Unraveling the origin of chiroptical properties in 2D achiral-chiral hybrid lead perovskites from first-principles calculations

Chiral hybrid organic-inorganic perovskites are an emerging class of non-magnetic spintronic materials. Alloying organic achiral cations with the chiral ones creates new avenues to tune the chiroptical properties, e.g., circular dichroism (CD) response, to a greater extent. However, how the achiral-chiral cation mixing contributes to engineering the electronic and chiroptical properties is far from understood. We provide insights into the structure-property relationship in the achiral-chiral mixed system from first-principles calculations. We demonstrate that the achiral-chiral cation mixing leads to stronger asymmetric hydrogen bonding between chiral organic cations and inorganic sublattices, resulting in larger spin-splitting and enhanced CD signals. Our results shed light on the origin of electronic and chiroptical properties in the 2D mixed achiral-chiral hybrid organic-inorganic perovskites.