Bilayer TiO2 Photoanode Consisting of Microspheres and Pyramids with Reinforced Interface Connection and Light Utilization for Dye-Sensitized Solar Cells

TiO 2 pyramids with planar-surface morphology presenting in the phases of anatase and brookite are successfully prepared, the height of which is 300-500   nm and 80-200   nm wide at the bottom. The pyramids exhibit excellent reflectance in the visible-near infrared region. When introducing the pyramids as a scattering layer covering the layer composed of TiO 2 nanoparticles , the energy conversion efficiency of dye-sensitized solar cell (DSSC) is enhanced from 6.49% to 7.25%. However, the pyramids overlayer falls from the nanoparticles underlayer easily, and the fill factor of the DSSC with the pyramids layer also become much lower. To solve the problem, we substitute TiO 2 microspheres underlayer for NP underlayer. As the tips of pyramids could be inserted into the submicron-sized gaps between the TiO 2 microspheres, the interface connection between layers of photoanode is reinforced. Current-Voltage measurement shows that the fill factor of the DSSC is much improved, and the DSSC has achieved 8.35% energy conversion efficiency. This study shows that the novel bilayer photoanode with improved light utilization and interface connection is an interesting structure for high efficiency DSSCs.