Solution-Processed High-Performance Tetrathienothiophene-Based Small Molecular Blends for Ambipolar Charge Transport

Four soluble dialkylated tetrathienoacene (TTAR)-based small molecular semiconductors featuring the combination of a TTAR central core, π-conjugated spacers comprising bithiophene (bT) or thiophene (T), and with/without cyanoacrylate (CA) end-capping moieties are synthesized and characterized. The molecule DbT-TTAR exhibits a promising hole mobility up to 0.36 cm² V⁻¹ s⁻¹ due to the enhanced crystallinity of the microribbon-like films. Binary blends of the p-type DbT-TTAR and the n-type dicyanomethylene substituted dithienothiophene-quinoid (DTTQ-11) are investigated in terms of film morphology, microstructure, and organic field-effect transistor (OFET) performance. The data indicate that as the DbT-TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron-only) to ambipolar and then back to unipolar (hole-only). With a 1:1 weight ratio of DbT-TTAR DTTQ-11 in the blend, well-defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm² V⁻¹ s⁻¹, respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high-performance solution-processable OFETs.