A method for preparing a perovskite active layer in a solar cell

Abstract

The application provides a preparation method of a perovskite active layer in a solar cell and belongs to the technical field of solar cells. The method introduces a secondary anti-solvent into the process of preparing a perovskite film by using a primary anti-solvent, and introduces a passivation material MAI (methylamine iodine) with a passivation effect on the perovskite into the secondary anti-solvent, so as to pre-compensate I vacancy defects caused by the volatilization of an organic salt in a subsequent annealing process, then passivation treatment is performed by using a conventional surface passivation method, so that two kinds of passivation materials are simultaneously used to passivate surface defects, the surface defect state density is further reduced, the open-circuit voltage and the fill factor of the solar cell are significantly improved, the photoelectric conversion efficiency of the solar cell is increased, and the device performance is improved. The method can not only realize the surface passivation effect of the perovskite active layer, but also improve the crystallization kinetics and the crystallization quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, and particularly relates to a preparation method of a perovskite active layer in a solar cell. BACKGROUND

[0002] As a new type of photovoltaic material, perovskite has achieved a maximum certified conversion efficiency of 25.7% in just a few decades. Due to its adjustable optical band gap, large optical absorption coefficient, long carrier diffusion length, and low cost, perovskite has become a hot and important research topic. Although the efficiency of perovskite solar cells has been rapidly developed, its instability under conditions such as water, light, and heat is still an important factor limiting the further development and commercial application of perovskite solar cells. At present, a large number of studies focus on optimizing the perovskite absorption layer (composition, defect passivation, additives), interface management, and device encapsulation, but the stability of perovskite has not been solved. Recently, researchers have found that introducing long-chain cations into three-dimensional perovskite to form mixed-dimensional perovskite or quasi-two-dimensional perovskite is an effective method to improve the stability of devices. The introduction of large organic cations can effectively block the contact of water and oxygen with the inorganic layer, and also effectively block phase separation and inhibit ion migration, thereby achieving the effect of improving the stability of devices.

[0003] The structure general formula of 2D perovskite is (A') m (A) n-1 B n X 3n+1 wherein A' is a large organic cation connecting the inorganic layer, and n is the number of inorganic framework layers between two organic cations. Due to its excellent chemical tunability (tunable large organic cation, tunable composition, and tunable n value), the device performance of 2D perovskite is also flexible and adjustable.

[0004] At present, high-efficiency two-dimensional perovskite is mostly prepared by one-step anti-solvent method. The use of anti-solvent can promote the separation of solvent from the thin film, adjust the crystal nucleation, and form a high-quality thin film. However, due to the ionic nature of the perovskite lattice, the perovskite thin film treated by one-step anti-solvent method inevitably produces a large number of defects. In addition, the residual solvent in the thin film will produce by-products affecting the purity of the perovskite phase and the performance of the device.

[0005] During the fabrication of perovskite thin films, annealing process is usually needed to further promote the growth of perovskite crystals, so as to obtain high-quality perovskite absorber layer. However, the organic component in the perovskite composition is thermally unstable, such as the continuous annealing temperature exceeding 85℃ will make the MAI component volatilize, so as to form a large number of halogen vacancies on the surface of perovskite. In addition, the complex solution precursor composition and rapid heating annealing will also form a large number of other types of defects on the surface of perovskite light absorption layer, such as I interstitial, Pb / I anti-site defects or Pb 0 Defects, etc., which will form electron / hole recombination centers at the interface, seriously affecting the cell efficiency. Studies have shown that the surface defect state density of perovskite thin film is more than twice that of bulk material.

[0006] In recent years, many researchers use surface passivation strategies to further improve the performance of 2D perovskite. Chen Gang et al. (Meng K, Wang X, Li Z, et al. Self-passivation of low-dimensional hybrid halide perovskites guided by structural characteristics and degradation kinetics [J]. Energy Environ Sci, 2021, 14(4): 2357-68.) use BAI self-passivation strategy to treat the surface of two-dimensional perovskite, which improves the performance of (BA)2(MA)3Pb4I 13 (n = 4) device to 17% and significantly improves the thermal and humidity stability. Biding Qin et al. (Huang Y, Li Y, Lim E L, et al. Stable layered 2D perovskite solar cells with an efficiency of over 19% via multifunctional interfacial engineering [J]. J Am Chem Soc, 2021, 143(10): 3911-7.) introduce GABr on the upper surface to induce surface secondary crystallization, which finally improves the performance of GA2MA4Pb5I 16(n = 5) to 19.3%. Zhang et al. (Li K, Yue S, Li X, et al. High Efficiency Perovskite Solar Cells Employing Quasi-2D Ruddlesden-Popper / Dion-Jacobson Heterojunctions [J]. Adv Funct Mater, 2022, 32(21): 2200024.) used BDAI2 to form a DJ-type two-dimensional phase on the surface to passivate the RP-type two-dimensional phase. This heterojunction not only improves the interface charge separation but also reduces the surface defect state density, ultimately achieving an efficiency of 18.34% and a high open voltage of 1.24 V. However, the above method can only use one passivation material to solve part of the surface defects. When two materials are used for surface passivation at the same time, due to the incompatibility of the two passivation materials, the surface defect state cannot be fully reduced, and the surface passivation effect cannot be improved. SUMMARY

[0007] The purpose of the present application is to provide a method for preparing a perovskite active layer in a solar cell, which can simultaneously passivate the surface defects of the perovskite active layer with two passivation materials, reduce the surface defect state density, and improve the performance of the cell.

[0008] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0009] The present application provides a method for preparing a perovskite active layer in a solar cell, comprising the following steps:

[0010] A perovskite active layer precursor solution is spin-coated on a substrate. During the spin-coating process, a first anti-solvent and a second anti-solvent are added dropwise in sequence. The obtained thin film is subjected to surface passivation treatment to obtain a perovskite active layer.

[0011] The second anti-solvent includes a passivation material, and the passivation material includes methylamine iodide, methylamine chloride, formamidine iodide, or guanidine bromide.

[0012] Preferably, the first anti-solvent and the second anti-solvent independently include isopropyl alcohol, ethanol, butanol, chlorobenzene, ethyl acetate, anisole, diethyl ether, toluene, or mesitylene.

[0013] Preferably, the concentration of the passivation material in the second anti-solvent is 0.5-5 mg / mL.

[0014] Preferably, the time for adding the first anti-solvent is within 10-20 s after the start of the spin-coating program; and the time for adding the second anti-solvent is within 10-20 s after the addition of the first anti-solvent and within 10-20 s before the end of the spin-coating program.

[0015] Preferably, the concentration of the perovskite active layer precursor solution is 1.3-1.4 mol / L; the volume ratio of the perovskite active layer precursor solution, the first anti-solvent and the second anti-solvent is (50-60):150:(20-30).

[0016] Preferably, the surface passivation material used in the surface passivation treatment comprises methylamine iodide, n-butylamine iodide or choline chloride.

[0017] Preferably, the surface passivation treatment process comprises spin coating a surface passivation material solution on the thin film and performing annealing treatment; the concentration of the surface passivation material in the surface passivation material solution is 1 mg / mL.

[0018] Preferably, the substrate is an electron transport layer or a hole transport layer; the material corresponding to the electron transport layer is one or more of tin dioxide, titanium dioxide, zinc oxide, [6,6]-phenyl C 61 butyric acid methyl ester, fullerene and graphene; the material of the hole transport layer is one or more of inorganic material, organic material and self-assembled monolayer material.

[0019] Preferably, the perovskite active layer precursor in the perovskite active layer precursor solution comprises an ABX3 type perovskite semiconductor material or an (A') m (A) n-1 B n X 3n+1 type perovskite semiconductor material, A' is a large organic cation, the large organic cation comprises n-butylamine iodide, phenethylamine iodide or 1,4-butanediamine hydroiodide, A is one or more of methylamine cation, formamidinium cation, Cs and Rb, B is lead and / or tin, and X is at least one of iodine, bromine and chlorine.

[0020] Preferably, the perovskite type of the solar cell is two-dimensional perovskite, three-dimensional perovskite or mixed-dimensional perovskite.

[0021] The application provides a preparation method of a perovskite active layer in a solar cell.

[0022] The advantages of the method of the present application are: 1) on the basis of traditional surface post-treatment passivation, the surface defect state density can be reduced by nearly 2 times; 2) the secondary anti-solvent is added dropwise, which can further extract the solvent in the film, reduce the residual organic solvent in the film, make the phase transition more sufficient, improve the crystallization kinetics, improve the crystallization quality of the film, thereby improve the open voltage and fill factor of the battery, and obtain a perovskite solar cell with higher efficiency; 3) the energy level difference between the hole transport layer can be reduced, which is beneficial to the extraction and transmission of holes.

[0023] For two-dimensional perovskite, the use of secondary anti-solvent in the present application can optimize the n value distribution, so that small n value phases exist only on the upper surface of the two-dimensional perovskite, and the lower part is mainly 3D-like phase. This phase structure distribution can effectively improve the efficiency and stability of the two-dimensional perovskite.

[0024] The method described in the present application is simple to operate and easy to implement, and is suitable for perovskite solar cells prepared by one-step anti-solvent solution method (including narrow band gap 1.1-1.3 eV, normal band gap 1.4-1.6 eV and wide band gap 1.6-1.8 eV solar cells), and is also suitable for wide band gap perovskite / silicon two-end laminated solar cells prepared by one-step anti-solvent solution method. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Flow chart for preparing perovskite active layer according to the present application;

[0026] Figure 2 Structure diagram of N-I-P type two-dimensional perovskite solar cell in Example 1 and Comparative Example 1;

[0027] Figure 3 Structure diagram of P-I-N type wide band gap perovskite solar cell in Example 3 and Comparative Example 2;

[0028] Figure 4 Structure diagram of perovskite / silicon heterojunction laminated solar cell device in Example 4, wherein the silicon heterojunction bottom cell is a double-side texturing structure;

[0029] Figure 5 J-V diagram of N-I-P type two-dimensional perovskite cell in Comparative Example 1;

[0030] Figure 6 J-V diagram of N-I-P type two-dimensional perovskite cell after optimization by 3 mg / mL MAI / IPA secondary anti-solvent in Example 1;

[0031] Figure 7 J-V diagram of N-I-P type two-dimensional perovskite cell after optimization by 3 mg / mL MACl / IPA secondary anti-solvent in Example 2;

[0032] Figure 8J-V curve of P-I-N type wide bandgap perovskite cell in Example 3 with 3 mg / mL MAI / IPA secondary anti-solvent optimization;

[0033] Figure 9 J-V curve of P-I-N type wide bandgap perovskite cell in Example 3 with 3 mg / mL MAI / IPA secondary anti-solvent optimization;

[0034] Figure 10 J-V curve of wide bandgap perovskite / silicon heterojunction tandem solar cell in Example 4 with 3 mg / mL MAI / IPA secondary anti-solvent optimization, wherein the silicon heterojunction bottom cell is a double-side texturing structure;

[0035] Figure 11 Charge defect density N obtained by space charge limited current (SCLC) method for perovskite devices of Comparative Example 1 and Example 1 t Comparative diagram, wherein the device structure is Glass / ITO / SnO2 / perovskite absorber layer / passivation layer / PCBM / BCP / Ag. DETAILED DESCRIPTION

[0036] The present application provides a preparation method of a perovskite active layer in a solar cell, comprising the following steps:

[0037] A perovskite active layer precursor solution is spin-coated on a substrate, and in the spin-coating process, a first anti-solvent and a second anti-solvent are added dropwise in sequence, and the obtained thin film is subjected to surface passivation treatment to obtain a perovskite active layer.

[0038] The second anti-solvent comprises a passivation material, and the passivation material comprises methylamine iodide, methylamine chloride, formamidine iodide or guanidine bromide.

[0039] In the present application, if not otherwise specified, the required materials or reagents are commercially available and well known to those skilled in the art.

[0040] In the present application, the perovskite type of the solar cell is preferably two-dimensional perovskite, three-dimensional perovskite or mixed-dimensional perovskite; the cell structure of the solar cell is preferably P-I-N type or N-I-P type; the band gap is preferably 1.10-1.80 eV; the structure of the solar cell is preferably planar or mesoporous. The perovskite used in the solar cell is an organic-inorganic hybrid perovskite material, an inorganic perovskite material or a wide bandgap perovskite-crystalline silicon tandem layer material. The present application does not have special limitations on the area of the solar cell, which can be adjusted according to actual needs.

[0041] The present application does not have special limitations on the layer structure of the solar cell and the preparation method, and the perovskite solar cell with the corresponding layer structure can be prepared according to the methods well known in the art; in the present application, the structure of the perovskite solar cell preferably comprises a bottom substrate, a transparent conductive layer, a hole transport layer, a perovskite active layer, an electron transport layer and a metal electrode layer.

[0042] The present application does not have special limitations on the materials of the bottom substrate and the transparent conductive layer, and the corresponding materials well known in the art can be used. The present application does not have special limitations on the processing process of the bottom substrate and the transparent conductive layer, and the process can be performed according to the methods well known in the art.

[0043] In the present application, the material of the metal electrode layer is preferably one or more of gold (Au), silver (Ag), copper (Cu), aluminum (Al) and carbon material; the present application does not have special limitations on the carbon material, and the corresponding materials well known in the art can be used; the metal electrode layer is preferably prepared by a thermal evaporation method or a screen printing method.

[0044] In the embodiments of the present application, the specific structure of the N-I-P type two-dimensional perovskite solar cell comprises, from top to bottom, a silver electrode, a Spiro-OMeTAD hole transport layer, a perovskite active layer, a SnO2 electron transport layer and an ITO transparent conductive glass; the specific structure of the P-I-N type wide-bandgap perovskite solar cell comprises, from top to bottom, an Ag electrode, a BCP buffer layer, a PCBM electron transport layer, a perovskite active layer, a NiOx+Poly-TPD hole transport layer and an ITO transparent conductive glass; the P-I-N type wide-bandgap perovskite is combined with a double-side texturing silicon heterojunction to prepare a perovskite / silicon heterojunction laminated solar cell, and the effective area of the cell is 0.5003 cm 2 , from top to bottom, a front metal grid electrode silver, a transparent conductive film IZO, a buffer layer SnO2, an electron transport layer C 60 , a perovskite active layer, a Poly-TPD / NiOx double hole transport layer, a connecting layer ITO, a silicon heterojunction bottom cell electron selection layer a-si:H(n), a passivation layer a-si:H(i), a silicon substrate N-Si, a passivation layer a-si:H(i), a hole selection layer a-si:H(p), ITO and a back electrode silver.

[0045] In the present application, the matrix is preferably an electron transport layer or a hole transport layer; the material corresponding to the electron transport layer is tin dioxide, titanium dioxide, zinc oxide, [6,6]-phenyl C 61 methyl butyrate (PCBM), fullerene (C 60) and graphene, when the material corresponding to the electron transport layer is two or more of the above, the present application does not have special limitation on the ratio of different kinds of materials, and any ratio is acceptable. In the present application, the material of the hole transport layer is preferably one or more of inorganic material, organic material and self-assembled monolayer material; the inorganic material is preferably poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), nickel oxide (NiOx) or cuprous thiocyanate (CuSCN), the organic material is preferably 2,2,7,7-tetra(N,N-di-p-tolyl)amino-9,9-spirobifluorene (Spiro-TTB) or 2,2',7,7'-tetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD); the self-assembled monolayer material is preferably one or more of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) and [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz). When the material of the hole transport layer is more than one of the above, the present application does not have special limitation on the ratio of different kinds of hole transport layer, which can be adjusted according to actual needs. The present application does not have special limitation on the preparation process of the electron transport layer and the hole transport layer, which can be prepared according to the process well known in the art.

[0046] In the present application, the perovskite active layer precursor in the perovskite active layer precursor solution includes ABX3 type perovskite semiconductor material or (A') m (A) n-1 B n X 3n+1 type perovskite semiconductor material, A' is a large organic cation, which preferably includes n-butylamine iodide, phenethylamine iodide or 1,4-butanediamine hydroiodide, A is one or more of methylamine cation, formamidinium cation, Cs and Rb, B is lead and / or tin, and X is at least one of iodine, bromine and chlorine. The present application does not have special limitation on the specific type of the ABX3 type or (A') m (A) n-1 B n X 3n+1 type perovskite semiconductor material, and any perovskite semiconductor material composed of the above elements is acceptable.

[0047] In the present application, the concentration of the perovskite active layer precursor solution is preferably 1.3-1.4 mol / L.

[0048] The present application does not have special limitation on the preparation process of the perovskite active layer precursor solution and the solvents and specific components used therein, and the corresponding perovskite active layer precursor solution can be prepared according to the processes well known in the art.

[0049] The present application does not have special limitation on the rate and time of the spin coating, and the processes well known in the art can be used; in the embodiments of the present application, the spin coating is performed at a speed of 3000 rpm for 40 s, or at a speed of 5000 rpm for 50 s.

[0050] In the present application, the first and second anti-solvents preferably independently include isopropyl alcohol, ethanol, butanol, chlorobenzene, ethyl acetate, anisole, diethyl ether, toluene or mesitylene.

[0051] The present application preferably adjusts the type of the second anti-solvent according to the perovskite structure; for two-dimensional perovskite, an alcohol is preferably used as the second anti-solvent; for three-dimensional perovskite, the type of the second anti-solvent is preferably different from that of the first anti-solvent.

[0052] In the present application, the time for adding the first anti-solvent is within 10-20 s after the start of the spin coating process, and more preferably 15 s; the time for adding the second anti-solvent is within 10-20 s after the addition of the first anti-solvent and within 10-20 s before the end of the spin coating process, and more preferably 15 s after the addition of the first anti-solvent.

[0053] In the present application, the second anti-solvent includes a passivation material, and the passivation material is methylamine iodide, methylamine chloride, formamidine iodide or guanidine bromide; the concentration of the passivation material in the second anti-solvent is preferably 0.5-5 mg / mL, and more preferably 3 mg / mL.

[0054] In the present application, the amount ratio of the perovskite active layer precursor solution, the first anti-solvent and the second anti-solvent is preferably (50-60):150:(20-30).

[0055] After the addition of the second anti-solvent and the completion of the spin coating, the present application preferably anneals the obtained product to form a thin film; the present application does not have special limitation on the specific process of the annealing, and the processes well known in the art can be used; in the embodiments of the present application, the annealing is performed at 100℃ for 10 min.

[0056] In the present application, the surface passivation material used in the surface passivation treatment comprises methylamine iodine, n-butylamine iodine or choline chloride; the process of the surface passivation treatment preferably comprises: spin coating a surface passivation material solution on the thin film, performing annealing treatment, forming a passivation layer on the thin film, and obtaining a perovskite active layer. In the present application, the concentration of the surface passivation material in the surface passivation material solution is preferably 1 mg / mL. The present application does not have special limitations on the process of spin coating the surface passivation material solution, which can be performed according to processes well known in the art; in the embodiments of the present application, the spin coating is performed at a speed of 5000 rpm for 30 s. The present application does not have special limitations on the specific process of the annealing treatment, which can be performed according to processes well known in the art; in the embodiments of the present application, the annealing is performed at 100℃ for 10 min.

[0057] After the use of the secondary anti-solvent in the present application, the band gap of the thin film does not change, and the surface is more n-type, which is conducive to reducing the energy level difference between the hole transport layer and the surface, and improving the extraction and transport of holes. In the embodiments of the present application, since the secondary anti-solvent used is IPA (isopropyl alcohol), the solubility of MAI in IPA is lower than that of FAI (formamidinium iodide), so after the use of the IPA anti-solvent, relatively more MAI will be left on the surface. MAI and the large organic cations in the two-dimensional perovskite will preferentially react with PbI2, and the crystallization barrier of the two-dimensional perovskite is relatively small, so after the IPA treatment, more two-dimensional phases will be formed on the surface, and more three-dimensional-like phases will be formed in the bulk region, which is conducive to obtaining a two-dimensional device with higher efficiency.

[0058] Figure 1 The flow chart for preparing the perovskite active layer in the embodiments of the present application is as follows: spin coating a perovskite two-dimensional precursor solution on a substrate, adding ethyl acetate anti-solvent after spin coating for 15 s, adding methylamine iodine / isopropyl alcohol anti-solvent as a secondary anti-solvent when the total spin coating time is 30 s, and then performing annealing and surface post-treatment in sequence to obtain a perovskite active layer.

[0059] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0060] Comparative Example 1

[0061] The solar cell structure of the present comparative example is a N-I-P type two-dimensional perovskite solar cell, which is prepared by using a one-step anti-solvent method, and the specific structure is as follows: Figure 2As shown, from top to bottom in turn includes: silver electrode, Spiro-OMeTAD hole transport layer, perovskite active layer, SnO2 electron transport layer and ITO transparent conductive glass.

[0062] Specific preparation method:

[0063] 1) Glass as substrate, on the surface of the glass substrate deposition of transparent conductive ITO layer, the resulting ITO glass substrate with Hill glass cleaner, deionized water, acetone and isopropanol ultrasonic cleaning, N2 drying, ITO substrate UV ozone treatment 20 min, get ITO substrate;

[0064] 2) In air, the mass fraction of 2.67% of nano SnO2 aqueous solution with 4000 r / min spin coating on the ITO substrate, spin coating time is 30 s, 80 ℃ annealing 30 min, form electron transport layer, cooling to room temperature after transfer to the glove box;

[0065] 3) 0.16 mmol BDAI2(1,4-butanediamine hydroiodide), 0.2 mmol MAI(methylamine iodine) + FAI(methylamidine iodine), 0.8 mmol PbI2(lead iodide), 0.28 mmol MACl(methylamine chloride) and 0.08 mmol PbCl2(lead chloride) are dissolved in 1 mL DMF(N,N-dimethylformamide), and 99.1 μL NMP(N-methyl pyrrolidone) is added to obtain a two-dimensional precursor solution(concentration of 1.3 mol / L); take 50 μL of the two-dimensional precursor solution with a rotation speed of 3000 rpm spin coating 40 s, wherein 150 μL of ethyl acetate anti-solvent is added at the count of 25 s before spin coating ends, after spin coating, in the air atmosphere of 30-40% relative humidity, 100 ℃ annealing 10 min, cooling to room temperature, forming perovskite film;

[0066] 4) 1 mg BAI(n-butylamine iodine) is dissolved in 1 mL of isopropanol, and 50 μL of the resulting solution is spin coated at a rotation speed of 5000 rpm for 30 s, and annealed on a 100 ℃ heating table for 10 min, forming a passivation layer on the perovskite film, obtaining a perovskite active layer;

[0067] 5) Take 72.3 mg Spiro-OMeTAD dissolved in 1 mL of chlorobenzene, take 40 μL of the resulting solution with a rotation speed of 4000 rpm spin coating 30 s, forming a hole transport layer;

[0068] 6) The silver electrode is formed on the hole transport layer by thermal evaporation, and the N-I-P type two-dimensional perovskite solar cell is obtained.

[0069] Comparative example 2

[0070] The specific structure of the P-I-N type wide bandgap perovskite solar cell provided by the present comparative example is shown in the following, and includes, from top to bottom, an Ag electrode, a BCP buffer layer, a PCBM electron transport layer, a perovskite active layer, a NiOx+Poly-TPD hole transport layer, and an ITO transparent conductive glass. Figure 3

[0071] The specific preparation method is as follows:

[0072] 1) A glass was used as a substrate, and a transparent conductive ITO layer was deposited on the upper surface of the glass plate. The obtained ITO glass substrate was sequentially ultrasonically cleaned with a Hilgenberg cleaning agent, deionized water, acetone, and isopropanol, and then dried with N2. The obtained ITO substrate was subjected to ultraviolet ozone treatment for 20 min to obtain an ITO substrate;

[0073] 2) In air, 25 mg / mL of a NiOx aqueous solution was spin-coated on the ITO substrate for 30 s, and then annealed at 120°C for 20 min. After cooling to room temperature, the sample was transferred to a glove box. A 0.5 mg / mL Poly-TPD solution in chlorobenzene was spin-coated at a speed of 5000 rpm for 30 s to form a double hole transport layer;

[0074] 3) 74.3 mg of CsI (cesium iodide), 174.2 mg of FAI, 466.1 mg of PbI2, and 102.3 mg of PbBr2 were dissolved in 1 mL of a mixed solvent of DMF and DMSO (DMF:DMSO volume ratio = 3:1) to obtain a wide bandgap precursor solution (concentration of 1.4 mol / L), and the bandgap was 1.67 eV. 60 μL of the wide bandgap precursor solution was spin-coated at a speed of 5000 rpm for 50 s, and 150 μL of ethyl acetate anti-solvent was added dropwise at the 25th second. After spin coating, the sample was annealed at 100°C in the glove box for 30 min. After cooling to room temperature, 1 mg of choline chloride was dissolved in 1 mL of isopropanol, and 50 μL of the obtained solution was spin-coated at a speed of 5000 rpm for 30 s. The sample was annealed on a heating stage at 100°C for 10 min to form a passivation layer, and a perovskite active layer was obtained;

[0075] 4) 20 mg of PCBM was dissolved in 1 mL of chlorobenzene, and 40 μL of the obtained solution was spin-coated at a speed of 4000 rpm for 30 s to form an electron transport layer;

[0076] 5) A saturated BCP solution (isopropanol as the solvent) with a concentration of 0.5 mg / mL was prepared, and 60 μL of the obtained solution was spin-coated at a speed of 6000 rpm for 30 s to form a buffer layer;

[0077] 6) A silver electrode was evaporated on the buffer layer to obtain a P-I-N type wide bandgap perovskite solar cell.

[0078] Example 1​

[0079] The difference from Comparative Example 1 is only that 3 mg of MAI (methylamine iodide) is dissolved in 1 mL of IPA (isopropyl alcohol) to obtain MAI / IPA anti-solvent as the second anti-solvent;

[0080] In step 3, 50 μL of the two-dimensional precursor solution is spin-coated at a speed of 3000 rpm for 40 s, wherein 150 μL of ethyl acetate anti-solvent is added at the 25th second before the end of the spin-coating, and 20 μL of MAI / IPA anti-solvent is added at the 10th second before the end of the spin-coating. After the spin-coating, the perovskite film is formed by annealing at 100°C for 10 min in an air atmosphere with a relative humidity of 30-40%, and then cooled to room temperature.

[0081] The rest is the same as Comparative Example 1.

[0082] Example 2

[0083] The difference from Example 1 is only that MAI (methylamine iodide) is replaced by MACl (methylamine chloride).

[0084] Example 3

[0085] The difference from Comparative Example 2 is only that 3 mg of MAI is dissolved in 1 mL of isopropyl alcohol to obtain MAI / IPA anti-solvent as the second anti-solvent;

[0086] In step 3, 60 μL of the wide-bandgap precursor solution is spin-coated at a speed of 5000 rpm for 50 s, wherein 150 μL of ethyl acetate anti-solvent is added at the 25th second, and 20 μL of the MAI / IPA anti-solvent is added at the 10th second. After the spin-coating, the perovskite film is formed by annealing at 100°C for 30 min in a glove box.

[0087] The rest is the same as Comparative Example 2.

[0088] Example 4

[0089] This example provides a P-I-N type wide-bandgap perovskite and a bifacial textured silicon heterojunction combined to prepare a perovskite / silicon heterojunction stacked solar cell. The effective area of the cell is 0.5003 cm 2 , and the specific structure is shown in Figure 4 . From top to bottom, it includes a front metal grid electrode silver, a transparent conductive film IZO, a buffer layer SnO2, an electron transport layer C 60 , a perovskite active layer, a Poly-TPD / NiOx double hole transport layer, a connecting layer ITO, a silicon heterojunction bottom cell electron selection layer a-si:H(n), a passivation layer a-si:H(i), a silicon substrate N-Si, a passivation layer a-si:H(i), a hole selection layer a-si:H(p), ITO, and a back electrode silver.

[0090] Preparation method:

[0091] ITO with a thickness of 20 nm was prepared on the front surface of a commercial silicon heterojunction cell substrate as a connecting layer by sputtering deposition technology;

[0092] NiOx was sputtered as a hole transport layer; a chlorobenzene solution of 0.5 mg / mL Poly-TPD was spin-coated at a speed of 5000 rpm for 30 s to form a double hole transport layer;

[0093] The preparation process of the perovskite layer PVSK was the same as that of Example 3;

[0094] 20 nm C 60 was thermally evaporated on the top of the perovskite layer as an electron transport layer;

[0095] A 30 nm SnO2 buffer layer was deposited by thermal atomic layer deposition technology;

[0096] IZO with a thickness of 85 nm was sputtered on the SnO2 buffer layer;

[0097] Metallic silver electrodes were thermally evaporated at both ends to obtain a perovskite / silicon heterojunction stacked solar cell.

[0098] Performance test

[0099] 1) Under the irradiation of a standard solar intensity (AM 1.5, 100 mW / cm 2 ), the photoelectric properties of the solar cells prepared in Comparative Examples 1-2 and Examples 1-4 were tested, and the results are shown in Figures 5 to 10 ;

[0100] Figure 5 The J-V graph of the N-I-P type two-dimensional perovskite cell in Comparative Example 1 is shown in Figure 5 , the open-circuit voltage of the cell is 1.09 V, the fill factor is 73.94%, the short-circuit current density is 21.04 mA / cm 2 , and the photoelectric conversion efficiency is 16.89%.

[0101] Figure 6 The J-V graph of the N-I-P type two-dimensional perovskite cell in Example 1 after secondary anti-solvent optimization of 3 mg / mL MAI / IPA is shown in Figure 6 , after secondary anti-solvent treatment, the open-circuit voltage of the device increased to 1.16 V, the fill factor increased to 78.88%, the short-circuit current density was 21.37 mA / cm 2 , and the final photoelectric conversion efficiency reached 19.55%.

[0102] Figure 7The JV diagram for the NIP-type two-dimensional perovskite solar cell optimized with a secondary antisolvent of 3 mg / mL MACl / IPA in Example 2 is shown below. Figure 7 As shown, after secondary anti-solvent treatment, the device's open-circuit voltage increased to 1.12V, the fill factor increased to 77.36%, and the short-circuit current density was 21.22mA / cm². 2 The final photoelectric conversion efficiency reached 18.34%.

[0103] Figure 8 The JV diagram for the PIN-type wide-bandgap perovskite solar cell in Comparative Example 2 is shown below. Figure 8 As shown, the battery open-circuit voltage is 1.09V, the fill factor is 80.22%, and the short-circuit current density is 19.78mA / cm². 2 The photoelectric conversion efficiency is 17.36%.

[0104] Figure 9 The figure shows the JV diagram of the PIN wide-bandgap perovskite solar cell optimized with 3 mg / mL MAI / IPA secondary antisolvent in Example 3. As shown, after secondary antisolvent treatment, the open-circuit voltage of the device increased to 1.12 V, the fill factor increased to 82.23%, and the short-circuit current density was 20.98 mA / cm². 2 The final photoelectric conversion efficiency reached 19.32%.

[0105] Figure 10 The image shows the JV diagram of the wide-bandgap perovskite / silicon heterojunction tandem solar cell optimized with 3 mg / mL MAI / IPA secondary antisolvent in Example 4. The silicon heterojunction bottom cell has a double-sided texturized structure, as shown below. Figure 10 As shown, the battery's photoelectric conversion efficiency is 23.02%, and its short-circuit current density is 17.11 mA / cm². 2 The fill factor is 76.47%, and the open-circuit voltage is 1.76V.

[0106] 2) The charge defect state density N of the perovskite devices obtained in Comparative Example 1 and Example 1 was characterized using space charge confinement current (SCLC) technology. t And using a perovskite device without any surface passivation as a reference, the results are shown in [reference]. Figure 11 The device structure is Glass / ITO / SnO2 / perovskite absorber layer / passivation layer / PCBM / BCP / Ag. Figure 11 The effects of conventional surface treatment in Comparative Example 1 and the combination of secondary anti-solvent treatment and conventional surface passivation in Example 1 on the corresponding charge defect state densities are shown. Figure 11 It can be seen that the defect state density of the perovskite device without any surface passivation (the specific preparation method is the same as Comparative Example 1, but without the surface treatment process using n-butylamine iodine in step 4) is 4.0 × 10⁻⁶.16 cm -3 After surface passivation in Comparative Example 1, the defect state density is reduced to 2.04 x 10 16 cm -3 After secondary anti-solvent treatment combined with surface passivation in Example 1, the defect state density is further reduced to 1.06 x 10 16 cm -3 It is shown that the method of the present application can reduce the surface defect state density by nearly 2 times on the basis of conventional surface post-treatment passivation.

[0107] As can be seen from the above examples, by adding the secondary anti-solvent containing the passivation material, and then performing surface passivation treatment, the present application can minimize the perovskite surface defects to the greatest extent, and can improve the crystalline quality of the perovskite thin film, so as to significantly improve the open-circuit voltage and fill factor of the two-dimensional perovskite and wide-bandgap perovskite, and the efficiency of the wide-bandgap perovskite-based / crystalline silicon two-end stacked cell is also obviously improved, and the method is simple and easy to implement.

[0108] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a perovskite active layer in a solar cell, comprising the following steps: spinning a perovskite active layer precursor solution on a substrate, and in the spinning process, sequentially dropping a first anti-solvent and a second anti-solvent; after dropping the second anti-solvent, completing the spinning, and annealing the obtained product to form a thin film; carrying out surface passivation treatment on the obtained thin film to obtain the perovskite active layer; the second anti-solvent comprises a passivation material, the passivation material is methylamine iodide, methylamine chloride, formamidine iodide or guanidine bromide, and the concentration of the passivation material in the second anti-solvent is 0.5-5 mg / mL; the time for dropping the first anti-solvent is within 10-20 s after the start of the spinning process, and the time for dropping the second anti-solvent is within 10-20 s after the dropping of the first anti-solvent and within 10-20 s before the end of the spinning process; the surface passivation treatment process comprises: spinning a surface passivation material solution on the thin film and carrying out annealing treatment, and the concentration of the surface passivation material in the surface passivation material solution is 1 mg / mL; the surface passivation material used in the surface passivation treatment is methylamine iodide, n-butylamine iodide or choline chloride; The perovskite active layer precursor in the perovskite active layer precursor solution includes a perovskite semiconductor material of ABX3 type or (A') m (A) n-1 B n X 3n+1 type perovskite semiconductor material, A' is a large organic cation, the large organic cation includes n-butylamine iodine, phenylethylamine iodine or 1,4-butanediamine hydroiodide, A is one or more of methylamine cation, formamidinium cation, Cs and Rb, B is lead and / or tin, and X is at least one of iodine, bromine and chlorine; the first anti-solvent and the second anti-solvent independently comprise isopropyl alcohol, ethanol, butanol, chlorobenzene, ethyl acetate, anisole, diethyl ether, toluene or mesitylene.

2. The production method according to claim 1, characterized by, The concentration of the perovskite active layer precursor solution is 1.3-1.4 mol / L, and the volume ratio of the perovskite active layer precursor solution, the first anti-solvent and the second anti-solvent is (50-60) : 150 : (20-30).

3. The preparation method according to claim 1, characterized in that, The base is an electron transport layer or a hole transport layer; the material corresponding to the electron transport layer is tin dioxide, titanium dioxide, zinc oxide, [6,6]-phenyl C 61 methyl butyrate, fullerene and graphene; the material of the hole transport layer is one or more of inorganic material, organic material and self-assembled monolayer material.

4. The preparation method according to claim 1, characterized in that, The perovskite type of the solar cell is two-dimensional perovskite, three-dimensional perovskite or mixed-dimensional perovskite.

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