A Universal Approach for Controllable Synthesis of n-Specific Layer 2D Perovskite Nanoplates.

2D perovskites with chemical formula A' 2 A n-1 B n X 3n+1 have recently attracted considerable attention due to their tunable optical and electronic properties by varying the chemical composition. While high color-purity emitting perovskite nanomaterials have been accomplished through changing the halide composition, the preparation of single-phase, specific n-layer 2D perovskite nanomaterials is still pending because of the fast nucleation process of nanoparticles. In this study, we demonstrated a facile, rational and efficacious approach to synthesize monodisperse 2D perovskite nanoplates with a designated n number for both lead- and tin-based perovskite through kinetic control. We found that casting carboxylic acid additives in the reaction medium would promote selective formation of the kinetic product, multi-layer 2D perovskite, in preference to the single layer thermodynamic one. The resulted n-specific layer 2D perovskites show a trend where decreasing the number of octahedral layers per inorganic sheet leads to an increase of photoluminescence energy, radiative decay rate, and a significant boost in photostability.