Preparation Of All Inorganic Perovskite Nanocrystals And Their Application In Optoelectronic Devices

As a new kind of semiconductor materials,metal halide perovskite is considered to be one of the most promising optoelectronic device materials because of its excellent optoelectronic properties such as low binding energy,long carrier life and high defect tolerance.In particular,all-inorganic lead halide perovskite nanocrystalline Cs Pb X₃(X=Cl,Br,I)has excellent optical properties such as simple preparation method,large absorption cross section,high fluorescence quantum efficiency,narrow emission spectrum line and tunable fluorescence emission wavelength.It shows great application prospects in solar cells,light-emitting diodes(LEDs),photodetectors and lasers.Although lead halide perovskite nanocrystals have many advantages,their photoelectric application research is still in its infancy.How to improve their device performance is a problem of concern.In addition,the commercial application of lead halide perovskite is also hindered due to the toxic heavy metal lead.More importantly,when perovskite is exposed to humidity,high temperature or ultraviolet light,its crystal structure will be destroyed rapidly,which will lead to the instability of device performance.These seriously restrict the commercial application process of lead halide perovskite devices,so the solutions to the above problems have always been the focus of scientists'research.This paper focuses on the optoelectronic device application of perovskite nanocrystals,as well as the preparation and stability of all inorganic lead-free perovskite nanocrystals.The specific work contents are as follows:(1)Based on the advantages of high light absorption and good stability of Cs Pb Br₃,we combined it with one-dimensional titanium dioxide(Ti O₂)nanorod array to improve the photoelectric response characteristics of Ti O₂based metal semiconductor metal(MSM)Schottky UV detector.The Au/Cs Pb Br₃@Ti O₂/Au photodetector obtains very low dark current and high photocurrent,and the switching ratio is greatly improved.Compared with Au/Ti O₂/Au photodetector,the optical sensitivity(0.02 m A/W)and detectivity(5.59×10~8Jones),The sensitivity and detectivity of Au/Cs Pb Br₃@Ti O₂/Au photodetector are greatly improved,reaching3.6 m A/W and 6.64×10¹⁰Jones,respectively.(2)Aiming at the toxicity of heavy metal lead,we successfully prepared all inorganic Cs Eu Cl₃lead-free perovskite blue nanocrystals by using the rare earth element divalent europium(Eu²⁺)instead of lead ion.Through the stability study of Cs Eu Cl₃lead-free perovskite nanocrystals,it is found that the nanocrystals show very poor stability in the natural environment,and the nanocrystals will decompose rapidly under the influence of water and oxygen in the air.(3)In order to improve the stability of perovskite nanocrystals,we coated the nanocrystals with different silane coupling agents,and tried to explore the optimal process of highly stable Cs Eu Cl₃lead-free perovskite nanocrystals.The research shows that after TMOS coating,the storage time of Cs Eu Cl₃lead-free perovskite nanocrystals is increased by 10 times,and the stability in air is also improved.We prepared blue LED through packaging Cs Eu Cl₃perovskite nanocrystals.At the same time,we found that Cs Eu Cl₃perovskite nanocrystals will have an obvious fluorescence blue shift during storage,and we also observed the"hollow"structure naturally formed during the storage of nanocrystals for the first time.The first principle calculation shows that the fluorescence blue shift of Cs Eu Cl₃perovskite nanocrystals is closely related to the evolution of internal defects and the formation of"hollow"structure.