# Visible Light‐Driven Heterojunction Array Based on Type‐I In2S3/In2O3 for Selective Multi‐Gas Discrimination

## TL;DR

A visible light-driven gas sensor array using a type-I In2S3/In2O3 heterostructure improves NO2 detection and enables selective sensing of multiple gases.

## Contribution

A new type-I In2S3/In2O3 heterostructure enables selective multi-gas detection under visible light, previously unreported for light-activated sensors.

## Key findings

- The In2S3/In2O3 heterostructure shows 56 times higher NO2 response than pristine In2O3 under blue light.
- Noble metal decoration allows selective detection of NO2, NH3, C2H5OH, and H2.
- The sensor exhibits excellent selectivity, reliability, and humidity stability.

## Abstract

Visible light‐activated chemoresistive gas sensors offer a promising solution for minimizing power consumption, preventing material degradation, and enabling room temperature operation. However, their lower photon energy compared to UV light results in slower recovery and reduced sensitivity to NO2, while detecting gases like volatile organic compounds and amines remains challenging. This work presents a visible light‐driven gas sensor array based on type‐I In2S3/In2O3 heterostructure. The In2S3 layer is uniformly deposited on In2O3 nanorods, forming type‐I band alignment. Under blue light illumination, photoexcited electron‐hole pairs migrate to the In2S3 surface, enhancing surface reactivity and enabling 56 times higher NO2 response than pristine In2O3, with excellent selectivity, reliability, and humidity stability. Noble metal (Pd, Pt, and Au) decoration on the In2S3‐In2O3 array also allows truly selective detection of NO2, NH3, C2H5OH, and H2, which has not been reported previously for light‐activated gas sensors. This work introduces a new strategy to optimize visible light‐driven gas detection, advancing electronic nose technologies.

Visible light activation has been explored for low‐temperature operation, prevention of material degradation, and safe gas sensing. A finely tuned type‐I band junction within the In2S3‐In2O3 heterostructure promotes efficient transfer of photogenerated excitons to the In2S3 surface, thereby maximizing surface reactivity under blue light illumination. Noble metal‐decorated In2S3‐In2O3 heterostructure demonstrated selective detection of NO2, NH3, H2, and C2H5OH.