Fully Solution-Processed Low-Voltage Driven Transparent Oxide Thin Film Transistors

In this work, transparent ZnO thin-film transistors (TFTs) are fabricated on ITO glass substrate with only solution processes. The active ZnO channels are deposited by spray pyrolysis. The gate dielectric is a spin-coated high dielectric constant (k) titanium-silicon oxide (TSO) layer, while the source/drain (S/D) electrodes are patterned by two-step spray-printing of silver nanowire (AgNWs)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent conductive composite through a shadow mask. The composition and microstructural characteristics of the films, as well as their TFTs performance, are systematically studied as a function of the temperature. The introduction of TSO high k dielectric, with ultraviolet (UV)-assisted post-annealing, significantly improves the device performance and achieves a maximum electron mobility (µ_max) value as high as 56.2 cm² V⁻¹ s⁻¹ when measured with thermally-evaporated Al top electrode. For fully solution-processed transparent TFTs with low temperature fabricated AgNWs/PEDOT:PSS S/D electrodes, the µ_max is calculated to be 9.1 cm² V⁻¹ s⁻¹ operating at a relatively low voltage of <3 V. The TFTs also show hysteresis-free electrical characteristics and optical transparency of ≈80% in the visible region of the optical spectrum.