Effects of ZnO coating on the performance of TiO2 nanostructured thin films for dye-sensitized solar cells

ZnO-coated TiO2 (ZTO) thin films were deposited on ITO substrates by a sol-gel method for application as the work electrode for dye-sensitized solar cells (DSSCs). The I-V curve and the incident photon-to-current conversion efficiency (IPCE) value of DSSCs for ZTO thin films were studied and compared with single TiO2 films. The results show that the short-circuit photocurrent (J (sc)) and open-circuit voltage (V (oc)) values increased from 3.7 mA/cm(2) and 0.68 V for the DSSCs with a single TiO2 film to 4.5 mA/cm(2) and 0.72 V, respectively, for the DSSCs with a ZTO thin film. It indicated that the DSSCs with a ZTO thin film contributed to provide an inherent energy barrier that suppressed charge recombination significantly. In addition, the higher IPCE value in the ZTO thin film is attributed to the better charge separation by a fast electron transfer process using two semiconductors with different conduction band edges and energy positions.