Theoretical insights into single- and co-sensitization of indolocarbazole-based dyes on anatase (101) surface for efficient dye-sensitized solar cells

Co-sensitization strategy is an efficient approach to improve the power conversion efficiency of dye-sensitized solar cells (DSSCs). In this work, we firstly investigated the properties of three designed indolocarbazole-based dyes (D₁-π₁-D₂-π₂-A, IPZ-TV, IPZ-2TV and IPZ-3TV) using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The thiophene vinylene group as a π₂-bridge into the reference dye IPZ can improve the light-harvesting capacity. Among the three designed dyes, IPZ-2TV with two thiophene units is of the best performance because of the excellent intramolecular charge transfer (ICT) characteristic and outstanding photovoltaic performance. Then, using the best performing IPZ-2TV with a co-sensitizer adsorption on TiO₂ surface, the interaction between IPZ-2TV and TiO₂ is significantly enhanced. Besides, the co-sensitization combination of IPZ-2TV + BPO exhibits superior ICT and absorption characteristics, allowing us conclude that IPZ-based dyes are more likely to be co-sensitized with the metal-complex sensitizers to enhance the performance of DSSCs.