Influence of nitrogen dopants on N-doped TiO 2 electrodes and their applications in dye-sensitized solar cells

Abstract

Three different types of nanocrystalline, N-doped TiO 2 electrodes were synthesized using several nitrogen dopants through wet methods. The obtained nanocrystalline, N-doped TiO 2 electrodes possessed different crystallite sizes, surface areas, and N-doping amounts. Characterizations were performed to reveal the nitrogen-doping processes for the wet methods using ammonia, urea, and triethylamine as the nitrogen dopants. Additionally, a high conversion efficiency of 8.32% was achieved by the dye-sensitized solar cells, based on the N-doped TiO 2 electrodes. For instance, in comparison with the commercial P25 (5.76%) and pure anatase TiO 2 electrodes (7.14%), significant improvements (44% and 17%, respectively) in the efficiencies were obtained. The findings also indicated that the ammonia nitrogen dopant was more efficient than other two nitrogen dopants. The electron transports, electron lifetimes, and charge recombination in the dye-sensitized N-doped TiO 2 solar cells also differed from those in the pure TiO 2-based dye-sensitized solar cells (DSCs). Specifically, an enhanced photocurrent of ca. 36% in N-doped DSCs resulted from the synergistic effects of the high dye uptake and the efficient electron transport. Moreover, the relationship between charge and voltage revealed that less charge was needed to get a high open-circuit voltage in the N-doping films.