Cu doping of Sb₂Se₃ thin films via thermal evaporation: tailoring structural and optical properties for enhanced photovoltaic performance

Abstract

In this study, Cu-doped Sb₂Se₃ thin films were successfully grown using the thermal evaporation method, and their structural and optical properties were systematically investigated. Three different samples with thickness of ∼400 nm were analyzed: undoped, 1 %, and 2 % Cu-doped Sb₂Se₃. X-ray diffraction (XRD) analysis revealed well-defined peaks, confirming the orthorhombic crystalline nature of the films. Scanning electron microscopy (SEM) images showed a uniform surface morphology without any significant defects. The optical properties were examined through transmission measurements. The band gap energy determined by Tauc analysis decreased from 1.27 to 1.21 eV as the Cu doping increased from 0 % to 2 %, indicating that Cu incorporation modifies the electronic structure of Sb₂Se₃. Similarly, Urbach energy increased from 0.148 to 0.168 eV depending on Cu content, suggesting a rise in localized states due to increased structural disorder. These findings demonstrate that Cu doping influences the electronic structure and defect states of Sb₂Se₃, which is crucial for optimizing its performance in photovoltaic and optoelectronic applications.