Annealing method of perovskite thin film and perovskite thin film thereof

Abstract

The invention provides an annealing method of a perovskite thin film and the perovskite thin film. The annealing method of the perovskite thin film comprises the step of placing the perovskite thin film formed by a perovskite precursor solution on a planar microwave sensitive body material for microwave annealing. According to the annealing method of the perovskite thin film, rapid and uniform annealing of the perovskite thin film can be realized, and the crystallinity and uniformity of the perovskite thin film are greatly improved, so that the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite solar cells, and particularly relates to an annealing method for a perovskite thin film and the perovskite thin film thereof. Background Art

[0002] Perovskite solar cells (PSCs), as a new type of solar cells, have received extensive attention in recent years due to their excellent optoelectronic properties, high photoelectric conversion efficiency, and low-cost solution preparation process. Compared with traditional silicon-based solar cells, perovskite materials have advantages such as adjustable bandgap, good light absorption characteristics, and high carrier mobility, enabling significant technological progress in a short period. Generally, the basic structure of PSCs consists of a transparent metal oxide (TCO) substrate, an electron transport layer (ETL), a perovskite light-absorbing layer, a hole transport layer (HTL), and a metal electrode. The properties and interface characteristics of functional layers such as ETL, perovskite light-absorbing layer, and HTL directly determine the optoelectronic performance of PSCs devices. Currently, the research on perovskite solar cells mainly focuses on improving the photoelectric conversion efficiency and device stability. The photoelectric conversion efficiency has been increased from 3.8% in the early stage to over 25% currently.

[0003] During the solution preparation process of the perovskite light-absorbing layer, annealing treatment is a key step to obtain high-quality thin films, which is used to improve the crystal quality of the perovskite thin film and reduce the defect density, directly affecting the final performance of the solar cell. In the industrial production process of perovskite solar cells, hot plate annealing is widely used as the standard process for annealing the perovskite light-absorbing layer due to its simple process and easy control. It is usually used to control the crystallization process of the perovskite thin film to ensure that the thin film has good crystal quality and appropriate thickness to achieve the best photoelectric conversion efficiency. However, in large-scale batch production, hot plate annealing has limitations such as low efficiency, high energy consumption, and uneven annealing between the center and edge of the thin film, seriously affecting the quality of the perovskite light-absorbing layer and increasing the battery manufacturing cost. It is one of the key problems restricting the further large-scale and industrialization of perovskite solar cells.

[0004] To solve the problems brought by the above-mentioned conventional hot plate annealing, various annealing strategies including rapid thermal annealing, far-infrared annealing, laser annealing, vapor-assisted annealing, etc. have been applied to a certain extent, but there are still problems such as high cost, complex process, and poor repeatability.

[0005] CN115835657A discloses a microwave annealing treatment method. By controlling the thickness ratio of the perovskite thin film and the wet film, the amount of residual solvent in the thin film is controlled. During microwave annealing, heat conduction mainly depends on the residual solvent in the wet film absorbing microwave energy to generate polarization and produce a thermal effect outward. On the one hand, after annealing, the residual solvent in the thin film is completely removed, and a perovskite light-absorbing layer with high crystallinity is obtained; on the other hand, to a certain extent, it alleviates the heating uniformity problem of conventional hot plate annealing, the solvent volatilizes faster, and the thin film is heated more uniformly.

[0006] Generally, the problems existing in microwave annealing are as follows: (1) Complex process regulation: In microwave annealing, the thermal effect is mainly generated by the solvent absorbing microwave energy. The annealing temperature is directly related to the solvent composition of the perovskite wet film and the perovskite components. For the differences in solvents and components of different perovskite wet films, the microwave power and heating time need to be finely regulated to achieve the same ideal effect. (2) Poor process repeatability and material sensitivity: The actual temperature that perovskite can reach after absorbing microwave energy is uncontrollable. The uniformity of the film layer may lead to uneven distribution of the annealing temperature. The allowable minor component differences in actual production may also cause changes in the annealing temperature, resulting in a decrease in the consistency of battery performance. (3) Narrow temperature control window: Generally, the annealing temperature that the perovskite wet film can reach by itself after absorbing microwave energy is within 200 degrees Celsius, and the actual annealing temperature is affected by solvents and solutes, and the temperature window may be further narrowed or even unable to meet the ideal annealing temperature of the current material system, seriously restricting the performance of the battery. Summary of the Invention

[0007] In order to overcome the problems existing in the above-mentioned prior art, the present invention provides an annealing method for perovskite thin films and the perovskite thin films thereof. The annealing method for perovskite thin films of the present invention can achieve rapid and uniform annealing of perovskite thin films, greatly improve the crystallinity and uniformity of perovskite thin films, and thus improve the photoelectric conversion efficiency of the battery.

[0008] Specifically, the first aspect of the present invention provides an annealing method for perovskite thin films, which includes: the step of placing a perovskite thin film formed from a perovskite precursor solution on a planar microwave-sensitive material for microwave annealing.

[0009] In one or more embodiments, the microwave-sensitive material is selected from one or more of silicon wafers, graphite powder, and graphite plates.

[0010] In one or more embodiments, the time required for microwave annealing is capped at heating the perovskite material to be treated to 5 - 10 °C below the tolerance temperature of the perovskite material to be treated.

[0011] In one or more embodiments, the time of the microwave annealing is within 10 min, such as 0.2 - 10 min, or 1 - 3 min, or 3 - 8 min.

[0012] In one or more embodiments, the upper limit value of the heating temperature of the microwave annealing is controlled to be 200 °C.

[0013] In one or more embodiments, the microwave power is 100 W - 1000 W, such as 100 - 400 W, 400 - 500 W, 500 - 800 W, or 800 - 1000 W.

[0014] In one or more embodiments, the process parameters of the microwave annealing are as follows: the microwave susceptor is a silicon wafer, the microwave power is 800 - 1000 W, and the annealing time is 1 - 3 min.

[0015] In one or more embodiments, the microwave susceptor is a graphite plate, the microwave power is 400 - 500 W, and the annealing time is 1 - 2 min.

[0016] In one or more embodiments, the microwave susceptor is graphite powder, the microwave power is 400 - 500 W, and the heating time is 0.2 - 1 min.

[0017] In one or more embodiments, in the perovskite precursor solution, the chemical formula of the perovskite is denoted as ABX 3 structure, A includes one or more of formamidinium cations, methylammonium cations, and cesium ions, B includes lead ions and / or tin ions, and X is a halogen anion.

[0018] In one or more embodiments, the concentration of the perovskite in the perovskite precursor solution is 1 mol / L - 2 mol / L.

[0019] In one or more embodiments, the solvent of the perovskite precursor solution is selected from one or more of N,N - dimethylformamide, N - methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

[0020] In one or more embodiments, the perovskite thin film is obtained by coating the perovskite precursor solution on a conductive substrate, and the conductive substrate is a conductive substrate or a conductive substrate + hole - transporting layer.

[0021] The second aspect of the present invention provides a method for preparing a perovskite thin film, which includes the following steps:

[0022] Step S1: Provide a perovskite precursor solution;

[0023] Step S2: Coat the perovskite precursor solution on a conductive substrate to obtain a perovskite wet film, and obtain a perovskite thin film after removing the solvent through crystallization treatment;

[0024] Step S3: placing the perovskite film on a planar microwave sensitive material and performing microwave annealing treatment.

[0025] In one or more embodiments, the microwave annealing process is as described in any of the embodiments herein.

[0026] A third aspect of the present invention provides a perovskite film, which is prepared by the annealing method of a perovskite film as described in any embodiment of the present invention or the preparation method of a perovskite film as described in any embodiment of the present invention.

[0027] A fourth aspect of the present invention provides a method for preparing a perovskite solar cell, the method comprising the steps of sequentially arranging a hole transport layer, a perovskite light absorption layer, a passivation layer, an electron transport layer, a buffer layer and an electrode on a conductive substrate, wherein the perovskite light absorption layer is arranged using the steps of preparing a perovskite film as described in any embodiment of the present invention.

[0028] A fifth aspect of the present invention provides the use of a planar microwave sensitive body material in preparing a perovskite film with improved crystallinity and uniformity.

[0029] A sixth aspect of the present invention provides the use of the annealing method of a perovskite film as described in any embodiment of the present invention in the preparation of a perovskite solar cell.

[0030] Beneficial effects of the present invention:

[0031] (1) Rapid and uniform annealing: Compared with conventional hot plate annealing, the energy of electromagnetic waves during hybrid microwave annealing can make the wet film solvent evaporate quickly and produce the effect of low-temperature pre-annealing; hybrid microwave annealing is a hybrid annealing mode that combines thermal conduction and dielectric heating. Electromagnetic waves can generate additional electromagnetic fields in the perovskite film, which helps to eliminate a large amount of stress during the crystallization process of the film and produce fewer defects; after absorbing microwave energy, the microwave sensitive body can quickly heat up within 1 to 2 minutes, and perform rapid and uniform gradient annealing on the perovskite film it carries, thereby improving the quality of the film.

[0032] (2) Low energy consumption: Compared with the conventional flat-plate processing method of thermal annealing, annealing based on microwave equipment and microwave sensitive materials has higher space utilization rate and can process multiple pieces at a time. The addition of microwave sensitive materials makes annealing more efficient and generates lower energy consumption per unit of heat energy.

[0033] (3) Wide temperature control window: Different microwave-sensitive materials can rapidly heat up from room temperature after absorbing microwave energy, and the maximum temperatures they can reach are different, which can adapt to the ideal annealing temperatures of different perovskite materials. For example, when a silicon wafer is microwave-heated (2.45 GHz, 800 W), the maximum temperature can reach 300 to 500 degrees Celsius, and the maximum temperature of graphite powder can reach over 1000 degrees Celsius; based on different microwave-sensitive materials, the power and time of microwave heating can be adjusted to control the required upper temperature limit and gradient heating time to achieve different annealing effects.

[0034] (4) Strong material adaptability and wider application: Compared with existing general microwave heating methods, the temperature of hybrid microwave annealing does not depend on the composition of the wet film (solvent, perovskite components, etc.) and is less affected by differences in the wet film composition; hybrid microwave annealing mainly regulates the annealing conditions by relying on the heating characteristics of different microwave-sensitive materials, the power of microwaves, and the heating time, can adapt to different perovskite material systems, and can also be used for the annealing treatment of other functional layers (HTL, ETL, passivation layer). Description of the Drawings

[0035] Figure 1 Schematic diagram of the hybrid microwave annealing method provided for Example 1.

[0036] Figure 2 Schematic diagram of the structure of the perovskite solar cell prepared in Example 1.

[0037] Figure 3 SEM scanning images of the perovskite thin films of Examples 1-3 and Comparative Examples 1-2.

[0038] Description of the reference numerals: 1, conductive substrate; 2, hole transport layer; 3, perovskite light-absorbing layer; 4, passivation layer; 5, electron transport layer; 6, buffer layer; 7, electrode. Detailed Embodiments

[0039] 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 shall have the ordinary meaning understood by those skilled in the art regarding the present invention. In case of conflict, the definition in this specification shall prevail.

[0040] 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.

[0041] In this text, terms such as "comprising", "including", "containing" and similar terms encompass the meanings of "consisting essentially of" and "consisting of". For example, when this text discloses 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.

[0042] In this text, 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 ranges (including integers and fractions).

[0043] In this text, unless otherwise specified, percentages refer to mass percentages and ratios refer to mass ratios.

[0044] In this text, when describing embodiments or examples, it should be understood that it is 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 can be covered within the scope defined by the claims.

[0045] In this text, for the sake of concise 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.

[0046] The present invention provides a hybrid microwave annealing method that can be used for the perovskite light-absorbing layer or perovskite thin film in perovskite solar cells. It is an efficient annealing scheme that combines heat conduction and dielectric heating, which can achieve rapid microwave annealing with controllable temperature and a wider temperature control window, and obtain a perovskite thin film with uniform annealing temperature and high quality. This method uses a microwave susceptor that matches the size of the perovskite thin film as a heating carrier and places it at the bottom of the FTO during microwave annealing; when the microwave is started, the pre-prepared perovskite wet film absorbs microwave energy, causing the solvent to volatilize uniformly and rapidly, while achieving low-temperature pre-annealing. At the same time, the microwave susceptor at the bottom can rapidly heat up within 1 to 2 minutes after absorbing microwave energy, performing rapid gradient annealing of the perovskite thin film at a specific temperature. The annealing time and end temperature can be jointly regulated by the type of microwave susceptor, microwave power and operating time. Compared with regulating the wet film composition to produce different annealing effects, the process of selecting the microwave susceptor, regulating the microwave power and heating time in this method is simple and easy to operate, and can quickly adapt to different perovskite materials (all-inorganic, all-organic and organic-inorganic hybrid perovskites have different optimal annealing temperatures, and all-inorganic perovskites even require temperatures above 200 °C).

[0047] The present invention provides an annealing method for a perovskite light-absorbing layer or a perovskite thin film, including the step of placing a perovskite thin film formed from a perovskite precursor solution on a planar microwave-sensitive material and performing microwave annealing.

[0048] In this article, the microwave-sensitive material refers to a material that can rapidly heat up within 1 to 2 minutes after absorbing microwave energy, including but not limited to one or more of silicon wafers, graphite powder, and graphite plate materials.

[0049] In the present invention, the time required for microwave annealing is limited to heating the perovskite material to be processed to 5 - 10 °C below the tolerance temperature (without decomposition) of the perovskite material to be processed, so as to protect the perovskite thin film from being damaged during the high-temperature rapid annealing process. In some embodiments, the time for microwave annealing is within 10 min, such as 0.2 - 10 min, 1 - 3 min, or 3 - 8 min. In some embodiments, the upper limit value of the heating temperature for microwave annealing can be controlled at 200 °C.

[0050] In the present invention, the time and end temperature of microwave annealing can be jointly regulated according to the type of microwave-sensitive body and the microwave power. In some embodiments, real-time infrared temperature measurement can be performed on the surface of the microwave-sensitive body and the perovskite thin film, and according to the heating rate of different microwave-sensitive bodies at different powers, the time required for microwave annealing can be controlled. By selecting a suitable microwave-sensitive body and microwave power, the annealing time is controlled within 10 min, making the energy consumption and efficiency of the hybrid microwave annealing of the present invention significantly superior to conventional hot plate annealing and general microwave annealing. In some embodiments, the microwave power is 100W - 1000W, such as 100 - 400W, 400 - 500W, 500 - 800W, or 800 - 1000W. In some embodiments, the microwave-sensitive body is a silicon wafer, the microwave power is 800 - 1000W, and the annealing time is 1 - 3 min. In some embodiments, the microwave-sensitive body is a graphite plate, the microwave power is 400 - 500W, and the annealing time is 1 - 2 min. In some embodiments, the microwave-sensitive body is graphite powder, the microwave power is 400 - 500W, and the heating time is 0.2 - 1 min.

[0051] In the present invention, the microwave frequency can be 915 MHz - 2450 MHz. The commonly used frequencies for industrial microwave heating in China are usually 915 MHz and 2450 MHz. In the actual application process, the microwave frequency is adjustable within this range.

[0052] In the present invention, the planar size of the microwave-sensitive material can be slightly larger than the size of the thin film to ensure uniform heating of the thin film. In some embodiments, the length and width of the microwave-sensitive material can be at least 5% larger than the length and width of the thin film. In some embodiments, the planar size of the microwave-sensitive material can be (20 - 40) * (20 - 50) cm, such as 32 * 42 cm.

[0053] In the present invention, the thickness of the microwave sensitive body can vary according to the type of microwave sensitive body material. In some embodiments, the thickness of the silicon wafer as the microwave sensitive body material is 200 - 3500 μm, such as about 300 μm. In some embodiments, the thickness of the graphite plate as the microwave sensitive body material is 0.5 - 2 m, such as about 1 mm. In some embodiments, the thickness of the graphite powder as the microwave sensitive body is about 1 - 2.5 mm, such as about 2 mm. In some specific embodiments, graphite powder with a mesh number of 400 - 800 is selected, densely paved under the glass substrate, and the surface is gently compacted, with a thickness of about 1 - 2.5 mm.

[0054] In some embodiments, a perovskite active material and a solvent are mixed to obtain a perovskite precursor solution.

[0055] In the perovskite precursor solution, the concentration of the perovskite active material can be 1 mol / L to 2 mol / L. In some embodiments, the solvent of the perovskite precursor solution is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

[0056] In some embodiments, the perovskite can be one or more of all-inorganic, all-organic, and organic-inorganic hybrid perovskite materials.

[0057] In some embodiments, the chemical formula of the perovskite is denoted as ABX 3 structure, where A includes one or more of formamidinium cations, methylammonium cations, and cesium ions, B includes lead ions and / or tin ions, and X is a halogen anion. Preferably, A includes formamidinium cations and cesium ions, wherein the content of formamidinium cations is 70% - 95%, and the content of cesium ions is 5% - 30%. Optionally, A further includes methylammonium cations, and the content of methylammonium cations is 5% - 15%. Preferably, X includes I– and Br–, wherein the content of Br– is 0 - 30%, and the content of I– is 70% - 100%; optionally, X further includes Cl-, and the content of Cl- is 5% - 15%.

[0058] thin film

[0059] In some embodiments, the perovskite precursor solution is coated on a conductive substrate to obtain a perovskite wet film, and then through crystallization treatment, a perovskite thin film formed from the perovskite precursor solution is obtained.

[0060] The conductive substrate in the present invention is a conductive lining or a conductive lining + hole transport layer. Materials applicable to the conductive lining include, but are not limited to, indium tin oxide (ITO) transparent conductive glass, fluorine-doped tin oxide (FTO) transparent conductive glass, indium oxide doped with tungsten (IWO) transparent conductive glass, and aluminum-doped zinc oxide (AZO) transparent conductive glass. Materials applicable to the hole transport layer include, but are not limited to, organic hole transport materials, inorganic hole transport materials, self-assembled monolayer materials (Self-Assembled Monolayer, abbreviated as SAM), etc., and SAM materials are preferred. In some embodiments, the hole transport materials include [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (abbreviated as 2PACZ), (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid (abbreviated as MeO-2PACZ), (4-(3,6-dimethyl-9H-carbazol-9-yl)ethyl)phosphonic acid (abbreviated as Me-4PACZ), (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanotitanium)phosphonic acid (abbreviated as MPA-CPA), and (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid (abbreviated as DMAcPA), PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate), NiOx, and one or more of CuSCN.

[0061] In the present invention, the size of the conductive substrate can be (20-40)*(20-50) cm, for example, 30*30 cm or 30*40 cm. The area of the conductive substrate can be 0.05-0.2 m 2 , for example, around 0.1 m 2 .

[0062] In the present invention, the perovskite precursor solution can be coated on the conductive substrate by a coating method such as a doctor blade coating method or a slot die coating method to obtain a perovskite wet film. The coating process parameters are not particularly limited, and the parameters in these processes can be adjusted according to the target thickness of the perovskite wet film. The doctor blade coating method or the slot die coating method helps to obtain a uniform and dense wet film and has good process repeatability.

[0063] In some embodiments, the method for crystallizing the perovskite wet film is a air knife blowing method or a vacuum drying method. The crystallization treatment helps the solvent in the wet film to volatilize at normal or low temperature to obtain a film with uniform nucleation. The process parameters of the crystallization treatment are not particularly limited, and the parameters in these processes can be adjusted according to the content of the solute and solvent in the wet film to achieve a perovskite film after rapid removal of the solvent. After the crystallization treatment, most of the solvent in the perovskite wet film has been removed, and a deep yellow transparent solute supersaturated film is obtained.

[0064] In the present invention, the area of the perovskite film can be ≥0.1 m2 The hybrid microwave annealing treatment method of the present invention has more advantages in the annealing treatment of large-area thin films, and is an efficient and uniform annealing scheme proposed for the problem of uneven crystallization in the annealing process of large-area wet films. For small-area perovskite wet films, no significant annealing non-uniformity problem will occur on a small area. For example, even when using conventional hot plate annealing, there is no obvious difference in the central temperature and the temperature around the small-area glass, while on the large-area glass, the central temperature is high, the wet film starts to crystallize and undergo phase transformation first, and the temperature around is low, resulting in late crystallization and uneven film quality and low cell efficiency.

[0065] In some embodiments, the present invention provides a method for preparing a perovskite thin film, which includes the following steps:

[0066] Step S1: Provide a perovskite precursor solution;

[0067] Step S2: Coat the perovskite precursor solution on a conductive substrate to obtain a perovskite wet film, and obtain a perovskite thin film through crystallization treatment;

[0068] Step S3: Place the perovskite thin film on a planar microwave-sensitive material and perform microwave annealing treatment.

[0069] Method for preparing a perovskite solar cell

[0070] The present invention also provides a method for preparing a perovskite solar cell, which includes the steps of sequentially disposing a hole transport layer, a perovskite light-absorbing layer, a passivation layer, an electron transport layer, a buffer layer, and an electrode on a conductive substrate. Among them, the step of disposing the perovskite light-absorbing layer can adopt the steps of preparing the perovskite thin film described herein.

[0071] The materials suitable for the conductive substrate of the present invention include, but are not limited to, indium tin oxide (ITO) transparent conductive glass, fluorine-doped tin oxide (FTO) transparent conductive glass, indium tungsten oxide (IWO) transparent conductive glass, and aluminum-doped zinc oxide (AZO) transparent conductive glass, etc. There is no special limitation on the preparation of the conductive substrate, and the conventional methods for preparing the conductive substrate in the art can be adopted, such as the magnetron sputtering process. The process parameters can be adjusted according to the target thickness of the conductive substrate.

[0072] Materials suitable for the hole transport layer of the present invention include, but are not limited to, organic hole transport materials, inorganic hole transport materials, self-assembled monolayer materials (Self-Assembled Monolayer, abbreviated as SAM), etc., and SAM materials are preferred. In some embodiments, the hole transport material includes [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (abbreviated as 2PACZ), (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid (abbreviated as MeO-2PACZ), (4-(3,6-dimethyl-9H-carbazol-9-yl)ethyl)phosphonic acid (abbreviated as Me-4PACZ), (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanotitanium)phosphonic acid (abbreviated as MPA-CPA), and (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)yl)butyl)phosphonic acid (abbreviated as DMAcPA), PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate), NiOx, and one or more of CuSCN. There is no particular limitation on the preparation of the hole transport layer, and conventional methods for preparing the hole transport layer in the art can be used, such as coating on a conductive substrate by a doctor blade coating method or a slot coating method. The process parameters can be adjusted according to the target thickness of the hole transport layer. In some embodiments, the wet film of the hole transport layer can also be annealed by the hybrid microwave annealing method described above, so that the solvent volatilizes more quickly and evenly, avoiding the aggregation phenomenon of solute molecules due to the difference in the solvent evaporation rate, which directly affects the device performance.

[0073] Materials suitable for the passivation layer of the present invention include 2-thiopheneethylamine hydrochloride (TEACl), 1,4-benzenediamine hydroiodide (PDADI), phenethylamine iodide (PEAI), etc. There is no particular limitation on the preparation of the passivation layer, and conventional methods for preparing the passivation layer in the art can be used, such as coating on the perovskite light-absorbing layer by a doctor blade coating method or a slot coating method. The process parameters can be adjusted according to the target thickness of the passivation layer. In some embodiments, the thickness of the passivation layer can be 1-5 nm or 3-5 nm. In some embodiments, the wet film of the passivation layer can also be annealed by the above hybrid microwave annealing method. The electromagnetic field provided by the microwave helps the ion rearrangement and coordination optimization between the passivation layer and the perovskite light-absorbing layer, reduces interface defects, and improves the passivation effect.

[0074] Materials suitable for the electron transport layer of the present invention include, but are not limited to, PCBM ([6,6]-phenyl-C71-butyric acid isomethyl ester), TiO 2 , SnO 2 , ZnO 2 , Al 2 O 3, C60, and ICBA (indenyl-C60 bisadduct). There is no particular limitation on the preparation of the electron transport layer, and conventional methods in the art for preparing the electron transport layer can be used, including but not limited to one or more of spin coating, spraying, spray pyrolysis, slot coating, and atomic layer deposition. Process parameters can be adjusted according to the target thickness of the electron transport layer.

[0075] Materials suitable for the buffer layer of the present invention include but are not limited to BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) or MoOx (molybdenum oxide), etc. There is no particular limitation on the preparation of the buffer layer, and conventional methods in the art for preparing the buffer layer can be used, including but not limited to one or more of spin coating, spraying, spray pyrolysis, slot coating, and atomic layer deposition. Process parameters can be adjusted according to the target thickness of the buffer layer.

[0076] Materials suitable for the electrodes of the present invention can be selected from one or more of silver, copper, Au (gold), ITO, IZO, AZO, and IWO.

[0077] Therefore, the present invention also provides a perovskite solar cell, which may include a conductive substrate, a hole transport layer, a perovskite light-absorbing layer (the perovskite thin film described herein), a passivation layer, an electron transport layer, a buffer layer, and an electrode arranged in sequence.

[0078] 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 starting compounds in the examples can be obtained through commercial channels.

[0079] Example 1

[0080] Step S1a: Provide a conductive substrate 1, the conductive substrate 1 is fluorine-doped tin oxide (FTO), with a size of 300*400 mm; and clean the conductive substrate 1, and blow it dry with nitrogen after cleaning;

[0081] Step S2a: Dissolve the material Me-4PACz of the hole transport layer in an ethanol solution to prepare a hole transport layer solution, with the concentration of Me-4PACz being 0.6 mg / mL; then coat the hole transport layer solution on the upper surface of the conductive substrate 1 by the method of slot coating and perform hot plate annealing treatment to remove the solvent, to obtain a prepared hole transport layer 2, the annealing temperature is 100 °C, the time is 5 min, and the thickness of the hole transport layer 2 is 1.5 nm;

[0082] Step S3a: Mix the perovskite materials FAI, PbI 2 , MACl, PbCl 2, After mixing CsI powder to obtain a mixture, 25 mL of an organic solvent (DMF:NMP volume ratio of 6.5:1) was added to the mixture to dissolve the mixture, obtaining a perovskite precursor solution with a molar concentration of 1.2 mol / L of FA 0.9 Cs 0.1 PbI 3 ; The perovskite precursor solution was coated on the upper surface of the hole transport layer 2 by slot coating to form a perovskite wet film; after the wet film was dried in vacuum, a hybrid microwave annealing treatment was carried out. The specific steps were as follows: A silicon wafer was used as the microwave susceptor, with a size of 320*420 mm and a thickness of about 300 μm. The perovskite wet film was placed on the silicon wafer and then transferred to a microwave device, and microwave heating treatment was carried out at a certain power. During this period, an infrared probe was used to monitor the temperature of the perovskite film and the microwave susceptor. The microwave frequency was 2450 MHz, the microwave power was 1000 W, and the microwave heating time was 3 min; the upper limit of the microwave heating temperature was 200 °C; a perovskite light-absorbing layer (perovskite film) 3 was obtained. The schematic diagram of its hybrid microwave annealing method is as Figure 1 shown.

[0083] Step S4a: The passivation layer material 1,4-phenylenediamine hydroiodide (PDADI) was deposited on the upper surface of the perovskite light-absorbing layer 3 by evaporation to form a passivation layer 4 with a thickness of 1 nm;

[0084] Step S5a: C was deposited on the upper surface of the passivation layer 4 by thermal evaporation 60 to form an electron transport layer 5 with a thickness of 15 nm;

[0085] Step S6a: Tin oxide (SnO 2 ) was deposited on the upper surface of the electron transport layer 5 by atomic layer deposition to form a buffer layer 6 with a thickness of 20 nm;

[0086] Step S7a: Cu was deposited on the upper surface of the buffer layer 6 by thermal evaporation to form an electrode 7 with a thickness of 100 nm.

[0087] The finally prepared perovskite solar cell is as Figure 2 shown, which includes a conductive substrate 1, a hole transport layer 2, a perovskite light-absorbing layer 3, a passivation layer 4, an electron transport layer 5, a buffer layer 6, and an electrode 7 stacked in sequence.

[0088] Example 2

[0089] The perovskite solar cell of Example 2 was prepared according to the preparation method of Example 1, except that in step S3a, the microwave susceptor in the preparation method of the perovskite light-absorbing layer was a thin graphite plate with dimensions of 320*420 mm and a thickness of about 1 mm; the microwave frequency was 2450 MHz, the microwave power was 500 W, the heating time was 1 - 2 min, and the upper limit of the heating temperature was 200 °C.

[0090] Example 3

[0091] The perovskite solar cell of Example 3 was prepared according to the preparation method of Example 1, except that in step S3a, the microwave susceptor in the preparation method of the perovskite light-absorbing layer was graphite powder with a mesh number of 800, which was densely paved under the glass substrate and the surface was gently compacted, with a thickness of about 2 mm; the microwave frequency was 2450 MHz, the microwave power was 500 W, the heating time was 1 - 2 min, and the upper limit of the heating temperature was 200 °C.

[0092] Comparative Example 1

[0093] The perovskite solar cell of Comparative Example 1 was prepared according to the preparation method of Example 1, except that in the preparation method of step S3a, the annealing treatment was carried out by conventional hot plate annealing, the annealing temperature was 130 °C, and the annealing time was 20 min.

[0094] Comparative Example 2

[0095] The perovskite solar cell of Comparative Example 2 was prepared according to the preparation method of Example 1, except that in step S3a, no microwave susceptor was used in the preparation method of the perovskite light-absorbing layer. The perovskite thin film after vacuum drying was directly placed in the microwave equipment. The microwave power was 1000 W, the microwave heating time was 8 min, the microwave frequency was 2450 MHz, and the upper limit of the heating temperature was 200 °C. When there was no microwave susceptor, after the perovskite thin film absorbed microwave energy, it reached 200 ± 5 °C in about 7 min.

[0096] Test Example 1

[0097] The perovskite solar cells prepared in Examples 1 - 3 and Comparative Examples 1 - 2 of the present application were subjected to performance tests to obtain the open-circuit voltage Voc, fill factor FF, short-circuit current density Jsc, and photoelectric conversion efficiency PCE of the corresponding battery devices.

[0098] The test temperature was 25 ± 1 °C. The current density–voltage curves (J-V curves) of the devices were measured by a source meter (Keithley 2400) under the AM1.5G (100 mW / cm 2) Obtained under illumination. Before testing, the light intensity was calibrated by a standard silicon cell, and the scanning rate was 10 mV / s.

[0099] The test results are shown in Table 1.

[0100] Table 1 Performance test results of perovskite solar cells in Examples 1 - 3 and Comparative Examples 1 - 2

[0101]

[0102] As can be seen from Table 1, compared with Comparative Example 1, in Examples 1 - 3, when using silicon wafers or thin graphite plates or graphite powder as microwave sensitives to perform microwave annealing on the perovskite wet film after vacuum drying treatment, the wet film is more stable during the crystallization process, the perovskite annealing is more uniform and efficient, the internal defects of the film are significantly reduced, and the non-radiative recombination of the perovskite film is reduced. Moreover, the heating rate of the silicon wafer after absorbing microwave energy is more appropriate compared with the graphite plate and graphite powder.

[0103] Compared with Comparative Example 1, the short-circuit current density of Example 1 increased by about 1.25 mA / cm 2 , the open-circuit voltage increased by 70 mV, and the power conversion efficiency increased from 17.02% to 20.11%. From the results of Example 1 and Comparative Example 2, it can be seen that when microwave direct annealing is carried out without using a microwave sensitive, the perovskite wet film directly absorbs microwave energy, causing the solvent to volatilize rapidly and form a phase. However, due to the differences in the composition and thickness uniformity of the perovskite wet film; the perovskite film finally obtained in Comparative Example 2 has limited improvement compared with Comparative Example 1, the open-circuit voltage increased by 20 mV, and the short-circuit current density increased by about 0.49 mA / cm 2 , but the increase in the fill factor is not significant, and the power conversion efficiency only increased to 0.56%.

[0104] Test Example 2

[0105] Perform SEM scans on the perovskite films of Examples 1 - 3 and Comparative Examples 1 - 2, and the obtained images are as Figure 3 shown.

[0106] Through Figure 3From the scanning electron microscope images, it can be seen that the grain size in the perovskite film of Comparative Example 1 annealed by conventional hot plate is comparable to that in the perovskite film of Comparative Example 2 annealed by conventional microwave, but the grain arrangement is not dense and the grain boundaries are obvious, meaning that the density of bulk defects is greater and the recombination of bulk phase defects is more serious. In the perovskite film of Comparative Example 2 annealed by conventional microwave, the grain boundaries are significantly reduced. After the perovskite films of Examples 1-3 are treated by hybrid microwave annealing with microwave-sensitive bodies, the perovskite grain arrangement is more dense and the micro-flatness of the film surface is significantly improved, indicating that the bulk phase defects of the film are significantly reduced and the crystallization quality is greatly improved. This shows that the microwave annealing mode and the use of a suitable microwave-sensitive body can achieve rapid and uniform annealing of the perovskite film, greatly improve the crystallinity of the perovskite film and effectively improve the uniformity during large-area preparation, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

Claims

1. A method for annealing a perovskite film, characterized in that: It includes: The perovskite film formed from the perovskite precursor solution is placed on a planar microwave sensitive material for microwave annealing.

2. The annealing method according to claim 1, characterized in that The microwave sensitive body material is selected from one or more of silicon wafers, graphite powder and graphite plates.

3. The annealing method according to claim 1, characterized in that The time required for microwave annealing is limited to heating the perovskite material to be treated to a temperature 5-10° C. lower than the tolerable temperature of the perovskite material to be treated.

4. The annealing method according to claim 3, characterized in that: The microwave annealing time is within 10 min, such as 0.2-10 min or 1-3 min or 3-8 min; and / or The upper limit of the heating temperature of microwave annealing is controlled to be 200°C.

5. The annealing method according to claim 1, characterized in that: The microwave power is 100W-1000W, such as 100-400W, 400-500w, 500-800w or 800-1000w.

6. The annealing method according to claim 1, characterized in that: The process parameters of the microwave annealing are: The microwave sensitive body is a silicon wafer, the microwave power is 800-1000W, and the annealing time is 1-3min; or The microwave sensitive body is a graphite plate, the microwave power is 400-500W, and the annealing time is 1-2min; or the microwave sensitive body is graphite powder, the microwave power is 400-500W, and the heating time is 0.2-1min.

7. The annealing method according to claim 1, characterized in that: In the perovskite precursor solution, the chemical formula of the perovskite is recorded as an ABX3 structure, A includes one or more of a methylammonium cation, a methylammonium cation and a cesium ion, B includes a lead ion and / or a tin ion, and X is a halogen anion; The concentration of perovskite in the perovskite precursor solution is 1 mol / L to 2 mol / L; The solvent of the perovskite precursor solution is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and acetonitrile; The perovskite film is obtained by coating a perovskite precursor solution on a conductive substrate, and the conductive substrate is a conductive substrate, or a conductive substrate + a hole transport layer.

8. A method for preparing a perovskite film, comprising the following steps: Step S1: providing a perovskite precursor solution; Step S2: coating the perovskite precursor solution on a conductive substrate to obtain a perovskite wet film, and performing a crystallization treatment to obtain a perovskite thin film after removing the solvent; Step S3: placing the perovskite film on a planar microwave sensitive material and performing microwave annealing treatment.

9. The method according to claim 8, characterized in that The microwave annealing treatment is as described in any one of claims 1-7.

10. A perovskite film, characterized in that: The film is prepared by the annealing method of the perovskite film according to any one of claims 1 to 7 or the preparation method of the perovskite film according to claim 8 or 9.

11. A method for preparing a perovskite solar cell, characterized in that: The method comprises the steps of sequentially arranging a hole transport layer, a perovskite light absorbing layer, a passivation layer, an electron transport layer, a buffer layer and an electrode on a conductive substrate, wherein the perovskite light absorbing layer is arranged by adopting the steps of preparing a perovskite film as described in claim 8 or 9. 12.Select from the following applications: Application of planar microwave sensitive materials in the preparation of perovskite films with improved crystallinity and uniformity; Use of the annealing method of the perovskite film according to any one of claims 1 to 7 in the preparation of a perovskite solar cell.

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