Fluorine functionalized asymmetric indo [2,3-b]quinoxaline framework based D-A copolymer for fullerene polymer solar cells

Abstract Innovating molecular structure of copolymer donor materials is still one of the prominent approach to obtain high-performance polymer solar cells (PSCs). In this paper, two novel wide bandgap (WBG) copolymers, namely PBDTTS-IQ and PBDTTS-DFIQ, based on asymmetric planar aromatic core indo [( Li et al., 2012; Wang et al., 2020) 2,32,3-b]quinoxaline (IQ) as acceptor unit through tuning side chains with fluorine (F) atom engineering and exemplary alkylthio-thienyl substituted benzodithiophene (BDTTS) donor group, are synthesized and finally employed as the photovoltaic donor materials for fullerene polymer solar cells (PSCs). After blending with PC71BM acceptor, the PBDTTS-DFIQ:PC71BM blend film presented better efficient exciton dissociation and charge extraction, more balanced electron/hole mobility (μh/μe), and nice morphology in comparison with PBDTTS-IQ:PC71BM blend film. Encouragingly, the PBDTTS-DFIQ:PC71BM based PSCs exhibits a higher power conversion efficiency (PCE) of 7.4% than that of the device based on the PBDTTS-IQ:PC71BM blend with a PCE of 4.96%, which thanks to an enhancement of open-circuit voltage (Voc) of 0.84 V, short current density (Jsc) of 13.26 mA cm−2 and fill factor (FF) of 66.00% simultaneously. These results demonstrate that this asymmetric IQ framework is a wonderful acceptor moiety to build light-harvesting copolymers for highly efficient PSCs.