WS2 thin films a new candidate for solar cells

Polycrystalline thin films of the layered semiconductor tungsten disulphide were prepared by sulphurization of RF sputtered tungsten films in a closed tube system. Two types of crystal orientation were obtained depending on the sulphur source temperature. By atomic force microscopy on films with the van der Waals planes parallel to the substrate atomic resolution of WS₂ surfaces could be observed for the first time. With as-grown WS₂ films and n-ZnO as window material it was possible to fabricate photosensitive heterojunctions for the first time. These devices were prepared with the ohmic Au contact close to the ZnO emitter layer on top of the WS₂ films. Despite that this planar diode geometry is not optimized yet, I-V measurements revealed open-circuit voltages up to 360 mV and short-circuit currents with a maximum of I_SC=0.65 mA/cm² under simulated Sun illumination