Large Optical Anisotropy Factors of a Chiral Bismuth Iodide Hybrid Organic-Inorganic Semiconductor

Chiral materials are important tools for interconverting the spin angular momentum of circularly polarized light with electronic spin to help realize a wide variety of emerging spin-based technologies. Here we demonstrate that thin films of a Bismuth-based chiral 0D hybrid organic-inorganic semiconductor (HOIS) exhibit large anisotropy values for circularly polarized light emission (CPLE) that approach 50% circular polarization. The observed anisotropy is strongly correlated with the crystallographic orientation of the thin film and is also strongly temperature-dependent, with a marked anti-correlation with exciton transition linewidth. Detailed analysis of the CPLE anisotropy indicates large contributions from structure-dependent scattering that are analogous to the so-called “LDLB” effect observed for circular dichroism, caused by interactions between linear dichroism and linear birefringence. Although this effect has been observed for organic thin-film composites, this first demonstration in a HOIS system provides a unique route for enhancing carrier spin polarization and polarization-dependent emission in self-assembled hybrid semiconductors. These results provide a fundamental framework for understanding and harnessing the properties of low dimensional and low symmetry chiral HOIS materials for circularly polarized light applications.