Bias tunable transport modulation and gas selectivity in layered BiOI: A DFT NEGF study

Understanding the interplay between adsorption energetics and charge transport modulation is essential for the rational design of low-power and bias-tunable gas sensors. Here, we present a comprehensive first principles study of gas selectivity in layered bismuth oxyiodide (BiOI) by integrating density functional theory with non-equilibrium Green's function transport calculations. The adsorption and bias dependent transport responses toward NO 2 , NH 3 , CO 2 , and representative volatile organic compounds are systematically examined. While NH 3 and NO 2 exhibit strong chemisorption and localized electronic perturbation, CO 2 interacts via weak physisorption, demonstrating that adsorption strength alone does not determine sensing performance. Instead, transmission channel evolution near the Fermi level governs the sensing response. Bias dependent calculations reveal an electrically tunable sensitivity hierarchy, where weakly adsorbed CO 2 preserves conductive pathways and exhibits pronounced low bias sensitivity despite minimal charge transfer. Recovery time analysis further highlights the trade-off between transport modulation and reversibility for strongly adsorbed species. These results establish a transport centered selectivity framework for layered BiOI and provide mechanistic insight into electric field-controlled gas sensing under ambient conditions.