Enhanced performance of benzothieno[3,2-b]thiophene (BTT)-based bottom-contact thin-film transistors

Three new benzothieno[3,2-b]thiophene (BTT; 1) derivatives, which were end-functionalized with phenyl (BTT-P; 2), benzothiophenyl (BTT-BT; 3), and benzothieno[3,2-b]thiophenyl groups (BBTT; 4; dimer of 1), were synthesized and characterized in organic thin-film transistors (OTFTs). A new and improved synthetic method for BTTs was developed, which enabled the efficient realization of new BTT-based semiconductors. The crystal structure of BBTT was determined by single-crystal X-ray diffraction. Within this family, BBTT, which had the largest conjugation of the BTT derivatives in this study, exhibited the highest p-channel characteristic, with a carrier mobility as high as 0.22 cm² V^-1 s^-1 and a current on/off ratio of 1×10 ⁷, as well as good ambient stability for bottom-contact/bottom-gate OTFT devices. The device characteristics were correlated with the film morphologies and microstructures of the corresponding compounds.