ABSTRACT

The combination of chirality and semiconducting properties has enabled chiral metal-halide semiconductors (MHS) as a promising candidate for spin- and polarization-resolved optoelectronic devices. Although several chiral MHS with rich chemical and structural diversity have been reported lately, the macroscopic origin of chiroptical activity remains unknown, let alone the quantitative comparison of chiroptical activity across different systems and the structure-chirality relationships. This is largely stemming from the lack of a quantitative descriptor of chiroptical activity for chiral MHS. Here, through a combination of spectroscopic measurements and Mueller matrix analysis, we discover that the previously reported “apparent” anisotropy factor measured from circular dichroism (CD) in chiral MHS thin films is not an intrinsic chiroptical property, resulting from an interference from the film’s linear birefringence (LB) and linear dichroism (LD) due to macroscopic anisotropies. We verify the presence of LB and LD effects in both one-dimensional (1D) and zero-dimensional (0D) chiral MHS thin films. As such, we propose spectroscopic methods to decouple the genuine CD from other spurious contributions, which allows to compare the intrinsic chiroptical activity quantitatively across different chiral metal-halide systems. The relation between structure and the genuine chiroptical activity is then discovered, which can be well described by the chirality-induced spin-orbit coupling (SOC) in the chiral structures. Our study unveils the macroscopic origin of chiroptical activity of chiral MHS and provides important design principles for obtaining high anisotropic factors for future chiral photonics and electronics.

Reference

1. Yu, Z.-G. The Journal of Physical Chemistry Letters 2020, 11, 8638-8646,