Dynamic Control of Band Alignment and Built‐In Potential in High Performance Self‐Powered InSe/SnS 2 Van der Waals Photodetectors via Gas Molecular Physisorption

Molecular physisorption provides a versatile strategy to dynamically tailor the optoelectronic properties of van der Waals (vdW) heterostructures, enabling extended carrier lifetimes, broadened spectral response, and erasable memory effects in self‐powered photodetectors. Here, we report how NO 2 physisorption precisely modulates band alignment and built‐in potentials in self‐powered InSe/SnS 2 heterojunction photodetectors. Using electrostatic gating, we identify three distinct regimes: (I) a robust p–n configuration ( V g ≤ –50 V), where adsorption induces a collective electron‐withdrawing effect, enabling efficient p‐i‐n‐like behavior with near‐ideal charge separation; (II) an intermediate p–n regime (–50 V < V g < –30 V), where competing electron withdrawal and recombination effects allow dynamic tuning the electronic structure and optoelectronic properties, and (III) an illumination‐sensitive n–n + mode ( V g ≥ –30 V), where NO 2 molecules act as recombination centers, suppressing the built‐in potential. This dual control via gating and molecular adsorption provides unprecedented manipulation of charge separation and transport, opening avenues for next‐generation multifunctional optoelectronic devices.