In-situ Synthesis And Optical Properties Of All-inorganic CsPbBr₃ Perovskite Nanocrystals

Since Miyasaka et al first used organic-inorganic hybrid perovskite(OHP)as a new photosensitizer to replace the light absorbing layer in traditional dye cells in 2009,people have not stopped exploring the perovskite materials.Compared with OHP,all-inorganic perovskite has more excellent physical and chemical properties and is widely used in solar cells and liquid crystal displays.However,due to the characteristics of its ionic crystal,even all-inorganic perovskite,it is still prone to phase transition and decomposition under high temperature environment or in high polar solvents.Therefore,to promote its practical application i n the field of LCD,there are two major problems:One is the inherent instability of CsPbX ₃ perovskite nanocrystals in the hydrothermal environment,and the second is how to align CsPbX ₃ perovskite nanowires or nanorods to obtain enhanced polarized optical properties.This paper focuses on the CsPbBr₃ nano-system,for the first time using electrospinning technology in-situ synthesis of all-inorganic CsPbBr₃ nanorods with different aspect ratios,and systematically studied the influence of different factors on the aspect ratio and optical properties of perovskite nanorods.In addition,the coaxial electrospinning method is used to further enhance the hydrothermal stability of the perovskite nanocrystals.The main findings are as follows:(1)CsPbBr₃ nanorods were in-situ synthesized in PS polymer based on one-step electrospinning method.After optimization,the aspect ratio of the nanorods reached7.0 and had a uniform spatial distribution.Considering the nucleation process of perovskite nanocrystals in the polymer and the complicated viscous environment,the spinning temperature,the proportion of the perovskite precursor,the amount of oleylamine and the content of dimethyl sulfoxide were carefully adjusted and the effects on the morphology and optical properties of CsPbBr₃ nanorods were studied.The prepared composite CsPbBr₃@PS nanofibers have bright green emission,high PL quantum yield(PLQY)and narrow full wave at half maximum(FWHM).(2)When the coaxial CsPbBr₃ nanofiber film is placed in water for 0-30 days,the PL peak position hardly changes.Compared with uniaxial CsPbBr ₃ nanofibers(32.7%),the PLQY of coaxial nanofibers is significantly improved(41.5%),and can maintain84.3%of the initial value after being immersed in water for 10 days,and can still maintain 82.8%after being immersed in water for 30 days.Increase the concentration of the shell polymer,that is,add 1000 mg PS to the prefabricated shell solvent,and place the prepared coaxial nanofiber film in water for 0-30 days and regularly check its PLQY changes.The initial PLQY reached 42.8%,and it can maintain 89.5%of the initial value after soaking in water for 10 days,and can still maintain 88.3%after 30days.The water stability is further improved.(3)Heat the coaxial fiber film in a constant temperature drying oven at 80?for0-300 minutes,during which the PL and PLQY changes are regularly checked.Compared with uniaxial CsPbBr₃ nanofibers,the thermal stability of coaxial fibers is significantly improved,and the PL peak red shift is very small.When heated in a drying oven for 5 min,the PLQY of the coaxial fiber is maintained at approximately 94%of the original value,and when the heating time reaches 120 min,it can also be maintai ned at approximately 65%of the original value.