Seawater-Powered PEC Photodetectors Based on a Layered Metal Dichalcogenide for Marine Underwater Optical Communication

In order to protect the ocean ecosystem, the pursuit of sustainable and self-powered photodetectors is critical for revolutionizing underwater optical communication (UOC) used for environmental hazard sensing. This step enables energy-efficient and real-time detection of marine ecosystem threats such as chemical contamination, oil spill, and eutrophication. Although layered metal dichalcogenides (LMDCs) with exceptional optoelectronic properties and chemical stability are the most suitable materials, their integration into UOC technology remains largely unexplored. To address this, the present study demonstrates and evaluates seawater-immersed photoelectrochemical photodetectors (PEC-PDs) based on SnSe₂, an emerging member from the LMDC family. Direct vapor transport-grown SnSe₂is well characterized in its thin-film form by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and PL spectroscopy, followed by utilization as photoelectrodes in the PEC-PD devices. Fabricated PEC-PDs exhibit a responsivity of 505.74 ± 4.65 μA/W at zero bias and 10.34 ± 0.16 mA/W at 0.4 V bias; they outperform conventional Na₂SO₄-based devices by 21-fold and 82-fold, respectively. To the best of our knowledge, this is the first report presenting an SnSe₂-based PEC-PD utilizing seawater electrolyte and its performance evaluation. A proof-of-concept UOC demonstration of the present study paves the way toward the next-generation green optoelectronic devices for self-sustainable marine technologies.