Seed‐Mediated Synthesis of Colloidal 2D Halide Perovskite Nanoplatelets

Abstract Colloidal synthesis of two‐dimensional lead halide perovskite nanoplatelets (2D LHP NPLs) with a general formula of L ₂ [APbX ₃ ] _n−1 PbX ₄ has been widely performed by using hot‐injection or ligand assisted reprecipitation methods. Herein, for the first time, we report on seed‐mediated synthesis of two and three monolayers (n=2, 3) lead halide perovskite nanoplatelets without using A‐site cation halide salt (AX; A=Cesium, methylammonium, formamidinium and, X=Cl, Br, I) and long chain alkylammonium halide salts (LX; L=oleylammonium, octylammonium, butylammonium and, X=Cl, Br, I). The nanocrystal seeds have been prepared by reacting lead (II) halide salt and coordinating ligands in a nonpolar solvent and then they have been reacted with cesium oleate, formamidinium oleate or methylamine. Our facile synthesis route enabling further understanding of the growth dynamics of LHP NPLs provides highly stable, monodisperse NPLs with very narrow absorption and emission linewidths (min. 68 meV), and high PLQY (max. 37.6%).