A novel ZnS/SiO2 double passivation layers for the CdS/CdSe quantum dots co-sensitized solar cells based on zinc titanium mixed metal oxides

The surface passivation strategy is one of the effective ways to improve the power conversion efficiency (PCE) of quantum dots-sensitized solar cells (QDSSCs). In this work, a novel ZnS/SiO2 coating serves as the passivation layers for the CdS/CdSe co-sensitized solar cells based on zinc titanium mixed metal oxides (MMOs) obtained from layered double hydroxides (LDHs) precursor. The incorporation of passivation layers effectively improved the performance of the corresponding CdS/CdSe quantum dots co-sensitized solar cells and the best PCE of 4.91% has been achieved, which represents an over 55% improvement than that of devices without passivation. The effects of ZnS/SiO2 double passivation layers were systematically investigated, especially by 2D time-resolved fluorescence imaging and electrochemical impedance spectroscopy technique. It was revealed that the existence of ZnS/SiO2 outer layers caused the suppression of charge recombination, higher electrons collection efficiency, and superior surface quality.