Layer-by-Layer Deposition of Hollow TiO2 Spheres with Enhanced Photoelectric Conversion Efficiency for Dye-Sensitized Solar Cell Applications

Fabricating photoanodes with a strong light-scattering effect can improve the photoconversion efficiency of dye-sensitized solar cells (DSSCs). In this work, a facile microwave hydrothermal process was developed to prepare Au@TiO2 core–shell nanostructures, and then the Au core was removed by etching, resulting in hollow TiO2. Morphological characterizations such as field emission scanning and transmission electron microscopy measurements have been used for the successful formation of core–shell and hollow TiO2 nanostructures. Next, we attempted to deposit the different-sized hollow TiO2-based microspheres simultaneously on the surface of small-sized TiO2 nanoparticles-based compact film as light-scattering layers via electrophoretic deposition. The deposited hollow TiO2 microspheres constitute bi- and tri-layers that not only improve the light-harvesting properties but also speed up the photogenerated charge transfer. Compared to commercial TiO2 compact film (4.75%), the resulting bi-layer and tri-layered films-based DSSCs displayed power conversion efficiencies of 6.33% and 8.08%, respectively. It is revealed that the deposited bi- and tri-layered films can enhance the light absorption ability via multiple photon reflection. This work validates a novel and controllable strategy to develop light-scattering layers with increased light-harvesting properties for highly efficient dye-sensitized solar cells.