A perovskite solar cell and its preparation method

Abstract

The present application provides a perovskite solar cell and a preparation method thereof. A layer of dynamic self-healing interfacial material is inserted between the hole transport layer and the perovskite active layer of the perovskite solar cell; the dynamic self-healing interfacial material is formed by cross-linking lipoic acid and polyethyleneimine according to a certain ratio. The perovskite solar cell provided by the present application realizes in-situ self-healing of the perovskite active layer interface through the dynamic interaction between the disulfide bond of lipoic acid and the amino group in polyethyleneimine in the dynamic self-healing interfacial material. At the same time, the dynamic self-healing interfacial material reduces the interfacial barrier and improves the charge extraction efficiency through molecular dipole interaction, neutralizes the dangling bonds on the interface through the carboxyl group of lipoic acid, reduces the non-radiative recombination loss and improves the photoelectric conversion efficiency. The rich amino functional groups in it can form stable coordination bonds with the uncoordinated Pb²⁺ on the interface to passivate the deep-level defects. The perovskite solar cell obtained by the technical solution of the present application can improve the service life and power generation efficiency.

Description

Technical Field

[0001] This application relates to the field of production and manufacturing of perovskite batteries or perovskite thin films, and specifically relates to a perovskite battery and a preparation method thereof. Background Art

[0002] Perovskite solar cells (PSCs) have become an important carrier for the development of next-generation photovoltaic technologies due to their advantages such as high photoelectric conversion efficiency, low-cost preparation, flexibility, and light weight.

[0003] Currently, perovskite batteries still face some key problems that need to be solved urgently in practical applications. For example, under conditions such as thermal stress or environmental aging in the polycrystalline perovskite layer, defects such as Pb²⁺ dangling bonds and I⁻ vacancies are easily formed at the interface, leading to non-radiative recombination and ion migration, which affect the photoelectric performance and stability of the battery; the difference in thermal expansion coefficients between the substrate and the perovskite layer causes microcracks at the interface, accelerating water and oxygen penetration and device performance degradation. In addition, under the action of environmental factors such as light and high temperature, perovskite materials are prone to chemical decomposition and structural degradation, manifested as physical damages such as lattice expansion and contraction, further exacerbating ion migration and the formation of defects, and ultimately resulting in a significant decrease in the power generation efficiency and shortened lifespan of perovskite batteries.

[0004] In order to improve the power generation efficiency of perovskite batteries, passivation materials are usually used to modify the interface of the perovskite active layer, which can passivate the interface of the perovskite active layer and even reduce defects such as Pb²⁺ dangling bonds and I⁻ vacancies. Existing passivation materials (such as PEAI, BAI, OACl, etc.) usually only play a passivation role and cannot self-repair the perovskite active layer after damage. The damage to the perovskite active layer needs to be achieved by using special dynamic self-repair materials. Existing dynamic self-repair materials are generally dynamic covalent polymer materials, and doping methods are mostly used to introduce perovskite active materials. However, this doping method not only easily destroys the crystallinity of perovskite materials, increases the complexity of the process, and cannot balance the luminescence efficiency and stability of the device, but also has a complex synthesis process and high cost.

[0005] In addition, to address the difference in thermal expansion coefficients between the substrate and the perovskite layer, a research team from East China University of Science and Technology recently successfully developed an ultra-thin protective layer, a substrate composed of hard graphene and special transparent plastic. The thickness of this protective layer is only one ten-thousandth of a hair strand. By increasing the compressive capacity of the material, it effectively reduces the expansion amplitude of the substrate caused by light. Experiments show that after the perovskite battery continuously operates under strong light and high temperature for 3670 hours with the use of this new protective layer, the power generation efficiency can still remain at 97%, greatly improving the possibility of its practical application. This substrate mainly physically enhances the resistance to external environmental impacts through the graphene protective layer.

[0006] In summary, the existing passivation materials, dynamic self-healing materials, and corresponding protective layers can only focus on solving one type of problem in the practical application of perovskite solar cells respectively, and cannot improve the stability, lifespan, and power generation efficiency of perovskite solar cells simultaneously in multiple aspects (such as interface passivation, defect reduction, dynamic self-healing, and electron extraction efficiency). Therefore, it is of great significance to develop a dynamic self-healing material that can balance the improvement of the power generation efficiency and stability of perovskite solar cells without damaging the perovskite active layer for the research and industrialization of perovskite photovoltaic modules. Summary of the Invention

[0007] In order to solve the various problems that occur in the practical application of perovskite solar cells and improve the power generation efficiency and stability of perovskite solar cells without damaging the perovskite active layer, the present application provides a perovskite solar cell and a preparation method thereof. The perovskite solar cell mainly inserts a special dynamic self-healing material between the hole transport layer and the perovskite active layer, and simultaneously acts on the chemical dynamic repair, interface passivation, defect reduction, and improvement of electron extraction efficiency of the perovskite active layer to achieve the improvement of the stability and power generation efficiency of the perovskite solar cell.

[0008] In the first aspect of the present application, a perovskite solar cell is provided. There is a dynamic self-healing interface layer between the hole transport layer and the perovskite active layer of the perovskite solar cell, and the self-healing material used in the dynamic self-healing interface layer is formed by cross-linking lipoic acid and polyethyleneimine.

[0009] Furthermore, the self-healing material is prepared by dissolving lipoic acid and polyethyleneimine in a mixed solvent of ethanol and deionized water at a molar mass ratio of 1:1 - 1:3, and adding a cross-linking promoter ZnCl₂ and then stirring. In one embodiment, the total concentration of the mixed solvent is 0.1 mg / mL - 0.5 mg / mL, wherein the volume ratio of ethanol to deionized water is 2:1; the content of the cross-linking promoter ZnCl₂ is 0.1 wt% - 0.3 wt%.

[0010] Preferably, the thickness of the dynamic self-healing interface layer is 5 nm - 20 nm, and the thickness of the perovskite active layer is 400 nm - 600 nm.

[0011] In terms of improving the stability and lifespan of perovskite solar cells, the above self-healing material can achieve in-situ self-healing at the interface of the perovskite active layer based on the dynamic interaction between the disulfide bond of lipoic acid and the amino group in polyethyleneimine. In terms of improving the power generation efficiency of perovskite solar cells, the self-healing material can play a role in the following aspects: reducing the interfacial potential barrier through molecular dipole interaction and enhancing the charge extraction efficiency (the carrier mobility is increased by about 20%-30%); neutralizing the dangling bonds on the interface through the carboxyl group (-COOH) of lipoic acid to reduce non-radiative recombination losses; the rich amino functional groups in polyethyleneimine form stable coordination bonds with the uncoordinated Pb²⁺ on the interface to passivate deep-level defects.

[0012] Corresponding to the above perovskite solar cell, the second aspect of the present application provides a method for preparing a perovskite solar cell. The method includes: sequentially laminating and preparing a hole transport layer, a dynamic self-healing interface layer, a perovskite active layer, and an electron transport layer on a conductive substrate; the self-healing material used for the dynamic self-healing interface layer is obtained by crosslinking lipoic acid and polyethyleneimine.

[0013] Further, the self-healing material is prepared by the following method: dissolving lipoic acid and polyethyleneimine (PEI) in a mixed solvent of ethanol and deionized water according to a molar mass ratio of 1:1 - 1:3, and adding a crosslinking promoter ZnCl2 and stirring to prepare the self-healing material. In one embodiment, the total concentration of the mixed solvent is 0.1mg / mL - 0.5mg / mL, the volume ratio of ethanol to deionized water is 2:1, and the content of the crosslinking promoter ZnCl2 is 0.1wt% - 0.3wt%.

[0014] Further, the dynamic self-healing interface layer is formed by slot-coating the self-healing material on the hole transport layer and then undergoing volatilization and annealing. In some embodiments, the thickness of the dynamic self-healing interface layer is set to 5nm - 20nm, the conductive substrate is set to transparent conductive glass or a flexible PET substrate, and the hole transport layer is set to have a thickness of 20nm - 50nm of PEDOT:PSS or Spiro-OMeTAD.

[0015] Further, the preparation of the perovskite active layer includes: dissolving a perovskite precursor in a solvent prepared by mixing DMF and DMSO with a volume ratio of 4:1 to prepare a perovskite active material; coating the perovskite active material on the hole transport layer, performing vacuum flash evaporation for a first preset duration, and then annealing for a second preset duration under specific annealing conditions to form a 400nm - 600nm dense perovskite thin film.

[0016] In addition, in order to form a perovskite solar cell with complete functions, the method further includes: sequentially laminating and preparing an electron transport layer, a hole blocking layer, and a back electrode on the perovskite active layer.

[0017] The technical solution provided by this application has multiple effects on the perovskite active layer, such as the dynamic self-repair function of damage, the optimization of interface contact, the reduction of interface defects, and the improvement of charge extraction efficiency by the molecular dipole electric field, etc., which greatly improves the power generation efficiency and working stability of the perovskite solar cell. The technical solution provided by this application can be used not only to prepare rigid perovskite photovoltaic modules, but also to prepare flexible perovskite photovoltaic modules, which greatly expands the application prospects of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of the perovskite solar cell provided by this application.

[0020] Figure 2a In one embodiment, it is a SEM image of the perovskite active layer before the self-repair verification thermal damage repair experiment of the perovskite solar cell provided by this application.

[0021] Figure 2b For Figure 2a In the shown embodiment, it is a SEM image of the perovskite active layer after thermal stress damage during the self-repair verification thermal damage repair process.

[0022] Figures 2c - 2e They are respectively SEM images of the self-repair results of the perovskite active layer corresponding to the molar mass ratios of thioctic acid (TA) to polyethyleneimine (PEI) in the self-repair material being 1:1, 1:2, and 1:3.

[0023] Figure 3 They are J-V curves obtained by testing the perovskite solar cell modules made of self-repair materials based on thioctic acid (TA) and polyethyleneimine (PEI) with molar mass ratios of 1:1, 1:2, and 1:3 respectively after self-repairing the simulated thermal damage.

[0024] Figure 4In an embodiment, after the perovskite battery module provided in the present application and the perovskite battery module without a dynamic self-healing interface layer are simulated for thermal damage and then post-treated at 40 °C for 48 h, the J-V curves obtained by testing are shown.

[0025] Figure 5a , Figure 5b In an embodiment, after the perovskite battery module provided in the present invention is thermally damaged, it is post-treated at 40 °C and 25 °C, 40 °C and 80 °C for 48 h (the post-treatment time is 1-72 hours, preferably 48 hours) for self-healing, and then the J-V curves obtained by testing are shown. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0027] As Figure 1 shown in the embodiment, the perovskite battery provided in the present application successively includes a conductive substrate 1, a hole transport layer 2, a dynamic self-healing interface layer 3, a perovskite active layer 4, an electron transport layer 5, a hole blocking layer 6, and a back electrode 7 from bottom to top. The dynamic self-healing interface layer 3 is located between the hole transport layer 2 and the perovskite active layer 4. Different from the existing self-healing materials, the self-healing material used in the dynamic self-healing interface layer 3 is obtained by cross-linking lipoic acid and polyethyleneimine in a corresponding ratio: lipoic acid and polyethyleneimine are dissolved in a mixed solvent of ethanol and deionized water according to a molar mass ratio of 1:1-1:3, and stirred after adding a cross-linking promoter ZnCl2.

[0028] In an embodiment, the total concentration of the mixed solvent is 0.1-0.5 mg / mL, wherein the volume ratio of ethanol to deionized water is 2:1; the content of the cross-linking promoter ZnCl2 is 0.1 wt%-0.3 wt%. The thickness of the dynamic self-healing interface layer is 5-20 nm, and the thickness of the perovskite active layer is 400-600 nm.

[0029] The self-healing material used in the dynamic self-healing interface layer 3 in the above perovskite battery improves the stability and power generation efficiency of the perovskite battery mainly through the following action mechanisms:

[0030] Based on the dynamic interaction between the disulfide bond of lipoic acid in the self-healing material and the amino group in polyethyleneimine, in-situ self-healing of the perovskite active layer interface is achieved. This can effectively improve the damage resistance, working stability, and lifespan of perovskite solar cells.

[0031] The self-healing material improves the power generation efficiency of perovskite solar cells through the following multiple effects: reducing the interface potential barrier through molecular dipole interaction and enhancing the charge extraction efficiency (the carrier mobility increases by about 20%-30%); neutralizing the dangling bonds on the interface through the carboxyl group (-COOH) of lipoic acid to reduce non-radiative recombination losses; the rich amino functional groups in polyethyleneimine form stable coordination bonds with the uncoordinated Pb²⁺ on the interface to passivate deep-level defects.

[0032] Experimental results show that after annealing the perovskite solar cells with the above structure at 40-60°C after thermal damage, the dynamic disulfide bond recombines to repair the interface microcracks, and the amino groups of PEI re-form a hydrogen bond network with the perovskite surface, recovering to about 97% of the initial efficiency.

[0033] In one embodiment, the above perovskite solar cell provided by the present application (taking the inverted-structure perovskite solar cell as an example) can be prepared through the following steps:

[0034] S1. Prepare a conductive substrate. The conductive substrate can be selected as ITO / FTO transparent conductive glass or a flexible PET substrate, that is, the perovskite solar cell provided by the present application can be a rigid solar cell or a flexible solar cell.

[0035] S2. Prepare a layer of hole transport layer (HTL) on the conductive substrate. The material used for the hole transport layer is , PEDOT:PSS or Spiro-OMeTAD, with a thickness of 20-50 nm.

[0036] S3. Coating process is used to coat the pre-prepared self-healing material on the hole transport layer to prepare a dynamic self-healing interface layer. The thickness of the self-healing interface layer can be set to 5-20 nm. The specific coating process can be slot coating, with a coating gap of 70-160 μm, a coating speed of 5-30 mm / s, a solvent evaporation time of 30-120 s, an annealing temperature of 80-120°C, and an annealing time of 5-20 min.

[0037] In this embodiment, the self-healing material can be prepared in the following manner: A mixed solvent of ethanol and deionized water with a total concentration of 0.1 - 0.5 mg / mL is pre-configured, where the volume ratio of ethanol to deionized water can be selected as 2:1. Lipoic acid and polyethyleneimine (PEI) are dissolved in the mixed solvent according to a molar mass ratio of 1:1 - 1:3, and crosslinking promoter ZnCl2 is added and stirred magnetically (crosslinked by lipoic acid and PEI through dynamic disulfide bonds (-S-S-) and hydrogen bonds). In the self-healing material, the content of crosslinking promoter ZnCl2 is 0.1wt% - 0.3wt%.

[0038] S4. A perovskite active layer is prepared on the dynamic self-healing interface layer using a prefabricated perovskite active material, and its thickness can be set to 400 nm - 600 nm.

[0039] Further, the preparation of the perovskite active layer includes: dissolving a perovskite precursor in a solvent prepared with DMF and DMSO in a volume ratio of 4:1 to obtain the perovskite active material; coating the perovskite active material on the hole transport layer, and after vacuum flash evaporation for a first preset duration, annealing for a second preset duration under specific annealing conditions to form a 400 - 600 nm dense perovskite thin film. Specifically, the corresponding coating process can be: coating gap 80 - 160 μm, coating speed 10 - 50 mm / s, vacuum flash evaporation time 60 - 180 s; annealing conditions are annealing at 150°C for 5 - 20 min.

[0040] S5. An electron transport layer (ETL), a hole blocking layer, and a back electrode are laminated on the perovskite active layer. Among them, the electron transport layer (ETL) can be made of SnO2, PCBM, or C60, and the thickness can be set to 30 - 80 nm; the hole blocking layer can be made of BCP or LiF, and the thickness can be set to 5 - 10 nm; the back electrode is generally made of Ag, Au, or Cu, with a thickness of 80 - 120 nm.

[0041] Preparation of the dynamic self-healing interface layer (DSIL): Preparation of the precursor solution: TA and PEI are dissolved in a mixed solvent of ethanol / deionized water (volume ratio 2:1) according to a molar ratio of 1:1 - 1:3, with a total concentration of 0.1 - 0.5 mg / mL; 0.1wt% - 0.3wt% of ZnCl2 is added as a crosslinking promoter and dissolved thoroughly by magnetic stirring. Coating process: slot coating, coating gap 70 - 160 μm, coating speed 5 - 30 mm / s, solvent evaporation time 30 - 120 s, annealing temperature 80 - 120°C, annealing time 5 - 20 min.

[0042] Preparation of perovskite active layer: The perovskite precursor solution was dissolved in DMF:DMSO (4:1, v / v). It was prepared by coating, with a coating gap of 80 - 160 μm, a coating speed of 10 - 50 mm / s, and a vacuum flash evaporation time of 60 - 180 s; the annealing condition was annealing at 150 °C for 5 - 20 min to form a dense perovskite thin film.

[0043] Self - healing verification of thermal damage experiment: By controlling the annealing temperature and time, the dynamic disulfide bond recombination was triggered to achieve the repair of interface micro - cracks. The specific steps are as follows: The perovskite solar cell prepared according to the above - mentioned embodiment (in the original state as Figure 2a shown) was placed in an 85 °C constant - temperature oven and aged for 24 hours to simulate the thermal stress damage during long - term operation. The SEM image of the perovskite active layer (with the same thickness, between 400 - 600 nm, preferably 550 nm) after thermal stress damage is as Figure 2b shown. Observation shows that interface micro - cracks with a width of 100 - 300 nm appear in the perovskite active layer. After environmental aging, it was post - treated at 40 °C for 48 h to test the self - healing result. Figures 2c - 2e They are respectively SEM images of the self - healing results generated by the self - healing interface layers (with the same thickness, between 5 - 10 nm) when the molar mass ratio of thioctic acid (TA) to polyethyleneimine (PEI) in the self - healing material is 1:1, 1:2, and 1:3. As Figures 2c - 2e can be seen, the perovskite solar cell provided by this application has good damage self - healing effect and interface passivation effect.

[0044] Correspondingly, Figure 3 The J - V curves (the relationship curves of short - circuit current density (J sc ) and open - circuit voltage (V oc )) were respectively measured for the perovskite solar cell modules after the above - mentioned 85 °C thermal damage repair using self - healing materials with the molar mass ratio of thioctic acid (TA) to polyethyleneimine (PEI) being 1:1, 1:2, and 1:3. As Figure 3 shown, through the comparison of the efficiency before and after the repair of the perovskite solar cell modules (the effective area of the experimental perovskite solar cell modules is 63.76 cm 2 , and the light intensity used is AM1.5G 100 mW / cm 2 ), it was found that the efficiency of the perovskite modules after the 40 °C post - treatment has recovered to varying degrees. When the doping ratio of TA / PEI is 1:2, its self - healing effect on the perovskite solar cell modules is the best, and the corresponding photoelectric conversion efficiency increases from the initial 9.68% to 17.68% after damage, recovering to 97% of the original efficiency.

[0045] Figure 4The J-V curves were obtained by testing the perovskite solar cell modules with a pre-prepared dynamic self-healing interface layer (the molar mass ratio of lipoic acid to polyethyleneimine (PEI) in the self-healing material is 1:2) and without a dynamic self-healing interface layer (the difference is only whether there is a dynamic self-healing interface layer) after aging in an 85°C constant temperature oven for 24 hours to simulate thermal stress damage and then post-treating at 40°C for 48 hours. Among them, the parameters of the perovskite solar cell module with a dynamic self-healing interface layer are the same as those of the perovskite solar cell module used in the above self-healing verification thermal damage experiment.

[0046] Figure 5a 、 Figure 5b The pre-prepared perovskite solar cell modules (the effective area of the module is 63.76 cm 2 , and the light intensity is AM1.5G 100 mW / cm 2 ) were placed in an 85°C constant temperature oven for 24 hours to simulate thermal stress damage (except that the molar mass ratio of the self-healing material lipoic acid to polyethyleneimine (PEI) is 1:2, the parameters of the pre-prepared perovskite solar cell modules are the same as those of the perovskite solar cell modules used in the above self-healing verification thermal damage experiment), and the J-V curve graphs obtained after post-treating at 40°C and 25°C, 40°C and 80°C for 48 hours respectively. From Figure 5a 、 Figure 5b the experimental results, it can be seen that a post-treatment temperature of about 40°C has a good effect on repairing the thermal damage of the perovskite solar cells provided in this application.

[0047] The above are only examples of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the technical solutions provided in the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A perovskite solar cell, characterized in that, There is a dynamic self-healing interface layer between the hole transport layer and the perovskite active layer of the perovskite solar cell. The self-healing material used to prepare the dynamic self-healing interface layer is cross-linked by lipoic acid and polyethyleneimine; the self-healing material is prepared by dissolving lipoic acid and polyethyleneimine in a mixed solvent of ethanol and deionized water according to a molar mass ratio of 1:1 - 1:3, and adding a cross-linking promoter ZnCl₂ and then stirring.

2. The perovskite cell according to claim 1, characterized in that, The thickness of the dynamic self-healing interface layer is 5 - 20 nm, and the thickness of the perovskite active layer is 400 - 600 nm.

3. A method for preparing a perovskite solar cell, characterized in that, The method includes: sequentially laminating and preparing a hole transport layer, a dynamic self-healing interface layer, a perovskite active layer, and an electron transport layer on a conductive substrate; the self-healing material used for the dynamic self-healing interface layer is cross-linked by lipoic acid and polyethyleneimine in the following manner: dissolving lipoic acid and polyethyleneimine (PEI) in a mixed solvent of ethanol and deionized water according to a molar mass ratio of 1:1 - 1:3 to obtain a mixed solution, and adding a cross-linking promoter ZnCl₂ to the mixed solution and stirring to prepare the self-healing material.

4. The method according to claim 3, wherein The total concentration of the mixed solution is 0.1 - 0.5 mg / mL, the volume ratio of ethanol to deionized water is 2:1, and the content of the cross-linking promoter ZnCl₂ is 0.1 - 0.3 wt%.

5. The method according to any one of claims 3-4, characterized in that The method includes: slot-coating the self-healing material on the hole transport layer, and forming the dynamic self-healing interface layer with a thickness of 5 - 20 nm through volatilization and annealing.

6. The method according to claim 5, characterized in that, The conductive substrate is provided as transparent conductive glass or a flexible PET substrate, and the hole transport layer is provided with a thickness of 20-50 nm of , PEDOT:PSS or Spiro-OMeTAD.

7. The method according to claim 5, characterized in that, The preparation of the perovskite active layer includes: dissolving a perovskite precursor in a solvent prepared by mixing DMF and DMSO with a volume ratio of 4:1 to prepare a perovskite active material; coating the perovskite active material on the hole transport layer, performing vacuum flash evaporation for a first preset time, and annealing for a second preset time under certain annealing conditions to form a 400 - 600 nm dense perovskite thin film.

8. The method according to claim 3, wherein The method further includes: sequentially laminating and preparing a hole blocking layer and a back electrode on the electron transport layer.

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