Transparent, Low-Hysteresis Complementary Inverters Using p-Channel SWNT and n-Channel IGZO TFTs for Light-to-Frequency Conversion.

Transparent and stable complementary inverters that can simultaneously support analog amplification and digital oscillation under optical stimulation are highly demanded for future see-through optoelectronic systems such as smart windows, augmented-reality interfaces, and on-skin photonic sensors. In this work, we report fully transparent, low hysteresis complementary inverters composed of a p-channel single-walled carbon nanotube (SWNT) thin-film transistor (TFT) with a top-gate iCVD pC1D1 polymer dielectric and an n-channel indium-gallium-zinc oxide (IGZO) TFT with a bottom-gate Al2O3 dielectric, both fabricated on ITO-coated glass substrates. The two TFTs exhibit well-matched output characteristics in opposite carrier polarities, enabling a CMOS-like inverter operation that delivers rail-to-rail switching, high voltage gain and a small hysteresis of less than 200 mV between forward and reverse sweeps. Furthermore, the UV photoresponse of the IGZO channel allows for systematic modulation of the inverter switching voltage (VM) and small-signal gain with the incident UV intensity. Cascading the proposed inverter into three-, five-, and seven-stage ring oscillators yields stable rail-to-rail oscillation in which the oscillation frequency (fosc) and the power consumption (P = CL · VDD2 · fosc · N) are tunable in real time by the UV intensity, realizing transparent light-to-frequency conversion at the circuit level. These results establish a route to low-power, see-through optoelectronic logic platforms that combine carbon-nanotube and oxide-semiconductor technologies on a common transparent substrate.