Photovoltage‐Competing Dynamics in Photoelectrochemical Devices: Achieving Self‐Powered Spectrally Distinctive Photodetection

Abstract Multiple‐band and spectrally distinctive photodetection play critical roles in building next‐generation colorful imaging, spectroscopy, artificial vision, and optically controlled logic circuits of the future. Unfortunately, it remains challenging for conventional semiconductor photodetectors to distinguish different spectrum bands with photon energy above the bandgap of the material. Herein, for the first time, a photocurrent polarity‐switchable photoelectrochemical device composed of group III‐nitride semiconductors, demonstrating a positive photocurrent density of 10.54 µA cm −2 upon 254 nm illumination and a negative photocurrent density of −0.08 µA cm −2 under 365 nm illumination without external power supply, is constructed. Such bidirectional photocurrent behavior arises from the photovoltage‐competing dynamics across two photoelectrodes. Importantly, a significant boost of the photocurrent and corresponding responsivity under 365 nm illumination can be achieved after decorating the counter electrode of n‐type AlGaN nanowires with platinum (Pt) nanoparticles, which promote a more efficient redox reaction in the device. It is envisioned that the photocurrent polarity‐switch behavior offers new routes to build multiple‐band photodetection devices for complex light‐induced sensing systems, covering a wide spectrum band from deep ultraviolet to infrared, by simply engineering the bandgaps of semiconductors.