Synthesis and Studies on 2-Hexylthieno[3,2-b]thiophene End-Capped Oligomers for OTFTs

The new semiconductors that were composed of a naphthalene or anthracene core unit and alkylated thienothiophene on both sides, 2,6-bis(5‘-hexyl-thieno[3,2-b]thiophen-2‘-yl)naphthalene (DH-TNT) and 2,6-bis(5‘-hexyl-thieno[3,2-b]thiophen-2‘-yl)anthracene (DH-TAT), were synthesized by Suzuki coupling reaction. The obtained oligomers were characterized by FT-IR, mass and elemental analysis, UV−visible spectroscopy, cyclovoltammetry, differencial scanning calorimetry, and thermogravimetric analysis. Vacuum-evaporated films were characterized by X-ray diffraction and atomic force microscopy (AFM). They all form highly ordered polycrystalline vacuum-evaporated films. DH-TAT exhibits excellent field-effect performances, with a hole mobility of 0.14 cm 2 /Vs, an on/off current ratio of 6.3 × 10 6, and a good threshold voltage of −14 V when it was deposited at T s = 120 °C on HMDS-treated SiO 2 . DH-TNT shows a hole mobility of 0.084 cm 2 /Vs and an on/off current ratio of 8.8 × 10 5 when it was deposited at T s = 100 °C.