A Full-Ring-Fused Perylenediimide Dimer for High-Performance n-Type Organic Field-Effect Transistors

Abstract

The design and synthesis of high-mobility n-type organic semiconductors remain a central research imperative in organic field-effect transistor (OFET) technology. While π-extended perylenediimides (PDIs) have been extensively investigated with tunable physicochemical properties, fully ring-fused PDI derivatives remain underexplored—primarily hindered by synthetic challenges inherent to cyclizing electron-deficient aromatic cores. Herein, we report f-2PDI, a fully ring-fused PDI dimer linked via a dithienothiophen-pyrrolobenzothiadiazole (TPBT) bridge, which is obtained through Scholl cyclization mediated by ferric chloride in nitromethane. Unlike the electron-rich thiophene-benzene bridging motifs utilized in previous PDI dimers, TPBT's electron-deficient fused backbone enhances electron affinity, synergizing with the electron-accepting character of PDI moieties to fine-tune frontier molecular orbital (FMO) energy levels and strengthen intermolecular electronic coupling. Comprehensive physicochemical characterization verifies low-lying FMO energy levels, broadened absorption, a highly planar backbone conformation, and enhanced packing order with a favorable edge-on orientation. These attributes translate to exceptional OFET electron mobility of 1.51 cm²·V^–1·s^–1—two orders of magnitude greater than that of its unfused analog s-2PDI (0.012 cm²·V^–1·s^–1). This striking mobility improvement underscores the effectiveness of full ring fusion in optimizing solid-state charge transport, with particular emphasis on the utility of electron-deficient bridging units for tailoring charge transport properties.

Keywords

Perylenediimides / Organic field-effect transistors / Planar backbone conformation / Electron mobility / Charge transport / Ring fusion

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