Optoelectronic structure investigation ​of Bi and Sb sulphides and their alloys ​for their application in photovoltaics

This thesis investigates the structural and optoelectronic characteristics of antimony bismuth sulfide ((SbxBi₁₋ₓ)₂S₃) thin films for photovoltaic purposes. These alloys, consisting of readily available and non-toxic metals, provide a customizable bandgap and advantageous absorption properties ideal for solar energy collection. Thin films were deposited by the Close-Spaced Sublimation (CSS) method and studied using X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM), and density of states (DOS) analysis. XRD data validated orthorhombic crystal formations exhibiting consistent lattice contraction in relation to elevated Sb concentration. UV-Vis experiments indicated direct bandgaps between about 1.2 eV and 1.6 eV, dependent on composition; however, DOS analysis detected deep defect states in some alloys that may constrain photovoltaic performance. The results indicate that precise compositional adjustment of (SbxBi₁₋ₓ)₂S₃ is crucial for maximizing optoelectronic characteristics and improving their suitability as absorber layers in advanced thin-film solar cells.