Precursor Stoichiometry-Regulated Room-Temperature Synthesis and Surface Reconstruction of Highly Emissive CsPbI3 Perovskite Nanoplatelets

Room-temperature synthesis of uniform CsPbI3 nanoplatelets (NPLs) is hindered by their fast crystallization and instability. Here, we demonstrate a ligand-assisted reprecipitation (LARP) approach under ambient conditions in which the Cs/Pb precursor stoichiometry is used to regulate the room-temperature crystallization and optical properties of CsPbI3 NPLs. Such regulation permits fine-tuning of the optical band gap, delivering uniform NPLs characterized by a stable, narrow-band photoluminescence emission at 660 nm. Subsequent surface reconstruction by sodium lauryl sulfate (SLS) effectively suppresses the nonradiative recombination pathway with an impressive photoluminescence quantum yield of 99.2%. It simultaneously enhances the film uniformity, charge transport efficiency, and ambient stability. Density functional theory calculations reveal that such improvements stem from the strong binding energy by the SLS ligand. The resulting light-emitting diodes exhibit electroluminescence at 660 nm, an external quantum efficiency of 1.43%, and a lifetime of 938 s. This work establishes a versatile room-temperature route for the controlled synthesis and surface engineering of highly emissive perovskite NPLs.