Twisted Fused-Ring Thiophene Organic Dye-Sensitized Solar Cells

Fused-ring thiophene compounds emerged as an important type of building blocks for organic dyes toward the dye-sensitized solar cells (DSSCs) because of their good charge transfer and light-harvesting properties. Nevertheless, some fused-ring thiophenes have a lack of desired alkyl chains or side alkyl chains, which may induce a severe charge recombination in devices. In this work, the hex-1-en-1-ylbenzene (HEYB) unit was introduced in two new fused-ring thiophene organic dyes (M60 and M59), resulting in a modest dihedral angle (∼36°) between the donor and spacer in dyes. The effect of the HEYB unit on optical, electrochemical, and photovoltaic properties has been investigated by comparing with their congeners (M42 and M58) without the HEYB unit. It is found that introduction of the HEYB unit in arylamine donor enhanced the driving force for dye regeneration and beneficial for suppressing dye aggregation as well as reducing the charge recombination. Device performance characteristics demonstrate that introduction of the HEYB unit in the arylamine donor is a feasible strategy toward enhancing the performance of fused-ring thiophene organic dyes. Benefiting from this strategy, a dye-sensitized solar cell employing the M60 photosensitizer and a cobalt electrolyte exhibits a good power conversion efficiency of 9.75% measured under the 100 mW cm–2, simulated AM1.5 sunlight.