No abstract

The emerging photoelectrochemical‐type photodetector (PEC‐PD), because of its unique device architecture by using an aqueous electrolyte, is naturally applicable in the pursuit of underwater optical communication without sophisticated device packaging and assembling. Unfortunately, the traditional PEC detecting process typically involves a large electrochemical workstation with long cables and wire connections for photo signal acquisition, which hinders its applications in wireless optical communication. In this work, an AlGaN nanowire‐based self‐powered PEC‐PD is fabricated that uses seawater as an electrolyte, and then an optical communication system including the PEC‐PD and a portable electrochemical workstation as the signal receiver for data communication is built. Essentially, the self‐power PEC‐PD shows a high responsivity of −15.5 mA W–1, a fast response/recovery time of ≈100 ms, and high stability operation in the seawater electrolyte. Foremost, the optical communication system shows high accuracy in wireless transmission of ASCII code signals in a seawater environment. Such a demonstration offers a new device architecture for possible under‐seawater communication systems by leveraging the unique operation principle of photoelectrochemical devices in the future.

The p–n junction with bipolar characteristics sets the fundamental unit to build electronics while its unique rectification behavior constrains the degree of carrier tunability for expanded functionalities. Herein, a bipolar‐junction photoelectrode employed with a gallium nitride (GaN) p–n homojunction nanowire array that operates in electrolyte is reported, demonstrating bipolar photoresponse controlled by different wavelengths of light. Significantly, with rational decoration of a ruthenium oxides (RuOx) layer on nanowires guided by theoretical modeling, the resulting RuOx/p–n GaN photoelectrode exhibits unambiguously boosted bipolar photoresponse by an enhancement of 775% and 3000% for positive and negative photocurrents, respectively, compared to the pristine nanowires. The loading of the RuOx layer on nanowire surface optimizes surface band bending, which facilitates charge transfer across the GaN/electrolyte interface, meanwhile promoting the efficiency of redox reaction for both hydrogen evolution reaction and oxygen evolution reaction which corresponds to the negative and positive photocurrents, respectively. Finally, a dual‐channel optical communication system incorporated with such photoelectrode is constructed with using only one photoelectrode to decode dual‐band signals with encrypted property. The proposed bipolar device architecture presents a viable route to manipulate the carrier dynamics for the development of a plethora of multifunctional optoelectronic devices for future sensing, communication, and imaging systems.