Modulation of Energy Band Positions in Sb2S3 Thin Films for Enhanced Photovoltaic Performance of FTO/TiO2/Sb2S3/P3HT/Au Solar Cell

Antimony sulfide (Sb₂S₃) has the potential as an absorber material in photovoltaics due to its suitable bandgap and favorable optoelectronic properties. However, its energy band positions are not extensively explored which are essential for effective charge separation and transfer. This study examines the energy band positions of Sb₂S₃ thin films as a function of annealing temperature. Sb₂S₃ thin films are grown by a combination of successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) method to enhance the crystallinity, tune the bandgap, and overall quality of Sb₂S₃ films to enhance the photovoltaic performance. Optical bandgap decreases from 2.41 to 1.67 eV from the as-deposited films to annealed at 300 °C due to changes in interatomic distances. Energy band positions of Sb₂S₃ films are measured both by cost-effective electrochemical cyclic voltammetry and Mott–Schottky analysis and validated the findings using ultraviolet photoelectron spectroscopy (UPS). The conductivity of Sb₂S₃ is found to be n-type. Thin-film solar cells are then fabricated by employing Sb₂S₃ as an absorber layer in an FTO/TiO₂/Sb₂S₃/P3HT/Au structure, achieving an enhanced power conversion efficiency, increasing from 0.4 to 2.8% after annealing. These findings demonstrate the potential of Sb₂S₃ as a low-cost absorber material for thin-film photovoltaics.