Spacer Cation Alloying Enables Markedly Improved Chiroptical Properties of Two‐Dimensional Chiral Hybrid Perovskite Nanosheets

Abstract The combination of unique features of chirality and promising attributes of 2D halide perovskites opens an enticing avenue for the rational design of chiral materials in chiroptoelectronics and spintronics. Despite several impressive approaches available to prepare 2D perovskites with chirality, it poses significant challenges to having a general route to a myriad of high‐quality nanoscale 2D chiral perovskites with tunable and enhanced chiroptical properties. Herein, a robust spacer cation alloying strategy to craft 2D chiral perovskite nanosheets (NSs) is reported, exhibiting a markedly improved circular dichroism signal over the pure chiral cation‐based counterparts. The experimental studies and density functional theory (DFT) modeling revealed that the introduction of achiral cations promoted the defect passivation of NSs via optimization of the binding energy of the cations on the NS surface. More importantly, the compelling effects of spacer cation alloying on the chiroptical properties are readily extended to 2D perovskite NSs with other chiral A‐site cations, lead‐less B‐site cations and X‐site halide anions of interest. This study provides a powerful platform to produce a wide diversity of 2D chiral perovskite nanomaterials and regulate their chiroptical properties via innovative and convenient cation alloying, which may boost the development of chiroptical devices.