The degradation of perovskite solar cells in the presence of trace water and oxygen poses a challenge for their commercial impact given the appreciable permeability of cost-effective encapsulants. Point defects were recently shown to be a major source of decomposition due to their high affinity for water and oxygen molecules. Here, we report that, in single-cation/halide perovskites, local lattice strain facilitates the formation of vacancies and that cation/halide mixing suppresses their formation via strain relaxation. We then show that judiciously selected dopants can maximize the formation energy of defects responsible for degradation. Cd-containing cells show an order of magnitude enhanced unencapsulated stability compared to state-of-art mixed perovskite solar cells, for both shelf storage and maximum power point operation in ambient air at a relative humidity of 50%. We conclude by testing the generalizability of the defect engineering concept, demonstrating both vacancy-formation suppressors (such as Zn) and promoters (such as Hg).
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This publication is partly based on work supported by an award (KUS-11-009-21) from the King Abdullah University of Science and Technology, by the Ontario Research Fund and by the Natural Sciences and Engineering Research Council of Canada. M.I.S. acknowledges the support of the Banting Postdoctoral Fellowship Program, administered by the Government of Canada. The work of A. Jain is supported by the IBM Canada Research and Development Center through the Southern Ontario Smart Computing Innovation Platform (SOSCIP) postdoctoral fellowship. DFT calculations were performed on the IBM BlueGene Q supercomputer with support from the SOSCIP. H.T. acknowledges the Netherlands Organization for Scientific Research (NWO) for a Rubicon grant (680-50-1511) in support of his postdoctoral research at the University of Toronto. We thank R. Wolowiec, D. Kopilovic, L. Levina and E. Palmiano for their help during the course of the study.
The authors declare no competing interests.
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Saidaminov, M.I., Kim, J., Jain, A. et al. Suppression of atomic vacancies via incorporation of isovalent small ions to increase the stability of halide perovskite solar cells in ambient air. Nat Energy 3, 648–654 (2018). https://doi.org/10.1038/s41560-018-0192-2
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