Efficient Flexible Counter Electrode Based on Modified Graphite Paper and in Situ Grown Copper Sulfide for Quantum Dot Sensitized Solar Cells

Flexible counter electrode (CE) plays an important role in portable quantum dot sensitized solar cells (QDSCs). However, the present power conversion efficiency (PCE) of bendable QDSC is rather limited partly due to the unsatisfactory conductivity, flexibility, catalytic activity, and fabrication technique of CE. In this work, flexible CEs composed of CuxS and graphite paper (GP) are built and fabricated through a facile successive ionic layer adsorption reaction (SILAR) method. Through designing and optimizing of the surface property of GP, coverage, and thickness of catalyst, excellently performed CEs are achieved with the maximal PCE of 8.70% under one full sun illumination for Zn–Cu–In–Se QDSCs. Further, fully flexible QDSCs assembled with the as-prepared CEs and plastic photoanodes show a high PCE of 2.45% under the same illumination.