A facile route to fabricate an anodic TiO ₂ nanotube-nanoparticle hybrid structure for high efficiency dye-sensitized solar cells

The relatively low internal surface area of anodized TiO ₂ nanotube arrays (TNAs) limits dye adsorption and light capturing in TNA-based dye-sensitized solar cells (DSSCs). Here, water treatment of as-anodized TNAs at room temperature was used to tailor the geometry of TNA walls in a controllable way, leading to a hybrid tube wall structure with the outer shell in a tubular morphology and the inner surface consisting of small particles. To enable front-side illumination in DSSCs, the TNAs with porous inner walls were transferred to transparent conductive oxide substrates by a self-detaching and transfer technique. The roughened water-treated TNAs show significantly enhanced internal surface area, leading to improved dye-loading and light-harvesting capabilities. Optimized performance was achieved after water treatment for 2 days, with a power conversion efficiency of 6.06%, increased by ∼33% compared to conventional TNAs. Furthermore, the hybrid TNA nanostructure provides excellent electron transfer and recombination characteristics, thus promising for high efficiency DSSCs.