Optimization of thin-film formation of naphthalene tetracarboxylic diimide derivatives with head and tail structure and application to transistors

Abstract

Herein, we characterized vacuum-evaporated thin-films of several new naphthalene tetracarboxylic diimide derivatives (C12-NTCDI-R) as n-type organic thin-film transistor (TFT) materials. They have head and tail structure with dodecyl chain and phenylalkyl (benzyl or phenylethyl) groups. By introducing fluorine groups into the phenylalkyl groups, the electron transport properties were enhanced. In addition, modifying the substrate surfaces with a fluorine-rich polymer material and annealing at the appropriate temperature allowed the TFT devices with C12-NTCDI-F2Bn (R = 3,5-difluorobenzyl) to reach a maximum electron mobility (μ e) of 0.11 cm2 V−1 s−1. Furthermore, the alteration of the number of methylene carbons in the side chain of phenylalkyl groups in C12-NTCDI-R (namely, phenylethyl was used as R) affected the thermal behavior of their molecules during the thin-film formation. For the TFT device with C12-NTCDI-PhEt (R = phenylethyl), the μ e reached the maximum value of 0.16 cm2 V−1 s−1 by just surface modification, without annealing.