Effect of electron donor and acceptor in dithienopyrrolobenzothiadiazole-based organic dyes for efficient quasi-solid-state dye-sensitized solar cells

Three new organic dyes H1-3 with dithienopyrrolobenzothiadiazole moiety as the pi-bridge have been synthesized and applied in quasi-solid-state dye-sensitized solar cells. The influences of different electron acceptor of the sensitizers on the photo-physical, electrochemical and photovoltaic performances have been studied. The results show that the inserted electron-withdrawing unit benzothiadiazole in the acceptor part can obviously enhance the light-harvesting ability of the dyes. In addition, the introduced benzothiadiazole moiety in acceptor can increase the pi-electron distribution in LUMO level, which may facilitate to the photogenergated electrons injection into TiO2 film. The effects of different electron donor on the solar cell performances have been evaluated. The dihexyloxy substituted triphenylamine is better to suppress the intermolecular aggregation and restrain electron recombination. Finally, the quasi-solid-state solar cell sensitized by dye H2 with 1 mM chenodeoxycholic acid as the co-adsorbent obtains a power conversion efficiency of 7.56%, which close to the level of dye N719 (7.66%) under the same condition.