Dual function of molybdenum sulfide/C-cloth in enhancing the performance of fullerene nanosheets based solar cell and supercapacitor

Abstract

Quantum dot solar cells (QDSCs) with hexagonal fullerene nanosheets (C₆₀-NS) embedded in a titanium oxide/cadmium sulfide (TiO₂/CdS) photoanode coupled with a carbon-cloth (C-cloth) coated with molybdenum sulfide (MoS₂) counter electrode (CE) are studied for the first time. C₆₀-NS due to a favorable work function of 4.57 eV and a conductance of 1.44 μS, enable faster electron injection from the conduction band of cadmium sulfide to the current collector, in contrast to the bulk fullerene based TiO₂/CdS solar cell. The champion cell with the TiO₂/C₆₀-NS/CdS photoanode and a MoS₂/C-cloth CE exhibits a high power conversion efficiency of 5.6%, greater by ∼14% relative to its' analogue cell with bulk fullerene. A large area cell of 1 cm² dimensions with TiO₂/C₆₀-NS/CdS gives a PCE of 2.9%. The effect of MoS₂ in improving the efficiency of the cell with a TiO₂/C₆₀-NS/CdS photoanode is realized in terms of enhanced electrocatalytic activity for polysulfide reduction, and lower charge transfer resistance at the polysulfide/CE interface compared to a cell with the same photoanode but having pristine carbon-cloth as the CE. The ability of MoS₂ for catalyzing the oxidized polysulfide species at the CE and C₆₀-NS for improving the charge collection at the photoanode serve as indicators for their wider utilization in solar cells. It also serves as a good supercapacitor material. A MoS₂/C-cloth based symmetric cell exhibits a specific capacitance of 645 F g⁻¹ at 2 A g⁻¹, which shows its' potential for energy storage as well. By integrating the QDSC and the supercapacitor, the resulting integrated device acquires a photovoltage of 0.7 V, under 1 sun illumination.