Highly flexible printed carbon nanotube thin film transistors using cross-linked poly(4-vinylphenol) as the gate dielectric and application for photosenstive light-emitting diode circuit

In this work, cross-linked poly(4-vinylphenol) (PVP) was utilized in printed single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) as the gate dielectric layer to achieve low operating voltage, environmental stability and high flexibility. The printed top-gate TFTs on polyethylene terephthalate (PET) substrates exhibited effective mobility up to 8.4 cm2V−1s−1 (based on device capacitances measured at 0.1 Hz), on/off ratio of 106 and subthreshold swing (ss) of 63.8 mV/dec at operation voltage of only 1 V. The printed TFTs exhibited excellent mechanical flexibility and stability under ambient conditions due to the use of cross-linked PVP as dielectric layers. No obvious discrepancies in electrical properties were observed after bending 15000 cycles at the radius of 5 mm. A photosensitive light-emitting diode (LED) circuit was constructed, which was composed of two commercial LEDs and the printed SWCNT TFTs. One LED was mounted on top of the gate electrode, acting as a photon sensor to modulate the gate voltage of TFT. The second LED was connected to the source electrode to act as an illuminating device. The circuit could drive the illuminating LED at Vdd of −0.75 V and Vds = −2 V with lighting intensity varying from 0 to 8.96 μW/cm2.