Importance of varying electron-accepting moieties in regular conjugated terpolymers for use in polymer solar cells

• Three regular A1-D-A2-D terpolymers with the combination of two different acceptors and one donor were synthesized.
• Diketopyrrolopyrrole, isoindigo, and thienoisoindigo, were used as acceptor in terpolymers.
• PDPP-T-IID showed lower-lying HOMO level of −5.29 eV than other two.
• The PDPP-T-IID/PC71BM-based device exhibited a high power conversion efficiency of 6.95%.

Three A1-D-A2-D regular conjugated terpolymers containing diketopyrrolopyrrole, isoindigo, or thienoisoindigo moieties were synthesized. Each terpolymer with the combination of two different acceptors and thiophene as common donor displayed strong absorption from 500 nm to the near-IR region as well as different molecular energy levels. Among three terpolymers, bulk heterojunction polymer solar cell made of the terpolymer containing diketopyrrolopyrrole, isoindigo, and thiophene moieties and phenyl-C71-butyric acid methyl ester showed the highest power conversion efficiency of 6.95% due to its appropriate internal morphology and the high open circuit voltage conferred by the relatively low-lying highest occupied molecular orbital level of the polymer.

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