Revealing the Divergence in Nonradiative Recombination Dynamics of Deep-Level Defects in CsGeBr 3 : Intrinsic Tolerance of Br Vacancies versus Strain-Induced Passivation of Cs Br Antisites

This study employs first-principles calculations combined with nonadiabatic molecular dynamics simulations to investigate the electronic structure and thermodynamic stability of intrinsic point defects in the lead-free perovskite CsGeBr 3 and their impact on nonradiative carrier recombination. V Cs and V Ge are shallow defects with negligible recombination activity, whereas V Br and Cs Br antisite defects introduce deep-level states and are favored under Br-poor or Cs-rich conditions. Despite both being deep-level defects, V Br and Cs Br exhibit different recombination behaviors. Under room-temperature conditions, V Br undergoes local structural reconstruction, forming stable Ge–Ge dimers that suppress nonadiabatic coupling with band-edge states, rendering it ineffective as a recombination center. In contrast, Cs Br maintains strong coupling with band-edge states and acts as an efficient recombination center. Furthermore, uniaxial compressive strain passivates Cs Br by shifting its defect level toward the conduction band edge. These results provide insights into defect tolerance and strain-mediated defect passivation in CsGeBr 3 and related perovskites.