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

• A novel π-conjugated oligomer (TPTzR) is synthesized.
• TPTzR is comprised of thiazolothiazole-core with triphenyl amine and terminal alkylated-bithiophene units.
• The Jsc significantly increase with the introduction of TPA unit.
• TPTzR exhibit liquid-crystal property and used for solution-processed small molecule organic solar cells (SMOSCs).
• Fabricated SMOSC shows good power conversion efficiency of ∼2.43%.

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 (D2) 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.

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