Fluorinated Head-to-Head Dialkoxybithiophene: A New Electron-Donating Building Block for High-Performance Polymer Semiconductors

Abstract

New building blocks with good solubility and optimized optoelectrical property are critical for materials development in organic electronics. Herein, a new head-to-head linkage containing a donor unit, 4,4'-difluoro-3,3'-dialkoxy-2,2'-bithiophene (BTfOR), is synthesized. The dialkoxy chains afford good materials solubility and also planar backbone via noncovalent (thienyl) S.(alkoxy) O interactions. Compared to the reported 3,3'-dialkoxy-2,2'-bithiophene (BTOR), F addition leads to BTfOR with lower-lying frontier molecular orbitals and can further promote polymer packing via additional F ... S or F ... H interactions. BTfOR can be readily stannylated to afford tin monomer with high purity and excellent reactivity toward Stille polymerization. As a proof of concept for materials design, BTfOR-based homopolymer (PBTfOR) is synthesized, showing high molecular weight and strong aggregation. Moreover, the HOMO (-4.98 eV) of PBTfOR is greatly lower than that (-4.54 eV) of nonfluorinated counterpart PBTOR, which is attributed to the addition of F atoms. When incorporated into thin-film transistors, PBTfOR exhibits a remarkable hole mobility of 0.57 cm(2) V-1 s(-1), showing an exceptional example of high-mobility head-to-head polythiophene. This study demonstrates that introduction of F atoms can lead to BTfOR with optimized physicochemical properties, and the new BTfOR should find promising use for constructing donor-acceptor copolymers for high-performance electronic devices.