Perovskite thin film preparation method, solar cell and preparation method thereof

Abstract

The invention provides a preparation method of a perovskite thin film, a solar cell comprising a perovskite light absorption layer and a preparation method of the solar cell, relates to the technical field of solar cells, and aims to improve the wettability of a perovskite precursor solution on a substrate, optimize the crystal quality of the perovskite thin film and improve the longitudinal transmission performance of carriers. According to the preparation method of the perovskite thin film, tetrahydrofuran is added into a perovskite precursor solution for preparing the perovskite thin film according to the volume ratio of (1: 0.1)-(1: 0.3).

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a perovskite film, a solar cell and a method for preparing the same. Background Art

[0002] Organic-inorganic hybrid perovskites have excellent properties such as large absorption coefficient, small exciton binding energy, long carrier diffusion length, and high carrier mobility. As ideal photovoltaic absorption materials, they have attracted widespread attention. Perovskite solar cells are divided into two device structures: formal (nip) and trans (pin). Compared with formal devices, trans-structure devices have the advantages of simpler preparation process, low-temperature film formation, no obvious hysteresis effect, and suitable for combining with traditional solar cells (such as silicon-based cells, copper indium gallium selenide, etc.) to prepare stacked devices, etc., and have attracted more and more attention.

[0003] The structure of an inverted perovskite solar cell device includes ITO (transparent conductive layer) / HTL (hole transport layer) / PVSK (perovskite) / ETL (electronic transport layer) / metal electrode (Cu or Ag). Since the hole transport layer currently used is mostly organic polymer, the perovskite precursor solution has poor wettability relative to the organic polymer, and direct spin coating is difficult to form a film. In addition, the crystal quality of the perovskite film is crucial to the conversion efficiency and stability of the titanium ore battery or related stacked batteries, and it is urgent to further improve it. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a perovskite film, a solar cell comprising a perovskite light-absorbing layer and a method for preparing the same, which can improve the wettability of a perovskite precursor solution on a substrate, optimize the crystallization quality of the perovskite film, and improve the longitudinal transport performance of carriers.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a perovskite film. In the preparation method, tetrahydrofuran is added to a perovskite precursor solution for preparing the perovskite film, and the volume ratio of the perovskite precursor solution to the tetrahydrofuran is (1:0.1) to (1:0.25).

[0006] Optionally, the perovskite precursor solution is a precursor solution for preparing a perovskite thin film by a one-step solution process.

[0007] Optionally, tetrahydrofuran is added to the perovskite precursor solution at a volume ratio of 1:0.17 to 1:0.23.

[0008] Optionally, the concentration of the perovskite precursor solution is 1.2 mol / L to 1.8 mol / L.

[0009] Optionally, the solvent of the perovskite precursor solution is a mixed solvent of DMF and DMSO, or a mixed solvent of DMF and NMP.

[0010] Optionally, for a single-junction perovskite cell, the concentration of the perovskite precursor solution is 1.3-1.6 mol / L; and the amount of tetrahydrofuran added is 0.2 to 0.3 times the volume of the perovskite precursor solution.

[0011] Optionally, the perovskite film is made of a wide bandgap perovskite material greater than 1.6 ev, the concentration of the perovskite precursor solution is 1.65 to 1.8 mol / L, and the amount of tetrahydrofuran added is 0.15 to 0.25 times the volume of the perovskite precursor solution.

[0012] Preferably, for the perovskite light-absorbing layer in the crystalline silicon perovskite tandem cell, the concentration of the perovskite precursor solution is 1.7 mol / L, and the amount of tetrahydrofuran added is 0.2 times the volume of the perovskite precursor solution.

[0013] Optionally, the solvent of the perovskite precursor solution is a mixed solvent of DMF and DMSO in a volume ratio of 4:1; the solute of the perovskite precursor solution includes MACl, PbCI2, CsI, PbBr2, FAI and PbI2.

[0014] In a second aspect, the present application also provides a solvent system for preparing a perovskite film by a solution process, comprising at least one perovskite solvent, and tetrahydrofuran added at 12% to 36% of the volume of the perovskite solvent.

[0015] In a third aspect, an embodiment of the present application further provides a method for preparing a perovskite solar cell, wherein the perovskite light-absorbing layer of the perovskite solar cell is made by any of the above-mentioned perovskite thin film preparation methods, or the perovskite light-absorbing layer is prepared by using the above-mentioned solvent system.

[0016] Optionally, before preparing the perovskite light-absorbing layer of the perovskite solar cell, the method further includes: coating a mixed solution of Poly-TPD and PTAA on a substrate to form a hole transport layer; and forming a modification layer of the hole transport layer on the hole transport layer.

[0017] In a fourth aspect, an embodiment of the present application further provides a solar cell comprising a perovskite light absorbing layer, wherein the perovskite light absorbing layer is prepared using any of the above-mentioned perovskite thin film preparation methods, or the perovskite light absorbing layer is prepared using the above-mentioned solvent system.

[0018] Optionally, the solar cell containing the perovskite light-absorbing layer includes a perovskite solar cell, a crystalline silicon perovskite tandem solar cell, a full perovskite tandem cell, and a thin film cell and a perovskite tandem cell.

[0019] Optionally, the solar cell is a crystalline silicon perovskite tandem solar cell, the crystalline silicon perovskite tandem solar cell comprises a perovskite sub-cell with an inverted structure, and the perovskite sub-cell comprises the perovskite light-absorbing layer.

[0020] The embodiment of the present application provides a method for preparing a perovskite film, wherein tetrahydrofuran (THF) is added to a perovskite precursor solution for preparing the perovskite film at a volume ratio of (1:0.1) to (1:0.3). Adding THF to the perovskite precursor solution is beneficial to shortening the time for the perovskite to transform from an intermediate phase to a black cubic phase, thereby promoting the improvement of the crystallization quality of the perovskite film, reducing the lateral grain boundaries of the perovskite film, improving the longitudinal transmission efficiency of carriers, and improving the fill factor of photovoltaic devices.

[0021] Moreover, the polarity of the organic solvent used in the perovskite precursor solution is generally relatively large. For example, the polarities of the commonly used DMF and DMSO are 6.4 and 7.2 respectively, while the polarity of tetrahydrofuran is 4.2. Adding tetrahydrofuran with lower polarity to the perovskite precursor solution can reduce the polarity of the perovskite precursor solution and improve its coating properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a method for preparing a perovskite film by a solution method provided in Example 1 of the present application;

[0023] Figure 2 A flow chart of a method for preparing a perovskite solar cell provided in Example 4 of the present application;

[0024] Figure 3(A) to Figure 3(D) A box plot of efficiency, short-circuit current, power factor and voltage of a perovskite solar cell provided in Example 4 of the present application;

[0025] Figure 4 A schematic diagram of the structure of a perovskite solar cell provided in Example 4 of the present application;

[0026] Figure 5(A) to Figure 5(D) A box plot of efficiency, short-circuit current, power factor and voltage of the crystalline silicon perovskite tandem solar cell provided in Example 5 of the present application;

[0027] Figure 6 A comparison chart of adding different amounts of tetrahydrofuran to the perovskite precursor solution provided in this application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. 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.

[0029] The technical scheme of the present application will be described below in conjunction with specific embodiments. It should be clear to those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present application. If no specific techniques or conditions are specified in the embodiments, the conventional techniques or conditions in the art or the product instructions are used. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0030] Embodiment 1

[0031] An embodiment of the present application provides a method for preparing a perovskite film. In the preparation method, tetrahydrofuran is added to a perovskite precursor solution for preparing the perovskite film, and the volume ratio of the perovskite precursor solution to the tetrahydrofuran is (1:0.1) to (1:0.3).

[0032] In some embodiments, a method for preparing a perovskite film by a solution process is provided, such as Figure 1 As shown, including:

[0033] Step 101: prepare a perovskite precursor solution.

[0034] Step 102: Add tetrahydrofuran to the prepared perovskite precursor solution at a volume ratio of (1:0.1) to (1:0.3) of the perovskite precursor solution.

[0035] Step 103 , coating the perovskite precursor solution added with tetrahydrofuran on a substrate to form a film, and performing annealing treatment, such as annealing treatment at 100 to 150° C. for 10 to 20 minutes.

[0036] In other embodiments, tetrahydrofuran may be added to the solvent first, and then the raw materials (ie, solutes) for forming perovskite such as MACl, PbCI2, CsI, PbBr2, FAI and PbI2 may be added.

[0037] The perovskite described in this application is an ABX3 structure, generally a cubic or octahedral structure. In the perovskite crystal, the B-site ion is located at the center of the cubic unit cell, surrounded by 6 X-site ions to form a coordinated cubic octahedron, with a coordination number of 6; the A-site ion is located at the corner of the cubic unit cell, surrounded by 12 X-site ions to form a coordinated octahedron, with a coordination number of 12. Among them, the A-site ion and the X-site ion have similar radii and together form a cubic close packing.

[0038] In perovskite solar cells, the A-site ion is a monovalent cation, usually a cesium ion (Cs + ), methylamine ion (CH3(NH)2 + , M.A. + ) and formamidinium ion (HC(NH2)2 + , F.A. + ) etc. A-site ions mainly compensate for lattice charge and adjust the perovskite energy band, thereby improving the photovoltaic performance of the device. B-site ions refer to divalent metal cations, mainly Pb 2+ (R B =0.119nm) and Sn 2+ (R B =0.110nm). X ion is a halogen anion, i.e., I - (R X =0.220nm), Cl - (R X =0.181nm) and Br - (R X =0.196nm).

[0039] The A-site ions, B-site ions and X-site ions in the perovskite may include more than one ion, such as Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3, including two A-site ions and two X-site ions. The symmetry of perovskites including more than one A-site ion, more than one B-site ion, or more than one X-site ion is usually lower than the symmetry of CaTiO3.

[0040] The perovskite film described herein is a film layer made of the above perovskite material. The "perovskite light-absorbing layer" described herein refers to a perovskite film made of a perovskite material that can absorb light and thereby generate free charge carriers.

[0041] The perovskite material can be a narrow bandgap perovskite or a wide bandgap perovskite. Exemplarily, the perovskite material may include any one of the following: FACsPbIBrCl, FAMACsPbIBrCl, FACsDMAPbIBrCl, CsDMAPbIBrCl, FACsPbIBr, FAMACsPbIBr, FACsDMAPbIBr, CsDMAPbIBr, FACsPbI, FAMACsPbI, FACsDMAPbI, CsDMAPbI, FACsPbSnI, FAMACsPbSnI, FACsDMAPbSnI and CsDMAPbSnI. If more than two A-site ions (or B-site ions, or X-site ions) are included, the ratio of the two or more A-site ions can be changed as needed.

[0042] Perovskite precursor solutions are mostly present in the form of organic-inorganic mixtures, including solvents and raw materials for preparing perovskites, such as cation solutions, metal ion solutions, etc. Perovskite thin films can be prepared by depositing the perovskite precursor solution on a substrate and performing a heat treatment.

[0043] For example, the perovskite material can be methylammonium lead trihalide CH3NH3PbX3, where X is a halogen ion, such as an iodide ion, a bromide ion, or a chloride ion. The perovskite optical band gap is between about 1.2 and 2.5 eV (depending on the halide content). The perovskite material can also be Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3 or Cs 0.22 FA 0.78 Pb(I 0.765 Br 0.135 ).

[0044] The present application adds THF to the perovskite precursor solution, and utilizes the high volatility of THF and its miscibility with the perovskite solvent to promote the transformation of the perovskite from the intermediate phase to the black cubic phase and shorten the transformation time, reduce the particle size of the polycrystalline film, and promote the improvement of the crystallization quality of the perovskite film, thereby reducing the leakage of current in the perovskite device and improving the fill factor of the photovoltaic device.

[0045] For example, in the one-step solution method for preparing a wide bandgap perovskite film, tetrahydrofuran is added to the perovskite precursor solution at a volume ratio of (1:0.15) to (1:0.25) to improve the crystallization quality of the perovskite film, and after the device is made, the current leakage of the device can be reduced and the fill factor can be improved. Among them, the wide bandgap perovskite refers to a perovskite with a bandgap greater than 1.6 eV.

[0046] Further preferably, tetrahydrofuran is added to the perovskite precursor solution at a volume ratio of (1:0.17) to (1:0.23) of the perovskite precursor solution to tetrahydrofuran. The experimental results are better when the addition ratio of tetrahydrofuran is in this range. Adding THF to the perovskite precursor solution is beneficial to shorten the time for the perovskite to transform from the intermediate phase to the black cubic phase. At the same time, after the tetrahydrofuran with a suitable ratio (about (1:0.17) to (1:0.23)) is mutually dissolved with the perovskite solution, the perovskite can be pre-crystallized in the solution, thereby promoting the improvement of the crystallization quality of the perovskite film, reducing the lateral grain boundaries of the perovskite film, improving the longitudinal transmission efficiency of the carriers, and improving the fill factor of the photovoltaic device.

[0047] Among them, the specific components of the solute (i.e., the raw material for forming perovskite) in the above-mentioned perovskite precursor solution can be adjusted according to the band gap width required by the device design, so no specific limitation is made. The solvent of the perovskite precursor solution can be selected according to the specific components of the perovskite, and no specific limitation is made. The solvent of the perovskite precursor solution can be, for example, a mixture of one or more (two or more) of the following: dimethylformamide, dimethylethanol, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, γ-butyrolactone, methylammonium acetate and dimethylacetamide.

[0048] In some embodiments, the solvent of the perovskite precursor solution is a mixed solvent of DMF (N, N-dimethylformamide) and DMSO (dimethyl sulfoxide), or a mixed solvent of DMF and NMP (N-methylpyrrolidone). If the solvent is all DMF, part of PbI2 cannot be dissolved, so DMSO needs to be added to dissolve it. It is preferred to use a mixed solvent of DMF and DMSO mixed in a volume ratio of 4:1, which has good solubility for the raw materials for perovskite preparation. A certain amount of tetrahydrofuran is added according to the volume of the precursor solution, and the perovskite film prepared is of better quality.

[0049] For example, a wide bandgap perovskite Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 ) A 3.5% MAPbCl3 precursor solution, whose solutes include MACl, PbCI2, CsI, PbBr2, FAI and PbI2, and the solvent is a mixed solvent of DMF and DMSO in a volume ratio of 4:1, and tetrahydrofuran is added in a ratio of (1:0.15) to (1:0.25) of the solution volume.

[0050] In some embodiments, the concentration of the perovskite precursor solution is 1.2 mol / L to 1.8 mol / L. The concentration here refers to the ratio of the amount of perovskite that can be theoretically generated by the perovskite precursor solution to the volume of the solution. 0.22 FA0.78 Pb(I 0.85 Br 0.15 )3, the concentration of the precursor solution (i.e., the perovskite concentration) can be measured by the concentration of Pb ions, or by the sum of the concentrations of Cs ions and FA ions. Preferably, the concentration of the perovskite precursor solution is 1.3 mol / L to 1.8 mol / L.

[0051] For crystalline silicon perovskite tandem cells, the perovskite light-absorbing layer is made of a wide bandgap perovskite material greater than 1.6ev, and a one-step solution method is preferred for preparation. The concentration of the perovskite precursor solution used in the one-step solution method is preferably 1.65mol / L to 1.8mol / L. Exemplarily, for the wide bandgap perovskite film of the tandem cell, the concentration of the precursor solution is 1.65mol / L, 1.68mol / L, 1.7mol / L, 1.72mol / L, 1.75mol / L or 1.8mol / L. At this time, the amount of tetrahydrofuran added is 0.15 to 0.25 times the volume of the above-mentioned perovskite precursor solution.

[0052] For example, when the perovskite light-absorbing layer in the crystalline silicon perovskite stacked cell is prepared by one-step solution, the concentration of the perovskite precursor solution is 1.65-1.75 mol / L, and the volume ratio of the amount of tetrahydrofuran added to the perovskite precursor solution is (1:0.17)-(1:0.23), and more preferably 1:0.20. The solvent of the perovskite precursor solution can be a mixed solvent of DMF and DMSO in a volume ratio of 4:1; the solute of the perovskite precursor solution can include MACl, PbCI2, CsI, PbBr2, FAI and PbI2, and the generated perovskite film is Cs 0.22 FA 0.78 Pb(I y Br 1-y )3·n%MAPbCl3, y is greater than 0 and less than 1, and n is less than 10.

[0053] Preferably, the concentration of the perovskite precursor solution is 1.7 mol / L, and about 0.2 ml of tetrahydrofuran is added per milliliter of the perovskite precursor solution, so that the quality of the film and the device performance are relatively good.

[0054] Adding highly volatile THF to the perovskite precursor solution is beneficial to shorten the time it takes for the perovskite to transform from the intermediate phase to the black cubic phase. At the same time, after the appropriate ratio of tetrahydrofuran (for wide-bandgap perovskite, the ratio is about 1:0.2) and the perovskite solution are dissolved in each other, the perovskite can be pre-crystallized in the solution, thereby promoting the improvement of the crystallization quality of the perovskite film, reducing the lateral grain boundaries of the perovskite film, improving the longitudinal transmission efficiency of the carriers, and improving the fill factor of the photovoltaic device.

[0055] For a single-junction perovskite cell, the perovskite light-absorbing layer uses a perovskite material with a band gap of about 1.4 to 1.6 eV. When the perovskite light-absorbing layer is prepared, the concentration of the perovskite precursor solution is 1.3 mol / L to 1.6 mol / L, such as 1.3 mol / L, 1.35 mol / L, 1.4 mol / L, 1.45 mol / L, 1.50 mol / L, 1.55 mol / L or 1.6 mol / L; correspondingly, the amount of tetrahydrofuran added is about 0.2 to 0.3 times the volume of the above perovskite precursor solution. For example, 0.2 to 0.3 ml of tetrahydrofuran, such as 0.2, 0.25 or 0.3 ml, can be added to each milliliter of the perovskite precursor solution.

[0056] Compared with crystalline silicon perovskite stacked cells, the concentration of the perovskite precursor solution used in the perovskite light-absorbing layer of the single-junction perovskite cell is relatively low, that is, the solvent content in the solution is relatively high. Correspondingly, the volume ratio of tetrahydrofuran added to the solution must be greater than 1:0.2 to work, that is, tetrahydrofuran is approximately 0.2 to 0.3 times the volume of the above-mentioned perovskite precursor solution. The specific optimal addition ratio can be determined based on experiments.

[0057] In some embodiments, the perovskite precursor solution is Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3 configured precursor solution; the concentration of the perovskite precursor solution is 1.4 mol / L; the volume ratio of the added amount of tetrahydrofuran to the perovskite precursor solution is preferably (0.17:1) to (0.23:1), and more preferably 0.2:1.

[0058] In other embodiments, the perovskite precursor solution is Cs 0.22 FA 0.78 Pb(I 0.765 Br 0.135 )3 configured precursor solution; the concentration of the perovskite precursor solution is 1.4 mol / L; the volume ratio of the added amount of tetrahydrofuran to the perovskite precursor solution is (0.17:1) to (0.23:1), and more preferably 0.2:1.

[0059] The method for preparing a wide-bandgap perovskite film by a solution process provided in this embodiment includes adding THF to a perovskite precursor solution at a certain volume ratio (such as a volume ratio of the perovskite precursor solution to tetrahydrofuran of (1:0.17) to (1:0.23)), which is beneficial to shortening the time for the perovskite to transform from an intermediate phase to a black cubic phase, reducing the particle size of the polycrystalline film, and promoting the improvement of the crystallization quality of the perovskite film, thereby reducing the leakage of current in the perovskite device and improving the fill factor of the photovoltaic device.

[0060] An embodiment of the present application further provides a solvent system for preparing a perovskite film by a solution process, wherein the solvent system comprises at least one perovskite solvent and tetrahydrofuran added at 12% to 36% of the volume of the solvent.

[0061] Compared with the prior art, the solvent system provided in this embodiment adds a certain proportion of pseudo solvent tetrahydrofuran (also called pseudo solvent because the raw material components of perovskite are not soluble in tetrahydrofuran) to the perovskite solvent. Since tetrahydrofuran has high volatility, low polarity and is miscible with the perovskite solvent, it can improve the coating performance of the perovskite precursor solution, and is beneficial to shorten the time for perovskite to transform from the intermediate phase to the black cubic phase, reduce the particle size of the polycrystalline film, and promote the improvement of the crystallization quality of the perovskite film.

[0062] The perovskite solvent is used to prepare a perovskite precursor solution in the solution method for preparing perovskite. The perovskite solvent includes but is not limited to a mixture of one or more of the following: dimethylformamide, dimethylethanol, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, γ-butyrolactone, methylammonium acetate and dimethylacetamide.

[0063] In this embodiment, raw materials for preparing perovskite (such as MACl, PbCI2, CsI, PbBr2, FAI and PbI2) can be added to the solvent, and the perovskite precursor solution is formed after the impurities are fully filtered out after being dissolved. Those skilled in the art have found that the volume of 1.5 ml of solvent becomes 1.8 ml after being configured into a perovskite precursor solution with a concentration of 1.4 mol / L. Based on this, the amount of THF added is 12% to 36% of the volume of the solvent.

[0064] Preferably, a wide bandgap perovskite solvent system comprises a perovskite solvent and tetrahydrofuran, wherein the amount of tetrahydrofuran added is 20.4% to 27.6% of the volume of the perovskite solvent.

[0065] More preferably, the amount of tetrahydrofuran added is about 24% of the volume of the perovskite solvent.

[0066] Exemplarily, a solvent system for a wide bandgap perovskite according to the present embodiment is prepared by the following method: first, DMF and DMSO are mixed in a volume ratio of 4:1 to form a mixed solvent, and then tetrahydrofuran is added according to the volume of the mixed solvent, and the added amount is a volume ratio of (1:0.24). Among them, the amount of tetrahydrofuran added is calculated based on the volume of the solution obtained after the solvent and the perovskite raw material are mixed and dissolved and the impurities are filtered out, or converted to the corresponding solvent volume. For example, when the solvent is 1.5mL, the solvent and the perovskite raw material are configured into a solution with a concentration of 1.4mol / L, and 1.8mL of the perovskite precursor solution is obtained after filtering the impurities. When calculating the amount of tetrahydrofuran added, the volume of the solvent is calculated as 1.5mL, and the volume of the perovskite precursor solution is calculated as 1.8mL.

[0067] The embodiments of the present application also provide a use of tetrahydrofuran as a solvent additive or a precursor solution additive in a method for preparing a perovskite film by a solution process. Tetrahydrofuran has high volatility and low polarity. When added to a perovskite precursor solution, it can improve the coating performance of the perovskite precursor solution, and is conducive to shortening the time for perovskite to transform from an intermediate phase to a black cubic phase, reducing the particle size of a polycrystalline film, and promoting the improvement of the crystallization quality of the perovskite film.

[0068] The embodiment of the present application also provides a method for preparing a solar cell including a perovskite light absorbing layer, wherein the perovskite light absorbing layer is prepared by any of the above-mentioned perovskite thin film preparation methods, or the above-mentioned solvent system is used when preparing the perovskite light absorbing layer. The perovskite thin film prepared by the method of this embodiment has good crystal quality, can reduce the leakage of current in the device, and improve the conversion efficiency and fill factor of the photovoltaic device.

[0069] Before preparing the perovskite light absorbing layer, a mixed solution of Poly-TPD and PTAA may be coated on the substrate to form a hole transport layer; and then a modification layer of the hole transport layer is formed on the hole transport layer. For example, a PFNBr solution may be coated to form a PFNBr modification layer. A perovskite precursor solution added with tetrahydrofuran is then coated on the modification layer to prepare the perovskite light absorbing layer.

[0070] The above-mentioned solar cell containing a perovskite light absorbing layer refers to a solar cell containing at least one layer of a perovskite light absorbing layer, which can be a single-junction, double-junction or multi-junction solar cell. For example, the solar cell containing a perovskite light absorbing layer can be a single-junction perovskite solar cell, a crystalline silicon perovskite stacked cell, or a full perovskite multi-junction solar cell. In addition, the solar cell containing a perovskite light absorbing layer can be a two-terminal, three-terminal or four-terminal solar cell.

[0071] An embodiment of the present application further provides a solar cell comprising a perovskite light absorbing layer, wherein the perovskite light absorbing layer is prepared using any of the above-mentioned perovskite thin film preparation methods, or the above-mentioned solvent system with tetrahydrofuran added is used when preparing the perovskite light absorbing layer.

[0072] Optionally, the solar cell comprising a perovskite light-absorbing layer includes but is not limited to a perovskite solar cell, a crystalline silicon perovskite tandem solar cell, and a full perovskite tandem cell.

[0073] In some embodiments, the perovskite subcell in the crystalline silicon perovskite tandem solar cell is a trans-structured perovskite subcell.

[0074] In summary, the perovskite film preparation method provided in this embodiment, as well as the solar cell based on the preparation method and the preparation method thereof, can improve the wettability of the perovskite solution on the substrate, optimize the crystallization quality of the perovskite film layer, improve the longitudinal transport performance of carriers, reduce the atypical non-radiative recombination loss of the perovskite bulk phase, and thereby improve the fill factor of the device, due to the addition of tetrahydrofuran to the perovskite precursor solution.

[0075] Embodiment 2

[0076] This embodiment provides a method for preparing a perovskite film, comprising the following steps:

[0077] The perovskite precursor solution was prepared by using DMF and DMSO as solvents, with a volume ratio of DMF to DMSO of DMF:DMSO = 4:1. The solutes were MACl, PbCI2, CsI, PbBr2, FAI and PbI2, and the amount of each component was calculated based on the Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3·5% MAPbCl3, the concentration is calculated as 1.4 mol / L. The amount of THF added is calculated as 15%, 20% and 20% of the volume of the perovskite precursor solution.

[0078] In the specific operation, firstly press 1.4 mol / L Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3.5% MAPbCl3 solution, calculate the ratio of the above solutes, then weigh the above solutes according to the calculated ratio, and place them in a mixed solvent (DMF and DMSO are mixed in a volume ratio of 4:1), stir on a shaking table at 50°C for 2 hours to fully dissolve them for use; filter the reserved perovskite precursor solution and divide it into multiple portions of equal volume, add THF at a solution volume ratio of 15%, 20% and 25%, mix them thoroughly and set them aside.

[0079] Preparation of perovskite film: The perovskite film was prepared by a one-step solution method. The perovskite precursor solution containing THF additive was coated into a film by spin coating, wherein the spin coating speed was 4000 rpm / s, the coating time was 10s, and the acceleration at the beginning was 4000 rpm / s. 2 .

[0080] Treat by dropping anti-solvent or other drying methods, then anneal at 120°C for 20 minutes.

[0081] The method for preparing the perovskite film provided in this embodiment has improved coating performance and crystallization quality of the perovskite film due to the addition of tetrahydrofuran to the perovskite precursor solution for preparing the perovskite film, thereby reducing the current leakage in the perovskite device and improving the fill factor of the device.

[0082] Embodiment 3

[0083] This embodiment provides a method for preparing a wide bandgap perovskite film by a one-step solution process, comprising:

[0084] Step 1: Prepare a perovskite precursor solution, the solution concentration can be 1.65 mol / L to 1.8 mol / L.

[0085] Step 2: Add tetrahydrofuran to the prepared perovskite precursor solution at a volume ratio of (1:0.17) to (1:0.23) of the perovskite precursor solution to tetrahydrofuran.

[0086] Step 3: coating the perovskite precursor solution added with tetrahydrofuran on a substrate to form a film, and performing annealing treatment, such as annealing treatment at 100 to 150° C. for 10 to 20 minutes.

[0087] In other embodiments, tetrahydrofuran may be added first, and then solutes such as MACl, PbCI2, CsI, PbBr2, FAI and PbI2 may be added to prepare a perovskite precursor solution.

[0088] Embodiment 4

[0089] This embodiment provides a method for preparing a perovskite solar cell and a single-junction perovskite solar cell prepared according to the method. Figure 2 As shown, the preparation method mainly comprises the following steps:

[0090] Step 201, placing the ITO conductive glass into a UV device and performing UV cleaning for a certain period of time;

[0091] Step 202, preparing a mixed hole transport layer;

[0092] Select Poly-TPD as the solute and chlorobenzene as the solvent, prepare a solution at a concentration of 4 mg / mL, and then stir at 50°C for half an hour. Select PTAA as the solute and chlorobenzene as the solvent, prepare a solution at a concentration of 4 mg / mL, and stir at 50°C for half an hour. Then mix the above Poly-TPD solution and PTAA solution at a volume ratio of Poly-TPD:PTAA=7:3. Take 50μL (the amount taken is related to the coating area) of the mixed solution each time for spin coating, and anneal to obtain a hole transport layer.

[0093] Step 203: prepare a modification layer of the hole transport layer (referred to as hole modification layer) PFNBr layer.

[0094] Methanol was selected as the solvent and PFNBr as the solute, and the solution was prepared at a concentration of 1 mg / mL. After standing for a period of time, the supernatant was taken and diluted to 0.25 mg / mL. 70 μL was taken each time for spin coating on the hole transport layer. The spin coating process parameters were as follows: rotation speed 5000 rpm / s, spin coating time 20s, initial acceleration 5000 rpm / s 2 .

[0095] Step 204: prepare a perovskite light-absorbing layer.

[0096] Prepare the perovskite precursor solution: DMF and DMSO are used as solvents, and the volume ratio of the two is DMF:DMSO=4:1. The solutes are MACl, PbCI2, CsI, PbBr2, FAI and PbI2, and the ratio of each solute is determined according to the perovskite composition. For example, in this embodiment, 1.4 mol / L Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3.5% MAPbCl3 solution was used to determine the dosage of MACl, PbCl2, CsI, PbBr2, FAI and PbI.

[0097] In the verification experiment provided in this embodiment, the amount of THF added in this step is 5%, 15%, 20%, 25%, 30% and 40% of the volume of the perovskite precursor solution, respectively.

[0098] Preparation of perovskite film: the solute was added to the mixed solvent (DMF and DMSO), and stirred on a shaking table at 50°C for 2 hours to fully dissolve it for use; the reserved perovskite precursor solution was filtered, and then the perovskite precursor solution without THF additive and with THF additive was stirred at 4000 rpm / s for 10s and 4000 rpm / s for 10s. 2 The nanostructured carbon nanotubes were spin-coated on the hole modification layer and then annealed at 120 °C for 20 min.

[0099] Step 205: Prepare a passivation layer

[0100] Prepare the passivation layer precursor liquid: the solute is 2 mg / ml GABr and 0.4 mg / ml OAMI, the solvent is IPA (propan-2-ol, isopropanol), mix the two (2 mg / ml GABr and 0.4 mg / ml OAMI) and dissolve them in IPA (propan-2-ol, isopropanol) to form the passivation layer precursor liquid.

[0101] The passivation layer also adopts spin coating process, and the process parameters are as follows:

[0102] Step 1: 300rpm / s, 5s, 500rpm / s 2 ; Count down 2S to start dripping

[0103] Step 2: 300rpm / s, 10s, 4000rpm / s 2

[0104] Step 206, preparing a C60 electron transport layer and a modification layer of the electron transport layer (referred to as the electron modification layer) SnO2 layer, wherein the C60 electron transport layer is formed by vacuum evaporation method, and the SnO2 modification layer is formed by atomic layer deposition method.

[0105] Step 207: Prepare an Ag metal electrode layer.

[0106] like Figures 3(A) to 3(D) The box plots are respectively the efficiency, short-circuit current, power factor and voltage of the solar cell samples prepared by the above method of this embodiment. In these figures, the amount of THF added from left to right is 5%, 15%, 20%, 25%, 30% and 40% of the volume of the perovskite precursor solution. As shown in the following table, when the amount of THF added is 20% of the precursor solution, the device performance of the sample is the best.

[0107] THF addition amount efficiency Short circuit current Power Factor Voltage No THF added 18.617 20.68 76.69 1.14 5％ 17.32 20.09 76.84 1.12 15％ 17.48 20.01 77.63 1.12 20％ 18.41 20.25 79.42 1.14 25％ 17.72 19.76 78.68 1.13 40％ 17.67 20.18 77.42 1.13

[0108] This embodiment also provides a perovskite solar cell prepared according to the above method, the structure of which is as follows Figure 4 As shown, from bottom to top, it includes: ITO conductive glass 10, hole transport layer 11, hole modification 12, perovskite light absorption layer 13, passivation layer 14, C60 electron transport layer 15, electron modification layer 16 and metal electrode layer (not shown in the figure), and the metal electrode layer is a patterned film layer for collecting current.

[0109] The hole transport layer 11 of this embodiment is a mixed hole layer made of Poly-TPD and PTAA at a ratio of 7:3; the hole modification 12 is a PFNBr layer, and the electron modification layer 16 is a SnO2 layer. The perovskite solar cell of this embodiment can realize the interconnection of adjacent battery cells through P1, P2, and P3 laser engraving processes.

[0110] Embodiment 5

[0111] This embodiment provides a method for preparing a crystalline silicon perovskite laminated solar cell, which is different from the fourth embodiment in that: (1) the hole transport layer 11 of this embodiment is formed on the intermediate composite layer instead of the ITO glass in the fourth embodiment, that is, before preparing the perovskite light absorbing layer, it also includes the process of preparing a silicon heterojunction cell and an intermediate composite layer; (2) the concentration of the perovskite precursor solution used in preparing the perovskite light absorbing layer is 1.7 mol / L, and the Cs 0.22 FA 0.78 Pb(I 0.765 Br 0.135 )3Calculate the solute ratio.

[0112] Figure 5(A) to Figure 5(D) The box diagram of the efficiency, short-circuit current, power factor and voltage of the crystalline silicon perovskite tandem solar cell prepared by the preparation method of the embodiment of the present application. Among them, the volume ratio of the added THF to the perovskite precursor solution is 0% (ref: not added), 20%, 40% and 50%. As shown in the following table, when the amount of THF added is 20% of the volume of the precursor solution, the efficiency is 28.89%, the power factor is 79.44%, the open circuit voltage is 1.83eV, the short circuit current is 19.34, and the overall device performance is the best.

[0113] THF addition amount efficiency Short circuit current Power Factor Voltage No THF added 27.18 19.82 76.21 1.79 20％ 28.89 19.34 79.44 1.83 40％ 27.75 19.89 76.87 1.81 50％ 28.15 19.89 76.42 1.80

[0114] This embodiment also provides a crystalline silicon perovskite solar cell prepared according to the above method, which includes, from bottom to top, a silicon heterojunction cell (HJT), an intermediate composite layer, a hole transport layer, a hole modification layer, a perovskite light absorption layer, a passivation layer, a C60 electron transport layer, an electron modification layer and a metal electrode layer. The perovskite light absorption layer is Cs 0.22 FA 0.78 Pb(I 0.765 Br 0.135 )3 floors.

[0115] At the edge, the back electrode of the silicon heterojunction subcell of the first battery unit and the metal electrode layer of the adjacent second battery unit can be connected in series through a connector in another patent of the company to form a battery assembly.

[0116] In addition, in other embodiments, the material of the hole transport layer can also be any hole transport layer material suitable for perovskite solar cells. For example, the material of the hole transport layer can be one of PTAA, PEDOT:PSS, Spiro-OMeTAD, Poly-TPD, NiOX, CuSCN, CuI, and V2O5.

[0117] When the perovskite light-absorbing layer is prepared, the coating of the perovskite precursor solution can be carried out by any conventional deposition process, such as spin coating, spray coating, and slit coating process.

[0118] The perovskite precursor solution includes an organic cation, an inorganic halide and a solvent. The inorganic cation in the inorganic halide can be Pb 2+ , Cs 2+ ,Ge 2+ Any one of; its halide ion can be I — Br — , Cl — Any one of. The organic cation is, for example, CH3NH3 + (MA + ) and / or CH(CH2)2 + (FA + ), the anion in the organic cation solution may also be any of the halide ions. Further, the inorganic halide is preferably lead iodide.

[0119] The solutes in the organic cationic solution can be selected from FAI and MACl, and the ratio of FAI to MACl is 10:1. The solvent can be any one of formamide, acetamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone or γ-butyrolactone, or a combination of at least two thereof.

[0120] Although the present invention is described using single-junction perovskite solar cells and crystalline silicon perovskite tandem cells as examples, those skilled in the art will understand after reading this specification that the present invention can also be more widely applied to other solar cell architectures (such as multi-junction solar cell structures), and can be used to manufacture other structures containing perovskite light-absorbing layers, such as organic light-emitting diodes (OLEDs), organic thin-film transistors (OTFTs), and electrochromic devices in other optoelectronic devices.

[0121] It is understood that after reading this specification, those skilled in the art can use a variety of perovskite layers without departing from the scope of the present invention. Other perovskites suitable for use in the present invention include, but are not limited to, Csx FA 1-x Pb(Br y I 1-y )3. Pure formamidine-based perovskite (FAPbI3), tin-containing perovskite Csx FA 1-x Pcq 1-z (Br y I 1-y )3, etc. Further, without departing from the scope of the present invention, those skilled in the art will appreciate that a variety of selective methods can be used to form the perovskite layer.

[0122] In addition, it can be seen from Figure 5 that adding tetrahydrofuran to the perovskite precursor solution can dilute the solution, but the electrical parameters of the device formed by the diluted solution are almost unaffected, and even improved within a certain ratio range, which can save the use of perovskite raw materials and toxic solvents, thereby improving yield and reducing costs.

[0123] THF addition experiment:

[0124] DMF and DMSO were selected as solvents, and the volume ratio of DMF and DMSO was DMF:DMSO=4:1; MACl, PbCI2, CsI, PbBr2, FAI and PbI2 were selected as solutes, and the amount of each component was calculated according to the Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3·5% MAPbCl3 was calculated and the concentration of perovskite precursor solution was 1.7M.

[0125] Then THF was added dropwise, and the added amounts were 0% (i.e. no THF was added, marked as Ref), 10%, 20%, 25%, 30%, 35% and 62.5% of the volume of the perovskite precursor solution. The results are shown in Figure 6 When the amount of THF added was 10%, 20%, 25%, 30% and 35%, the solution was still transparent, and when the amount of THF added was about 62.5%, the solution became turbid, indicating that solids were precipitated.

[0126] THF is miscible with the solvents DMF and DMSO, but the solutes (MACl, PbCI2, CsI, PbBr2, FAI and PbI2) are insoluble in THF. As the amount of THF added to the perovskite precursor solution increases, more solvents DMF and DMSO that are miscible with THF become available, that is, THF and the solutes (MACl, PbCI2, CsI, PbBr2, FAI and PbI2) in the solution "compete" for the solvent, causing the originally dissolved solutes to precipitate and the solution to become turbid.

[0127] Adding THF to the perovskite precursor solution has the effect of reducing the solvent and promoting the crystallization of perovskite. The inventors of the present application found that by utilizing the mutual solubility of THF in the perovskite solvent, when an appropriate amount of THF (THF accounts for about 17% to 23%) is added to the perovskite precursor solution, it is speculated that the solute will precipitate and nucleate in the solution in trace amounts. In the wet perovskite process, since there is already pre-nucleated perovskite in the wet film, the transformation of the wet film to the black phase perovskite film can be accelerated. At the same time, since THF is a highly volatile solvent, its self-volatile characteristics during the wet process quickly reduce the Gibbs free energy required to overcome the crystallization of the wet film, making the perovskite film quality higher.

[0128] When the THF volume content is large (e.g., above 25% in this experiment), the device parameters show a downward trend, such as Figure 3(A) to Figure 3(D) The corresponding samples are 25%, 30% and 40%, Figure 5(A) to Figure 5(D) The experimental results show that when the THF addition amount is less than about 62.5%, that is, before the perovskite precipitation phenomenon occurs in the solution, the device effect is best when the THF addition amount is about 20%.

[0129] It can be understood that the technical features of this embodiment can be used in any combination without conflict.

[0130] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a perovskite film, characterized in that: Tetrahydrofuran is added to the perovskite precursor solution for preparing the perovskite film, and the volume ratio of the perovskite precursor solution to the tetrahydrofuran is (1:0.1) to (1:0.3).

2. The method for preparing a perovskite thin film according to claim 1, characterized in that: The perovskite precursor solution is a precursor solution for preparing a perovskite film by a one-step solution method; tetrahydrofuran is added to the perovskite precursor solution at a volume ratio of 1:0.17 to 1:0.

23.

3. The method for preparing a perovskite thin film according to claim 2, characterized in that: The concentration of the perovskite precursor solution is 1.2 mol / L to 1.8 mol / L; the solvent of the perovskite precursor solution is a mixed solvent of DMF and DMSO, or a mixed solvent of DMF and NMP.

4. The method for preparing a perovskite thin film according to claim 1, characterized in that: For a single-junction perovskite cell, the concentration of the perovskite precursor solution is 1.3-1.6 mol / L; the amount of tetrahydrofuran added is 0.2-0.3 times the volume of the perovskite precursor solution.

5. The method for preparing a perovskite thin film according to claim 1, characterized in that: For crystalline silicon perovskite stacked cells, the perovskite film is made of a wide bandgap perovskite material greater than 1.6 ev, the concentration of the perovskite precursor solution is 1.65-1.8 mol / L, and the amount of tetrahydrofuran added is 0.15-0.25 times the volume of the perovskite precursor solution.

6. The method for preparing a perovskite thin film according to any one of claims 1 to 5, characterized in that: The solvent of the perovskite precursor solution is a mixed solvent formed by mixing DMF and DMSO in a volume ratio of 4:1; the solute of the perovskite precursor solution includes MACl, PbCI2, CsI, PbBr2, FAI and PbI2.

7. A solvent system for preparing perovskite thin films by a solution process, characterized in that: The invention comprises at least one perovskite solvent and tetrahydrofuran added in an amount of 12% to 36% by volume of the perovskite solvent.

8. A method for preparing a solar cell comprising a perovskite light absorbing layer, characterized in that: The perovskite light absorbing layer is prepared by the perovskite thin film preparation method according to any one of claims 1 to 6, or the solvent system according to claim 7 is used in the preparation of the perovskite light absorbing layer.

9. The preparation method according to claim 8, characterized in that: Before preparing the perovskite light absorbing layer, the method further comprises: coating a mixed solution of Poly-TPD and PTAA on a substrate to form a hole transport layer; A modification layer of the hole transport layer is formed on the hole transport layer.

10. A solar cell comprising a perovskite light absorbing layer, characterized in that: The perovskite light absorbing layer is prepared by the perovskite thin film preparation method according to any one of claims 1 to 6, or the solvent system according to claim 7 is used in the preparation of the perovskite light absorbing layer.

11. The solar cell according to claim 10, characterized in that The solar cell is a crystalline silicon perovskite tandem solar cell, which includes a trans-structured perovskite sub-cell, and the perovskite sub-cell includes the perovskite light-absorbing layer.

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