Naphthalene diimide self-assembled ribbons with high electrical conductivity and mobility without doping

The thermally activated electrical conductivity and charge transfer properties of self-assembled naphthalene diimide molecule have been studied with N,N'di(hexadecyl)naphthalene tetracarboxylic diimide (HD-NDI) derivative. The self-assembly of HD-NDI has been resulted in one-dimensional large micron-size ribbons. The aggregate formation and self-assembling property have been extensively studied by absorption, fluorescence and X-ray diffraction analysis. Absorption and fluorescence measurements were taken in variety of solvents in fresh and aged samples, and the study suggested J-type aggregation for self-assembly formation. The electrical conductivity of self-assembled HD-NDI material was measured as a function of temperature where the conductivity increased with temperature and the highest conductivity (1 × 10⁻⁵ S/cm) was obtained at 250 °C. SEM images clearly show the formation of ribbons of micron size. Further the electron transport property of HD-NDI was also evaluated by SCLC method at room temperature by fabricating electron-only devices with annealing the film at ~ 200 °C. HD-NDI shows excellent electron mobility (1.8 × 10⁻³ cm² V⁻¹ s⁻¹) because of effective channel formation due to self-assembly of HD-NDI molecules, and this material may find potential application in variety of electronic devices.