Substitution of lead with tin suppresses ionic transport in halide perovskite optoelectronics.
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Despite the rapid rise in the performance of a variety of perovskite optoelectronic devices with vertical charge transport, the effects of ion migration remain a common and longstanding Achilles' heel limiting the long-term operational stability of lead halide perovskite devices. However, there is still limited understanding of the impact of tin (Sn) substitution on the ion dynamics of lead (Pb) halide perovskites. Here, we employ scan-rate-dependent current-voltage measurements on Pb and mixed Pb-Sn perovskite solar cells to show that short circuit current losses at lower scan rates, which can be traced to the presence of mobile ions, are present in both kinds of perovskites. To understand the kinetics of ion migration, we carry out scan-rate-dependent hysteresis analyses and temperature-dependent impedance spectroscopy measurements, which demonstrate suppressed ion migration in Pb-Sn devices compared to their Pb-only analogues. By linking these experimental observations to first-principles calculations on mixed Pb-Sn perovskites, we reveal the key role played by Sn vacancies in increasing the iodide ion migration barrier due to local structural distortions. These results highlight the beneficial effect of Sn substitution in mitigating undesirable ion migration in halide perovskites, with potential implications for future device development.
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Acknowledgements: K. D. acknowledges the support of the Cambridge Trust for the Cambridge India Ramanujan Scholarship and Cambridge Philosophical Society for the research studentship. This work received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (HYPERION, grant agreement no. 756962). M. S. I. and D. G acknowledge ARCHER2 supercomputer resources via membership of the HEC Materials Chemistry Consortium funded by the EPSRC (EP/R029431). D. G. acknowledges the IIT Delhi SEED Grant (PLN12/04MS), the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), India for Start-up Research Grant SRG/2022/00l234 and the IIT Delhi HPC facility for computational resources. P. J. C. and M. P. thank the EPSRC Centre for Doctoral Training in New and Sustainable Photovoltaics (EP/L01551X/2) for funding. S. P. S. acknowledges funding support from SERB (SRG/2020/001641 and IPA/2021/000096). S. D. S. acknowledges support from the Royal Society and Tata Group (UF150033). The authors acknowledge the Engineering and Physical Sciences Research Council (EPSRC) for funding (EP/R023980/1, EP/T02030X/1, EP/V012932/1). For the purpose of open access, the authors have applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.
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1754-5706
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Royal Society (UF150033)
Engineering and Physical Sciences Research Council (EP/R023980/1)
EPSRC (EP/T02030X/1)
EPSRC (EP/V012932/1)
Engineering and Physical Sciences Research Council (EP/X035859/1)