New synthetic approaches for hexacene and its application in thin-film transistors

Hexacene is a valuable aromatic compound with special optoelectronic properties. Here, a stable new precursor of hexacene, 5,6,15,16-tetrahydro-5,16-epoxyhexacene, was synthesized through a three-step route in a total yield of 31%. Then two methods for the synthesis of hexacene based on this new precursor were developed. One is realized by dehydration of 5,6,15,16-tetrahydro-5,16-epoxyhexacene by thermal activation on the Cu(110) surface under ultrahigh vacuum (UHV) conditions. The other is copper powder-catalyzed dehydrogenation of another precursor 6,15-dihydrohexacene, which provided pure hexacene by vacuum sublimation in the dark. Organic thin-film transistors (OFETs) were fabricated using hexacene through a vacuum deposition method. And a comprehensive study of the hole-transfer properties of OFETs was performed. The best film mobility of hexacene was observed at 0.123 cm2 V−1 s−1 with an on/off ratio of 1.16 × 104 and a threshold of 2.65 V.