Transition metal - Graphene oxide nanohybrid materials as counter electrodes for high efficiency quantum dot solar cells

We report the synthesis of new nanocomposite hybrids, based on graphene oxide (GO) incorporating Cu and Co transition metals. GO was produced through graphite oxidation using powerful oxidizing reagents and consecutively was functionalized with the use of CTAB and PSS surfactants. The resulting materials were further decorated with Cu and/or Co using an electrostatic self-assembly process through solvothermal treatment with the corresponding metal chlorides in an autoclave. The influence of metal precursor concentration in the final material characteristics was examined, using mass ratios of 1/4.5 and 1/9 for GO/Cu and GO/Co, and 1/4.5, 1/9 and 1/18 for the bimetallic GO/(Cu-Co) nanohybrid materials, respectively. The produced nanohybrid materials (GO/Cu, GO/Co and GO/(Cu-Co)) were characterized morphologically, structurally and electrochemically and consequently, they were incorporated in quantum dot sensitized solar cells (QDSCs). The novel hybrid materials work effectively as counter electrodes (CE) in CdS-ZnS/CdSe-based QDSCs presenting high photocurrent density (Jsc) and open-circuit voltage (Voc) values leading to enhanced photovoltaic performance. Optimization of the electrocatalytic activity as a function of the GO/(Cu-Co) mass ratio results in cells with a power conversion efficiency (PCE) of 8.73%.