Double-N doping: a new discovery about N-doped TiO2 applied in dye-sensitized solar cells

In this paper, we first investigated the optimal amount of ammonia to add, using ammonia as the single dopant for use in dye-sensitized solar cells (DSSCs). Using this optimal amount of ammonia, urea was introduced as the second N dopant. The DSSCs produced by double-N doped samples combine the advantages of increased visible light absorption with ammonia as the nitrogen dopant and enlarged interface area with urea as the second nitrogen dopant. Not only was Voc increased, but Jsc was also enhanced. We observed that the double-N doped sample forms a new microstructure with more mesopores, which enhance the transfer of electrolyte. Because these mesopores are the combination core of generated electrons and holes, they need to be kept in delicate balance. When urea is brought in as the double-N dopant, the doped amount of N atoms was improved. As a result, η is increased to 7.58%, a 14% improvement compared with single-N doped TiO2.