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-<i>d</i>;2′,3′-<i>d</i>′]­benzo­[1,2-<i>b</i>;4,5-<i>b</i>′]­dithiophene compounds (<b>QDTBDT</b>s) with alkyl chains branched at different positions were synthesized. Thin-film transistor characteristics showed that the type of charge carriers in <b>QDTBDT</b>s could be tuned by changing the branching position of the alkyl chains. <b>QDTBDT-2C</b> 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. <b>QDTBDT-4C</b>-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. <b>QDTBDT-3C</b> 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 <b>QDTBDT-2C</b> displayed high gain and high noise margins