Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistor using Thermal Annealing

We present that the hole and electron transport properties in an ambipolar semiconducting polymer can be controlled with thermal annealing. We also show that the split-gate structure offers more accurate characterization for the hole and electron transport parameters such as saturation (μsat.), linear mobility (μlin.), turn- on (Vto), and threshold voltage (Vth) than conventional ambipolar transistor does. As a result, well-balanced hole and electron conduction could be achieved in an ambipolar semiconducting poly-(diketopyrrolopyrrole-terthiophene) (PDPP-3T). It was also observed that hole de-doping (electron doping-like) occurred with thermal annealing, which removed the dipole formation by atmospheric oxygen. Such a recuperation from the atmospherically doped to intrinsically un-doped state changed the characteristics in hole and electron transport, which agreed with the shift in the measured ultraviolet photoelectron spectroscopy (UPS) spectrum. A complementary logic inverter with balanced charging and discharging was demonstrated based on the findings.