Novel semiconductors based on functionalized benzo[ d, d′]thieno[3,2- b;4,5- b′]dithiophenes and the effects of thin film growth conditions on organic field effect transistor performance

A series of benzo[d,d]thieno[3,2-b;4,5-b]dithiophene (BTDT) derivatives, end-functionalized with phenyl (P) and benzothiophenyl (BT), were synthesized and characterized. A facile, one-pot synthesis of BTDT was developed which enables the efficient realization of a new BTDT-based semiconductor series for organic thin-film transistors (OTFTs). The crystal structure of P-BTDT was determined via single-crystal X-ray diffraction. Various combinations of dielectric surface treatment methods, substrate temperature, and deposition flux rate sequences have significant effects on device performance. Films deposited on octadecyltrichlorosilane (OTS)-treated SiO₂ substrates under properly adjusted substrate temperature and deposition flux rate achieve an efficaceous compromise between high film crystallinity and good film grain interconnectivity, resulting in good OTFT performance, with mobility greater than 0.70 cm²V^-1 s^-1 and I_on/I _off greater than 10⁸.