Efficiency Enhancement of Quantum Dot Sensitized TiO₂/ZnO Nanorod Arrays Solar Cells by Plasmonic Ag Nanoparticles

A high efficiency quantum dot sensitized solar cell (QDSC) based on Ag nanoparticles (NPs) decorated TiO₂/ZnO nanorod arrays (NAs) photoelectrode has been constructed. The incorporation of Ag NPs to TiO₂/ZnO NAs photoelectrode not only increases light harvesting efficiency and facilitates exciton dissociation but also decreases surface charge recombination and prolongs electron lifetime, which collectively contribute to improving the J_sc of the CdS/CdSe QDs cosensitized solar cells. The direct contact of Ag NPs with TiO₂ NPs is undergoing Fermi level alignment; thus, the apparent Fermi level is supposed to trigger an upward shift of more negative potential, which results in an increase the V_oc of the QDSCs. As a result, the power conversion efficiency of the QDSCs with Ag NPs decorated TiO₂/ZnO NAs photoelectrode reached 5.92%, which is about 22% enhancement of the efficiency for the solar cells without Ag NPs (4.80%).