fig4
Figure 4. UPS spectrum of (A) control and (B) Zn doping Sb2S3 thin films; (C) schematic band diagram and (D) the summarized PCE of previous works of Sb2S3 solar cell. UPS: Ultraviolet photoelectron spectroscopy; FTO: fluorine-doped tin oxide; CdS: cadmium sulfide; PCE: power conversion efficiency.
