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

Abstract

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 neighboring 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 neighboring donor (JY67/JY68) causes a promotion in the dipole moment of the sensitizer, while dye JY69 with DTP as a neighboring donor inversely results in a decrease. Besides the open-circuit voltage (V_OC) and short-circuit current density (J_SC) rising together with dipole moment, the power conversion efficiency (PCE) displays near linear positive correlation to the vertical dipole moment (μ_normal) in this series. Finally, dye JY67 containing TPA and carbazole donor achieves the best photovoltaic performance. Accordingly, decorating such an X-shaped bridge with hetero-donors would be a promising strategy to improve the performance of multi-branched dyes in DSSCs.