New core-expanded naphthalene diimides with different functional groups for air-stable solution-processed organic n-type semiconductors

Among the reported organic n-type semiconductors, naphthalene diimide (NDI) derivatives have received increasing attention. In this paper, we report four non-symmetric core-expanded NDI derivatives 1–4. Electrochemical, absorption spectral and theoretical calculation studies show that LUMO energies of 1–4 are lower than that of parent NDI without substitution. OFET devices based on thin films of 1–4 which can be easily solution-processed are fabricated with conventional techniques and they show n-type semiconducting behaviours. Moreover, the performance of OFET devices of 1–4 can be significantly improved by annealing their thin films. OFETs of 3 exhibit electron mobility up to 0.17 cm2 V−1 s−1 with high on/off ratio (under ambient conditions) after annealing.