Transient surface photovoltage of p-type Cu₃BiS₃

Thin films of Cu₃BiS₃ were prepared by coevaporation. Hall-effect, Seebeck-effect, and surface photovoltage measurements show that Cu₃BiS₃ is a p-type semiconductor with Hall-mobility, free carrier concentration, and thermo-electric power of 4 cm² /V s, 2× 1016 cm-3, and 0.73 mV/K, respectively. The work function was determined by Kelvin probe force microscopy to be (4.37±0.04) eV before and (4.57±0.01) eV after deposition of a thin In₂S₃ layer. Transient surface photovoltage measurements at variable excitation wavelength showed the importance of defect states below the band gap for charge separation and the opportunity for surface defect passivation by a very thin In₂S₃ layer. The band bending at the Cu ₃BiS₃/In₂S₃ interface was obtained. The role of grain boundaries for charge transport and charge separation is discussed.