CsI to PbI2 is 1:1; stir it at 35°C for 4 hours, and then filter it through a polytetrafluoroethylene membrane (PTFE) with a pore size of 0.22 μm.

[0012] The perovskite films were deposited by a two-step spin coating method:

[0013] (1) 1000 rpm, 15 s, 1000 rpm / s 2 .

[0014] (2) 5000 rpm, 45 s, 1000 rpm / s 2 .

[0015] When there are 25 seconds left in step (2), 200 μL of chlorobenzene is added dropwise, followed by annealing at 180°C for 20 minutes.

[0016] Step 5: Spin-coat a layer of Spiro-OMeTAD on the surface of the perovskite absorber layer, 3000rpm, 30s, 1000rpm / s 2 .

[0017] Step 6: Evaporate a layer of metal electrode Ag on the surface of the hole transport layer with a thickness of 100 nm; after completion, a CsPbI3 perovskite solar cell is obtained.

[0018] Furthermore, the two-dimensional thin sheet material is one or more of graphene, molybdenum disulfide, molybdenum ditelluride with a hexagonal phase structure, and tin disulfide and palladium disulfide with a cubic phase.

[0019] Furthermore, a single-layer or multi-layer two-dimensional thin sheet material is prepared by mechanical or chemical exfoliation methods.

[0020] Furthermore, the solvent for dissolving the two-dimensional thin sheet material is one or more of N-methylpyrrolidone NMP, dimethyl sulfoxide DMSO and isopropyl alcohol IPA.

[0021] Furthermore, the two-dimensional thin film material is deposited on the substrate by static and dynamic spin coating, and then heated to evaporate the solvent, and the coverage of the nano-thin film is increased by multiple cycles of deposition, which are repeated 2 to 3 times.

[0022] Furthermore, the static spin coating speed is 3000rpm~4500rpm, and the spin coating time is 20s~25s; the dynamic spin coating speed is 4000rpm~5000rpm, and the spin coating time is 20~25s; the amount of the two-dimensional material supernatant absorbed is 50~100μL.

[0023] Furthermore, the above-mentioned heating treatment can be performed in two ways: one is a traditional heat treatment method, in which the film is heat treated after spin coating; the other is to preheat the substrate and the precursor solution, slowly cool down and stand for 15 minutes after spin coating, and then perform the heating treatment.

[0024] Furthermore, the perovskite layer is optimized:

[0025] (1) DMAI is introduced into the precursor to regulate the perovskite crystallization process and improve its film quality.

[0026] (2) A small amount of Cl or Br is doped into the X-site of the perovskite to enhance its phase stability.

[0027] (3) Two-dimensional organic molecules such as PEAI, PEABr or PEACl are used to passivate the perovskite surface.

[0028] Furthermore, the concentration of the additive DMAI is 1% to 5%; the concentration of doped Cl and Br is 0.5% to 2%; the concentration of the upper surface passivation is 1 mg / mL to 3 mg / mL, wherein the passivation material is at least one of PEAI, PEACl, and PEABr.

[0029] Plasma treatment is performed on the two-dimensional thin film material to provide artificially controllable perovskite nucleation sites, wherein the plasma treatment environment condition is at least one of a nitrogen environment or an oxygen environment, and the plasma treatment time is 10 minutes to 15 minutes.

[0030] The present invention discloses a method for preparing a perovskite solar cell with a van der Waals interface structure. The prepared CsPbI3 perovskite solar cell comprises a transparent electrode, an electron transport layer, a van der Waals interface layer constructed of two-dimensional material sheets, a perovskite active layer, a hole transport layer, and a metal electrode, which are sequentially stacked from bottom to top; wherein the cathode is FTO, the electron transport layer is SnO2, the perovskite active layer system is CsPbI3, the hole transport layer is Spiro-OMeTAD, and the anode is a metallic silver electrode.

[0031] The beneficial technical effects of the present invention are:

[0032] 1. Construct van der Waals interface to induce high-quality epitaxial growth of CsPbI3 perovskite film and effectively release the tensile strain in CsPbI3 perovskite to achieve controllable preparation of high-quality CsPbI3 perovskite film with stable black phase.

[0033] 2. Through research and analysis in the field of CsPbI3 perovskite batteries, it is concluded that there are still weak links in the current research on phase stability in perovskite films, and it is concluded that regulating interfacial interactions is a breakthrough for further stabilizing the perovskite black phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic flow chart of the preparation method of the present invention.

[0035] Figure 2 It is the phase transition process of inorganic CsPbI3 perovskite.

[0036] Figure 3 Schematic diagram of the formation of tensile and compressive strains in CsPbI3 perovskite induced by heating.

[0037] Figure 4 Schematic diagram of the generation of CsPbI3 perovskite yellow phase starting from near the interface.

[0038] Figure 5 Schematic diagram of stress evolution at chemical bond interface under heat treatment conditions.

[0039] Figure 6 Schematic diagram of stress evolution of van der Waals interface under heat treatment conditions.

[0040] Figure 7 This is a schematic diagram of the structure of the CsPbI3 perovskite battery prepared by the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Embodiment 1:

[0043] The perovskite solar cell with a van der Waals interface structure and the preparation method thereof are as follows: Figure 1 As shown, the following steps are included:

[0044] Step 1: Clean the FTO glass with detergent, deionized water, ethanol, and isopropanol in an ultrasonic machine for 20 minutes each; then blow dry the FTO glass with nitrogen and put it in an oven to dry.

[0045] Step 2: The cleaned and dried FTO glass substrate surface is subjected to UV plasma treatment for 20 minutes. The plasma generated by the UV cleaning machine is used to clean the organic matter remaining on the FTO surface, thereby improving the surface work function of the FTO glass and the surface wettability of the FTO glass.

[0046] Step 3: Spin-coat the SnO2 solution on the surface of the FTO glass substrate treated in step 2; the SnO2 solution is spin-coated at 2000 rpm, 40 s, and an acceleration of 1000 rpm / s 2 The substrate was spin-coated onto the treated FTO glass substrate surface; the spin-coated substrate was annealed at 120° C. for 25 minutes.

[0047] Step 4: Spin-coat the two-dimensional thin film material on the above electron transport layer at 4000 rpm, 25 s, 2000 rpm / s2, 100°C, 5 min; spin-coat once.

[0048] Step 5: Spin-coat the surface of the above-mentioned two-dimensional thin film material with a perovskite precursor solution. The perovskite absorption layer is prepared from a CsPbI3 precursor solution. The precursor solution concentration is 0.7M, which is prepared from a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1; the molar ratio of CsI and PbI2 is 1:1. Stir it at 35°C for 4 hours and then filter it through a polytetrafluoroethylene membrane (PTFE) with a pore size of 0.22μm.

[0049] The perovskite films were deposited by a two-step spin coating method:

[0050] (1) 1000 rpm, 15 s, 1000 rpm / s 2 .

[0051] (2) 5000 rpm, 45 s, 1000 rpm / s 2 .

[0052] When there are 25 seconds left in step (2), 200 μL of chlorobenzene is added dropwise, followed by annealing at 180°C for 20 minutes.

[0053] By spin coating a layer of two-dimensional thin film material between the substrate and the perovskite absorber layer, the interface between the perovskite absorber layer prepared in step 5 and the substrate is changed from a strong chemical bond to a weak van der Waals interaction. Since the perovskite absorber layer interacts with the underlying substrate with a weak van der Waals force, the lattice arrangement of the perovskite absorber layer is not affected by the substrate in the initial growth stage, but maintains the inherent lattice parameters, which is conducive to the preparation of high-quality films and improves its phase transition barrier. In addition, the van der Waals interaction is a weak interaction, and through microscopic interlayer sliding, the tensile stress caused by thermal mismatch can be effectively released, thereby reducing the induction effect on the yellow phase, effectively stabilizing the perovskite black phase, and finally obtaining a high-quality perovskite film.

[0054] Step 6: Spin-coat a layer of Spiro-OMeTAD on the surface of the perovskite absorber layer, 3000rpm, 30s, 1000rpm / s 2 .

[0055] Step 7: Evaporate a layer of metal electrode Ag on the surface of the hole transport layer with a thickness of 100nm.

[0056] Step 8: After completion, a CsPbI3 perovskite solar cell with a van der Waals interface structure is obtained in which a two-dimensional thin film material is interposed between the substrate and the perovskite active layer.

[0057] Embodiment 2:

[0058] The difference between Example 2 and Example 1 is that in step 4, the two-dimensional thin film material is spin-coated on the electron transport layer at 4000 rpm, 25 s, 2000 rpm / s2, 100°C, 5 min; the spin coating is repeated twice. The remaining steps are the same.

[0059] Embodiment 3:

[0060] The difference between Example 3 and Example 1 is that in step 4, the two-dimensional thin film material is spin-coated on the electron transport layer at 4000 rpm, 25 s, 2000 rpm / s2, 100°C, 5 min; the spin coating is repeated three times. The remaining steps are the same.

[0061] Embodiment 4:

[0062] The difference between Example 4 and Example 1 is that in step 5, a perovskite precursor solution is spin-coated on the surface of the above-mentioned two-dimensional thin film material, and the perovskite absorption layer is prepared from a CsPbI3 precursor solution, and the precursor solution concentration is 0.7M, which is prepared from a mixed solvent of dimethylformamide DMF and dimethyl sulfoxide DMSO with a volume ratio of 4:1; it is stirred at 35°C for 4 hours, and then filtered through a polytetrafluoroethylene membrane (PTFE) with a pore size of 0.22μm. The perovskite film is deposited by two-step spin coating: (1) 1000rpm 15s 1000rpm / s 2 , (2) 5000rpm 45s 1000rpm / s 2 . When there are 25 seconds left in the second step, 200 μL of chlorobenzene is added dropwise. Then, annealing is performed at 210°C for 20 minutes; the remaining steps are the same.

[0063] Embodiment 5:

[0064] The difference between Example 5 and Example 1 is that in step 5, a perovskite precursor solution is spin-coated on the surface of the above-mentioned two-dimensional thin film material, and the perovskite absorption layer is prepared from a CsPbI3 precursor solution, and the precursor solution concentration is 0.7M, which is prepared from a mixed solvent of dimethylformamide DMF and dimethyl sulfoxide DMSO with a volume ratio of 4:1; it is stirred at 35°C for 4 hours, and then filtered through a polytetrafluoroethylene membrane (PTFE) with a pore size of 0.22μm. The perovskite film is deposited by two-step spin coating: (1) 1000rpm 15s 1000rpm / s 2 , (2) 5000rpm 45s 1000rpm / s 2 . When there are 25 seconds left in the second step, 200 μL of chlorobenzene is added. Then, annealing is performed at 260°C for 20 minutes; the rest of the steps are the same.

[0065] Embodiment 6:

[0066] The difference between Example 6 and Example 1 is that in step 5, a perovskite precursor solution is spin-coated on the surface of the above-mentioned two-dimensional thin film material. The perovskite absorption layer is prepared from a CsPbI3 precursor solution. The precursor solution concentration is 0.7M, which is prepared from a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1; it is stirred at 35°C for 4 hours and then filtered through a polytetrafluoroethylene membrane (PTFE) with a pore size of 0.22μm. The perovskite film is deposited by two-step spin coating: (1) 1000rpm 15s 1000rpm / s 2 , (2) 5000rpm 45s 1000rpm / s 2. When there are 25 seconds left in the second step, drop 200μL of chlorobenzene. The thickness of the absorption layer is about 700nm. Before spin coating the perovskite film, preheat the substrate and the precursor solution, slowly cool down and let stand for 15 minutes after spin coating, and then heat it again at 180℃. The rest of the steps are the same.

[0067] Embodiment 7:

[0068] The difference between Example 7 and Example 1 is the concentration of the precursor solution. The concentration of the precursor solution in Example 7 is 0.5 M, and the other steps are the same.

[0069] Embodiment 8:

[0070] The difference between Example 8 and Example 1 lies in the concentration of the precursor solution. The concentration of the precursor solution in Example 7 is 0.3 M, and the other steps are the same.

[0071] In order to solve the problem that the growth of CsPbI3 perovskite film based on chemical bond interface is adversely affected by the shortcomings of growth substrate lattice mismatch, large differences in surface morphology and chemical properties, the present invention provides a method for constructing a van der Waals interface between the substrate and the perovskite active layer, thereby improving the efficiency and stability of the device.

[0072] The present invention induces high-quality epitaxial growth of CsPbI3 perovskite film by constructing a van der Waals interface. The inorganic CsPbI3 perovskite phase transition process is as follows: Figure 2 As shown, its liquid phase epitaxial growth nucleation dynamics process realizes the controllable preparation of CsPbI3 thin films with low defects and effectively suppresses the phase change problem caused by defects.

[0073] The present invention effectively releases the tensile stress generated by thermal mismatch in CsPbI3 through weak interfacial van der Waals interaction. The tensile and compressive strains caused by heating in CsPbI3 perovskite form Figure 3 As shown, the CsPbI3 perovskite yellow phase begins to form near the interface. Figure 4 As shown, it overcomes the problem of residual stress-induced yellow phase.

[0074] The present invention changes the strong chemical bond effect at the interface between the CsPbI3 film and the substrate into a weak van der Waals interaction to further improve its phase stability. The stress evolution of the chemical bond interface under heat treatment conditions is as follows Figure 5 As shown in Figure 2, the stress evolution of the van der Waals interface under heat treatment conditions is as follows: Figure 6 shown.

[0075] The present invention provides a perovskite solar cell with a van der Waals interface structure and a preparation method thereof. The prepared CsPbI3 perovskite solar cell is as follows: Figure 7As shown, it includes a transparent electrode, an electron transport layer, a van der Waals interface layer constructed of two-dimensional material sheets, a perovskite active layer, a hole transport layer, and a metal electrode stacked in sequence from bottom to top; wherein the cathode is FTO, the electron transport layer is SnO2, the perovskite active layer system is CsPbI3, the hole transport layer is Spiro-OMeTAD, and the anode is a metallic silver electrode.

[0076] Furthermore, considering that different crystal structure symmetries will affect epitaxial growth (such as crystal orientation, etc.), a two-dimensional sheet material with the same cubic phase and a different hexagonal phase as CsPbI3 perovskite and a van der Waals surface is selected. The two-dimensional sheet material is one or more of graphene, molybdenum disulfide, molybdenum ditelluride with a hexagonal phase structure, and tin disulfide and palladium disulfide with a cubic phase.

[0077] Furthermore, a single-layer or multi-layer two-dimensional thin sheet material is prepared by mechanical or chemical exfoliation methods.

[0078] Furthermore, the solvent for dissolving the two-dimensional thin sheet material is one or more of N-methylpyrrolidone NMP, dimethyl sulfoxide DMSO and isopropyl alcohol IPA.

[0079] Furthermore, the two-dimensional thin film material is deposited on the substrate by static and dynamic spin coating, and then heated to evaporate the solvent, and the coverage of the nano-thin film is increased by multiple cycles of deposition, which are repeated 2 to 3 times.

[0080] Furthermore, the static spin coating speed is 3000rpm~4500rpm, and the spin coating time is 20s~25s; the dynamic spin coating speed is 4000rpm~5000rpm, and the spin coating time is 20~25s; the amount of the two-dimensional material supernatant absorbed is 50~100μL.

[0081] Furthermore, the above-mentioned heating treatment can be performed in two ways: one is a traditional heat treatment method, in which the film is heat treated after spin coating; the other is to preheat the substrate and the precursor solution, slowly cool down and stand for 15 minutes after spin coating, and then perform the heating treatment.

[0082] Furthermore, the perovskite layer is optimized:

[0083] (1) DMAI is introduced into the precursor to regulate the perovskite crystallization process and improve its film quality.

[0084] (2) A small amount of Cl or Br is doped into the X-site of the perovskite to enhance its phase stability.

[0085] (3) Two-dimensional organic molecules such as PEAI, PEABr or PEACl are used to passivate the perovskite surface.

[0086] Furthermore, the concentration of the additive DMAI is 1% to 5%; the concentration of doped Cl and Br is 0.5% to 2%; the concentration of the upper surface passivation is 1 mg / mL to 3 mg / mL, wherein the passivation material is at least one of PEAI, PEACl, and PEABr.

[0087] Plasma treatment is performed on the two-dimensional thin film material to provide artificially controllable perovskite nucleation sites, wherein the plasma treatment environment condition is at least one of a nitrogen environment or an oxygen environment, and the plasma treatment time is 10 minutes to 15 minutes.

[0088] Obviously, the embodiments described above are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention.

Claims

1. A method for preparing a perovskite solar cell having a van der Waals interface structure, characterized in that: The following steps are involved: Step 1: Clean the FTO glass with detergent, deionized water, ethanol, and isopropanol in an ultrasonic machine for 20 minutes each; then blow dry the FTO glass with nitrogen and put it in an oven to dry; Step 2: The cleaned and dried FTO glass substrate surface is treated with UV plasma for 20 minutes to clean the organic matter remaining on the FTO surface, thereby improving the surface work function of the FTO and the surface wettability of the FTO glass; Step 3: Spin-coat the SnO2 solution on the surface of the FTO glass substrate treated in step 2; the SnO2 solution is spin-coated at 2000 rpm, 40 s, and an acceleration of 1000 rpm / s 2 Spin coating onto the treated FTO glass substrate surface; annealing the spin-coated substrate at 120°C for 25 minutes; Step 4: Spin coating a two-dimensional thin film material with a van der Waals surface on the surface of the SnO2 substrate, and then spin coating a perovskite precursor solution. The perovskite absorption layer is prepared from a CsPbI3 precursor solution, which is prepared from a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 4:1, and the molar ratio of CsI to PbI2 is 1:1; It was stirred at 35°C for 4 hours, and then filtered through a polytetrafluoroethylene membrane PTFE with a pore size of 0.22 μm; The perovskite films were deposited by a two-step spin coating method: (1)1000rpm、15s、1000rpm / s 2 ; (2)5000rpm、45s、1000rpm / s 2 ; When there were 25 seconds left in step (2), 200 μL of chlorobenzene was added, followed by annealing at 180°C for 20 minutes; Step 5: Spin-coat a layer of Spiro-OMeTAD on the surface of the perovskite absorber layer, 3000rpm, 30s, 1000rpm / s 2 ; Step 6: Evaporate a layer of metal electrode Ag on the surface of the hole transport layer with a thickness of 100 nm; after completion, a CsPbI3 perovskite solar cell is obtained.

2. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 1, characterized in that: The two-dimensional sheet material is one or more of graphene, molybdenum disulfide, molybdenum ditelluride with a hexagonal phase structure, and tin disulfide and palladium disulfide with a cubic phase.

3. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 1, characterized in that: In the step 4, a two-dimensional sheet material with a single-layer or multi-layer structure is prepared by mechanical stripping or chemical stripping.

4. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 3, characterized in that: The solvent for dissolving the two-dimensional thin sheet material is one or more of N-methylpyrrolidone NMP, dimethyl sulfoxide DMSO and isopropyl alcohol IPA.

5. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 3, characterized in that: The two-dimensional thin film material is deposited on the substrate by static and dynamic spin coating, and then heated to evaporate the solvent. The coverage of the nano-thin film is increased by multiple cycles of deposition, which are repeated 2 to 3 times.

6. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 5, characterized in that: The static spin coating speed is 3000rpm-4500rpm, and the spin coating time is 20s-25s; the dynamic spin coating speed is 4000rpm-5000rpm, and the spin coating time is 20-25s; the amount of the two-dimensional material supernatant absorbed is 50-100μL.

7. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 5, characterized in that: The heating treatment is carried out in two ways: one is a conventional heat treatment method, in which the film is heat treated after spin coating; the other is to preheat the substrate and the precursor solution, slowly cool down and stand for 15 minutes after spin coating, and then heat treat.

8. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 1, characterized in that: It also includes optimization of the perovskite layer: (1) Introducing DMAI into the precursor to regulate the perovskite crystallization process and improve its film quality; (2) a small amount of Cl or Br is doped into the X-site of the perovskite to enhance its phase stability; (3) Two-dimensional organic molecules such as PEAI, PEABr or PEACl are used to passivate the perovskite surface.

9. The method for preparing a perovskite solar cell having a van der Waals interface structure according to claim 8, characterized in that: The concentration of the additive DMAI is 1% to 5%; the concentration of doped Cl and Br is 0.5% to 2%; the concentration of the upper surface passivation is 1 mg / mL to 3 mg / mL, wherein the passivation material is at least one of PEAI, PEACl, and PEABr; Plasma treatment is performed on the two-dimensional thin film material to provide artificially controllable perovskite nucleation sites, wherein the plasma treatment environment condition is at least one of a nitrogen environment or an oxygen environment, and the plasma treatment time is 10 minutes to 15 minutes.

10. The CsPbI3 perovskite solar cell prepared by the method for preparing a perovskite solar cell with a van der Waals interface structure according to claim 1, characterized in that: It includes a transparent electrode, an electron transport layer, a van der Waals interface layer constructed of two-dimensional material sheets, a perovskite active layer, a hole transport layer, and a metal electrode, which are stacked in sequence from bottom to top; among them, the cathode is FTO, the electron transport layer is SnO2, the perovskite active layer system is CsPbI3, the hole transport layer is Spiro-OMeTAD, and the anode is a metallic silver electrode.

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