Engineering the intermediate band states in amorphous Ti3+-doped TiO2 for hybrid dye-sensitized solar cell applications

Ti3+-doped amorphous TiO2 nanoparticles (a-TiO2:Ti3+), which are an intermediate band semiconductor, were fabricated by high intensity ultraviolet pulsed laser ablation in water. The absorption band of a-TiO2: Ti3+ nanoparticles, which appears between the visible and infrared regions, is much wider than that of the rutile TiO2 nanoparticles. The intermediate band, which has a recombination lifetime of 0.71 ms, is found to be 1.61 eV above the valence band (VB) top of TiO2. It can be shown that the a-TiO2:Ti3+/TiO2 nanotube hybrid dye-sensitized solar cells (DSSCs) not only have a high fill factor and large open circuit voltage, but also have high photovoltaic conversion efficiency as compared to TiO2 nanotube DSSCs. Considering that most of the current solar cells use only a single photoelectric conversion material (PCM), our results will promote the research on multi-PCM hybrid solar cells.