Organic dyes containing indolodithienopyrrole unit for dye-sensitized solar cells

Abstract The π-bridge plays a significant role on the optical and electrochemical properties of an organic dyes. In this study, an oligo-aromatic group, the 4,5-dihexyl-4,5-dihydrothieno[2″,3″:4′,5′]pyrrolo[2′,3′:4,5]thieno[3,2- b ]indole (DPTI) is first introduced as the π-bridge in organic dyes (M81, M83 and M84) for dye-sensitized solar cells (DSSCs). For comparison, a reference dye M82 without the DPTI unit has also been prepared. We have carefully examined their optical and electrochemical properties and device performance. It is found that introduction of the DPTI unit enhanced the light harvesting of dyes and reduced the charge recombination in devices. Among these DPTI dyes, the sensitizer M84 containing a twisted structure achieves a power conversion efficiency of 7.59% measured under the 100 mW cm −2 , simulated AM1.5 sunlight.