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 CsGeBr3 and their impact on nonradiative carrier recombination. VCs and VGe are shallow defects with negligible recombination activity, whereas VBr and CsBr antisite defects introduce deep-level states and are favored under Br-poor or Cs-rich conditions. Despite both being deep-level defects, VBr and CsBr exhibit different recombination behaviors. Under room-temperature conditions, VBr 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, CsBr maintains strong coupling with band-edge states and acts as an efficient recombination center. Furthermore, uniaxial compressive strain passivates CsBr by shifting its defect level toward the conduction band edge. These results provide insights into defect tolerance and strain-mediated defect passivation in CsGeBr3 and related perovskites.
Kang et al. (Tue,) studied this question.