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.

Observation of polarity-switchable photoconductivity in III-nitride/MoSx core-shell nanowires

“… Photodetector Type Working mechanism Wavelength [nm] Photocurrent magnitude Responsivity [mA W −1 ] Ref. a-MoS x @p-AlGaN/n-GaN PEC PD p-n junction/PEC effect 254 μA cm −2 −100.42 This work 365 μA cm −2 29.5 Pt/p-AlGaN/n-GaN PEC PD p-n junction/PEC effect 254 μA cm −2 −175 41 365 μA cm −2 31 AlGaN/Pt-GaN cell PEC PD Photovoltage-competing/PEC effect 254 μA cm −2 11.39 42 365 μA cm −2 −0.3 Pt/p-GaN PEC PD Carrier transport/PEC effect 285 μA cm −2 −7.2 43 365 μA cm −2 1.1 α-Ga 2 O 3 /Cu 2 O PEC PD p-n junction/PEC effect 254 μA 0.42 44 365 μA −0.57 Au/TiO 2 PEC PD Plasmon/PEC effect 400 nA −0.6 36 800 nA 0.15 p-SnS/p-Si Solid-state PD Photovoltage 400 μA ...…”

“…Essentially, the pursuit of polarity-switchable photoconductivity behavior has recently attracted considerable interests [35][36][37] , because the polarity-switchable photocurrent can be employed to distinguish spectrum bands while measuring corresponding light intensity, which has been realized in many solid-state devices [37][38][39][40] . The proposed III-nitride/a-MoS x core-shell nanostructures demonstrate a polarityswitchable photoconductivity under different-energy photon illumination, i.e., it exhibits a polarity-switchable photoresponse with a responsivity of −100.42 mA W −1 under 254 nm illumination, and 29.5 mA W −1 under 365 nm illumination, one of the highest value among reported polarity-switchable devices 36,[38][39][40][41][42][43][44][45][46][47][48][49][50] . Moreover, the underlying mechanism of polarity-switchable photoconductivity behavior is revealed via density functional theory (DFT) calculations.…”

Self-Assembly Nanopillar/Superlattice Hierarchical Structure: Boosting AlGaN Crystalline Quality and Achieving High-Performance Ultraviolet Avalanche Photodetector

“…A tunable wide energy bandgap enables the intrinsic wavelength of AlGaN to cover a large range of UVA to DUV (200–365 nm), thus rendering AlGaN crucial to UV detection and luminescence fields. In addition, the AlGaN heterostructure plays a significant role in transistors as well as photodetectors due to its non-negligible polarization effects. − Accordingly, the development of AlGaN materials and devices could effectively promote the progress of semiconductor techniques. − …”

Coupling Plasmonic Pt Nanoparticles with AlGaN Nanostructures for Enhanced Broadband Photoelectrochemical-Detection Applications

“…In addition, compared with conventional solid-state photodetectors (e.g., photoconductive-type, Schottky-type, and so forth), the emerging photoelectrochemical type operates with a combination of physical and electrolyte-assisted chemical processes which offers more flexibility and tunability in detecting the incident light signals. 17 In this work, we demonstrated a highly deep UV-sensitive broadband photodetector based on the plasmonic Pt nanoparticles (NPs) combined with the p-type AlGaN nanostructures, which operates in a photoelectrochemical mode. Benefiting from the hot charge injection and near-field electromagnetic amplification induced by LSPR, the Ptdecorated photodetectors maintained a high UV sensitivity and exhibited a significant boost of UV photoresponsivity, that is, 7-fold under 254 nm illumination and 64-fold under 365 illumination as compared to those devices composed of pristine nanostructures.…”

“…To realize near UV or even solar-blind photodetection with high responsivity, wide band gap semiconductors such as group III-nitrides or III-oxides are frequently chosen, whereas these materials are generally used to construct the UV-specific photodetectors with narrow response spectra, which may limit their photodetecting application in the broadband range. , To overcome those fundamental limits, the plasmonic metals combined with the UV-responsive semiconductor may be an alternative approach to construct a UV-sensitive broadband photodetector, which can satisfy the requirements of UV–visible broadband light communication, spectral analysis, environment monitoring, and spectroscopic applications. , Bearing these in mind, we are aiming to construct such a device that can maintain a high UV-responsive performance while broadening its detection range. In addition, compared with conventional solid-state photodetectors (e.g., photoconductive-type, Schottky-type, and so forth), the emerging photoelectrochemical type operates with a combination of physical and electrolyte-assisted chemical processes which offers more flexibility and tunability in detecting the incident light signals …”