Highly Sensitive Piezotronic p-n and n-p Heterojunction Diodes as Wearable Pressure Sensors

This article details a comparison between all-inorganic thin-film piezotronic p-n/n-p heterojunction diodes as wearable pressure sensors, with a comprehensive exploration of how the p-n junction outperforms the n-p junction, addressing fabrication and interface engineering impacts. Both configurations are considered as signal-mediated devices (current and voltage) and demonstrate proper amplification along with high signal-to-noise-ratio (SNR) which is highly desirable in wearable sensory units. Analytical modeling, equivalent circuit, and energy band diagrams elaborate their working principle and justify high sensitivity of devices. A preliminary experimental study on single-pixel devices testifies priority of the p-n junction diode. Owing to ease of large-scale fabrication, a wearable sensory system has also been tested through integration of a pixelated array of piezotronic p-n heterojunction diodes and an acquisition board.