Research On Perovskite Nucleation Crystallization Regulation And Performance Optimization Of CsPbBr₃ Light-emitting Diodes

Metal halide perovskite has great application potential in light-emitting diodes,solar cells,photodetectors,lasers and other photoelectric devices because of its excellent electronic properties.Perovskite light-emitting diodes（PeLEDs）based on metal halide perovskite are highly competitive in the fields of technology such as next-generation lighting and display due to their narrow emission spectrum and high quantum yields.In recent years,the performance of PeLEDs has developed rapidly,with the external quantum efficiency（EQE）rapidly exceeding 20%.However,to further improve the performance of PeLEDs and promote its commercial application,there are still a number of key issues that limit the efficiency and stability of materials and devices to be solved.Among them,the quality of perovskite films,including crystal quality and surface morphology,is an important factor affecting the efficiency and stability of the device,and it is still necessary to develop simple and effective methods to improve the quality of perovskite films and optimize their optoelectronic properties.Compared with organic-inorganic hybrid perovskite materials,all-inorganic perovskite materials have better thermal and chemical stability.This paper focuses on the study of all-inorganic CsPbBr₃ films and light-emitting devices,and proposes nucleation and crystallization control approaches such as laser irradiation of perovskite films and thermal imprinting to reduce defects of polycrystalline films,improve film quality and optimize device performance.The specific research content can be summarized in the following three aspects:1.The defects of the CsPbBr₃ film are reduced by laser irradiation inducing the recrystallization.Aiming at the defect reduction of CsPbBr₃ polycrystalline films,a nanosecond laser with a wavelength of 355nm was used to irradiate the surface of perovskite.By optimizing parameters such as power density and irradiation time,the defects of the films were reduced by recrystallization after laser irradiation,and the quality of CsPbBr₃ films was improved.The performance of PeLEDs has also been significantly improved,with a maximum luminance and current efficiency of 43300cd/m² and 14.55 cd/A,respectively,and a maximum EQE of 4.09%.The enhancement of luminance and efficiency are up to 112%and 127%,compared with PeLEDs without laser treatment.2.Thermal imprinting with the nanostructured template improves the quality of CsPbBr₃ film.The purpose of this section is to use nanostructure thermal imprinting to increase the surface coverage of CsPbBr₃ thin films,limit the grain size and improve the crystal quality,so as to improve the luminance and efficiency of PeLEDs.In the process of thermal imprinting of CsPbBr₃ thin films by nanostructured templates,the formation of local stress in the nanoscale region is achieved through the periodic nanostructure,and the nucleation and growth of CsPbBr₃ are manipulated,which can limit the grain size accompanied by improving the surface coverage and crystallization quality of the thin films.Thus,by optimizing the nanostructure period,appropriate grain size and improved crystalline quality can be achieved simultaneously.PeLEDs fabricated by imprinting nanostructured templates with a period of 320 nm have a maximum luminance and efficiency of up to 67600 cd/m² and 16.36 cd/A,which are found to be 123%and 100%higher than the non-imprinted PeLEDs,respectively.3.Surface defects of CsPbBr₃ perovskite film passivated by thermal imprinting inducing two-dimensional perovskite growth.The passivating agent PBABr was transferred to the surface of CsPbBr₃ by thermal imprinting process.The passivating agent and the uncoordinated Cs⁺and Pb²⁺on the surface of perovskite formed two-dimensional perovskite,effectively passivated the surface defects of CsPbBr₃.Therefore,the performance of PeLEDs was significantly improved.Compared with the unimprinted PeLEDs,the luminance of the device increases from 20130 cd/m² to 40350cd/m²,and the current efficiency increases from 4.19 cd/A to 12.99 cd/A.