Unveiling the photovoltaic potential of eco-friendly β–CaSiY₃ (Y = S, Se) chalcogenide perovskites: A first-principles investigation

Abstract

Abstract Chalcogenide perovskites have recently emerged as promising materials for next–generation optoelectronic and photovoltaic related applications due to their chemical stability and tunable electronic properties. In this work, the effects of sulfur (S) replacement by selenium (Se) on the structural, electronic, optical, and mechanical properties of β–CaSiY3 (Y = S, Se) chalcogenide perovskites are systematically investigated using first–principles density functional theory. Calculations are carried out within the PBE–GGA framework and further refined using the hybrid YS–PBE0 functional and the TB–mBJ potential to obtain reliable band-gap values. Both compounds exhibit direct band-gap semiconducting behavior at the Γ point. Mechanical stability of the orthorhombic β–phase is confirmed through compliance with the Born stability criteria, while negative formation enthalpies indicate thermodynamic favorability. A significant reduction in the band-gap energy is observed with increasing chalcogen ionic radius, with Eg decreasing from 2.54 eV for CaSiS3 to 0.94 eV for CaSiSe3. Optical absorption analysis reveals strong photon absorption predominantly in the ultraviolet region. These findings highlight the tunability and stability of Si–based chalcogenide perovskites and suggest their potential suitability for optoelectronic devices, including ultraviolet photodetectors, multijunction, and tandem solar cells.