Pentafluorosulfanyl-functionalised BODIPY push–pull dyes for p-type dye-sensitized solar cells

We report a push–pull BODIPY-based dye functionalised with an electronegative SF(5) group at the meso position for applications in photocathodes in tandem dye-sensitized solar cells (DSSCs). The push–pull character enhances charge-transfer from the mesoporous NiO cathode surface towards the redox mediator. A Knoevenagel condensation reaction was used to introduce the carboxylic acid to anchor the dye to the oxide surface, via a styryl linker which increases the conjugation in the molecule and shifts the absorption to the red. The room-temperature synthesis and high yields, make the dye promising for manufacture on a large scale. The dye was applied in p-DSSCs giving a power conversion efficiency (0.066%), a short circuit photocurrent (J(SC)) of 3.84 mA cm(−2), open circuit voltage (V(OC)) of 58 mV and fill factor of 30%.