Controlled Sulfidation Approach for Copper Sulfide–Carbon Hybrid as an Effective Counter Electrode in Quantum-Dot-Sensitized Solar Cells

Because of their good conductivities and high catalytic activities, carbon materials and copper sulfides have been individually and jointly used as counter electrodes in quantum-dot-sensitized solar cells (QDSCs). However, obtaining a combination of high conversion efficiency and stability is still challenging. In this work, we present a facile method for fabricating Cu1.8S–C hybrid counter electrodes through the sulfidation of a copper–carbon composite synthesized by grinding a mixture of organic binder, commercial copper powder, and carbon material containing activated carbon and carbon black in a designed mass ratio. The assembled CdSeTe-sensitized QDSCs achieved a high PCE of 8.40%, larger than that of pure carbon (5.25%) and comparable to that of conventional CuxS/brass-based QDSCs (8.44%). Significantly, the devices based on Cu1.8S–C showed excellent stability. The improved performance is mainly attributed to the good conductivity and stability of carbon and the high catalytic activity of Cu1.8S.