Vertical nanosheet-structured ZnO/TiO2 photoelectrodes for highly efficient CdS quantum dot sensitized solar cells

Employing vertical nanosheet-structured films as photoanodes of quantum dot sensitized solar cells (QDSCs) might provide a direct pathway for the photo-exited electrons. Here, the vertical ZnO, ZnO/TiO 2 and TiO 2 nanosheet-structured films were prepared by a feasible deposition processes . These films were sensitized with CdS quantum dots and assembled with CuS counter electrodes to fabricate QDSCs. The photoelectric properties of ZnO/TiO 2 composite films were superior to both pure ZnO and TiO 2 films. The effects of TiO 2 coating were investigated using electrochemical impedance spectroscopy (EIS). It was found that the photo-excited electron lifetimes in the photoanode were significantly improved with TiO 2 layer. The optimum power conversion efficiency was about 1.95% under AM 1.5   G illumination (100   mW cm −2 ), with a short circuit current density, open circuit voltage, and fill factor of 6.11   mA   cm −2 , 0.562   V and 0.57, respectively.