Improved light harvesting via energy transfer within a benzothiadiazole-based antenna–sensitizer dyad for dye-sensitized solar cells

We describe the design, synthesis and application in dye-sensitized solar cells (DSSCs) of a fully organic dyad consisting of a visible light-harvesting D-A-π-A dye covalently linked to a small antenna that can absorb higher energy photons. Thanks to its precise molecular design, not previously applied in DSSCs, the dyad showed an excellent overlap between the antenna emission spectrum and the dye absorption spectrum, providing a high energy transfer efficiency of 88%, which is among the best reported for such systems. Cells featuring the dyad as a sensitizer showed increased light-harvesting efficiency compared to those built with a reference dye without the antenna, resulting in a 35% higher average power conversion efficiency.