Synthesis And Properties Of Hybrid Perovskite FAPbBr₃ Nanocrystals

Recently,organic-inorganic hybrid perovskite nanocrystals have been widely used in light-emitting diodes,displays and other related fields due to their high luminescent quantum yield(PLQY),adjustable fluorescence spectral range and narrow fluorescence half-peak width(FWHM).Compared with the all-inorganic perovskite CsPbBr3 nanocrystals,the hybrid perovskite FAPbBr3 is less stable due to the fact that the A-site ions are organic cations.In addition to the inherent instability,external factors such as air humidity,temperature,and light radiation will also destroy the structure of nanocrystals and cause them to degrade slowly,thereby affecting the optoelectronic properties of nanocrystals.However,FAPbBr3 nanocrystals are easy to obtain pure green fluorescence makes its application in related fields more popular.Therefore,it is of great significance to find a method to synthesize efficient and stable luminescent FAPbBr3 nanocrystals.This work proposes the synthesis of FAPbBr3 nanocrystals using the short-chain ligand didodecylamine to completely replace oleylamine.And on this basis,the surface of nanocrystals is modified by ligand post-treatment to achieve the goal of improving the stability and optical properties of nanocrystals.The specific research contents are as follows:(1)In order to obtain FAPbBr3 nanocrystals that can emit ultranarrow FWHM,and reduce the surface defect density,a modified hot-injection method was proposed to synthesize FAPbBr3 nanocrystals.TRPL,TEM,XPS and other tests showed that FAPbBr3 nanocrystals with pure green fluorescence(fluorescence peak at 530 nm),PLQY as high as 98.1%and FWHM of 18.7 nm were successfully prepared.Compared with the FAPbBr3 reported in recent years,the FAPbBr3 nanocrystals synthesized in this work can not only achieve high PLQY,but also have the narrowest FWHM of the fluorescence spectrum emitted by the nanocrystals,which has certain advantages in applications in related fields.(2)Study the optical properties and stability of FAPbBr3 nanocrystals surface treated with didodecyldimethylammonium bromide.The results show that the PLQY of FAPbBr3 nanocrystals treated with didodecyldimethylammonium bromide can be increased from 60.9%to 97.5%,and photostability of FAPbBr3 nanocrystals in air and thermal stability under heating conditions are significantly improved after post-treament.First,the nanocrystal solution was kept at 100℃ and continuously heated for four hours,which still retained 76.9%of the original fluorescence intensity,while the best sample without post-treatment retained only 22.0%.In addition,the photostability of FAPbBr3 nanocrystals post-treated with didodecvldimethvlammonium bromide can still maintain 97.5%of the initial fluorescence intensity after continuous blue light irradiation at 450 nm/7 W for 96 h.while after 96 h of continuous violet light irradiation at 365 nm/5 W,it still maintained 58.3%of the initial intensity.However,the fluorescence intensity of the untreated samples decreased rapidly after being continuously irradiated with blue light of 450 nm/7 W and violet light of 365 nm/5 W for 96 h,only maintaining 32.7%and 4.5%of the initial intensity.It can be seen that the improvement of the stability of FAPbBr3 nanocrystals is helpful for applications in related fields such as light-emitting diodes.