Surface States in Ternary CdSSe Quantum Dot Solar Cells

Ternary CdSSe quantum dot-sensitized solar cells (QDSCs) have demonstrated advantages such as wide absorption ranges and tunable band structures. However, the oxygen additives absorbed on such multicomponent quantum dot (QD) surfaces induce band bending at the TiO2/CdSSe interface and prevent charge transport in QDSCs, as determined via X-ray photoelectron spectroscopy (XPS) and synchrotron-based X-ray Absorption Near-Edge Structure (XANES) analysis. Annealing of TiO2/CdSSe QDs photoanodes was conducted at different temperatures under Ar atmospheres to eliminate oxygen additives and interfacial band bending. The short-circuit current (Jsc) of the annealed ternary CdSSe QDSCs is obviously improved, whereas the TiCl4 treatment and MgO coating of the TiO2 nanocrystals are assisted by the annealing to compensate for the loss of opencircuit voltage (V-oc) and fill factor (FF). Ternary CdSSe QDSCs with efficiencies of 4.72% have been achieved using the optimized