Dye-sensitized solar cells are part of the third generation of solar cells. Although these systems are rather cheap, their efficiencies (11-12 %) must be improved. Best cells are based on TiO2. Unfortunately, TiO2 preparation requires high temperature sintering which makes DSC unusable for several applications. ZnO which can be prepared at low temperature and with various different morphologies appears to be an interesting alternative material to TiO2. Here are presented results on the optimization of ZnO based DSC. Two strategies of improvement were investigated: optimizing the transport of electrons in the cells and maximizing the light harvesting. First, the influence of the structure of the semi-conductor films (TiO2 and ZnO) on the conduction properties of electrons and the performances of the cells was studied. Electrodeposited ZnO gave the best efficiency of all ZnO based DSC tested thanks to an efficient charge collection at the back contact of the photoelectrode. Then the sensitization step of ZnO happened to be a key parameter in the preparation of the cells. The sensitization influence on the light harvesting, the recombination rate in the cells, and the durability of the device was studied. Finally, new means of light trapping in the cells were tested. Three scattering layer deposition techniques are presented: the sol-gel depositon of scattering particulate films, ZnO platelets electrodeposition and particle occlusion during ZnO electrodeposition. Finally, the efficiency limitations in ZnO-DSC and breakthrough strategies to improve the performances are discussed
