Donor-free oligothiophene based dyes with di-anchor architecture for dye-sensitized solar cells

Traditionally, metal free DSSCs are fabricated from sensitizers designed using a donor–pi–acceptor (D–π–A) architecture. More recently, non-conventional dyes without strong donor units have emerged and have provided competitive power conversion efficiencies (PCEs) with respect to their (D–π–A)-based counterparts. Here, we report the synthesis and DSSC fabrication of oligothiophene molecules featuring two anchoring groups that do not possess strong donor moieties and are able to adopt V- and U-shape conformations. PCEs of 3.70% were obtained with the smaller 5-thiophene dyes (5T2A, 5T2A-E) possessing higher PCEs than their larger 8-thiophene counterparts containing diacetylene units (8T4A, 8T4A-E). Comparison to the DSSC properties of the analogous linear dye 5T, indicates that the architecture and structure of this series of dyes are likely responsible for their lower performance.