Abstract Battery‐free photodetection is necessary for underwater optical communication, which poses extremely high requirements in terms of the self‐powering capability of photodetectors (PDs) and their ability to operate in harsh liquid environments. Emerging photoelectrochemical (PEC) PDs are appealing owing to their inherent aqueous operation behaviors with highly tunable photoresponses. Herein, a novel self‐powered PEC ultraviolet (UV) PD applicable to all‐scenario harsh underwater environments, including seawater at different latitudes and solutions with different pH values and temperatures, is demonstrated based on integrated self‐supporting SiC/SnO 2 heterojunction nanoarrays. The SiC/SnO 2 heterojunction nanoarrays are achieved by utilizing the anodic oxidation and chemical bath deposition. The SiC/SnO 2 PEC PD demonstrates excellent photodetection performance with rapid rise/decay times ( τ r / τ d , 30/120 ms), high responsivity ( R λ , 1.97 A W −1 ), remarkable detectivity ( D * , 1.98 × 10 11 Jones), and large external quantum efficiency ( EQE , 65.5%) in seawater under 375 nm UV light illumination with zero bias voltage. Moreover, the PEC PD delivers a high photoresponse and excellent aging stability in different latitudes of the world's oceans. The photodetection capability is robust even under harsh conditions, such as strongly acidic and alkaline liquid conditions, and at high temperatures. The developed device is a new type of photodetection device for future all‐scenario underwater optical communication.

Self‐Powered High‐Responsivity Self‐Supporting SiC/SnO<sub>2</sub> Nanoarray Photoelectrochemical Ultraviolet Photodetector: Toward All‐Scenario Harsh Underwater Applications

Self‐Powered High‐Responsivity Self‐Supporting SiC/SnO2 Nanoarray Photoelectrochemical Ultraviolet Photodetector: Toward All‐Scenario Harsh Underwater Applications