p-type Cu₃BiS₃ thin films for solar cell absorber layer via one stage thermal evaporation

Ternary copper sulphides, especially copper-bismuth-sulphide (Cu-Bi-S), are alternative solar absorber materials due to their earth-abundant and non-toxic constituent elements, compared to the conventional copper indium gallium sulphide and cadmium telluride films. In this study, Cu-Bi-S thin films were deposited onto soda lime glass substrates using a one stage co-evaporation process from Cu₂S and Bi₂S₃ sources, with the deposition temperatures varied from room temperature to 400 °C. X-ray diffraction analysis confirmed that Cu₃BiS₃ was the dominant phase in the Cu-rich films, and the crystalline quality of the films was significantly improved with increasing the deposition temperature. An optical bandgap of 1.4 eV was achieved for the film deposited at 400 °C, which demonstrated a Hall mobility of 3.95 cm²/V-s and a carrier concentration of 7.48 × 10¹⁶ cm⁻³. Cu₃BiS₃ films deposited at 375 and 400 °C were implemented into superstrate solar cell structures (glass/ITO/n-CdS/p-Cu₃BiS₃/Al).