# Dynamic Control of Band Alignment and Built‐In Potential in High Performance Self‐Powered InSe/SnS2 Van der Waals Photodetectors via Gas Molecular Physisorption

## TL;DR

This paper shows how gas molecules can dynamically control the performance of self-powered photodetectors made from layered materials.

## Contribution

The study introduces precise modulation of band alignment and built-in potential using NO2 physisorption in InSe/SnS2 heterojunctions.

## Key findings

- NO2 physisorption enables three distinct operational regimes in photodetectors based on gate voltage.
- Adsorption induces an electron-withdrawing effect, enhancing charge separation in p–n configurations.
- NO2 molecules act as recombination centers at higher gate voltages, suppressing built-in potential.

## Abstract

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 NO2 physisorption precisely modulates band alignment and built‐in potentials in self‐powered InSe/SnS2 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 NO2 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.

Built‐in potential, originating from band alignment, is the heart of the van der Waals (vdW) self‐powered heterojunction photodetectors. By leveraging NO2 physisorption, we dynamically tune the band alignment and built‐in potential in self‐powered InSe/SnS2 heterojunction photodetectors. This approach enables unprecedented control over charge separation and transport, paving the way for next‐generation multifunctional optoelectronic devices based on vdW heterostructures.© 2026 WILEY‐VCH GmbH