Tetraphenylethylene-bridged double-branched sensitizers featuring hetero donors for dye-sensitized solar cells

Four tetraphenylethylene-bridged X-shaped photosensitizers JY66-69 containing one triphenylamine (TPA) donor and another donor TPA, carbazole, phenothiazine or dithieno[3,2-b:2’,3’-d]pyrrole (DTP) as the neighbour donor were designed and applied in dye-sensitized solar cells. Compared with the symmetrical twin TPA-based dye JY66, the introduction of carbazole or phenothiazine neighbour donor (JY67/JY68) causes a promotion in dipole moment of the sensitizer, while dye JY69 with DTP as neighbour donor inversely results in a decrease. Besides the open-circuit voltage (VOC) and short-circuit current density (JSC) rising together with dipole moment, the power conversion efficiency (PCE) displays near linear positive correlation to the vertical dipole moment (μnormal) in this series. Finally, dye JY67 containing TPA and carbazole donor achieves the best photovoltaic performance. Accordingly, decorating such X-shaped bridge with hetero-donors would be a promising strategy to improve the performance of multi-branched dyes in DSSCs.