Thiadiazolo[3,4-c]pyridine Acceptor Based Blue Sensitizers for High Efficiency Dye-Sensitized Solar Cells

Two new [1,2,5]thiadiazolo[3,4-c]pyridine-containing D-A-pi-A organic dyes (PT-1 and PT-2) have been designed and synthesized for utilization in dye-sensitized solar cells. PT-2 sensitizer, which was synthesized by incorporating the 4,4-bis(2-ethylhexyl)-4H-cyclopenta[1,2-b:5,4-b']dithiophene moiety as an additional pi-bridge into the organic sensitizer PT-1, not only brings about significant changes in the absorption spectrum but also suppresses the charge recombination rate as compared to PT-1. Moreover, PT-2 exhibits an aesthetic blue color covering a broad spectral range into the NIR region. The incident-photon to electron-conversion efficiency of PT-2 shows an onset approaching 850 nm with power conversion efficiency of 6.796 fabricated when utilizing an iodide-based redox electrolyte. These results demonstrate that these [1,2,5]thiadiazolo[3,4-c]pyridine-based sensitizers are quite promising candidates to use for lowering the HOMO-LUMO gap and shifting the spectral response toward the NIR.