Hollow Co9S8 nanoneedle arrays directly grown on fluorine-doped tin oxide (FTO) transparent conducting substrates were successfully prepared using a simple sacrificial template method. The performances of CdS/CdSe quantum dot-sensitized solar cells (QDSCs) employing such Co9S8 counter electrodes were remarkably improved compared to those using conventional Pt counter electrodes, primarily due to their higher electrocatalytic activity in the reduction of polysulfide electrolytes.
