Amin Acid-Mediated Synthesis Of Shape-Controlled CsPbBr₃ Perovskite Nanocrystals

Since the first success utilization of hybrid organic-inorganic lead halide perovskite materials in photovoltaic devices,in 2009,the classic perovskite materials have attracted widespread attention.However,hybrid organic-inorganic perovskite is extremely sensitive to oxygen and moisture in the environment,and these have become the great obstacle in storage and device fabrication,which limits its application in optoelectronic field.All inorganic halide perovskite nanocrystals are expected to be promising materials for next generation optoelectronic devices,due to their better stability,ultrahigh photoluminescence quantum yield(PL QY),and composition dependent luminescence covering the whole visible region with narrow line-width.In this paper,we synthesized all inorganic cesium lead halide perovskite nanocrystals at room temperature,through a simple and rapid way,ligand-assisted reprecipitation method.By changing the surface ligands,we synthesized nanocrystals with different morphology,and nanocrystals with different compositions that emitting different fluorescence were obtained through anion exchange.We found that the introduction of amino acids,such as phenylalanine and tryptophan,in the synthesis,we could control the morphology of nanocrystals,resulting in spherical dots,two-dimensional nanoplatelets and nanocubes.We have studied the role of tryptophan in the nucleation and growth transition of nanocrystals by controlling the changes of the precursors and the ligands in the precursor solution,and gave the corresponding mechanism explanation.By controlling the adding amount of tryptophan,two-dimensional nanoplatelets with a thickness of 4 to 8 layers can be accurately obtained.We found that there are certain relations between the thickness and the band gap of nanoplatelets.By controlling the thickness of nanoplatelets,we can obtained the nanocrystals with specific optical properties.Considering the strong quantum confinement effect exhibited by two-dimensional nanomaterials,we believe this feature will help to prepare high-performance optoelectronic devices,in the future.