Tracing the Origin of Chiropticity in Lead-Halide Perovskite Nanomaterials.

Chiral lead-halide perovskite nanomaterials are promising platforms for circularly polarized photonics and spin-selective transport, yet the origin of their chiroptical response is often difficult to establish. Conventional explanations focus on chiral ligands, lattice distortion, and spin-orbit-coupled electronic structure in the final material. For colloidal nanomaterials in particular, high surface-to-volume ratios and growth through precursor complexes and cluster intermediates make formation history and surface chemistry especially important. Circular dichroism (CD), circularly polarized luminescence (CPL), and chirality-induced spin selectivity (CISS) establish asymmetric optical or spin responses but do not by themselves reveal when asymmetry first appears or where it is retained. We compare ligand-induced, structural, electronic, assembly-induced, interfacial, and precursor-mediated mechanisms by asking when asymmetry is first selected during formation and where it is retained in the final material. We also discuss the measurements and controls needed to distinguish among these mechanisms in these nanomaterials.