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 AZrX₃ (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 AZrS₃ and AZrSe₃. 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 AZrS_3-Se (x = 0, 1, 2, 3) are mainly explored for the first time. The predicted direct band gaps of nine compounds AZrS_3-Se (x = 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 CaZrSe₃, SrZrSe₃, and BaZrSe₃ are proposed to be the most promising candidates for photovoltaic applications owing to their promising properties.