Solution-processed flexible metal-oxide thin-film transistors operating beyond 20 MHz

Complementary metal-oxide-semiconductor, an elementary building block, allows for a high degree of implementation of logic circuits with relatively low power consumption and low manufacturing cost, which plays a vital role not only in current Si electronics, but also in printed flexible devices. To meet the looming challenges of the Internet of Things, p-channel thin-film transistors (TFTs) with an excellent mobility and processability have been increasingly developed using organic semiconductors. However, owing to the inherent electron-donating nature of organic compounds, the high performance of n-channel organic TFTs has yet to be demonstrated. Here, in this paper, we developed state-of-the-art solution-processed indium-zinc-oxide (IZO) TFTs with high electron mobility, sharp turn-on characteristics at 0 V, and excellent atmospheric stability and compatibility with wet patterning processes. With the damage-free lithography process in conjunction with the ultimate optimization of entire device processes, IZO-based TFT arrays were successfully fabricated via a solution process on flexible polyimide substrates. A cutoff frequency of 23 MHz in air was achieved, which is almost twice as fast as the frequency used in a near-field communication band. Furthermore, the as-fabricated IZO-based TFTs even function well under bending stress. Therefore, the current concept and technique is expected to open up opportunities to develop practical flexible devices with high-speed operation.