Influence of nitrogen dopants on N-doped TiO2 electrodes and their applications in dye-sensitized solar cells

Three different types of nanocryst., N-doped TiO2 electrodes were synthesized using several nitrogen dopants through wet methods. The obtained nanocryst., N-doped TiO2 electrodes possessed different crystallite sizes, surface areas, and N-doping amts. Characterizations were performed to reveal the nitrogen-doping processes for the wet methods using ammonia, urea, and triethylamine as the nitrogen dopants. Addnl., a high conversion efficiency of 8.32% was achieved by the dye-sensitized solar cells, based on the N-doped TiO2 electrodes. For instance, in comparison with the com. P25 (5.76%) and pure anatase TiO2 electrodes (7.14%), significant improvements (44% and 17%, resp.) 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 TiO2 solar cells also differed from those in the pure TiO2-based dye-sensitized solar cells (DSCs). Specifically, an enhanced photocurrent of ∼36% in N-doped DSCs resulted from the synergistic effects of the high dye uptake and the efficient electron transport. Moreover, the relation between charge and voltage revealed that less charge was needed to get a high open-circuit voltage in the N-doping films.