Prebaking of an SnS source with sulfur for achieving higher photovoltaic performance in VTD-SnS thin films for solar cells

Abstract

Given its preeminent photovoltaic properties, tin sulfide (SnS) has attracted remarkable interest and has been explored as an absorber for thin-film solar cells in the last few decades. However, the power conversion efficiency (PCE) of SnS-based solar cells is typically below 4%. The deficit in open circuit voltage (V_OC) of devices with shunt losses can be reduced by altering the sulfur vacancy and surface roughness of the vapor transport deposition (VTD)-SnS absorber. Therefore, this paper reports an effective approach to strengthen the efficiency of the VTD-SnS device by reducing the sulfur vacancy (V_S). To this end, the SnS source was prebaked with a very small amount of sulfur powder in the same tube before the absorber layer deposition, and the efficiency of the fabricated VTD-SnS solar cell increased from 3.39 to 4.82%. This improvement was attributed to the reduction in the V_S and the improved surface profile of the film. The reduction in the V_S resulted in a decrease in the bulk defects, thus enhancing the collection of generated charge carriers. Additionally, the dark current of the prebaked source device reduced, indicating the improved shunt properties of the prebaked film; nevertheless, the shunt properties can be further enhanced by improving the interfacial properties and surface roughness of the film.