Chirality transfer induced in a lead-halide perovskite cluster through sruface chemistry modification

The chiroptical properties of materials are of interest for various applications, including structure determination, polarized photo-detectors/luminescence sources, and spintronics. Inducing chiroptical activity into semiconductors is a challenge due to the difficulty of controllably creating asymmetric crystal structures. One promising method is chirality transfer by capping nanocrystals with chiral organic ligands. Experimentally, chiral capped nanocrystals show emergent chiroptical signatures, but the mechanisms for chirality transfer remain unclear. We utilize TDDFT to explore chirality transfer in CsPbX₃ (X=Cl, I) clusters capped with chiral diaminocyclohexane (DACH) enantiomers. When DACH is bound to the cluster surface, perovskite optical transitions gain chiroptical activity that is dependent on the binding configuration. We find that this chirality transfer is best rationalized by the coupling of the static dipoles from the adsorbed chiral molecules to the optical transition dipole of the perovskite cluster. The ratio of circular dichroism to absorption, known as the anisotropy factor, increases proportionally to surface ligand density and provides mechanistic insight for improving the chiroptical functionality of semiconductor nanomaterials.