Environmentally Stable, Solution-Processed Indium Boron Zinc Oxide Thin-Film Transistors

In this work, solution-processed indium-boron-zinc-oxide (IBZO) thin-film transistors (TFT) have been fabricated by spin-coating. Properties such as the dissociation energy, electronegativity, ionic size and Lewis acid strength significantly influence the electrical properties of amorphous oxide active channel layers. Based on this reasoning, boron was chosen as a carrier suppressor to improve mobility and stability of the thin-film transistor. Boron concentration in precursor solution was varied from 0 at.% to 20 at.% while the indium concentration was fixed at 70 at.% and zinc concentration was decreased with respect to boron concentration. The IBZO thin films were deposited using spin-coating and post-annealed at 350°C. X-ray diffraction and high-resolution transmission electron microscopy studies confirmed the amorphous nature of the thin film. All the IBZO films were seen to be highly transparent (∼ 83%) in the visible region. The environmental electrical stability of the indium-zinc-oxide (IZO) and IBZO were studied, which revealed that the IBZO TFT with 10 at.% boron concentration has a saturated field effect mobility of 0.28 cm² V⁻¹ s⁻¹, threshold voltage of 8 V and I_ON/I_OFF of 8.54 × 10⁵ after 30 days of exposure to ambient atmosphere, with no shift in the turn-on voltage, whereas the IZO TFT exhibited an enormous shift in turn-on voltage from −26 V to −13 V.