Study On Interfacial Modification Strategy To Improve The Performance Of Perovskite Solar Cells

With the fast development of human society,the problem of energy shortage becomes more and more obvious.In order to achieve the goal of sustainable development,it is urgent to develop the new clean energy.The solar cells are devices that utilize photovoltaic effect occurred at the semiconductor to convert the energy of sunlight into electric energy.Perovskite solar cells（PSCs）have attracted the attention of many researchers due to its excellent photovoltaic performance.The maximum power conversion efficiency（PCE）of PSCs has been reached 25.7%at present.Though,PSCs presents the great potential application in photovoltaic field,there are still have lots of problems in achieving the purpose of commercialization.For example,it include that energy level doesn’t match well,a large number of defect states located on the surface and grain boundaries of perovskite film,ion migration appeared at PSCs,ect.The above factors limit the practical process of PSCs,seriously.We carried out the work to improve the photovoltaic performance of PSCs,from the perspective of energy level,defect passivation and interface engineering.In our research of PSCs,the perovskite absorption layer adopts organic-inorganic hybrid perovskite structure(Cs（FAPb I₃）_x（MAPbBr₃）_1-x.The main contents of this paper are as follow:（1）The AgBiS₂was added between mesoporous titanium dioxide（meso-Ti O₂）and the perovskite layer by means of vapor deposition.The introduction of AgBiS₂could improve not only the adaptability between Ti O₂and perovskite layer,but also the transfer efficiency of carriers at the interface between Ti O₂and perovskite layer.Meanwhile,the lead vacancies were passivated by element of sulfur,and then high efficiency and stability of PSCs was prepared.Finally,we fabricated the PSCs with optimized PCE of 19.19%.The optimized device could maintain good humidity and ultraviolet（UV）stability under the external environment.（2）The method of traditional solvent-annealing has been improved,which the source of solvents used as solvent-annealing has been changed into the solvent mixed with solute（Dimethyl Sulfoxide mixed with Polyethylene Glycol,abbreviated as DMSO-PEG）.A new source used as solvent-annealing was finished.And it was introduced into the fabrication process of perovskite film.Finally,the AgBiS₂modified layer and DMSO-PEG were integrated into the same device to achieve the high efficiency and moisture stability of PSCs.The results showed that The PEG was introduced into the preparation process of perovskite film,which could not only delay the crystallization rate and improve the quality of the perovskite film,but also interact with Pb²⁺on the perovskite surface to passivate the surface defects of the perovskite film.It could effectively inhibit the photogenerated carrier recombination at the electron transport layer/perovskite interface.Finally,the PCE of the device reached 21.19%.In addition,the moisture stability of perovskite films treated with DMSO and PEG has been significantly improved.（3）Interfacial passivation strategy is one of the most effective methods to reduce the density of defect states located on the interface and prepare the high efficiency and stability of PSCs.Therefore,we utilized the interfacial modification strategy and introduced the Cs₃Cu₂I₅nanocrystals modified layer into the interface of perovskite/hole transport layer.It could reduce the defects located on the surface and grain boundaries of perovskite film by means of solid-state inter-diffusion process.The defects located on the surface and grain boundaries of perovskite films,were repaired by solid-state inter-diffusion process of multi-cation halide perovskite nanocrystals.The distribution of Cs⁺and Cu²⁺has a great influence on the passivation of ion defects.Finally,the high efficiency and stability of PSCs was achieved.Based on the above advantages,the optimized PCE of PSCs was reached 22.03%after interfacial modification.This method could significantly inhibit the occurrence of hysteresis phenomenon and improve the stability of PSCs.