First principles study on interface between dual-channel anchorable organic dyes and TiO2 for dye-sensitized solar cells

Four A-D-A-D-A organic dyes with different auxiliary acceptor or donor groups have been theoretically investigated by first principle as potential photosensitizers in dye-sensitized solar cells. Judging from the isolated dyes, 2PZ-SP with diphenyl-substituted pyrido[3,4-b]pyrazine-2,5-thiophene as auxiliary acceptor is not suitable to be taken as organic dye in DSSCs because of the inappropriate electron density distribution. However, it is difficult to distinguish the performance of other three dyes since no one has all superiorities. After the dye is adsorbed on TiO2 surface, the deviation between LUMO energy level of dye and conduction band of TiO2 (101) surface is further enlarged, which is favorable for the electron injection. Moreover, 2PZ-PP stands out because of the smallest H-L energy gap and the shortest injection time. Finally, a new D-pi-A dye with the identical donor, pi group, and acceptor groups is designed to compare with 2PZ-BT. It is found that 2PZ-BT has the absolute advantage to be potential dye for DSSCs. Besides the suitable groups, the appropriate configuration is more critical aspect to determine the performance.