Piezotronic N+ -ITO/P-NiO/N-ZnO Heterojunction Thin-Film Diode as a Flexible Energy Scavenger

This paper reports on an all-oxide thin film piezotronic P-N heterojunction diode incorporating vertically-stacked structure of N+-ITO/P-type nickel oxide/N-type zinc oxide as a flexible energy scavenger and its diode characteristics on signal regulation which simplifies an essential element for harvesting which is signal rectification circuitry. An energy band diagram, theoretical modeling and equivalent small-signal circuit elaborate its working principle and device physics. Signal amplification due to introduction of in-series capacitances related to junction formation has also been addressed. A preliminary experimental study demonstrates applicability of such a flexible energy scavenger in various gratis non-stop thrusts originating from human body motions such as: simple tapping (as in typing) and walking actions for generating $\mu $ W-range power. Moreover, focusing on a simple power management system along with analysis of voltage waveforms in response to both resistive and capacitive loads unveils that the device is capable of quickly charging a capacitor and discharging it slowly allowing for possible energy storage. The estimation on generated power by a pixelated array that is obtainable due to ease of large-area fabrication processes and a single-pixel strip-based device exabits its feasibility as an energy source to power up some IoT nodes.