Electrodeposited cobalt-copper sulfide counter electrodes for highly efficient quantum dot sensitized solar cells

A series of novel composite Cobalt-Copper Sulfide (CoS-CuS) counter electrodes were developed for Quantum Dot Sensitized Solar Cells (QDSSCs) based on core-shell cadmium sulfide-cadmium selenide quantum dots. The new electrodes were prepared by one-step electrodeposition from an aqueous solution containing cobalt chloride (CoCl2 center dot 6H(2)O), copper chloride (CuCl2 center dot 2H(2)O) and thiourea. The composite electrodes present rough morphology consisting of CuS agglomerates on a CoS continuous nanowire network, allowing easy electron transfer across the CE-electrolyte interface. The corresponding QDSSCs demonstrate power conversion efficiencies (PCE) exceeding 5%, under one sun illumination. By increasing the mesoporous layer thickness, adding a scattering layer and adjusting the QDs deposition conditions, a PCE as high as 7.49% was obtained. These very promising results further justify and account for the innovative character of the composite CoS-CuS counter electrodes. (C) 2016 Elsevier Ltd. All rights reserved.