Amino Acid-Mediated Synthesis of CsPbBr3 Perovskite Nanoplatelets with Tunable Thickness and Optical Properties

Metal halide perovskites (MHPs) have recently attracted considerable attentions due to their remarkable optoelectronic properties. Colloidal synthesis of MHPs provides a versatile route to precisely control their dimensionality and the related optoelectronic properties. Herein, we report on amino acid (Trp)-mediated synthesis of quasi-two-dimensional CsPbBr3 perovskite nanoplatelets (NPLs) with well-controlled and tunable thickness. The number of layers (n) could be finely tuned from 4 to 12 by simply adjusting Trp concentration, leading to gradual red shift of their photoluminescence (PL). This allows us to directly correlate their thickness with the band gap energy in the quantum confinement regime, which is in good agreement with theoretical model. We found that Trp is the only hydrophobic amino acid to promote the formation of 2D CsPbBr3 NPLs. The use of Trp derivatives for CsPbBr3 nanocrystal synthesis indicates that the carboxyl group, amine group, and indole ring of Trp act synergistically on CsPbBr3 NPL formation.