Novel organic sensitizer based on directly linked oligothiophenes to donor nitrogen atom for efficient dye-sensitized solar cells

•Direct linkage of an oligothiophenes spacer to the nitrogen atom of a donor amine.•Linkage of donor–acceptor bridge through an elongated oligothiophene π-spacer.•Enhancement of spectral response when compared with a fewer thiophene analogue.•Compatibility of new sensitizer with versatile electrolyte systems such as cobalt.

Through the embodiment of direct linkage of oligothiophenes to the nitrogen atom of a donor amine in the bridged donor–acceptor module, a novel and efficient organic sensitizer (AG3) has been designed, synthesized and applied in dye-sensitized solar cells. AG3 contained an electron donating (diphenylamine) and an electron accepting (cyanoacrylic acid) functionality linked through an elongated oligothiophene π-spacer. The target sensitizer was successfully synthesized, found to be highly soluble in common organic solvents, showed intense spectral response when compared with fewer thiophene analogue, and afforded 5.9%, 4.3% and 5.2% solar-to-energy conversion efficiencies with solvent-based, ionic liquid and cobalt-mediated electrolytes, respectively, when tested under irradiation of 100 mW cm−2 air mass 1.5 global (AM1.5G) sunlight.

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