Naphthalene diimide based near-infrared luminogens with aggregation-induced emission characteristics for biological imaging and high mobility ambipolar transistors

Organic conjugated materials combining high conductivity with strong solid-state emission are highly desired for organic electronic applications,yet still rather rare.Herein,a novel luminogen(TEN)comprised by linking naphthalene diimides and triphenyl ethylene with vinyl bridges is reported.TEN exhibits aggregation-induced emission(AIE)behavior of a strong nearinfrared fluorescence over 700 nm and the efficiency above 60.5%in the solid state,while also shows promising application in vivo bio-imaging with good permeability and extremely low background.Single crystal of TEN reveals intra-and intermolecular C–H…O hydrogen bonds,contributing to an inclined molecular stacking along the a-axis of the cell,creating a 1 D charge carrier transporting channel under a shortπ-πinteraction distance of 3.42?,which might benefit the solid emission and charge transport ability simultaneously.Solution processed bottom contact,top gate organic field effect transistors based on TEN reveal a high ambipolar charge transport ability with the hole mobility up to 0.13 cm2 V-1 s-1 and electron mobility up to0.010 cm2 V-1 s-1.Further atomic force microscopy and X-ray diffraction analysis on TEN thin film confirm the existence of the1 Dπ-πstacking channel,suggesting the stacking geometry revealed in crystal crucial for facilitating high charge carrier mobility while preserving the strong solid emission at the same time.

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices.Compared to p-type dopants,the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions.In this article,we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2)in organic thin film transistor devices by soluble anion dopants.The addition of the dopants resulted in the formation of stable radical anions in thin films,as confirmed by EPR spectroscopy.By tuning the dopant concentration via simple solution mixing,the transistor parameters could be readily controlled.Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced,which resulted in the transistor behaviour approaching the desirable gate voltage-independent model.Reduced hysteresis was also observed,thanks to the trap filling by the dopant.Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude.Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.