  Chalcogenide perovskites have emerged as non-toxic and stable photovoltaic
materials, acting as an alternative to lead halide hybrid perovskites having
similar optoelectronic properties. In the present work, we report the
electronic and optical properties of chalcogenide perovskites AZrS$_3$ (A=Ca,
Sr, Ba) by using the density functional theory (DFT) and many-body perturbation
theory (MBPT viz. G$_0$W$_0$ and BSE). This study includes excitonic analysis
for the aforementioned systems. The exciton binding energy (E$_\textrm{B}$) is
found to be larger than that of the halide perovskites, as the ionic
contribution to dielectric screening is negligible in the former. We also
observe a more stable charge-separated polaronic state as compared to that of
the bound exciton. Finally, on the basis of direct gap and absorption
coefficient, the estimated spectroscopic limited maximum efficiency (SLME) of
the solar cells is large and suggests the applicability of these perovskites in
photovoltaics.
