Controllable Synthesis And Surface Engineering Of All-Inorganic Metal Halide Perovskite Nanoparticles

Over the past several years,all-inorganic perovskite cesium lead halide(CsPbX3,X=C1,Br or I)nanocrystals(NCs)have attracted much attention due to their excellent photophysical properties and promising applications in optoelectronics and photovoltaics.Great progress has been made in the research of all-inorganic perovskite materials.For example,the external quantum efficiency(EQE)of CsPbBr3 NCs based LEDs has been promoted from 0.12%to 16.5%.The power conversion efficiency(PCE)of CsPbI3 NCs based solar cells has exceeded 13.4%.Despite the great progress,the stability of CsPbX3 against the deterioration of water and air is still a big challenge.Surface engineering,as the most common and effective method,has been developed to prepare highly stable all-inorganic perovskite NCs,which can be mainly classified into inert material coating and surface treatment.Although many works have been reported to synthesize high-quality perovskite NCs through surface engineering,there are still some problems need to be solved.First,a simple and convenient method is needed to achieve the coating of perovskite NCs on a single particle level.Second,in the case of surface treantment,cumbersome processes and complex compounds are cuasing problems for large scale synthesis.In order to solve these problems,we developed a facile method to synthesize CsPbBr3@SiO2 core-shell NPs.In addition,we used new surface ligands to prepare stable and highly efficient all-inorganic perovskite NCs.The main research contents are as follows:1.We report a facile one-pot approach to synthesize CsPbBr3@SiO2 core-shell nanoparticles(NPs),in which each core-shell NP has only one CsPbBr3 NC.The formation process has been carefully monitored.It has been found that the formation rates of both CsPbBr3 and SiO2 are critical for the successful preparation of core-shell NPs.The product shows much higher long-term stability in humid air and enhanced stability against ultrasonication treatment in water than that of naked CsPbBr3 NCs.2.From density functional theory(DFT)calculation results,it could be predicted that primary amines(L-type ligands)can significantly improve the photophysical properties and stability of CsPbBr3 NCs.Along this prediction,a room temperature re-precipitation method using oleylamine as the sole capping ligand has been developed to synthesize high-quality CsPbBr3 NC with near-unity photoluminescence quantum yield(PLQY)and dramatically improved stability against purification and water treatment.3.An amine-free synthesis method was employed to prepare high-quality CsPbX3 NCs with uniform size distribution and narrow emission width.To overcome the problems caused by the low solubility of widely used lead halide salt,Pb(acac)2 is used as the lead precursor.Hexadecyltrimethylammonium halide(CTAX,X=Cl or Br)is used to replace OAm.To further improve the stability of as-prepared CsPbX3 NCs,additional ammonium halide(NH4Cl,NH4Br and NH4I)has been added.