Measuring Electroabsorption and Circular Dichroism of Metal Halide Perovskites While Varying Organic Layer Composition

Two-dimensional metal halide perovskites (MHPs) are of great interest as newly developed and studied solar cells due to their high defect tolerance and high tunability. MHPs are semiconductors whose optical properties are heavily influenced by excitons, which are the bound state between negative electrons and positive holes in the material. As a result of their inorganic-organic structure, changes can be made to various molecules within the MHP which alter their exciton features as well as other intrinsic properties of the MHP. We specifically examined chiral MHPs, in which structural chirality can give rise to differences in electronic spin states which couple to photons being absorbed or emitted. This can be detected via circular dichroism, which is the difference in absorption of left and right circularly polarized light. We studied 2D lead iodide chiral perovskites whose organic material was S-methylbenzylamine where we added ligands on the benzene ring to induce differing chirality on our materials. We found that slight changes to the MHPs organic layer lead to relatively small effects on the exciton binding energy of the perovskite while still showing drastic changes in the circular dichroism.