Organic dyes containing dithieno[2,3-d:2′,3′-d′]-thieno[3,2-b:3′,2′-b′]dipyrrole core for efficient dye-sensitized solar cells

We report two new triarylamine-cyanoacrylic acid based push-pull dyes, X76 and X77, featuring the pi-conjugated linkers of dihexyl-and dihexyloxybenzene-substituted dithieno[2,3-d:2',3'-d'] thieno[3,2-b:3',2'-b']dipyrrole (DTDP), respectively. The absorption, electrochemical, and photovoltaic properties for all sensitizers have been systematically investigated. Both dyes containing a DTDP moiety showed good light harvesting ability as compared to that of the reference dye incorporating the hexyl-substituted dithieno[3,2-b:2',3'-d] pyrrole (DTP) linker. Moreover, the substituents of DTDP moiety significantly influenced the electrochemical and photovoltaic properties of the dyes. The incident photon-to-current efficiency (IPCE) of the X77-based device is higher at longer wavelengths, and extends to nearly 800 nm. A dye-sensitized solar cell employing the X77 photosensitizer and the Co-bpy electrolyte exhibits a power conversion efficiency of 6.6% measured under the 100 mW cm(-2) simulated AM1.5 sunlight.