Water‐Coupled Interfacial Modulation Enhances Photovoltaic and Pyroelectric Responses in Transparent Self‐Powered ZnO/NiO Photodetectors

ABSTRACT Transparent self‐powered photodetectors are attractive for smart windows, environmental monitoring, and underwater optoelectronics, yet using the surrounding medium remains largely unexplored. Here, we demonstrate a water‐assisted interfacial modulation strategy in a transparent FTO/ZnO/NiO/AgNW/ZnO photodetector, where direct water contact enhances performance. Water introduces two interfacial effects. First, refractive‐index matching at the ZnO/water interface suppresses Fresnel reflection, raising average visible transmittance from 61.0% to 77.02%. Second, an electric double layer (EDL) electrostatically modulates the ZnO surface, promoting charge separation and carrier transport. Under 365 nm illumination, the open‐circuit voltage ( V oc ) increases from 0.223 to 0.265 V, the short‐circuit current density from 0.751 to 0.797 mA cm −2 , and the power conversion efficiency from 1.63% to 2.53%. Impedance and Mott–Schottky analyses confirm reduced series resistance, enhanced interfacial capacitance, and a positive flat‐band shift. The water‐induced interfacial field strengthens transient polarization, yielding a responsivity of 93.1 mA W −1 , a specific detectivity of 1.52 × 10 11 Jones, an effective pyroelectric coefficient rising from 6.8 to 8.5 mC m −2 K −1 , and fast rise/fall times of 0.953/2.82 ms. These findings establish liquid‐interface engineering as an effective and reversible strategy for simultaneously enhancing transparency and photodetection, opening new opportunities for water‐compatible transparent electronics, intelligent glazing, and submerged optical sensing.