Photocurrent Polarity Controlled by Light Wavelength in Self-Powered ZnO Nanowires/SnS Photodetector System

Self-powered photodetectors are expected to play a crucial role in future nano-optoelectronic devices owing to their independent and sustainable operation. Based on the heterojunction between ZnO nanowires (NWs) and shuttle-like SnS, we design a self-powered photodetector exhibiting wide-range photoresponse and tunable spectral selectivity. Differently from conventional devices, a wavelength-induced photocurrent polarity is observed in the ZnO NWs/SnS photodetector, which enables the device to distinguish between photons in the UV and visible (VIS) regions. This is due to switching of the interfacial modulation by the pyroelectric-polarization potential (pyro-potential) inside ZnO NWs and thermoelectric-polarization potential (thermo-potential) inside SnS. A photocurrent enhancement of 125% and improved responsivity of 364 μA/W are obtained under the pyro-potential upon 690 nm light illumination, whereas reversed responsivity of -155 μA/W is obtained under the thermo-potential upon 365 nm light illumination. We believe the photocurrent polarity could be useful for improving resolution of dynamic light sensing/imaging.