Enhancement Mechanism of the Conversion Effficiency of Dye-Sensitized Solar Cells Based on Nitrogen‑, Fluorine‑, and Iodine-Doped TiO2 Photoanodes

We investigated the electronic structures of N-, F-, and I-doped anatase TiO2 to explore the enhancement mechanism of incident photon-to-current conversion efficiency (IPCE) in dye-sensitized solar cells (DSSCs) based on N-, F-, and I-doped anatase TiO2 photoanodes. The hybrid density functional calculation results indicate that n-type F and I doping is better than p-type N doping. The incorporation of I dopant is very favorable to improve the conductivity, the open-circuit voltage, and the visible-light absorption of anatase TiO2. Moreover, the I doping can facilitate the electron injection from the dye molecule to the TiO2 substrate by analyzing the calculated electronic properties of adsorbed dye/TiO2 complexes. As a result, the I doping can significantly enhance the IPCE of DSSCs. In addition, it is found that the metallic n-type doping on the Ti site of the TiO2 photoanode can be an effective approach to improve the performance of DSSCs. It is expected that this work can provide valuable information for the development of TiO2-based DSSCs.