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

Abstract

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 500nm 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.