Heterojunction Engineering Significantly Resisting Seawater and Photocorrosion Enable Photoelectrochemical Detectors’ Prolonged Lifespan

Optical communication technology is regarded as one of the most critical technologies for marine exploration and development, and the photodetector is the key to its realization. However, the complex marine environment (such as light attenuation and seawater corrosivity) hinders the applications of conventional photodetectors. Here, we report a p-GaAs/n-CdS photoelectrochemical photodetector with sensitivity, stability, and broadband response under seawater. The heterojunction synergy of electron-transport acceleration driven by the strong built-in electric field, a stepped energy band structure, and high electron mobility of n-CdS endows the rapid interfacial reaction and avoids photocorrosion caused by electron accumulation on GaAs. Benefiting from the aforementioned advantages, p-GaAs/n-CdS exhibits a markedly enhanced photodetection performance under the broadband range at 0 V compared with p-GaAs, which delivers short response times of 2.16/2.22 ms, a high detectivity of 1.06 × 10¹⁰ Jones, a fast responsivity of 17.3 mA W^–1, and an especially stable life prolonged by more than 10 times (from 150 to 1600 s) under seawater.