Nanosheet arrays of TiO2 synthesized by one step conversion of ZnO nanosheets: boosting of electron transport rate and application in dye solar cells†
A TiO2 replica of ZnO nanosheet films is synthesized using a chemical replacement process. ZnO nanosheets are grown by electrodeposition on fluorine doped tin oxide (FTO) films, and a dissolution/deposition process is used to convert the ZnO template into a TiO2 replica. Electron microscopy shows the final TiO2 structure follows the morphology of the initial ZnO template. X-ray diffraction and energy dispersive spectroscopy verify the total transformation of ZnO to TiO2. The as-synthesized TiO2 sheets are amorphous and after annealing turn into the anatase phase. The film of TiO2 nanosheets is used as the photoanode of a dye sensitized solar cell. Despite the low roughness factor of 100, a conversion efficiency of 3.3% with D35 as sensitizer is achieved. The nanosheets show remarkably faster electron transport and longer electron lifetime compared to the conventional TiO2 nanoparticle electrodes.