Effect of dihedral angle of bridge unit on the performance of dye-sensitized solar cell

In this work, we investigated the impact of bridge unit on their photo-physical and photovoltaic performance. Increased planarity of the dyes effectively extended the absorption, but reduces the efficiency. Interestingly we found that dyes with a thiophene conjugate unit showed inferior performance when compared with benzene. Theoretical computation indicates a large dihedral angle in the latter system. EIS analysis evidenced the severe recombination in the thiophene-based dye, showing that good planarity may lead to dye aggregation and decrease the efficiency.

Interestingly we found that dyes adopting the benzene unit as the conjugate spacer display better efficiency than those utilizing the thiophene unit. Theoretical analysis indicates that existence of a large dihedral angle between the benzene spacer and auxiliary acceptor. The large dihedral angles disrupt the planarity of the dye which may cause severe recombination, contributing to the improvement of the efficiency. Figure optionsDownload as PowerPoint slide