Sensing Mechanism of H₂O, NH₃, and O₂ on the Stability-Improved Cs₂Pb(SCN)₂Br₂ Surface: A Quantum Dynamics...

Although the perovskite sensing materials have shown high sensitivity and ideal selectivity toward neutral, oxidative, or reductive gases, their structural instability hampers the practical application. To exploit perovskite-based gas-sensing materials with improved stability and decent sensitivity, three adsorption complexes of H₂O, NH₃, and O₂ on the Cs₂Pb(SCN)₂Br₂ surface are built by doping Br^- and Cs⁺ in the parent (CH₃NH₃)₂Pb(SCN)₂I₂ structure and submitted to quantum dynamics simulations. Changes in the semiconductor material geometric structures during these dynamic processes are analyzed and adsorption ability and charge transfer between Cs₂Pb(SCN)₂Br₂ and the gas molecules are explored so as to further establish a correlation between the geometrical structure variations and the charge transfer. By comparing with the previous CH₃NH₃PbI₃ and (CH₃NH₃)₂Pb(SCN)₂I₂ adsorption systems, we propose the key factors that enhance the stability of perovskite structures in different atmospheres. The current work is expected to provide clues for developing innovative perovskite sensing materials or for constructing reasonable sensing mechanisms.