N-type organic field effect transistors based on naphthalene tetracarboxylic diimides derivatives containing halogen elements

Naphthalene tetracarboxylic diimides (NDIs) derivatives, functionalized with p-fluorophenyl (NDI-FAN), p-chlorophenyl (NDI-ClAN), p-fluorobenzyl (NDI-FBN), were synthesized and used to fabricated organic field effect transistors (OFETs) through vacuum evaporation. All materials display high decomposition temperature and low LUMO energy level facilitating air stable electron transport. OFETs devices based on N-octadecylphosphonic acid (ODPA) treated SiO2/Si substrate affords electron mobility up to 1.8 × 10−1 cm2v−1s−1 with high on/off ratio of 6.7 × 103 in air. Replaced the p-fluorophenyl by p-fluorobenzyl also leads to a comparable mobility reaching 1.1 × 10−1 cm2v−1s−1 with a low threshold voltage of 1.8 V. Microstructure and morphology of thin films were investigated to shed light on the reason for distinct electrical performance. These results demonstrate that fluorinated N-substituent is an alternative method to optimize molecular arrangement and device performance.