New tetrathiafulvalene fused-naphthalene diimides for solution-processible and air-stable p-type and ambipolar organic semiconductors

New conjugated electron donor-acceptor molecules with tetrathiafulvalene (TTF) fused-naphthalene diimide frameworks (1-6) are synthesized and investigated. The NDI cores are flanked by TTF and 2-(1,3-dithiol-2-ylidene)malonitrile moieties within 1-3, whereas compounds 4-6 contain two TTF moieties. Based on cyclic voltammetric and absorption spectral studies, the LUMO and HOMO energies of 1-3 are estimated to be ca. -4.3 eV and ca. -5.1 eV, and those of 4-6 are ca. -4.1 eV and ca. -5.0 eV, respectively. These values are consistent with theoretical calculations. Thin films of 1-6 are easily prepared with the spin-coating technique and the resulting OFETs are successfully fabricated with conventional procedures. The OFETs results reveal that compounds 1-3 behave as ambipolar semiconductors and 4-6 as p-type semiconductors. Among 1-3, compound 3 exhibits relatively high hole and electron mobilities in air, reaching 0.03 and 0.003 cm(2) V-1 s(-1), respectively, after annealing at 160 degrees C. The OFET based on a thin film of 5 shows the best performance with mu(h) = 0.31 cm(2) V-1 s(-1), I-on/(off) 10(4) among compounds 4-6 after annealing at 160 degrees C. The thin films of 1-6 are investigated with XRD and AFM, and the data can well interpret the variation of carrier mobilities of 1-6 after annealing. Moreover, the influences of alkyl chains in 1-6 on the intermolecular arrangements and carrier mobilities are also discussed.