Halide double perovskites are an emerging class of semiconductors with tremendous chemical and electronic diversity. While their bandstructure features can be understood from frontier-orbital models, chemical intuition for optical excitations remains incomplete. Here, we use \textit{ab initio} many-body perturbation theory within the GW and the Bethe-Salpeter Equation approach to calculate excited-state properties of a representative range of Cs2BB′Cl6 double perovskites. Our calculations reveal that double perovskites with different combinations of B and B′ cations display a broad variety of electronic bandstructures and dielectric properties, and form excitons with binding energies ranging over several orders of magnitude. We correlate these properties with the orbital-induced anisotropy of charge-carrier effective masses and the long-range behavior of the dielectric function, by comparing with the canonical conditions of the Wannier-Mott model. Furthermore, we derive chemically intuitive rules for predicting the nature of excitons in halide double perovskites using electronic structure information obtained from computationally inexpensive DFT calculations.
@article{arxiv.2306.11352,
title = {Chemical Mapping of Excitons in Halide Double Perovskites},
author = {Raisa-Ioana Biega and Yinan Chen and Marina R. Filip and Linn Leppert},
journal= {arXiv preprint arXiv:2306.11352},
year = {2023}
}