Polymer annealing pretreatment perovskite film, preparation method, application and battery

Abstract

The invention relates to a polymer annealing pretreatment perovskite film, a preparation method, application and a battery. The preparation method sequentially comprises the following steps: cleaning ITO glass, and preparing an electron transport layer on the ITO glass after ultraviolet ozone treatment; transferring the substrate into a glove box, and preparing a perovskite wet film through a two-step spin-coating method; spin-coating a polymer solution on the perovskite precursor wet film, wherein the polymer comprises a hydrophobic polymer material; and the perovskite precursor wet film spin-coated with the polymer solution is transferred to an air environment outside a glove box for annealing treatment, so that a perovskite light absorption layer is formed in the annealing process, and meanwhile, the polymer solution forms a polymer water-blocking packaging layer covering the perovskite light absorption layer. The method can effectively reduce the efficiency reduction caused by the humidity problem in the annealing process of the perovskite in the air when the perovskite is prepared by a two-step method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of perovskite solar cell box cover, and particularly relates to a polymer annealing pretreated perovskite film, a preparation method, application and a battery. BACKGROUND

[0002] Spin coating is one of the most common laboratory techniques for preparing perovskite thin films. It is widely used in the preparation of perovskite solar cells, photodetectors and other devices due to its simple operation, high uniformity and easy control. According to the different processing methods and film forming mechanisms, spin-coated perovskite is mainly divided into one-step spin coating and two-step spin coating. The one-step spin coating method is difficult to accurately control the crystallization process, and is prone to needle-shaped crystals, pores or unreacted precursor residues, and the thin film uniformity is poor (especially for large-area preparation). The two-step spin coating method has more complete ion reaction, high crystallinity (crystal size can reach microns), and less defects (especially bulk phase defects), and the device efficiency is generally higher than that of one-step method.

[0003] After two-step spin coating of perovskite, annealing in air is generally selected. The essence is to balance the process cost and film quality, and to use the trace amount of moisture and moderate oxygen in the air environment to control the perovskite crystallization kinetics and promote the formation of high crystallinity and low defect thin films. The environmental requirement is to avoid the degradation risk of air components (moisture, oxygen) on perovskite, while maximizing its promotion effect on crystallization. The core of the two-step method (first spin-coating PbI2, then spin-coating organic cation salt such as FAI / MAI) is to make the organic cation react with PbI2 to form perovskite phase (ABX3), and the necessity of annealing in air is reflected in: 1. "Accelerate ion diffusion" with air humidity, reduce unreacted defects The reaction of PbI2 with organic cations (such as FA + , MA + ) needs to be realized through "ion migration": organic cations need to diffuse into the PbI2 lattice to replace part of the positions to form a perovskite structure. The trace amount of moisture (usually 30-50% RH) in the air can act as a "weak medium" to slightly dissolve the ions on the surface of the organic cation salt (such as FA + ), reduce its diffusion activation energy (about 15% reduction), and accelerate the penetration into the PbI2 layer. Compared with the "pure thermal driven" diffusion in inert gas (N2 / Ar), this "humidity assisted diffusion" can reduce the residual PbI2 due to incomplete reaction (especially at the film interface), reduce bulk phase defects (such as iodine vacancies), and increase the purity of perovskite phase by more than 20%.

[0004] 2. Reduce "inert gas dependence", adapt to low-cost experiment and mass production needs Inert gas annealing requires a glove box or sealed reaction chamber, which is expensive (glove box costs approximately 100,000-200,000 RMB) and complex to operate (requiring continuous charging of high-purity N2 / Ar). However, for more stable perovskite systems (such as those containing Cs...),... + The ternary system, FA + (A binary system with inert gas as the main component), air annealing can be carried out directly in an open environment, eliminating the need for inert gas consumption (approximately 0.5-1 m³ per hour). 3 And equipment maintenance costs. Even for the less stable MA-based perovskites, the effects of oxygen and moisture in the air during short-term (5-10 minutes) annealing are significant.

[0005] 3. Utilizing oxygen to "passivate surface defects" and improve the conductivity of thin films. Trace amounts of O2 in the air (21% by volume) can react with uncoordinated Pb on the surface of the perovskite film. 2+ The oxygen binds to form Pb-O bonds, passivating surface dangling bonds (a common type of nonradiative recombination center). Experimental data show that perovskite films annealed in air can reduce surface defect state density by 30-40%, corresponding to a 10-15% increase in carrier mobility. This "oxygen passivation" effect cannot be achieved in an inert gas environment and requires additional processing steps (such as O2 plasma) to compensate. However, this process can be controlled within an acceptable range (device efficiency loss <1%), making it suitable for low-cost exploratory experiments.

[0006] The annealing process for perovskite is not suitable for all air environments and requires strict control of key parameters. The core principle is to utilize favorable air factors (humidity, O2) and avoid harmful factors (degradation caused by excessive water / oxygen), with humidity control being the most crucial. Annealing two-step perovskite films in high humidity environments (typically relative humidity RH > 60%) will trigger a series of chain reactions through the chemical interaction between water vapor and perovskite, as well as disruption of crystallization kinetics. This ultimately leads to a significant degradation in film quality and device performance. The specific adverse consequences can be analyzed from the following perspectives: I. Crystal structure destruction and impurity phase formation 1. Perovskite phase decomposition and chemical corrosion In high humidity environments, water vapor acts as a reaction medium in the hydrolysis of perovskite. Organic cations (such as MA) + FA + It readily reacts with water to produce volatile amines (such as methylamine MA=CH3NH2) and hydroiodic acid (HI), with the reaction formula being: CH3NH3PbI3+H2O→CH3NH2↑+PbI2+HI.

[0007] The generated HI further reacts with water vapor to form hydroiodic acid solution, which corrodes the perovskite lattice, leading to the degradation of Pb. 2+Leakage (concentration can be from 10 -7 mol / L to 10 -4 mol / L), and white flocculent Pb (OH)2impurity phase is formed on the surface of the film layer (Pb 4f orbital binding energy can be detected by XPS 0.8eV shift).

[0008] 2. Decreased crystalline integrity and increased grain boundary defects In the two-step method, the core of annealing is to promote the ion diffusion and lattice recombination of organic amine salt (such as CH3NH3I) and PbI2. High humidity will disturb the crystallization process in the following ways: Solvent evaporation imbalance: water vapor will delay the evaporation of residual solvents (such as DMF, DMSO) in the PbI2layer, resulting in uneven penetration rate of organic amine salt, and "dendritic growth" at the crystallization front, rather than dense polyhedral grains.

[0009] Grain boundary loosening: the size distribution of perovskite grains formed under high humidity changes from 200-300nm to 100-500nm (SEM observation), the grain boundary area increases by more than 30%, and the unreacted PbI2and organic amine salt are easily left at the grain boundary, forming carrier recombination centers.

[0010] Experimental data show that the photoluminescence (PL) intensity of the film layer annealed at RH=70% is only 50% of that at RH=30%, and the fluorescence lifetime is shortened from 200ns to 80ns, proving that the non-radiative recombination of carriers is significantly enhanced.

[0011] II. Direct degradation of device performance 1. Core electrical parameter degradation Open-circuit voltage (Voc) drop: grain boundary defects and impurity phases cause Fermi level pinning, Voc can be reduced from 1.1V to 0.9V (taking MAPbI3as an example).

[0012] Short-circuit current (Jsc) decay: water vapor-induced lattice distortion reduces the light absorption coefficient (from 1.5×10 5 cm -1 to 8×10 4 cm -1 at 550nm), while the carrier mobility decreases by more than 50%, resulting in a decrease in Jsc from 2 mA / cm 2 to 16 mA / cm 2 .

[0013] Fill factor (FF) reduction: interface contact resistance increases due to water vapor erosion (from 10Ω·cm 2 to 50Ω·cm 2 ), and the series resistance increases, resulting in a decrease in FF from 80% to less than 60%.

[0014] In summary, high humidity annealing can cause the initial efficiency of the device to drop from 21% to below 15%, or even completely fail.

[0015] 2. Long-term stability collapse High humidity annealing not only affects the immediate performance, but also hides the long-term aging risk: The hydrated perovskite phase formed during annealing (such as MAPbI3·H2O) is prone to phase transition during subsequent storage or operation, leading to film cracking and peeling.

[0016] Residual PbI2 will catalyze the generation of reactive oxygen species (ROS) under light, accelerating the oxidative degradation of the charge transport layer (such as Spiro-OMeTAD).

[0017] Experiments show that after 100 hours of storage in an RH=60% environment, the efficiency retention rate of devices annealed at high humidity (70% RH) is only 30%, while devices annealed at normal humidity (30% RH) can still maintain more than 80%.

[0018] Currently, for the two-step method of preparing perovskite solar cells, the main method is to control the temperature and humidity, which is more dependent on weather and geographical location, and the repeatability may be poor for perovskite.

[0019] Looking back at the development of perovskite materials, early studies of device physics revealed that perovskite crystal quality (e.g., crystallinity, film morphology, stoichiometry, etc.) profoundly affects the efficiency of cells and modules. At the same time, its stability has gradually improved, and the working life of high-efficiency cells has been extended to several thousand hours, gradually approaching the requirements of actual use. In the context of device aging, crystal quality has once again become the focus of research, focusing on the evolution of film properties over time, which is controlled by thermodynamic and kinetic factors, including composition, chemical potential, structure, phase transition and segregation, ion migration and defect concentration. In order to promote the commercialization of the perovskite photovoltaic industry, it is important to develop scalable solution processes with sufficient reproducibility. Research should extend the study of crystal quality from multiple angles, so as to accurately control the perovskite crystallization kinetics throughout the film under any atmosphere. However, it will be very difficult to do this. First, the formation of perovskite includes the reaction between Lewis acid and Lewis base, which occurs rapidly and spontaneously even at low temperatures. Second, the halide perovskite generally used in experiments is usually a mixture, where different components exhibit different reactivity and diffusivity during film growth. In addition, perovskite films are very sensitive to moisture and many solvents, which leads to considerable differences in every small change in conditions during processing.

[0020] According to the LaMer model, high-quality perovskite films usually have large grain sizes, which can be achieved by delaying nucleation and promoting crystal growth. Several strategies have been successfully applied to reduce the nucleation rate, which can effectively affect the crystallization kinetics, increase the grain size, and obtain high-quality perovskite films. In addition, it has been reported that higher annealing temperature or longer annealing time can increase the crystallinity of perovskite by increasing the crystal growth rate or inducing recrystallization process. However, it is often found that simultaneous defects caused by the loss of volatile components are disadvantageous, accompanied by significant inhomogeneity in the film on a larger area. In addition, local fluctuations in the processing atmosphere result in films with different qualities, thus poor reproducibility. Therefore, it is challenging to develop a simple, controllable and effective annealing technique to meet the requirements of scalable and repeatable manufacturing.

[0021] The team of Professor Hai-Rui Tan from Nanjing University proposed using low-polarity solvent n-butanol (nBA) to replace traditional ethanol / isopropanol, reducing the solution hygroscopicity. In an air environment, the evaporation rate of nBA can precisely control the water penetration, avoiding the decomposition of perovskite during annealing. This method makes the large-area perovskite / crystalline silicon tandem cell efficiency reach 29.4% (certified 28.7%), and still maintains 96.8% of the initial efficiency after 780 hours of maximum power point tracking. As a low-polarity solvent, the core mechanism of n-butanol (nBA) replacing traditional ethanol / isopropanol lies in precisely regulating the solvent evaporation rate and water penetration balance. Compared with ethanol (polarity index 4.3), the polarity index of n-butanol is lower (3.9), and the boiling point is higher (117.7°C), which can achieve better results in the two-step perovskite preparation.

[0022] The OACl pretreatment technology developed by the team of Professor Guo-Na Fang from Wuhan University can effectively reduce the surface halogen vacancies by 50% before annealing, and the surface halogen vacancies can be reduced by 50% before annealing. - Interaction with halogen vacancies, OA + Coordination with A-site vacancies, restructuring perovskite grain boundary structure. This method changes the decomposition mode of perovskite from grain boundary to surface, significantly improving the moisture and heat resistance. The unsealed device maintains 81% efficiency after 1000 hours of continuous operation in 55°C nitrogen, and the photoelectric conversion efficiency reaches 24.95%.

[0023] The low polarity (polarity index 3.9) and high boiling point (117.7°C) of n-butanol (nBA) enable it to suppress solution hygroscopicity and delay solvent evaporation in the two-step method, thereby reducing water vapor erosion of perovskite during annealing. However, when the humidity exceeds 60%, the hydrophobic advantage of n-butanol may be weakened by the following factors.

[0024] 1. Water vapor penetration risk: Although n-butanol evaporates slowly, water vapor in a high humidity environment can still penetrate through the grain boundaries or incomplete coverage areas, leading to perovskite decomposition; 2. Kinetics imbalance: High humidity can prolong the solvent evaporation time, which may lead to incomplete perovskite crystallization, increase the residual PbI2 content, and affect the stability of the device.

[0025] OACl through Cl - Coordination repair halogen vacancies and OA + Electrostatic adsorption of A-site vacancies, restructuring of perovskite grain boundary structure, and change of decomposition mode from grain boundary to surface. However, when the humidity exceeds 60%, the following problems may be highlighted: 1. Cl - Hydrolysis risk: Cl - May react with water vapor to generate HCl, corroding the perovskite surface.

[0026] 2. Interfacial side reaction: OACl is easy to decompose at high temperature (> 150℃), and the released amine substances may react with perovskite to form an insulating layer, reducing the fill factor.

[0027] In view of the above defects, the present design person actively studies and innovates to create a polymer annealing pretreatment perovskite film, a preparation method, an application and a battery, so that it has more industrial use value. SUMMARY

[0028] To solve the above technical problems, the purpose of the present application is to provide a polymer annealing pretreatment perovskite film, a preparation method, an application and a battery.

[0029] To achieve the above purpose, the present application adopts the following technical solutions: One of the purposes of the present application is: A preparation method of a polymer annealing pretreatment perovskite film, comprising the following steps in sequence: Step 1: Clean the ITO glass, and prepare an electron transport layer on it after ultraviolet ozone treatment; Step 2: Transfer the substrate into a glove box, and prepare a perovskite wet film by a two-step spin coating method; Step 3: Spin-coat a polymer solution on the perovskite precursor wet film, the polymer comprising a hydrophobic polymer material; Step 4: Anneal the perovskite precursor wet film with the spin-coated polymer solution in an air environment outside the glove box, so that the perovskite light-absorbing layer is formed during the annealing process, and the polymer solution forms a polymer water-blocking encapsulation layer covering the perovskite light-absorbing layer.

[0030] As a further improvement of the present application, the hydrophobic polymer material is a styrene-based block copolymer, and the styrene-based block copolymer is at least one or a combination of more than one of SEBS, SIS and SBS.

[0031] As a further improvement of the present application, the styrene block copolymer is SEBS.

[0032] As a further improvement of the present application, the solvent of the polymer solution is at least one or a combination of more than one of toluene, xylene, chlorobenzene, tetrahydrofuran; the concentration of the polymer solution ranges from 1 to 10 mg / mL.

[0033] As a further improvement of the present application, in step 3, the spin coating speed is 1000-6000 rpm, the spin coating time is 20-60 seconds, and the thickness of the polymer water-blocking encapsulation layer is 20-200 nm; in step 4, the annealing temperature is 100-180℃, and the annealing time is 5-30 minutes.

[0034] As a further improvement of the present application, in the step 4, annealing at 100-150℃ for 10-30 minutes in air with humidity of 10-90 RH%.

[0035] The second object of the present application is: A polymer annealing pretreated perovskite film, the perovskite film is prepared by the method of any one of the above; the perovskite film comprises a perovskite light-absorbing layer and a polymer water-blocking encapsulation layer covering thereon.

[0036] The third object of the present application is: A use of a polymer in the preparation of a perovskite solar cell, the polymer comprises a hydrophobic polymer material, the hydrophobic polymer material is a styrene block copolymer, a solution of the styrene block copolymer is spin-coated on a perovskite precursor wet film, and a polymer water-blocking encapsulation layer is formed after annealing treatment.

[0037] The fourth object of the present application is: A perovskite solar cell, the solar cell comprises a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode which are sequentially stacked, the perovskite light-absorbing layer is the perovskite film described above; or, a polymer water-blocking encapsulation layer described above is arranged between the perovskite light-absorbing layer and the hole transport layer.

[0038] As a further improvement of the present application, the material of the perovskite light-absorbing layer is an organic-inorganic hybrid perovskite material, and its general formula is ABX3; wherein the A-site cation is selected from one or more of formamidinium ion (FA + ), methylammonium ion (MA + ), cesium ion (Cs + ); the B-site cation is Pb 2+ ; and the X-site halide anion is selected from one or more of I - , Br - , Cl - .

[0039] By the above scheme, the present application has at least the following advantages: The present application can effectively reduce the efficiency decline of perovskite caused by humidity problem during the annealing process of perovskite in air when the perovskite is prepared by a two-step method.

[0040] The present application can reduce the high requirement for environment during the preparation of perovskite, and is more suitable for large-scale application.

[0041] The polymer encapsulation layer formed by the present application can effectively block the erosion of moisture and oxygen in the subsequent working environment, and significantly improve the long-term working stability of the device.

[0042] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, the following is the preferred embodiment of the present application and the detailed description of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, it should be understood that the following drawings only show some embodiments of the present application, therefore should not be regarded as a limitation on the scope, for those skilled in the art, without creative labor, other related drawings can also be obtained according to these drawings.

[0044] Figure 1 is the flowchart of the second embodiment of the present application; Figure 2 is the schematic diagram of the thin film of perovskite after annealing of the first embodiment of the present application; Figure 3 is the schematic diagram of the thin film after polymer annealing pretreatment in the second embodiment of the present application Figure 1 ; Figure 4 is the schematic diagram of the thin film after polymer annealing pretreatment in the second embodiment of the present application Figure 2 ; Figure 5 is the schematic diagram of the thin film after polymer annealing pretreatment in the second embodiment of the present application Figure 3 ; Figure 6 is the schematic diagram of the device efficiency of the first embodiment and the second embodiment of the present application when the annealing of perovskite thin film is carried out under the humidity close to 90RH%; Figure 7 is the schematic diagram of the test results of open-circuit voltage (Voc) of the first embodiment and the second embodiment of the present application under the conditions of 20℃ / 33RH% and 25℃ / about 90RH%, respectively; Figure 8are the test results of short-circuit current density (Jsc) of the first and second embodiments of the present application under conditions of 20℃ / 33RH% and 25℃ / about 90RH%, respectively; Figure 9 are the test results of fill factor (FF) of the first and second embodiments of the present application under conditions of 20℃ / 33RH% and 25℃ / about 90RH%, respectively; Figure 10 are the test results of photoelectric conversion efficiency (PCE) of the first and second embodiments of the present application under conditions of 20℃ / 33RH% and 25℃ / about 90RH%, respectively. DETAILED DESCRIPTION

[0045] The specific embodiments of the present application will be further described in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0046] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0047] First embodiment of the present application: The preparation method of the polymer annealing pre-processed perovskite film of the present embodiment comprises the following steps in sequence: Step 1: Clean the ITO glass, and prepare the electron transport layer thereon after ultraviolet ozone treatment.

[0048] Step 2: Transfer the substrate into a glove box, and prepare a perovskite wet film by a two-step spin coating method.

[0049] Steps 1 and 2, i.e., a CsFAMA ternary cation mixed halide perovskite layer is prepared by a two-step spin coating method.

[0050] Step 3: Directly anneal on a 150℃ hot stage.

[0051] The thin film of the perovskite after annealing in the present embodiment is shown in Figure 2 .

[0052] Second embodiment of the present application: The embodiment develops a method of annealing pre-treatment of perovskite film, which is used to regulate the growth process of perovskite film, less dependent on the processing atmosphere, and suitable for all-weather indoor manufacturing, and is an effective method of perovskite film formation regulation to improve the performance and stability of devices.

[0053] As Figure 1 The preparation method of the perovskite film of the embodiment comprises the following steps in sequence: Step 1: clean the ITO glass, and prepare an electron transport layer thereon after ultraviolet ozone treatment.

[0054] Step 2: transfer the substrate into a glove box, and prepare a perovskite wet film by a two-step spin coating method.

[0055] Step 1 and Step 2, namely, the CsFAMA ternary cation mixed halide perovskite layer is prepared by a two-step spin coating method.

[0056] Step 3: spin-coat a polymer solution on the perovskite precursor wet film, the spin-coating speed is 1000-6000 rpm, the spin-coating time is 20-60 seconds, and the thickness of the polymer water-blocking encapsulation layer is 20-200 nm. The polymer comprises a hydrophobic polymer material. The hydrophobic polymer material is a styrene-based block copolymer, and the styrene-based block copolymer is SEBS.

[0057] The solvent of the polymer solution is at least one or a combination of more than one of toluene, xylene, chlorobenzene, and tetrahydrofuran; and the concentration of the polymer solution ranges from 1 mg / mL to 10 mg / mL.

[0058] Step 4: transfer the perovskite precursor wet film on which the polymer solution is spin-coated to an air environment outside the glove box for annealing treatment, so that the perovskite light-absorbing layer is formed in the annealing process, and the polymer solution forms a polymer water-blocking encapsulation layer covering the perovskite light-absorbing layer.

[0059] The annealing treatment in the embodiment is as follows: The annealing temperature is 100-180°C, and the annealing time is 5-30 minutes.

[0060] The polymer annealing pre-treatment substantially leads to different film morphology and quality, such as Figures 3-5 After the polymer annealing pre-treatment, the color of the perovskite thin film changes obviously, that is, the polymer annealing pre-treatment realizes regulation in the perovskite film formation process.

[0061] The core of the embodiment lies in the unique sequence and combination of Step S2 and S3. The sequence of "spin-coating a polymer on a wet film" and then "annealing together" is a key that cannot be exchanged. The design makes the polymer solution layer play a dual role in the annealing process: Physical barrier: In the initial stage of heat treatment, the polymer solution layer acts as a layer of flowable liquid protection, effectively isolating the perovskite precursor from the high humidity environment, avoiding water-induced decomposition.

[0062] In-situ encapsulation layer formation: In the later stage of heat treatment, as the solvent evaporates, the polymer forms an integrated encapsulation layer in-situ, which is dense, hydrophobic, and closely adheres to the perovskite surface. This is fundamentally different from the method of covering a pre-prepared solid film (such as PDMS) in the prior art. The encapsulation layer formed by the present invention has better interface contact and better stability.

[0063] Synergy of SEBS (i.e. polymer water-blocking encapsulation layer) spin coating and annealing in this embodiment: Spin coating ensures uniform initial coverage of the SEBS layer, while the annealing process promotes further densification of the SEBS layer and may enable it to form a more intimate contact with the perovskite surface, while completing the crystallization process of the perovskite. These two steps must be carried out in sequence and are indispensable, together constituting the core of "polymer annealing pretreatment".

[0064] Synergy of SEBS layer and perovskite crystallization process in this embodiment: The SEBS layer may adjust the microenvironment of solvent evaporation and crystal growth on the surface of perovskite during the annealing process. Its hydrophobicity effectively blocks external water vapor, while its possible micropores or channels may allow selective permeation of solvent molecules, thereby avoiding problems such as bubbling and promoting more orderly crystallization. This is a dynamic and intelligent protection.

[0065] Seamless integration of this embodiment with traditional two-step method: This embodiment is an enhancement rather than a revolution of the existing two-step method. It is ingeniously embedded after spin coating of organic salt and before final annealing, without changing the core process of the previous and subsequent steps, demonstrating good compatibility and industrialization potential.

[0066] In order to evaluate the environmental tolerance of the polymer annealing pretreatment process, we performed annealing of perovskite thin films under a humidity of nearly 90 RH%. The equipment used and the device efficiency produced are shown in Figure 6 As can be seen from the statistical chart, under the environmental conditions of 90 RH%, the perovskite film under standard conditions (Pristine) will be easily eroded by moisture due to its hydrophilicity, resulting in a decrease in efficiency, with an average efficiency decrease of more than 3%. After polymer annealing pretreatment (SEBS), the perovskite film exhibits hydrophobicity and strong resistance to moisture invasion, with almost no efficiency loss under a humidity of 90 RH%.

[0067] Naturally, we placed the treated devices and the standard samples in a 50 RH% constant humidity incubator to evaluate the stability of the perovskite solar cells after polymer annealing pretreatment. After 450 hours, the efficiency of the devices treated by polymer annealing pretreatment still remained more than 80%, while the efficiency of the standard devices had decayed to about 60% of the original.

[0068] Generally speaking, reproducible processing under variable environmental conditions is one of the main criteria for the commercialization of perovskite PVs to ensure low manufacturing costs. However, perovskites have been shown to be sensitive to moisture, which leads to variations in performance when manufactured at different humidity levels. Even when perovskites are annealed in a water-free environment, such as in a glovebox, the crystal quality is significantly affected by various volatile organic compounds. The polymer annealing pretreatment method does not laboriously and expensively control the annealing atmosphere, but is less dependent on the manufacturing environment, as the polymer annealing pretreatment creates a stable microenvironment. Therefore, we also studied its reproducibility under all-weather indoor conditions.

[0069] CsFAMA perovskite solar cells were prepared in different humidity in the acrylic cavity, 20℃ / 33RH% and 25℃ / about 90RH%. As shown in FIG. 6, the efficiency of the standard sample decreased gradually with the increase of humidity, and the reproducibility became worse. However, there was no obvious performance difference in the SEBS annealing pretreatment device, most of which had a PCE of >20%, because the polymer annealing pretreatment effectively blocked the interference from the environmental conditions. This result shows the all-weather adaptability of the polymer annealing pretreatment technology for the wide manufacture of perovskite photovoltaic devices. Figures 7-10 wherein, Pristine is the first embodiment, and SEBS is the present embodiment.

[0070] The conventional annealing method strongly depends on the environmental atmosphere, resulting in a gradual decrease in the efficiency of the battery as the humidity increases, and the reproducibility becomes worse. There is no obvious performance difference in the SEBS annealing pretreatment device, most of which have a PCE of >20%, because the polymer annealing pretreatment effectively blocks the interference from the environmental conditions. This result shows the all-weather adaptability of the polymer annealing pretreatment technology for the wide manufacture of perovskite photovoltaic devices.

[0071] In addition, a dehumidifier or other equipment can also be used to reduce the indoor humidity to be controlled between 30-50 RH%, to ensure the high-quality crystallization of perovskite. Placing the perovskite in a glovebox with controllable humidity and controlling the humidity between 30-50 RH% is less costly than directly controlling the indoor humidity.

[0072] In summary, the "pretreatment + co-annealing" strategy of the present embodiment produces a "1+1>2" synergistic effect. It not only solves the humidity sensitivity problem in the film forming process, but also solves the stability problem of the device working for a long time at one time. The control of the crystallization environment and the packaging of the final device are realized at the same time by one-step process, which is not easily thought of by the prior art.

[0073] In traditional cognition, introducing other polymers in the key step of perovskite crystallization may hinder solvent evaporation, affect crystal growth, or introduce an insulating layer to cause device performance degradation. The present embodiment reverses the situation by selecting a specific hydrophobic block copolymer (such as SEBS) and optimizing the process. It is found that it not only does not degrade the performance, but also promotes the formation of high-quality perovskite thin films by creating a stable local microenvironment, especially in harsh environments, overcoming the technical bias.

[0074] Third embodiment of the present application: Unlike the second embodiment described above, the annealing process in the present embodiment uses inert gas-air step annealing: first pre-annealing at 100-120℃ for 5-10 minutes in nitrogen, then cleaning the surface residual organic salt with isopropanol, and finally annealing at 150-200℃ for 5-10 minutes in air with humidity of 30-40 RH%.

[0075] This process uses water vapor to promote the diffusion of organic salt, while avoiding direct exposure to a high-humidity environment, increasing the perovskite conversion rate to more than 98%, and improving the long-term stability of the device by 3 times.

[0076] Or in step 4, annealing in air with any humidity environment: annealing at 100-150℃ for 10-30 minutes in air with humidity of 10-90 RH%.

[0077] Fourth embodiment of the present application: The polymer annealing pre-treatment perovskite film of the present embodiment is prepared by any of the methods described above; the perovskite film includes a perovskite light-absorbing layer and a polymer water-blocking encapsulation layer covering it.

[0078] Fifth embodiment of the present application: The use of a polymer in the preparation of a perovskite solar cell in the present embodiment, the polymer comprises a hydrophobic polymer material, the hydrophobic polymer material is a styrene-based block copolymer, a solution of the styrene-based block copolymer is spin-coated on a perovskite precursor wet film, and a polymer water-blocking encapsulation layer is formed after annealing.

[0079] Sixth embodiment of the present application: The perovskite solar cell of the present embodiment includes a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode stacked in sequence, the perovskite light-absorbing layer is the perovskite film described above; or, a polymer water-blocking encapsulation layer is provided between the perovskite light-absorbing layer and the hole transport layer.

[0080] The material of the perovskite light-absorbing layer is an organic-inorganic hybrid perovskite material, and its general formula is ABX3; wherein the A-site cation is selected from formamidinium ion (FA +), a methylammonium ion (MA + ), a cesium ion (Cs + ) or a combination thereof; the B-site cation is Pb 2 + ; the halide anion at X is selected from one or more of I - , Br - , Cl - .

[0081] In the description of the present application, it is required to understand that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0082] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0083] The above is only the preferred embodiment of the present application, and is not used to limit the present application, it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be regarded as the protection scope of the present application.

Claims

1. A method for preparing a polymer-annealed pre-processed perovskite film, characterized by, The method comprises the following steps in sequence: Step 1: cleaning ITO glass, and preparing an electron transport layer on the ITO glass after UV-ozone treatment; Step 2: transferring the substrate into a glove box, and preparing a perovskite wet film by a two-step spin-coating method; Step 3: spin-coating a polymer solution on the perovskite precursor wet film, wherein the polymer comprises a hydrophobic polymer material; Step 4: transferring the perovskite precursor wet film spin-coated with the polymer solution to an air environment outside the glove box for annealing treatment, so that a perovskite light-absorbing layer is formed during the annealing process, and the polymer solution forms a polymer water-blocking encapsulation layer covering the perovskite light-absorbing layer.

2. The method of claim 1, wherein the annealing of the polymer pre-treated perovskite film is performed at a temperature of 100- 200 °C for 1- 10 minutes. The hydrophobic polymer material is a styrene-based block copolymer, and the styrene-based block copolymer is at least one or a combination of more than one of SEBS, SIS and SBS.

3. The method of claim 2, wherein the annealing is performed at a temperature of 150- 250 °C for 1-30 minutes. The styrene-based block copolymer is SEBS.

4. The method of claim 1, wherein the annealing of the polymer pre- treated perovskite film is performed at a temperature of 150- 250 °C for 1- 10 minutes. The solvent of the polymer solution is at least one or a combination of more than one of toluene, xylene, chlorobenzene and tetrahydrofuran; and the concentration of the polymer solution ranges from 1 to 10 mg / mL.

5. The method of claim 1, wherein the annealing of the polymer pre- treated perovskite film is performed at a temperature of 150- 250 °C for 1- 10 minutes. In the step 3, the spin-coating speed is 1000-6000 rpm, the spin-coating time is 20-60 seconds, and the thickness of the polymer water-blocking encapsulation layer is 20-200 nm; and in the step 4, the annealing temperature is 100-180℃, and the annealing time is 5-30 minutes.

6. The method of claim 1, wherein the annealing of the perovskite film is performed by a polymer annealing process. In the step 4, the annealing is performed at 100-150℃ for 10-30 minutes in air with a humidity of 10-90 RH%.

7. A polymer annealed pre-treated perovskite film, characterized in that, The perovskite film is prepared by the method of any one of claims 1-6; and the perovskite film comprises a perovskite light-absorbing layer and a polymer water-blocking encapsulation layer covering the perovskite light-absorbing layer.

8. Use of a polymer in the manufacture of a perovskite solar cell, characterized in that, The polymer comprises a hydrophobic polymer material, the hydrophobic polymer material is a styrene-based block copolymer, and a solution of the styrene-based block copolymer is spin-coated on a perovskite precursor wet film to form a polymer water-blocking encapsulation layer after annealing treatment.

9. A perovskite solar cell, characterized by, The solar cell comprises a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode which are stacked in sequence, and the perovskite light-absorbing layer is the perovskite film of claim 7; or a polymer water-blocking encapsulation layer as claimed in claim 7 is arranged between the perovskite light-absorbing layer and the hole transport layer.

10. The perovskite solar cell of claim 9, wherein the perovskite layer is formed by a two-step method. The material of the perovskite light-absorbing layer is an organic-inorganic hybrid perovskite material, and the general formula thereof is ABX3; wherein the A-site cation is selected from one or more of formamidinium ion (FA + ), methylammonium ion (MA + ), cesium ion (Cs + ); the B-site cation is Pb 2+ ; and the X-site halide anion is selected from one or more of I - , Br - , Cl - .

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