Oxygen Vacancy Gradient Enabled Tunable Threshold Voltage of Solution-Processed Metal Oxide Homojunction Thin-Film Transistors for Blood Glucose Concentration Monitoring.

Li, Pengsheng; Wang, Guangcan; Gao, Siying; Yin, Yanxue; Sun, Yinghui; Meng, You; Hong, Sukjoon; Liao, Lei et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Threshold voltage (<i>V</i><sub>TH</sub>) tunability is challenging for metal oxide thin-film transistors (TFTs) in future applications in multilevel logic, sensing, and neuromorphic computing. Herein, solution-processed metal oxide homojunction thin films are designed by integrating pristine In<sub>2</sub>O<sub>3</sub> and poly(vinyl alcohol)-doped In<sub>2</sub>O<sub>3</sub> layers with different stacking sequence and doping ratio. When configured as back-gated TFTs, asymmetric <i>V</i><sub>TH</sub> tuning over a large range (from -10.50 to 5.27 V) as well as tunable operation mode, <i>I</i><sub>on</sub>/<i>I</i><sub>off</sub>, field-effect mobility, and carrier concentration are achieved. These impressive behaviors result from oxygen vacancy gradient-induced built-in electric fields, which across the homojunction interface govern carrier redistribution within the channel. With tunable <i>V</i><sub>TH</sub>, the homojunction TFTs are first constructed as n-channel-metal-oxide-semiconductor inverters, achieving a maximum voltage gain of 10.06. Furthermore, the tunable <i>V</i><sub>TH</sub> enables multithreshold signal encoding, which is exploited to realize four-level blood glucose concentration monitoring, displaying an impressive accuracy of over 85%.