  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.
