Perovskite precursor solution, perovskite thin film, perovskite solar cell and preparation method

Abstract

The invention belongs to the photovoltaic field, and particularly relates to a perovskite precursor solution, a perovskite thin film, a perovskite solar cell and a preparation method. The perovskite precursor solution comprises a perovskite structure substance raw material and a solvent, the solvent comprises a first solvent, the first solvent is a compound of formula I, and in the formula I, R1 and R2 are as described in the specification. The compound shown in the formula I is used for replacing dimethyl sulfoxide in a traditional solvent, crystallization in the perovskite film forming process is delayed, perovskite growth is promoted, an intermediate phase formed by dimethyl sulfoxide and lead iodide is reduced, removal of redundant solvent in the subsequent film forming process is facilitated, and therefore the perovskite film forming quality is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaics, and particularly relates to a perovskite precursor solution, a perovskite thin film, a perovskite solar cell and a preparation method thereof. Background Art

[0002] As the third-generation high-efficiency thin-film battery, the efficiency of perovskite solar cells has been rapidly improved in recent years and has exceeded 25%. The key to the preparation of perovskite solar cells lies in the preparation (growth and nucleation) of the perovskite absorption layer. Currently, the mainstream solution method is used to prepare high-efficiency perovskite solar cells. The regulation of perovskite growth generally uses adding an appropriate amount of dimethyl sulfoxide (DMSO) to the solvent to delay crystallization. However, DMSO will react with lead iodide (PbI2) to form an intermediate, resulting in incomplete removal during the spin-coating annealing process.

[0003] On October 14, 2024, Yana Vaynzof of the Leibniz Institute for Solid State and Materials Research in Dresden integrated a highly uniform and dense micro quasi-two-dimensional (n = 5) perovskite processed with the novel green solvent glyoxal dimethyl acetal (Gly-F) into a solar cell. The perovskite thin film treated with the green solvent achieved an encouraging power conversion efficiency of 14.53%. However, the performance of this solar cell is lower than that of the perovskite based on N,N-dimethylformamide (DMF), probably because there is a low-n perovskite phase with a lateral orientation. The formation of low-dimensional perovskite using the green solvent forms a lateral low-dimensional perovskite phase, which hinders the transport of carriers when the perovskite device works and reduces the optoelectronic performance of the device. Summary of the Invention

[0004] To solve the problems existing in the prior art, without destroying N,N-dimethylformamide (DMF) which has the largest proportion in the mainstream solvent, the structure of DMSO is optimized, and a substituted sulfoxide structure is adopted. While maintaining the function of slowing down perovskite crystallization, the reaction with PbI2 is reduced, preventing the formation of intermediates from causing residual solution in the film after final annealing and reducing the device performance.

[0005] Specifically, the present invention provides a perovskite precursor solution, which comprises a perovskite structure material raw material and a solvent. The solvent comprises a first solvent and N,N-dimethylformamide. The first solvent is a compound of formula I:

[0006]

[0007] In formula I, R1 and R2 are each independently selected from C1-C4 alkyl, C6-C14 aryl, C1-C4 alkyl-substituted C6-C14 aryl, 5-14 membered heteroaryl, and C1-C4 alkyl-substituted 5-14 membered heteroaryl, and R1 and R2 are not both alkyl at the same time.

[0008] In one or more embodiments, each of R1 and R2 is independently selected from C1-C4 alkyl, phenyl, and C1-C4 alkyl-substituted phenyl, and R1 and R2 are not both alkyl at the same time.

[0009] In one or more embodiments, each of R1 and R2 is independently selected from methyl, phenyl, and tolyl, and R1 and R2 are not both methyl at the same time.

[0010] In one or more embodiments, the first solvent is one or more selected from methylphenyl sulfoxide, diphenyl sulfoxide, methyl p-tolyl sulfoxide, and 4,4-dimethylbenzene sulfoxide.

[0011] In one or more embodiments, in the perovskite precursor solution, the volume ratio of N,N-dimethylformamide to the first solvent is (9-4):1.

[0012] In one or more embodiments, the concentration of the perovskite structure substance theoretically generated from the raw materials of the perovskite structure substance in the perovskite precursor solution is 1-2 mol / L.

[0013] In one or more embodiments, the raw materials of the perovskite structure substance include AX and BX2; the A ion is one or more selected from methylammonium ion, formamidinium ion, cesium ion, and rubidium ion; the B ion is one or more selected from lead ion, tin ion, copper ion, zinc ion, gallium ion, and calcium ion; the X ion is selected from F - , I - , Br - , Cl - , BF4 - , and SCN - and one or more of the following.

[0014] Another aspect of the present invention provides a perovskite thin film, which is prepared from the perovskite precursor solution in any embodiment of the present invention.

[0015] Another aspect of the present invention also provides a method for preparing the perovskite thin film in any embodiment of the present invention, the method comprising coating the perovskite precursor solution in any embodiment of the present invention, and then annealing to obtain a perovskite thin film.

[0016] In one or more embodiments, the coating method is one or more of slot coating, blade coating, spin coating, inkjet printing, spray pyrolysis, or screen printing.

[0017] Another aspect of the present invention also provides a perovskite solar cell comprising the perovskite thin film in any embodiment of the present invention.

[0018] By replacing the methyl group in DMSO with an aromatic group, the electron density around the oxygen atom in the sulfoxide group is reduced. Through this electron delocalization effect, while maintaining the function of slowing down perovskite crystallization, the residence time of the intermediate phase (i.e., the intermediate formed by the solvent in the perovskite precursor and PbI2) is reduced, so that the residence time of the intermediate phase is not too long, the solvent removal efficiency is high, and the device performance is prevented from being reduced due to the solution residue in the perovskite film after annealing; at the same time, the residence time of the intermediate phase is not too short to prevent the formation of the intermediate phase, which is conducive to the orderly arrangement of perovskite grains, forming a more uniform and flat perovskite film, and ultimately improving the film-forming quality of the perovskite film and the device performance of the perovskite solar cell (especially the fill factor). Description of the Drawings

[0019] Figure 1 It is a structural diagram of a perovskite / heterojunction crystalline silicon tandem cell in some embodiments.

[0020] Figure 2 It is a diagram showing the change of the X-ray diffraction structure of a perovskite film with time during the annealing process for fabricating the perovskite film.

[0021] Figure 3 It is a steady-state fluorescence diagram of the perovskite films in Examples 1-2 and Comparative Example 1. Detailed Embodiments

[0022] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0024] In this article, terms such as "comprising", "including", "containing" and similar terms cover the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", "A consists essentially of B and C" and "A consists of B and C" should be considered to have been disclosed herein.

[0025] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0026] In this text, unless otherwise specified, percentages refer to mass percentages and ratios refer to mass ratios.

[0027] In this text, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described in the present invention are intended to be covered within the scope defined by the claims.

[0028] In this text, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0029] Definitions

[0030] The total number of carbon atoms present in certain chemical groups defined herein is represented by a simplified symbol in front of the group. For example, C1-C4 alkyl refers to an alkyl as defined below having a total of 1 to 4 carbon atoms. The total number of carbon atoms in the simplified symbol does not include the number of carbon atoms that may be present in substituents of the group.

[0031] As used herein, "alkyl" refers to a straight-chain or branched-chain monovalent saturated hydrocarbon group having a specified number of carbon atoms. Specific alkyl groups are those having 1 to 4 carbon atoms (C1-C4 alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl.

[0032] As used herein, "aryl" refers to an unsaturated aromatic carbocyclic group having a single ring (e.g., phenyl) or multiple fused rings (e.g., naphthyl or anthracenyl), where the fused rings may or may not be aromatic. In one variation, aryl contains 6 to 14 ring carbon atoms, preferably C6-C10 aryl. An aryl group having more than one ring and at least one of which is a non-aromatic ring may be attached to the parent structure at an aromatic ring position or at a non-aromatic ring position. In one variation, an aryl group having more than one ring and at least one of which is a non-aromatic ring is attached to the parent structure at an aromatic ring position. Examples of aryl groups include phenyl, naphthyl, phenanthryl, anthracenyl, indenyl, azulyl, biphenyl, biphenylene, and fluorenyl.

[0033] As used herein, as a group or as part of another group, the term "heteroaryl" refers to a conjugated ring system group or moiety having carbon atoms (e.g., 1 to 11 carbon atoms, 1 to 10 carbon atoms, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms) and heteroatoms selected from nitrogen, oxygen, and sulfur (e.g., 1 to 6 heteroatoms, such as 1, 2, 3, 4, or 5 heteroatoms) within the ring. In some embodiments, the heteroaryl may contain 5 to 14 ring atoms, 5 to 12 ring atoms, 5 to 10 ring carbon atoms, 5 to 8 ring atoms, 5 to 7 ring atoms, or 5 to 6 ring atoms. Unless otherwise specifically indicated in this specification, the heteroaryl may be a monocyclic, bicyclic, tricyclic, or more-ring ring system, and may also be fused with the aryl or heterocyclic group defined above. Examples of the heteroaryl fused with the aryl include, but are not limited to, benzopyridyl, benzopyrazolyl, benzimidazolyl, benzopyrrolyl, etc. The nitrogen, carbon, or sulfur atoms in the heteroaryl may be optionally oxidized; the nitrogen atom may be optionally quaternized.

[0034] The present invention provides a perovskite precursor solution that may contain a perovskite structure material raw material and a solvent, the solvent comprising a first solvent and N,N-dimethylformamide, and the first solvent having the structure of Formula I:

[0035]

[0036] In some embodiments, in the perovskite precursor solution of the present invention, the volume ratio of N,N-dimethylformamide to the first solvent is preferably (9 - 4):1, such as 8.5:1, 8:1, 7.5:1, 7:1, 6.5:1, 6:1, 5.5:1, 5:1, 4.5:1. In the present invention, by controlling the proportion of the first solvent within the above range, the film-forming quality of the perovskite film and the device performance of the perovskite solar cell can be effectively improved.

[0037] In some embodiments, the perovskite precursor solution of the present invention does not contain dimethyl sulfoxide.

[0038] In some embodiments, the solvent of the perovskite precursor solution of the present invention consists of a first solvent and N,N-dimethylformamide.

[0039] In the present invention, the perovskite structure material raw material may be AX and BX2, the A ion is a monovalent cation, and may include, but is not limited to, cesium ion (Cs + ), rubidium ion (Rb + ), methylammonium ion (CH3NH3 + , MA + ), and formamidinium ion (CH(NH2)2 + , FA + ) or more; the B ion is a divalent cation, and may include, but is not limited to, lead ion (Pb2+ ) and / or tin ions (Sn 2+ ); X ions are monovalent anions, which may include but are not limited to iodide ions (I - ), bromide ions (Br - ), and chloride ions (Cl - ), one or more of which; preferably, in the perovskite structure material raw material, A ions are selected from one or more of cesium ions, methylamine ions, and formamidinium ions; B ions are lead ions; X ions are iodide ions and / or bromide ions. Using the preferably perovskite structure material raw material is beneficial to preparing a ternary mixed organic halogen hybrid perovskite structure material, which has the most commercial prospects in terms of optoelectronic parameters and stability. In some embodiments, the perovskite structure material raw materials are PbI2, FAI, MABr, and CsBr.

[0040] In the perovskite precursor solution of the present invention, the concentration of the perovskite structure material theoretically generated from the perovskite structure material raw material is 1-2 mol / L, such as 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L.

[0041] The present invention provides a method for preparing a perovskite thin film, which includes coating the perovskite precursor solution of the present invention and then annealing to obtain a perovskite thin film.

[0042] The preparation method of the present invention further includes: filtering the perovskite precursor solution before coating.

[0043] In the present invention, the coating method can be slot coating, blade coating, spin coating, inkjet printing, or screen printing. In the present invention, the coating speed can be 5-30 millimeters per second.

[0044] In the present invention, the annealing process is one-step annealing or two-step annealing. The annealing temperature can be 100-150 °C, such as 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C. In the present invention, the annealing time can be 15-30 min, such as 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min.

[0045] The present invention provides a perovskite thin film with a high solvent removal rate. In the present invention, the thickness of the perovskite thin film can be 400 - 1200 nm, such as 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm. In a single-junction perovskite solar cell, the perovskite thickness can be 400 - 700 nm, such as 400 nm, 500 nm, 600 nm, 700 nm. In a tandem perovskite solar cell, the thickness of the perovskite thin film can be 800 - 1200 nm, such as 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm.

[0046] In the present invention, the perovskite thin film may contain a perovskite-structured substance, and the chemical formula of the perovskite-structured substance is ABX3, where the A ion is a monovalent cation and may include, but is not limited to, cesium ion (Cs + ), rubidium ion (Rb + ), methylammonium ion (CH3NH3 + , MA + ) and formamidinium ion (CH(NH2)2 + , FA + ) or one or more of them; the B ion is a divalent cation and may include, but is not limited to, lead ion (Pb 2+ ) and / or tin ion (Sn 2+ ); the X ion is a monovalent anion and may include, but is not limited to, iodide ion (I - ), bromide ion (Br - ) and chloride ion (Cl - ) or one or more of them. For example, the perovskite-structured substance may be Cs 0.05 MA 0.15 FA 0.8 PbI 2.28 Br 0.72 . In some embodiments, the perovskite-structured substance is FA a MA b Cs c Pb(I m Br n )3, where a + b + c = 1, m + n = 1, 0 < c ≤ 0.2, 0.8 ≤ a < 1. Preferably, in some embodiments, the perovskite-structured substance is the perovskite-structured substance in a tandem perovskite solar cell, FA is the main component, 0 < c ≤ 0.2, 0.8 ≤ a < 1.

[0047] The present invention provides a perovskite solar cell comprising the perovskite thin film of the present invention. In the present invention, the perovskite solar cell may include a single-junction perovskite solar cell or a tandem perovskite solar cell; the perovskite solar cell may include a normal perovskite solar cell (n-i-p type perovskite solar cell) or an inverted perovskite solar cell (p-i-n type perovskite solar cell). Specifically, the perovskite solar cell may be a normal single-junction perovskite solar cell, an inverted single-junction perovskite solar cell, or a tandem perovskite solar cell.

[0048] In the present invention, the normal single-junction perovskite solar cell may sequentially include a transparent conductive substrate, an electron transport layer, a perovskite thin film, a hole transport layer, and a metal electrode. In the present invention, the inverted single-junction perovskite solar cell may sequentially include a transparent conductive substrate, a hole transport layer, a perovskite thin film, an electron transport layer, a hole blocking layer, and a metal electrode. In the present invention, the tandem perovskite solar cell may sequentially include a bottom electrode, a bottom cell, a tunneling layer, a perovskite top cell, and a top electrode, and the top cell may sequentially include a hole transport layer, a perovskite thin film, and an electron transport layer.

[0049] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are conventional methods, reagents, and materials in the art unless otherwise specified. The raw material compounds in the examples can be obtained through commercial channels.

[0050] Example 1

[0051] This example prepares an inverted wide-bandgap perovskite / heterojunction silicon tandem solar cell with the structure as Figure 1 shown, and the specific steps are as follows:

[0052] Preparation of the perovskite precursor solution: Mix 39.5 mg of cesium iodide (CsI), 418 mg of formamidinium iodide (FAI), 51 mg of methylammonium bromide (MABr), 332 mg of lead bromide (PbBr2), and 1057 mg of lead iodide (PbI2), add them to 2 mL of a mixed solvent of N,N-dimethylformamide:methylphenylsulfoxide (MPSO) = 9:1 (v / v) for dissolution, and filter using a 0.22 μm oil filter to obtain a Cs 0.05 MA 0.15 FA 0.8 PbI 2.28 Br 0.72 perovskite precursor solution with a concentration of 1.7 mol / L;

[0053] (1) Preparation of the bottom cell:

[0054] Select n-type monocrystalline silicon, perform RCA standard process cleaning, use an aqueous KOH solution with n(H2O):n(KOH):n(H2O2) = 5:1:1 to etch the back surface of the silicon wafer to prepare a pyramid structure with a depth of 3.5 μm, and use an aqueous KOH solution with n(H2O):n(KOH):n(H2O2) = 10:1:2 to etch the front surface of the bone chip to prepare a pyramid structure with a depth of about 1 μm, obtaining a monocrystalline silicon substrate 1 with a thickness of 260 μm;

[0055] Adopt the plasma enhanced chemical vapor deposition (PECVD) process to deposit intrinsic amorphous silicon layers (a-Si(i)) on both sides of the monocrystalline silicon substrate 1 at 200 °C, obtaining a passivation layer 2 with a thickness of 5 nm;

[0056] Adopt the PECVD process to deposit a boron-doped nc-Si(p) layer on the surface of the passivation layer 2 on the back of the monocrystalline silicon substrate 1 at 200 °C, obtaining a hole transport layer 3 with a thickness of 20 nm;

[0057] Adopt the PECVD process to deposit a phosphorus-doped nc-Si(p) layer on the surface of the passivation layer 2 on the front of the monocrystalline silicon substrate 1 at 200 °C, obtaining an electron transport layer 6 with a thickness of 15 nm;

[0058] Furthermore, a bottom cell with a total thickness of 260 μm is obtained;

[0059] (2) Prepare the back electrode and the composite layer: Use magnetron sputtering to deposit indium oxide (In2O3) on the surface of the hole transport layer 3, obtaining a transparent electrode layer 4 with a thickness of 100 nm (sheet resistance is about 120 Ω / sq); then deposit silver at a low temperature (150 °C) on the surface of the transparent electrode layer 4 to obtain a silver grid line electrode 5 with a height of 8 μm and a width of 50 μm. The transparent electrode layer 4 and the silver grid line electrode 5 together form the back electrode; Use magnetron sputtering to deposit indium zinc oxide (IZO) on the surface of the electron transport layer 6, obtaining a composite layer 7 with a thickness of 10 nm;

[0060] (3) Prepare the hole transport layer: Dissolve [4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid (MeO-4PACZ) in an IPA solvent to prepare a MeO-4PACZ solution with a concentration of 1 mmol / mL. Take 80 μL of the MeO-4PACZ solution and drop it on the IZO surface of the composite layer 7, then spin-coat it at a speed of 4000 rpm for 15 s, and transfer it to a heating plate at 100 °C for annealing for 10 min after the spin-coating is completed, obtaining a hole transport layer 8 with a thickness of 1 nm;

[0061] (4) Preparation of perovskite light-absorbing layer: A broadband-gap perovskite light-absorbing layer was prepared by spin coating; the specific operation is as follows: Take 100 μL of perovskite precursor solution and drop it on the surface of the hole transport layer 8, then spin coat it at a speed of 4000 rpm for 40 s, and transfer it to a heating plate at 100 °C for annealing for 30 min after spin coating to obtain a perovskite light-absorbing layer 9 with a band gap of 1.68 eV and a thickness of 500 nm;

[0062] (5) Preparation of the passivation layer: LiFx was deposited on the surface of the perovskite light-absorbing layer 9 by thermal evaporation to obtain a first passivation layer 10 with a thickness of 1 nm; By spin coating method, take 80 μL of isopropanol solution of ethylenediamine iodide (EDAI) with a concentration of 0.3 mg / ml, drop it on the surface of the LiFx first passivation layer 10, then spin coat it at a speed of 4000 rpm for 15 s, and transfer it to a heating plate at 100 °C for annealing for 5 min after spin coating to obtain a second passivation layer 11 with a thickness of 3 nm; The first passivation layer 10 and the second passivation layer 11 together form the passivation layer;

[0063] (6) Preparation of the electron transport layer: Fullerene (C60) was deposited on the surface of the second passivation layer 11 by thermal evaporation to obtain an electron transport layer 12 with a thickness of 10 nm;

[0064] (7) Preparation of the buffer layer: Tin dioxide (SnO2) was deposited on the surface of the electron transport layer 12 by atomic layer deposition (ALD) to obtain a buffer layer 13 with a thickness of 15 nm;

[0065] (8) Preparation of the top electrode: Indium zinc oxide (IZO) was deposited on the surface of the buffer layer 13 by magnetron sputtering to obtain a transparent conductive layer 14 with a thickness of 50 nm; MgF was deposited on the transparent electrode layer 14 by thermal evaporation x , to obtain a MgF with a thickness of 110 nm x anti-reflection layer 15; Silver was deposited on the surface of the anti-reflection layer 15 by thermal evaporation through a mask to obtain a silver electrode 16 with a thickness of 400 nm; The transparent conductive layer 14, the anti-reflection layer 15 and the silver electrode 16 together form the top electrode, and at the same time, a trans-type broadband-gap perovskite / heterojunction silicon tandem solar cell is obtained.

[0066] Example 2

[0067] The difference between Example 2 and Example 1 is only that methylphenyl sulfoxide in the perovskite precursor solution is replaced with an equal volume of diphenyl sulfoxide (DPSO).

[0068] Example 3

[0069] The difference between Example 2 and Example 1 is only that methylphenyl sulfoxide in the perovskite precursor solution is replaced with an equal volume of methyl p-tolyl sulfoxide.

[0070] Example 4

[0071] Example 4 is different from Example 1 only in that methylphenyl sulfoxide in the perovskite precursor solution is replaced with 4,4-dimethylbenzene sulfoxide of the same volume.

[0072] Comparative Example 1

[0073] Other conditions of this comparative example are the same as those of Example 1, and the difference is only that the mixed solvent used in the perovskite precursor solution of this comparative example is N,N-dimethylformamide: dimethyl sulfoxide (DMSO) = 9:1 (v / v).

[0074] Test Example

[0075] I. Physical property test: The solvent removal efficiency of the perovskite thin films in Examples 1-2 and Comparative Example 1 was measured by an X-ray diffractometer (Bruker Corporation, model: Bruker D8 GADDS), and the measurement results are as Figure 2 shown. The steady-state fluorescence of the perovskite thin films in Examples 1-2 and Comparative Example 1 was measured by a fluorescence spectrophotometer (Horiba Scientific, model: Fluoroma-Modular), and the measurement results are as Figure 3 shown.

[0076] The solvent removal efficiency can be judged by the existence time of the intermediate phase formed by the solvent in the perovskite precursor solution and lead iodide. A short existence time of the intermediate phase indicates a weak binding force between the solvent in the perovskite precursor solution and lead iodide, and the intermediate phase will disappear quickly, promoting the formation of the final three-dimensional perovskite phase. Figure 2 is a graph showing the change of the X-ray diffraction structure of perovskite with time during annealing. At the ordinate q = 5, it represents the signal of the intermediate phase. By comparing the data of Examples 1-2 and Comparative Example 1, it can be found that the disappearance of the intermediate phase from fast to slow is DPSO (Example 2), MPSO (Example 1), DMSO (Comparative Example 1). The existence time of the intermediate phase formed by the solvent in the perovskite precursor solution and lead iodide can also be used to judge the film-forming quality of the perovskite thin film. The faster the intermediate phase disappears, the more conducive to the rapid combination and crystallization growth of FA and PbI2. Therefore, the film-forming quality of the perovskite thin films in Examples 1-2 is better than that of the perovskite thin film in Comparative Example 1.

[0077] By comparing the fluorescence intensities of the perovskite thin films in Examples 1-2 and Comparative Example 1 with a fluorescence spectrophotometer (the fluorescence intensity of a high-quality perovskite thin film is strong), the film-forming quality of perovskite can be judged. As can be seen from Figure 3, the quality of the perovskite thin films in Examples 1-2 is much greater than that of the perovskite thin film in Comparative Example 1, and among them, the quality of the perovskite thin film in Example 1 is the best.

[0078] II. At 25 °C under the standard AM 1.5G solar spectrum, using a solar simulator, set the voltage range to -0.3 - 2.05 V, and measure the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the inverted broadband-gap perovskite / heterojunction silicon tandem solar cells of Examples 1 - 4 and Comparative Example 1.

[0079] (1) Open-circuit voltage (Voc): The voltage value corresponding to when the current is zero.

[0080] (2) Short-circuit current density (Jsc): The current value when the voltage is zero is the short-circuit current (Isc), and the current magnitude per unit cell surface area is the short-circuit current density.

[0081] (3) Fill factor (FF): The ratio of the maximum output power (Pmax) of the cell to the product of the open-circuit voltage and the short-circuit current, and the calculation formula is (Pmax / Voc*Isc), where the maximum power point is the point where the cell output power reaches the maximum value.

[0082] (4) Photoelectric conversion efficiency (PCE): The photoelectric conversion efficiency refers to the ratio of the maximum output power to the incident light power (Pin), and the calculation formula is (Pmax / Pin)*100%.

[0083] The test results of the open-circuit voltage, short-circuit current density, fill factor, and photoelectric conversion efficiency of the inverted broadband-gap perovskite / heterojunction silicon tandem solar cells of Examples 1 - 4 and Comparative Example 1 are shown in Table 1. It can be seen from Table 1 that the device efficiency of the inverted broadband-gap perovskite / heterojunction silicon tandem solar cells prepared by replacing dimethyl sulfoxide in the traditional solvent with the compound of Formula I in the present invention is improved, especially the FF parameter is significantly improved.

[0084] Table 1: Cell performance parameters of the inverted broadband-gap perovskite / heterojunction silicon tandem solar cells of Examples 1 - 4 and Comparative Example 1

[0085] Device Voc (V) <![CDATA[Jsc(mA / cm 2 )]]> FF (%) PCE (%) Example 1 1.968 19.24 83.7 31.69 Example 2 1.955 19.21 82.3 30.91 Example 3 1.96 19.03 82.6 30.81 Example 4 1.957 19.31 83.1 31.40 Comparative Example 1 1.933 19.19 78.9 29.27

Claims

1. A perovskite precursor solution, characterized in that, The perovskite precursor solution contains raw materials of perovskite structure substances and a solvent. The solvent contains a first solvent and N,N-dimethylformamide. The first solvent is a compound of formula I: In formula I, R1 and R2 are each independently selected from C1-C4 alkyl, C6-C14 aryl, C1-C4 alkyl-substituted C6-C14 aryl, 5-14 membered heteroaryl, and C1-C4 alkyl-substituted 5-14 membered heteroaryl, and R1 and R2 are not both alkyl at the same time.

2. The perovskite precursor solution according to claim 1, wherein R1 and R2 are each independently selected from C1-C4 alkyl, phenyl, and C1-C4 alkyl-substituted phenyl, and R1 and R2 are not both alkyl at the same time.

3. The perovskite precursor solution according to claim 1, wherein R1 and R2 are each independently selected from methyl, phenyl, and tolyl, and R1 and R2 are not both methyl at the same time.

4. The perovskite precursor solution according to claim 1, wherein The first solvent is one or more selected from methylphenyl sulfoxide, diphenyl sulfoxide, methyl p-tolyl sulfoxide, and 4,4-dimethylbenzene sulfoxide.

5. The perovskite precursor solution according to claim 1, characterized in that, In the perovskite precursor solution, the volume ratio of N,N-dimethylformamide to the first solvent is (9-4):

1.

6. The perovskite precursor solution according to claim 1, characterized in that, The perovskite precursor solution has one or more of the following characteristics: The concentration of the perovskite structure substance theoretically generated from the raw materials of the perovskite structure substance in the perovskite precursor solution is 1-2 mol / L; The perovskite-structured material raw material contains AX and BX2; the A ion is one or more selected from methylammonium ion, formamidinium ion, cesium ion, and rubidium ion; the B ion is one or more selected from lead ion, tin ion, copper ion, zinc ion, gallium ion, and calcium ion; the X ion is one or more selected from F - , I - , Br - , Cl - , BF4 - , and SCN - .

7. A perovskite thin film, characterized in that, The perovskite thin film is prepared from the perovskite precursor solution according to any one of claims 1-6.

8. A method for preparing the perovskite thin film according to claim 7, characterized in that, The method includes coating the perovskite precursor solution according to any one of claims 1-6, and then annealing to obtain a perovskite thin film.

9. The method according to claim 8, wherein The coating method is one or more of slot coating, blade coating, spin coating, inkjet printing, spray pyrolysis, or screen printing.

10. A perovskite solar cell comprising the perovskite thin film according to claim 7.

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