DFT based computational investigations of the physical properties of chalcogenide perovskites CsXS3 (X=P, Ta) for optoelectronic and photovoltaic applications

In this study, we employed density functional theory (DFT) calculations to systematically characterize the structural, mechanical, electronic, thermal, and optical properties of CsXS₃ (X = P, Ta), one of the most promising members of the chalcogenide perovskite (CP) family. Our theoretical findings align strongly with reported syntheses of other CP's, highlighting CsXS₃ (X = P, Ta) as most stable compounds. These materials satisfy the Born stability criteria, indicating robust mechanical stability, exhibit anisotropy, and demonstrate acceptable resistance to deformation under external stress. CsPS₃ and CsTaS₃ feature direct bandgaps of 1.91 eV and 0.51 eV, with small photocarrier effective masses, high absorption coefficients (1.6 × 10⁶ and 2.1 × 10⁶ cm⁻ 1 ), low reflectivity (15 % and 20 %), reduced loss function (0.6 and 0.4) and low refractive index (2.5 and 3.1), respectively. These properties underscore the potential of CsXS₃ (X = P, Ta)-based CP's for developing more efficient and stable optoelectronic devices and indoor photovoltaics. Notably, CsPS₃ is a strong contender for thermoelectric applications due to its lower Debye temperature compared to other CP's. Overall, our results demonstrate the great promise of CsXS₃ (X = P, Ta) chalcogenide perovskites in advancing the field of renewable energy and optoelectronics.