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

Threshold voltage ( V TH ) 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 2 O 3 and poly(vinyl alcohol)-doped In 2 O 3 layers with different stacking sequence and doping ratio. When configured as back-gated TFTs, asymmetric V TH tuning over a large range (from −10.50 to 5.27 V) as well as tunable operation mode, I on / I off, 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 V TH, the homojunction TFTs are first constructed as n-channel-metal-oxide-semiconductor inverters, achieving a maximum voltage gain of 10.06. Furthermore, the tunable V TH enables multithreshold signal encoding, which is exploited to realize four-level blood glucose concentration monitoring, displaying an impressive accuracy of over 85%.