Computational study of the fundamental properties of Zr-based chalcogenide perovskites for optoelectronics.

Chalcogenide perovskites have recently attracted enormous attention since they show promising optoelectronic properties and high stability for photovoltaic applications. Herein, the relative stability and photoactive properties of chalcogenide perovskites AZrX (A = Ca, Sr, Ba; X = S, Se) including the needle-like (α phase) and distorted perovskite (β phase) structures are first revealed. The results show that the difference in the relative stability is large between the α and β phases for both AZrS and AZrSe. The fundamental direct-gap transition is only allowed for the β phase, which is further confirmed by its optical properties. It is indicated that the suitable direct-gap energy of the α phase is not desirable for thin-film solar cells. Therefore, the stability, and mechanical, electronic, and optical properties of the distorted chalcogenide perovskites AZrSSe ( = 0, 1, 2, 3) are mainly explored for the first time. The predicted direct band gaps of nine compounds AZrSSe ( = 1-3) are in the ideal range of 1.3-1.7 eV. Most compounds have small effective masses, low exciton binding energies, and high optical absorption coefficients in the visible region. Moreover, the mechanical, thermodynamic, and dynamic stabilities are identified for these compounds. Our findings suggest that CaZrSe, SrZrSe, and BaZrSe are proposed to be the most promising candidates for photovoltaic applications owing to their promising properties.