The development of highly efficient stretchable counter electrode (CE) and quantum dot sensitized solar cells (QDSCs) has still been challenging. In this work, flexible Cu/Ni film has been pre-prepared via a novel redox reaction between Ni foam and Cu ions. Further, the flexible Cu 2 S/Ni CE was fabricated for the first time by sulfidation of Cu/Ni film. A high photovoltaic conversion efficiency (PCE) of 8.94% for model CdSeTe QDSC composed of the flexible Cu 2 S/Ni CE and glass based photoanode was obtained, with the performance being strongly attributed to the excellent catalytic activity, high conductivity and good adhesion between Cu 2 S and Ni foam.Furthermore, flexible photovoltaic devices constructed by the as-prepared bendable Cu 2 S/Ni CE as well as TiO 2 based plastic photoanode have also been assembled with the highest PCE of 3.55%. The satisfactory mechanical property and stability after repeated bending have also been investigated.

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 Cu 1.8 S−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 Cu x S/brass-based QDSCs (8.44%). Significantly, the devices based on Cu 1.8 S−C showed excellent stability. The improved performance is mainly attributed to the good conductivity and stability of carbon and the high catalytic activity of Cu 1.8 S.