Circular Dichroism of 1D Chiral Halide Perovskites: A GW-BSE Study

Chiral halide perovskites (CHPs) combine structural chirality with strong spin–orbit coupling, enabling spin-selective transport and circularly polarized luminescence. However, the microscopic origin of circular dichroism (CD) in quantum-confined one-dimensional CHPs remains unresolved. Here, we employ many-body GW and Bethe–Salpeter equation calculations including electric dipole, quadrupole, and magnetic dipole contributions to investigate the chiroptical response of the R/S enantiomers of PEAPbI₃, CHEAPbI₃, and NEAPbI₃. We find that the CD signal follows the order CHEAPbI₃ > PEAPbI₃ > NEAPbI_3, demonstrating a strong cation ion tuning effect. Analysis reveals that the CD signal originates from anisotropic excitonic transitions generated by cation-induced chiral symmetry breaking in the Pb–I framework, whose effects are amplified by one-dimensional confinement and strong spin–orbit interaction. These results establish a microscopic mechanism linking lattice chirality, excitonic structure, and optical activity, providing design principles for chiral perovskite optoelectronic and spin-photonic devices.