Preparation of nanoporous MgO-coated TiO ₂ nanoparticles and their application to the electrode of dye-sensitized solar cells

Sol-gel-derived Mg(OH) ₂ gel was coated onto TiO ₂ nanoparticles, and the subsequent thermal topotactic decomposition of the gel formed a highly nanoporous MgO crystalline coating. The specific surface area of the electrode that was prepared from the core-shell-structured TiO ₂ nanoparticles significantly increased compared with that of the uncoated TiO ₂ electrode. The increase in the specific surface area of the MgO-coated TiO ₂ electrode was attributed to the highly nanoporous MgO coating layer that resulted from the topotactic reaction. Dye adsorption behavior and solar cell performance were significantly enhanced by employing the MgO-coated TiO ₂ electrode. Optimized coating of a MgO layer on TiO ₂ nanoparticles enhanced the energy conversion efficiency as much as 45% compared to that of the uncoated TiO ₂ electrode. This indicates that controlling the extrinsic parameters such as the specific surface area is very important to improve the energy conversion efficiency of TiO ₂-based solar cells.