Study On The Solvent Annealing Treatment In Regulating The Growth Of Hybrid Perovskite Thin Film And Their Properties

The organic-inorganic halide perovskite materials have been rapidly promoted to the frontier of material research due to their potential applications in the field of solar cells.One of the important factors affecting the performance of optoelectronic devices is the quality of perovskite film as a light absorption layer.Meanwhile,the solution method is one of the most important methods of preparing perovskite film.This method is simple and low cost,and can be carried out in atmospheric environment.However,due to the rapid transformation process from solution to film,the quality of the prepared film is often difficult to control.To explore the method for preparing perovskite film in atmospheric environment and improve the quality of thin film and device performance,we studied the perovskite thin film growth process,besides,the solvent annealing treatment was used and this method has been optimized,in a typical MAPb I₃ and Cs_0.05(MA_0.17FA_0.83)_0.95Pb(I_0.83Br_0.17)₃ system.We have achieved perovskite films with high quality,good morphology,large grain size which could reach micron grade.XRD,SEM,UV-Vis,PL technology was used to represent the phase,structure,morphology and optical properties of thin films.The crystal growth process was analyzed by Lamer growth model.On this basis,the solar cell device was prepared and the performance of the solar cell device has been obviously improved compared with the conventional one.The specific results are as follows:1.In terms of the preparation of perovskite film and solar device,our work includes:studying the method of methylamine gas slicing single crystal forming film,and the widely used method of adding anti-solvent to prepare perovskite film.It is found that mastering the dropping time of anti-solvent is a necessary condition for improving the film quality.In use of perovskite thin film prepared by the solution process,adjusting the weight ratio of reactant in the precursor could optimize the quality of thin film.During the process of preparing perovskite planar solar device,it was found that by oxidize the hole transport layer,the performance of the solar cell device could be improved,in which the main parameters of short circuit current density increased from10.14 m A/cm²to 16.51 m A/cm².2.The typical MAPb I₃ was used to develop the solvent atmosphere annealing method.The solvent annealing treatment was optimized and low-dose DMSO solvent was used for cycling treatment to prolong the film’s recrystallization time.The film with grain size increased 15 times was obtained.The average grain size increased from 0.189micron to 3.02 micron and the photoelectric conversion rate of the perovskite solar cell was increased from 11.9%to 14.25%.The effects of different solvents（DMF,DMSO and NMP）on perovskite films were also studied.It was found that organic solvents had similar effects on the film,and the average size of film grains increased to a certain extent comparing with the film prepared by traditional heat treatment.This process can be explained by Ostwald maturation theory.3.We prepared mixed cationic perovskite films and treated them with solvent annealing method,three kinds of organic solvent（DMF,DMSO,NMP）was used.The experiments have shown that using DMSO solvent annealing could significantly increase the grain size of the film.The steady-state fluorescence spectrum intensity of the films treated by solvent annealing method increased comparing with the films treated by traditional annealing method.The result of time-resolved photoluminescence spectrum show that carrier life expectancy of the films increased from 321.6 ns to 620.8ns illustrates the method of preparing thin film could improve the film quality.The mixed cationic perovskite solar cells with a high filling factor of 0.748 and a photoelectric conversion efficiency of 17.25%were prepared under atmospheric conditions.The defects and carrier transport process in the thin film were analyzed by electrical performance test.In conclusion,in view of improving the perovskite film quality in the atmosphere,we explored solvent vapor annealing treatment.By researching the process of thin film growth before and after regulation,the film with large size,high crystallinity was achieved.The results provide a theoretical basis for the low cost and high efficiency preparation of various organic perovskite films under atmospheric conditions,which is expected to provide support for the high efficiency preparation of perovskite solar cells.