Solution-processable thiadiazoloquinoxaline-based donor-acceptor small molecules for thin-film transistors

Although several [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ)-thiophene-based hybrid polymers have been demonstrated for application in organic field-effect transistors (OFETs), the research on the charge carrier mobility of conjugated donor (D)-acceptor (A) small molecules is rare. To enrich the TQ-containing small molecule family, in this paper, we designed and synthesized three novel TQ derivatives 1, 2, and 3 with thiophene units attached onto the TQ cores. The optoelectronic and OFET properties of as-prepared compounds 1-3 are investigated. Our results indicate that compounds 1-3 show typical p-type characteristics with mobility as high as 0.012, 0.05 and 0.0055 cm² V^-1 s^-1 and on/off current ratios of 3 × 10⁵, 1 × 10⁶ and 1 × 10⁴ under the optimized conditions, respectively. Due to the steric effect of the substituted bulky group, compound 3 adopts a looser packing mode with a larger π-π distance, which subsequently reduces the transport performance. Our results suggest that the D-A π-conjugated small molecules based on TQ could be good candidates for application in organic electronic devices.