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

Abstract

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 (µmax) 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 µmax 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.