Photovoltaic efficiency on dye-sensitized solar cells (DSSC) assembled using Ga-incorporated TiO2 materials

This study examined the photoelectric conversion efficiency of DSSC (dye-sensitized solar cell) when nanometer sized Ga (0.25, 0.50, and 1.00 mol%)–TiO2 prepared using a hydrothermal method was employed as a working electrode material. The particle sizes observed in the transmission electron microscopy images were <20 nm in all samples. However, with increasing Ga concentration, the size increased and the shapes transformed to a stick form. The absorption band was slightly blue-shifted upon the incorporation of gallium ions, but the intensity of the photoluminescence (PL) curves of the Ga-incorporated TiO2 was significantly smaller, with the smallest case being the 0.50 mol% Ga–TiO2, which was related to recombination between the excited electrons and holes. When Ga–TiO2 was applied in DSSC, the energy conversion efficiency was enhanced considerably compared to that using pure TiO2; it was approximately 4.57% with the N3 dye under 100 mW/cm2 of simulated sunlight. These results are in agreement with an electrostatic force microscopy (EFM) study showing that the electrons were transferred rapidly to the surface of Ga–TiO2 film, compared with that on a pure TiO2 film.