Investigating the single crystal OFET and photo-responsive characteristics based on an anthracene linked benzo[b]benzo[4,5]thieno[2,3-d]thiophene semiconductor

Organic single crystals have great potential in optoelectronic devices owing to their grain-boundary free nature and long exciton diffusion length. In this report, an anthracene linked benzo[b]benzo[4,5]thieno[2,3-d]thiophene semiconductor, 2-An-BTBT was designed and synthesized. Belt like organic single crystals based on 2-An-BTBT were grown via physical vapor transport method. Using an ultrathin wire as the shadow mask, organic field effect transistor (OFET) with a channel length of around 15 μm was fabricated and the highest mobility of 0.9 cm2V−1s−1 and average mobility of 0.58 cm2/V were obtained. Furthermore, photo-response characteristics of the 2-An-BTBT based device were also investigated. Photo-response of as high as 7136 AW-1 was achieved via 17.7 μW/cm2 @380 nm mono wavelength light illumination which is ascribed to the long exciton diffusion length of organic single crystal and ultra-short channel length of the fabricated OFET. Stable switching behavior with rising time and decline time of several seconds is attained which indicates the existence of shallow traps at the insulator/semiconductor interface.