Five-Ring Fused Tetracyanothienoquinoids as High-Performance and Solution-Processable n-Channel Organic Semiconductors: Effect of the Branching Position of Alkyl Chains

Abstract

Dicyanomethylene-substituted quinoidal dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene compounds (QDTBDTs) with alkyl chains branched at different positions were synthesized. Thin-film transistor characteristics showed that the type of charge carriers in QDTBDTs could be tuned by changing the branching position of the alkyl chains. QDTBDT-2C exhibited n-channel behavior, and the observed electron mobility was 0.57 cm2 V–1 s–1 without post-treatment, one of the highest values reported for spin-coated thin-film transistors with no annealing under ambient conditions. QDTBDT-4C-based transistors displayed electron-dominated ambipolar transport behavior, with electron mobilities reaching 0.2 cm2 V–1 s–1 and hole mobilities in the range of 10–3–10–4 cm2 V–1 s–1. QDTBDT-3C showed solution-concentration-dependent carrier transport characteristics, exhibiting n-type behavior at low solution concentrations and ambipolar performance at high solution concentrations with an electron mobility of 0.22 cm2 V–1 s–1 and a hole mobility of 0.034 cm2 V–1 s–1. CMOS-like inverters fabricated from QDTBDT-2C displayed high gain and high noise margins.