Diketopyrrolopyrrole-based conjugated small molecules bearing two different acceptor moieties for organic solar cells

•A1-D-A2-D-A1-type conjugated molecules were firstly demonstrated.•Three conjugated molecules containing DPP and another weaker acceptor were synthesized.•Thiophene carboxylate (3EhT), thienopyrroledione (TPD), and fluorinated thienothiophene (TT) were employed.•(TPD)(DPP)2 exhibited the highest power conversion efficiency of 3.37%.

Three A1-D-A2-D-A1-type conjugated molecules (A: acceptor, D: donor), containing diketopyrrolopyrrole (DPP) acceptors, another weaker acceptor, and thiophenes as common donors, were synthesized. The molecules exhibited strong absorption from 500 nm to the near-IR wavelength region, and different molecular energy levels. The three molecules synthesized were applied in solar cells made with phenyl-C71-butyric acid methyl ester, and thienopyrroledione (TPD) (DPP)2 exhibited the highest power conversion efficiency of 3.37% owing to its appropriate internal morphology and relatively high open circuit voltage, which is conferred by its relatively low-lying highest occupied molecular orbital level.

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