Role of iodine vacancies in nonradiative recombination in halide perovskites

Iodine vacancies have frequently been discussed as strong nonradiative recombination centers in halide perovskites. This proposition was mainly based on the presence of charge-state transition levels in the band gap, as found in early first-principles calculations. We have performed accurate hybrid density-functional calculations for vacancies in CsPbI3, CsSnI3, and CsGeI3 and find that the iodine vacancy does not have any transition levels in the band gap in CsPbI3, in contrast to the results from calculations based on semilocal functionals. The iodine vacancy does introduce levels in the band gap in CsSnI3 and CsGeI3, but our explicitly computed nonradiative capture coefficients [1] demonstrate that the defect has a negligible impact on nonradiative recombination. Our study corrects a widespread misunderstanding of the role of the iodine vacancy in iodide-based perovskites, and shifts the focus toward identifying and mitigating actual recombination centers in order to further improve the optoelectronic performance.



[1] J. Zhang, X. Zhang, M. E. Turiansky, and C. G. Van de Walle, PRX Energy 2, 013008 (2023).