Abstract
<title>Abstract</title> <p>This study provides a comprehensive first-principles investigation of cubic MgTiS₃ and MgTiSe₃ chalcogenide perovskites, highlighting their potential for photovoltaic and photodetection applications. Using Density Functional Theory (DFT) within the Quantum ESPRESSO framework, structural stability was confirmed through generalized gradient approximation (GGA), while band-gap accuracy was refined using the HSE06 hybrid functional. The compounds exhibit wide band gaps of 2.8 eV (MgTiSe₃) and 3.3 eV (MgTiS₃), placing them in the visible-to-near-UV spectral range. Density of states analysis revealed strong p–d hybridization between Ti-3d and S-3p/Se-4p orbitals, enabling efficient optical transitions and charge-carrier generation. Optical property evaluation showed high absorption coefficients (~ 10⁹ m⁻¹), refractive indices near 2.5, and optical conductivity around 18 S/m, confirming strong photon absorption with minimal energy loss. Chalcogen substitution was demonstrated as an effective band-gap engineering strategy, offering tunability for diverse optoelectronic applications. Importantly, these materials combine non-toxic composition, cubic symmetry, and robust stability, positioning them as sustainable alternatives to lead-based perovskites. By integrating structural, electronic, optical, and thermoelectric insights, this work provides theoretical guidance for experimental realization of MgTiS₃ and MgTiSe₃. The findings underscore their promise as efficient, stable, and environmentally friendly materials for next-generation solar cells, photodetectors, and optoelectronic devices.</p>