Enabling Chiroptical Properties in Achiral 2D Perovskites via Spiral Morphology

Chiral 2D halide perovskites are promising semiconducting materials for chiroptoelectronic and spintronic applications. Chirality is typically imparted into 2D perovskites through the incorporation of chiral ammonium spacer cations, resulting in a chiral crystal structure. However, the extent of chirality transfer from the chiral organic cations to the inorganic perovskite network remains debated. In this work, we present another approach to introduce chirality and chiroptical properties into 2D perovskites through nanostructure morphology. By tuning crystallization conditions at an air-water interface, a large family of 2D perovskites with achiral crystal structures can be directly grown into spiral microplates via a screw dislocation growth mechanism. We demonstrated the versatility of this method by synthesizing spiral microplates of 10 different 2D Ruddlesden-Popper lead halide perovskites with various spacer cations, A-site cations, <i>n</i> number, and halide anions. The microplates can then be transferred to arbitrary substrates and characterization with atomic force microscopy clearly revealed the spiral centers. Fluorescence-detected circular dichroism (FDCD) microscopy was used to investigate the resulting chiroptical properties of individual chiral objects and large, spatially dependent g-factors on the order of 10^-3were observed from (BA)₂(MA)₂Pb₃I₁₀ spiral microplates. These results show that screw dislocation-driven growth can be used as a generally applicable method for enabling chirality and chiroptical properties in 2D perovskites without the need for chiral cations.