Annulated thiophene perylene bisimides and their triphenyl-amine based oligomers have been synthesized. One of the oligomers FPTTPA has been demonstrated to be an efficient electron donor in bulk heterojunction (BHJ) organic solar cells, giving a power conversion efficiency of 1.42%.

A novel organic sensitizer JK-225 incorporating a planar indeno[1,2-b]thiophene bridging group was synthesized and compared to its prototype sensitizer JK-2. JK-225 affords a short circuit photocurrent of 13.84 mA cm À2 , an open circuit voltage of 790 mV, and a fill factor of 0.75, corresponding to an overall conversion efficiency of 8.2% under standard AM 1.5 sunlight, which is much higher than that of 6.9% in JK-2.

An efficient organic sensitizer (JK-306) featuring a planar indeno[1,2-b]thiophene as the π-linker of a bridging unit for dye-sensitized solar cells (DSSCs) was synthesized. The sensitizer had a strong molar absorption coefficient and a red-shifted absorption band compared with JK-305, which resulted in a significant increase in the short-circuit photocurrent density. We incorporated a highly congested bulky amino group into the 2',4'-dihexyloxybiphenyl-4-yl moiety, an electron donor, to diminish the charge recombination and to prevent aggregation of the sensitizer. Under standard AM 1.5G solar conditions, JK-306-sensitized cells in the presence of co-adsorbents chenodeoxycholic acid (CDCA) and 4-[bis(9,9-dimethyl-9H-fluoren-2-yl)amino]benzoic acid (HC-A), which afforded an overall conversion efficiency of 8.37% and 8.52%, respectively. Upon changing the I(-) /I3 (-) electrolyte to the Co(II) /Co(III) redox couple, the cell gave rise to a significantly improved conversion efficiency of 10.02% with the multifunctional HC-A, which is one of the highest values reported for DSSCs with a cobalt-based electrolyte. Furthermore, the JK-306-based solar cell with a polymer gel electrolyte revealed a high conversion efficiency of 7.61%, which is one of the highest values for cells based on organic sensitizers.