Light Trapping in Dye Sensitized Solar Cells with Length-Modulated TiO_2 Nanotubes

摘要

Highly oriented TiO_2 nanotube (NT) arrays were fabricated by anodizing Ti foils. The morphology of the NT arrays was characterized by scanning electron microscope. By adjusting the anodization time, the lengths and diameters of TiO_2 NT arrays changed from 6.7 to 19.5 (im, and 90 to 110 nm, respectively. As confirmed by X-ray diffraction and Raman spectra, the as-anodized TiO_2 NTs were amorphous but transformed into anatase phase after annealing at 450°C for 3 h. Reflectance spectrum of TiO_2 NT arrays showed that NT layer of longer length lowered the reflectance in the visible spectrum because of light trapping effects of NTs, thus enhancing light harvesting of NTs. Dye-sensitized solar cells were fabricated using TiO_2 NT arrays with different tube-lengths. Analysis of photocurrent density-voltage (J-V) characteristics showed that higher photoconversion efficiencies were achieved with longer NT lengths.