Novel liquid crystalline oligomer with thiazolothiazole-acceptor for efficient BHJ small molecule organic solar cells

A Novel and efficient π-conjugated, liquid crystalline semiconducting oligomer comprised of thiazolothiazole (acceptor) and two different donor units as - terminal alkyl-bithiophene (D₁) and triphenyl amine (D ₂) was strategically designed and synthesized in four steps synthetic route via-Suzuki cross-coupling reactions. The presence of terminal alkyl unit might induce good solubility as well as liquid-crystal (LC) property of oligomer. Differential scanning calorimetry reveals the presence of different LC phases of oligomer which affects the morphology of devices during solution-processed fabrication process by acquiring self-assembly behaviour. As photoactive materials, π-conjugated oligomer based organic solar cell showed significantly high photocurrent density of ∼12.05 mA/cm² with reasonably good power conversion efficiency of ∼2.43%. The high performance might due to the good absorption with improvement in the thin film morphology and good intermolecular interaction behaviour of the oligomer blending with fullerene (PC₆₀BM) acceptor.