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Defect calculations with quasiparticle correction: A revisited study of iodine defects in CH3NH3PbI3

Defect levels in semiconductor band gaps play a crucial role in functionalized semiconductors for practical applications in optoelectronics; however, first-principle defect calculations based on exchange–correlation functionals, such as local density approximation, grand gradient approximation (GGA), and hybrid functionals, either underestimate band gaps or misplace defect levels. In this study, we revisited iodine defects in CH3NH3PbI3 by combining the accuracy of total energy calculations of GGA and single-electron level calculation of the GW method. The combined approach predicted neutral Ii to be unstable and the transition level of Ii(+1/–1) to be close to the valence band maximum. Therefore, Ii may not be as detrimental as previously reported. Moreover, VI may be unstable in the –1 charged state but could still be detrimental owing to the deep transition level of VI(+1/0). These results could facilitate the further understanding of the intrinsic point defect and defect passivation observed in CH3NH3PbI3.