The development of new sensitizers and new sensitization methods is one of the important means to enhance the conversion efficiency of dye-sensitized solar cells (DSSCs); the ultimate goal is to broaden the spectral response of dyes, reduce electron recombination, and suppress dye aggregation. In this study, we have developed a series of new self-assembled dyes and applied them in DSSCs. We prepared two organic antenna chromophores S1 and S2 and coordinated them with two acceptors A1 and A2 via zinc to construct A-Zn-S series self-assembled dyes. This method is very simple and feasible and can avoid the complex synthesis steps of traditional dyes; the results show that the light-harvesting ability of devices can be improved and charge recombination can be reduced by adjusting the structures of the antenna chromophores and acceptors. The device with A2-Zn-S1 gave a power conversion efficiency of 4.25%, which was higher than those with A1-Zn-S1 (3.88%), A1-Zn-S2 (3.21%), and A2-Zn-S2 (3.52%); the main reason for this is that the different coordination combinations between the antenna chromophore and the acceptor show great differences in Voc and Jsc. The device based on A2-Zn-S1 showed a high Voc of 632 mV and a high Jsc of 9.54 mA cm-2; one reason for this is that S1 has better spectral responsiveness and another reason is that A2 has better steric resistance that effectively reduces charge recombination. Besides, IR spectra indicate that these self-assembled dyes anchored on a TiO2 surface by bicarboxyl anchoring groups are also very beneficial for improving the performance of dyes.
Keywords: DSSCs; anchor; organic antenna chromophores; phenothiazine; self-assembly.