Calculating the Circular Dichroism of Chiral Halide Perovskites: A Tight-Binding Approach

TL;DR

This paper introduces a DFT-parameterized tight-binding model to calculate the circular dichroism of chiral halide perovskites, revealing how structural helicity influences optical activity and aiding the design of new optoelectronic materials.

Contribution

It develops a computationally efficient model to understand and predict the chiroptical properties of chiral perovskites, bridging structural and optical insights.

Findings

Structural helicity determines CD magnitude

The model accurately predicts optical properties

Chiral framework influences electronic transitions

Abstract

Chiral metal halide perovskites have emerged as promising optoelectronic materials for emission and detection of circular polarized visible light. Despite chirality being realized by adding chiral organic cations or ligands, the chiroptical activity originates from the metal halide framework. The mechanism is not well understood, as an overarching modeling framework is lacking. Capturing chirality requires going beyond electric dipole transitions, the common approximation in condensed matter calculations. We present a density functional theory (DFT) parameterized tight-binding (TB) model, which allows us to calculate optical properties including circular dichroism (CD) at low computational cost. Comparing Pb-based chiral perovskites with different organic cations and halide anions, we find that the structural helicity within the metal halide layers determines the size of the CD. Our results mark an important step in understanding the complex correlations of structural, electronic and optical properties of chiral perovskites, and provide a useful tool to predict new compounds with desired properties for novel optoelectronic applications.