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.