Carbon-coated three-dimensional WS₂ film consisting of WO₃@WS₂ core-shell blocks and layered WS₂ nanostructures as counter electrodes for efficient dye-sensitized solar cells

Abstract

The possibility of using solar energy for electricity generation has inspired intensive enthusiasm on the development of solar cell devices. This work reports the synthesis of a novel counter electrode (CE) composed of WOx@WS2@carbon core-shell film and compares its electrical and electrocatalytic performances with other two CEs of WOx/carbon film and conventional Pt in the dye-sensitized solar cells (DSSCs). The WOx@WS2@carbon CE was prepared by a sulfurization treatment of a mesoporous WOx/carbon film coated on fluorine-doped tin oxide (FTO) glass. The well-interconnected three-dimensional (3D) WS2 structure with coated carbon film provides high electrocatalytic activity and fast reaction kinetics for the reduction of triiodide to iodide due to its sufficient active sites on 3D WS2 framework containing surface edge-oriented nanosheets and the facile electron transfer and electrolyte diffusion via the continuously carbon layer. Photovoltaic performance tests indicate the DSSC device with the counter electrode of WOx@WS2@carbon core-shell achieved the power conversion efficiency (PCE) of 7.71% compared favourably with the values of 6.00% from WOx/carbon CE and 7.34% from conventional Pt CE. Such results vividly mirror that the developed WOx@WS2@carbon core-shell can replace the conventional Pt film, realizing Pt-free counter electrodes for DSSCs.