Giant Apparent Optical Circular Dichroism in Thin Films of Bismuth‐Based Hybrid Organic–Inorganic Metal Halide Semiconductor Through Preferred Orientation

Abstract

AbstractIntroducing chirality into organic/inorganic hybrid materials can impart chiroptical properties such as circular dichroism. The ability to tune chiroptical properties in self‐assembled materials can have important implications for spintronic and optoelectronic applications. Here, a chiral organic cation, (R/S)‐4‐methoxy‐α‐methylbenzylammonium, is incorporated to synthesize the bismuth‐based hybrid organic–inorganic metal halide semiconductor, (R/S‐MeOMePMA)BiI4. Thin films of this Bi‐based compound demonstrate large chiroptical responses, with circular dichroism anisotropy (gCD) values up to ≈0.1, close to the highest value observed in another chiral metal‐halide semiconductor, (R‐MBA2CuCl4). Detailed investigation reveals that this large gCD in (R/S‐MeOMePMA)BiI4 is caused by the apparent CD effect. Careful selection of deposition conditions and the concomitant thin‐film orientation enables the control of gCD, with maximum value observed when its thin film has a well‐crystallized preferred (001) orientation parallel to the substrate. The results support a growing body of evidence that low symmetry plays an important role in achieving unusually large gCD in these chiral metal–halide materials and provides design rules for achieving large chiroptical response via morphology control.