# Band Structure-Driven Design of a α-CsPbI3 Ammonia Sensor for Industrial Applications

## TL;DR

This paper explores how α-CsPbI3 can be used as a selective ammonia sensor by studying its electronic structure and recombination behavior under different conditions.

## Contribution

The study introduces a novel ammonia sensing mechanism in α-CsPbI3 driven by defect-dependent electronic structures and temperature-modulated recombination pathways.

## Key findings

- NH3 selectively modifies the electronic structure of α-CsPbI3 by coordinating with Pb and Cs sites.
- Trap-assisted recombination dominates at room temperature, while NH3 enhances recombination at higher temperatures.
- Other analytes like CH3NH2 and NO2 have negligible effects on α-CsPbI3's band gap or recombination dynamics.

## Abstract

We investigate the defect-dependent electronic structure and gas-sensing potential of cubic α-CsPbI3 using first-principles density functional theory and nonadiabatic molecular dynamics. Among the intrinsic defects, interstitials, vacancies, antisites, and switches studied, the IPb and PbI antisite defects exhibit transition energy levels near the middle of the band gap, thus functioning as deep traps. Short-term adsorption of ammonia selectively modifies the electronic structure, coordinating with Pb at PbI sites and Cs at IPb sites, significantly altering recombination pathways. Detailed analysis reveals that NH3 reduces anharmonicity at IPb defects, enabling enhanced recombination at elevated temperatures, while trap-assisted recombination dominates at room temperature. Other analytes, including CH3NH2 and NO2, show negligible impact on the band gap or recombination dynamics, highlighting the potential selectivity of NH3 interactions. Ab initio nonadiabatic molecular dynamics simulations at 300 K and 600 K further demonstrate temperature-dependent modulation of carrier lifetimes, with NH3 accelerating recombination at ambient conditions and suppressing certain pathways at higher temperatures. These findings suggest that α-CsPbI3 can serve as a selective and sensitive ammonia sensor over a broad temperature range and offer insights for ammonia detection under industrially relevant conditions.