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 Cu2-xSe electrocatalysts were developed via a simple and scalable approach for CdS/CdSe QDs co-sensitized solar cells. Compared to Cu2S CE, remarkably improved photovoltaic performance was achieved for QDSSCs with Cu2-xSe CEs. The superior catalytic activity and electrical conductivity of Cu2-xSe 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 Cu2-xSe 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.