Effects of Surface Defects on Performance and Dynamics of CsPbI2Br Perovskite: First-Principles Nonadiabatic Molecular Dynamics Simulations

Inorganic mixed-halogen perovskites exhibit excellent photovoltaic properties and stability; yet, their photoelectric conversion efficiency is limited by inherent surface defects. In this work, we study the impact of defects on properties of CsPbI₂Br slabs using first-principles calculations, focusing on specific defects such as I vacancy (V_I), I interposition (I_i), and I substitution by Pb (Pb_I). Our findings reveal that these defects affect the geometric and optoelectronic properties as well as dynamics of charge carriers of slabs. We employ two theoretical frameworks (surface hopping and Redfield theory) of nonadiabatic molecular dynamics simulations to comprehensively study relaxation processes and obtain consistent results. The presence of V_I reduces carrier lifetimes, while the influence of Pb_I on carrier lifetimes is negligible. In contrast, I_i defects lead to prolonged carrier lifetimes. These insights provide valuable guidance for the rational design of perovskite photovoltaic devices, aiming to enhance their efficiency and stability.