Zirconium Based Chalcogenide Perovskites AZrS3 (A = Ca, Sr, Ba): Crystal Chemistry, Phase Behavior, Electronic and Optical Properties, Stability, and Energy Applications a Critical Review.

Zirconium based chalcogenide perovskites, AZrS3 (A = Ca, Sr, Ba), are lead free semiconductors composed of earth abundant elements and are of interest for photovoltaics and optoelectronics. The evidence base is, however, strongly unbalanced. Experimental work concerns mainly BaZrS3, which is orthorhombic (Pnma) at room temperature, has a measured optical gap of about 1.75–1.8 eV and shows band edge absorption coefficients above 105 cm−1. CaZrS3 remains largely computational, and SrZrS3 must be specified by polymorph because it also forms a non-perovskite, needle-like phase. This narrative critical review, based on a documented literature search, appraises experimental and first-principles studies of crystal chemistry, phase behavior, synthesis, electronic and optical properties, stability, defects and device relevance, and labels each benchmark as experimental, computed or simulated. Three evidence limitations are emphasized. First, the cubic (Pm3̄m) phase widely used in calculations is predicted by simulation to form only above about 880 K, whereas high temperature diffraction of BaZrS3 has so far revealed orthorhombic and tetragonal phases. Second, the reduction of the BaZrS3 gap from 1.78 to 1.51 eV by 4 at. % Ti alloying is experimental, whereas the reported photovoltaic efficiencies of 28–33% are device simulations, not measured devices. Third, inconsistent functionals and structural models prevent quantitative comparison across the Ca–Sr–Ba series. A minimum computational protocol and a staged assessment framework are proposed to support evidence-based comparison of the series.