Oriented Covalent Organic Framework Film on Graphene for Robust Ambipolar Vertical Organic Field-Effect Transistor

Periodically eclipsed pi-stacking columns in twodimensional covalent organic frameworks (2D COFs) could function as direct channel paths for charge carrier transport. Incorporating a well-defined 2D COF into organic electronic devices, however, is still a challenge. Herein, we have reported the solvothermal synthesis of a COFTFPy-PPDA film on single layer graphene (SLG), which was constructed via covalent imine-type linkage by employing 1,3,6,8-tetrakis(p-formylphcnyl)pyrene (TFPy) and p-phenylenediamine (PPDA) as building blocks. A vertical field-effect transistor (VFET) based on the heterostructure of COFTFPy-PPDA film and SLG shows ambipolar charge carrier behavior under lower modulating voltages. Work-function-tunable contact between SLG and COFTFPy-PPDA film and suitable injection barriers of charge carriers lead to the ambipolar transport with high current density on/off ratio (>10(5)) and high on-current density (>4.1 A cm(-2)). Interfacing 2D COF with graphene for VFET could shed light on the promising application prospect of 2D COFs in organic electronics and optoelectronics.