ZnO-Based Flexible UV Photodetector for Wearable Electronic Applications

Abstract

This study pivots on the ZnO-based flexible ultraviolet (UV) photodetector (PD) for wearable electronic applications. The high-quality ZnO thin film is deposited via reactive magnetron sputtering on a polyimide (PI) flexible substrate. Furthermore, metal-semiconductor-metal (MSM) PD device performance is investigated in both normal and device bending conditions to evaluate the various photography detecting performance parameters comprising I - V , responsivity (R), external quantum efficiency (EQE), and switching response. The important aspect of this study is, at higher voltage, the dark and photocurrent of the MSM PD at normal and bending conditions of substrate, does not change significantly. The morphology and optical property of the ZnO thin film is verified via atomic force microscope (AFM) and ellipsometry characterization. In addition, the device performance is attributed to governing physics, which are thermionic field-emission theory and piezophototronic effect, collectively. The peak R and EQE at 6 V for normal conditions are 0.5 A/W and 45%, respectively, which remain almost the same for bending conditions also. The rise time of the PD at the highest bending condition is 215 ms with an I OFF ratio for all the conditions higher than 10-2 times. The robust response of this flexible PD device under bent conditions at higher voltage clears the prospect of the PD for the Internet of Things (IoT) and other wearable electronic applications. © 2001-2012 IEEE.