Bipolar photovoltaic effect in <scp>InSe</scp> / <scp> MoO ₃ </scp> van der Waals heterostructure for spontaneous light polarization detection

Abstract Polarization is one of the most fundamental properties of light. Traditional polarization‐sensitive photodetectors, however, are limited in their ability to fully extract this information, as they translate the two orthogonal polarization states into currents of the same polarity. In this work, we unveil a new mechanism that could switch the photocurrent direction based on the polarization of the incident light. By leveraging the fact that shift current is not constrained by the built‐in electric field of the heterojunction, we engineer the dynamic cancellation between shift and drift currents under specific photon energy and polarization conditions, leading to a reversible switch in photocurrent polarity. This approach leads to a reversible change in photocurrent polarity, allowing the anisotropic ratio of the detector to exceed the conventional limit. Additionally, the detector can automatically assign opposite currents to orthogonal linear polarization states, effectively mapping polarization into a ternary state. This enhancement significantly increases the information density, making it particularly advantageous for applications such as optical computing and optical communications. image