In this article, we describe the use of hafnium oxide (HfO2) as a new and efficient blocking layer material to modify TiO2 electrodes in dye sensitized solar cells. Different thicknesses of HfO2 over-layers were prepared by simple dip coating from two different precursors and their effects on the performance of DSSCs were studied. The HfO2 modification remarkably increases dye adsorption, resulting from the fact that the surface of HfO2 is more basic than that of TiO2. Furthermore, the HfO2 coating demonstrated increased diffusion coefficient (D-e) and lifetime (tau(e)) of the photoelectrons, indicating the improved retardation of the back electron transfer, which increases short-circuit current (J(sc)) and open-circuit voltage (V-oc). Thereby, the photo conversion efficiency (eta) of the solar cell was greatly improved from 5.67 to 9.59% (an improvement of 69.02%) as the HfO2 layer was coated over TiO2 films. (C) 2012 Elsevier Ltd. All rights reserved.