Boosting the efficiency of quantum dot sensitized solar cells up to 7.11% through simultaneous engineering of photocathode and photoanode

We demonstrate a new strategy of boosting the efficiency of quantum dot sensitized solar cells (QDSSCs) by engineering the photocathode and photoanode simultaneously. Nanostructured photocathodes based on non-stoichiometric Cu<inf>2-x</inf>Se electrocatalysts were developed via a simple and scalable approach for CdS/CdSe QDs co-sensitized solar cells. Compared to Cu<inf>2</inf>S CE, remarkably improved photovoltaic performance was achieved for QDSSCs with Cu<inf>2-x</inf>Se CEs. The superior catalytic activity and electrical conductivity of Cu<inf>2-x</inf>Se CEs were verified by the electrochemical impedance spectra and Tafel-polarization measurements. To maximize the efficiency enhancement, the photoanodes were optimized by introducing a pillared porous titania composite as the scattering layers for further light harvesting and charge transfer improvement concurrently. The combination of effective Cu<inf>2-x</inf>Se electrocatalysts and pillared titania scattering layers contributed to one of the best reported efficiencies of 7.11% for CdS/CdSe QDs co-sensitized solar cells.