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We have successfully synthesized and characterized newly synthesized oxygen-heterocyclic and π-conjugated dimers, 9,9′-bi(benzo[b]naphtha[2,1-d]furan) (9-BBR), as a potential semiconductor material with good environmental stability for organic field-effect transistor (OFET) devices. As expected from DFT calculations, spectroscopic analyses allow us to confirm the compound has lower highest occupied molecular orbital (HOMO) energy level and larger HOMO–lowest unoccupied molecular orbital (LUMO) gap than those of pentacene. Absorption spectra of 9-BBR in an air-saturated solution remain unchanged, indicating substantial environmental stability; in fact, the mobility values of 9-BBR-based OFET devices are stable even in the presence of air. Maximum field-effect mobilities up to 10−2 cm2 V−1 s−1 are obtained by 9-BBR-based OFETs with hexamethyldisilazane (HMDS)-treated substrates at Tsub = 100 °C. X-ray diffraction and atomic force microscopy allow us to conclude that better characteristics of 9-BBR-based OFETs prepared at high Tsub are attributed to good crystallinity and large-sized grain morphology in the thin films.

We have successfully synthesized and characterized newly designed oxidation-resistant N,N′-dialkylated dihydrodiazapentacene (1a: alkyl = hexyl) and (1b: alkyl = stearyl) as stable semiconductor materials under ambient conditions for organic field-effect transistors (OFETs). The crystal structure analysis has allowed us to know that 1a has a face-to-face slipped π–π stacking motif, with the intermolecular distance being about 3.49 A, which forms a one-dimensional column. XRD and AFM measurements reveal that the vacuum deposited films of 1a and 1b are similar crystalline phases with molecules being tilted from the substrate plane. The OFETs fabricated using 1a and 1b exhibit typical p-type FET performances with mobilities of 3.2 × 10−3 and 3.0 × 10−5 cm2 V−1 s−1, respectively. The storage tests of OFETs using 1a in the presence of air for 3 months have proven high device stability with no significant changes in mobilities and on/off ratios. The relatively low mobilities can be attributed to the undesirable overlap of HOMOs and the strongly anisotropic one-dimensional π–π stacking.