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 cm(2) V-1 s(-1) with high on/off ratio (under ambient conditions) after annealing.