Low-temperature-processible, transparent, and air-operable n-channel fluorinated phenylethylated naphthalenetetracarboxylic diimìde semiconductors applied to flexible transistors

New N,N'-disubstituted-l,4,5,8-naphthalene tetracarboxylic acid diimides (NTCDI) with fluorinated phenylethyl groups were synthesized. In particular, N,N'-bis(2-(pentafluorophenyl)ethyl)-1,4,5,8-naphthalene tetracarboxylic acid diimide (5FPE-NTCDI) showed high electron mobility, more than 0.1 cm ²/(V s) in air, even though the film was deposited at room temperature. The correlation of the crystallinity, morphology, and mobility with the substrate temperature during deposition (T _sub) was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). The films of 5FPE-NTCDI exhibited a "thin film phase", mixed phase, and crystal bulk phase as T _sub was increased. The mixed phase on an octadecyltrimethoxysilane (OTS)-treated substrate also has high electron mobility due to well connected long fiber-shaped grains. The high mobility at low T _sub has enabled fabrication of flexible transistors on the clear plastic substrate poly(ethylene terephthalate) (PET). The highest mobility for a flexible, transparent transistor was 0.23 cm ²/(V s), obtained with low hysteresis.