Abstract
The iodine vacancy () has frequently been discussed as a strong nonradiative recombination center 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. In this work, we perform accurate hybrid-density-functional calculations for in , , and and find that does not have any transition levels in the band gap in , in contrast to the results from calculations based on semilocal functionals. The iodine vacancy does introduce levels in the band gap in and , but our explicitly computed nonradiative capture coefficients demonstrate that has a negligible impact on nonradiative recombination. Our study corrects a misunderstanding of the role of in the iodide-based perovskites, and shifts the focus toward identifying and mitigating actual recombination centers in order to further improve the optoelectronic performance.
- Received 7 December 2022
- Revised 22 February 2023
- Accepted 8 March 2023
DOI:https://doi.org/10.1103/PRXEnergy.2.013008
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Halide perovskites are extremely promising optoelectronic materials, but defects that induce nonradiative recombination act as a key bottleneck for solar conversion efficiencies. To optimize performance, such detrimental defects should be identified and passivated. Thus, understanding the microscopic nature of critical defects is vital for developing experimental strategies to passivate defects that serve as recombination centers. In halide perovskites, passivation of the iodine vacancy is often targeted due to its low formation energy. Previous calculations also suggest that the iodine vacancy is a deep-level defect and strong nonradiative recombination center. Here, the authors use a systematic first-principles study of three iodide perovskites to show that the iodine vacancy is not a defect of key concern for passivation. In some materials, the iodine vacancy does not have charge-state transition levels in the band gap, while in others the explicitly calculated nonradiative recombination rates indicate the vacancy does not cause strong nonradiative recombination. Overall, actual recombination centers should be the focus of performance optimization strategies for halide perovskite solar cells.
