Piezo-phototronic effect improved performance of n-ZnO nano-arrays/p-Cu2O film based pressure sensor synthesized on flexible Cu foil

Abstract

The piezo-phototronic effect has drawn great interest recently due to its improvement of optoelectronic devices performance by effectively controlling the carrier generation, separation, transport, and/or recombination at the interface/junction of the p–n junction. In this study, a compact sensitivity controllable pressure sensor with the n-ZnO nano-arrays/p-Cu2O film structure is synthesized on flexible Cu foil substrate, and the improved performance due to piezo-phototronic effect is characterized systematically. The heterostructure shows a nearly ideal rectifying behavior with substantial forward current of more than 1mA (at 3V) under pressure free and dark conditions, indicating excellent p-n junction was formed at the n-ZnO nano-arrays/p-Cu2O film interface. The linear dependence of switch ratio (SR) (I/I0) on the applied pressure and response time of ~1s were observed in the pressure sensor. The linear dependence can be further improved and a value up to 376% is reached by the illumination radiation of the 405nm violet light emitting diodes (LEDs), which had been tactfully embedded within the device. The advantages of embedding LEDs in the sensor lie in reducing of device volume as well as preventing influence of environment light on the sensor performance. Furthermore, a substantial enhancement in the sensitivity (I-I0/I0/∆P) of the pressure sensor is achieved by adjusting the illumination intensity, which reaches 918% at the illumination intensity of 11.7mW/cm2. The piezo-phototronic effect enhanced performance can be well elucidated by the corresponding energy band diagram. Our achievement provides a very promising method to improve the SR and sensitivity controllability of pressure sensor using piezo-phototronic effect.