Transient Charging Dynamics in Stacked <scp> Ga ₂ O ₃ </scp> / <scp>ZnO</scp> Photovoltaic Units Governing Wavelength‐Selective Polarity Switching

Developing self‐powered photodetectors capable of processing multidimensional optical signals is pivotal for next‐generation photonic computing and secure communications. However, conventional device architectures are typically limited to single‐mode intensity detection, and the complex photophysics within coupled photovoltaic units remain poorly understood. Here, we reveal a unified “Photovoltaic‐Capacitance” coupling mechanism within a vertically stacked, self‐powered Ga 2 O 3 /PEDOT:PSS and ZnO/Graphene architecture. We demonstrate that the system's wavelength‐selective, transient bipolar response is governed by the multifaceted charging and discharging dynamics between the two coupled units. The key to this mechanism is the ZnO/Graphene (3D/2D) interface, which we define as a novel “Photovoltaic Dynamic‐Capacitor” (PDC) component, exhibiting a defined four‐stage transient (instantaneous polarization, steady‐state saturation, reverse discharge, and relaxation). This architecture enables the Ga 2 O 3 unit (photovoltaic source) to dynamically charge the PDC under 270 nm illumination (+0.27 A/W), while 380 nm illumination directly activates the PDC itself, generating a reverse current (−0.009 A W −1 ). This universal (proven with MgZnO) and dynamically coupled architecture establishes a viable approach for self‐powered, multidimensional optical processing. We leverage this unique behavior to implement a physical layer secure communication protocol based on an innovative ternary optical logic (“1”, “0”, “−1”), offering enhanced anti‐jamming capabilities rooted in a new photonic degree of freedom.