Amine-Free CsPbBr3 Perovskite Nanoplatelets Produced with Monolayer-Precision Thickness Control

Ultrathin lead halide perovskite nanoplatelets (NPLs) can enable tunable emission across the entire visible spectrum of light. The band-gap tunability of NPLs does not require halide composition engineering, so halide segregation can be avoided. However, their photoluminescence quantum yield (PLQY) and optoelectronic applications are often hampered due to reversible protonation and deprotonation of conventional amine ligands. Herein, we demonstrate the synthesis of benzenesulfonate-terminated CsPbBr3 NPLs without the use of any amine, and we clarify their nucleation and growth mechanism. The thickness of amine-free NPLs is controlled with monolayer-level precision, and thus, their emission wavelength is tuned between 437 and 504 nm. Amine-free NPLs are solely terminated by a benzenesulfonate group, leading to a Cs-rich surface. The amine-free NPLs exhibit PLQYs up to 80%, and slow charge carrier relaxation. This work offers a comprehensive study of surface chemistry and ligand dynamics of perovskite NPLs.