Homogeneous Photosensitization of Complex TiO(2) Nanostructures for Efficient Solar Energy Conversion

TiO(2) nanostructures-based photoelectrochemical (PEC) cells are under worldwide attentions as the method to generate clean energy. For these devices, narrow-bandgap semiconductor photosensitizers such as CdS and CdSe are commonly used to couple with TiO(2) in order to harvest the visible sunlight and to enhance the conversion efficiency. Conventional methods for depositing the photosensitizers on TiO(2) such as dip coating, electrochemical deposition and chemical-vapor-deposition suffer from poor control in thickness and uniformity, and correspond to low photocurrent levels. Here we demonstrate a new method based on atomic layer deposition and ion exchange reaction (ALDIER) to achieve a highly controllable and homogeneous coating of sensitizer particles on arbitrary TiO(2) substrates. PEC tests made to CdSe-sensitized TiO(2) inverse opal photoanodes result in a drastically improved photocurrent level, up to ~15.7 mA/cm(2) at zero bias (vs Ag/AgCl), more than double that by conventional techniques such as successive ionic layer adsorption and reaction.