Enhanced photovoltaic performance of quinoxaline-based donor-acceptor type polymers with monocyano substituent

A series of quinoxaline-based polymers with CN group are synthesized to elucidate the effect of strong electron withdrawing CN groups on the photovoltaic properties of the polymers and to clarify the influence of CN group on the photovoltaic properties of conjugated polymers for manufacturing high-performance polymer solar cells. The reference polymer (PAB-Qx) without CN is prepared by the polymerization between electron-donating benzodithiophene (BDT) and electron-accepting 2,3-diphenylquinoxaline (DPQ) monomer. Subsequently, a CN group is substituted at the 6-position of the DPQ unit of the reference polymer to yield PAB-CNQx. An additional target polymer (PTB-CNQx) is prepared by replacing two 2-ethylhexyloxy groups on the BDT unit in PAB-QxCN with 2-ethylhexyl thiophene side chains. The photovoltaic properties of the polymers are examined by constructing a nonfullerene inverted-type PSCs. Owing to the positive contributions of the strong electron withdrawing CN group and alkylthienyl side chains, the power conversion efficiencies of the devices are significantly improved in the following order: PAB-Qx (4.35%), PAB-CNQx (8.66%), and PTB-CNQx (13.3%). Therefore, this study confirms the great potential of electron-withdrawing CN groups for developing highperformance quinoxaline-based polymers for photovoltaic applications.

Automated summary

A series of quinoxaline-based polymers containing CN groups were synthesized to investigate the effect of strong electron withdrawing CN groups on the photovoltaic properties. The power conversion efficiencies of the devices significantly improved due to the positive contributions of the CN group and alkylthienyl side chains, confirming the great potential for developing high-performance polymers for photovoltaic applications using electron-withdrawing CN groups.