Substitution of lead with tin suppresses ionic transport in halide perovskite optoelectronics
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, although there is still limited understanding of the impact of tin (Sn) substitution on the ion dynamics of lead (pb) halide perovskites.
Professor Saiful Islam and collaborators from the Universities of Cambridge, Bath, Loughborough and the Indian Institute of Technology Delhi and HBNI in Jatni, employed 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.
In their paper 'Substitution of lead with tin suppresses ionic transport in halide perovskite optoelectronics' published in Energy & Environment Science, the team carried out scan-rate dependent hystersis analyses and temperature-dependent impedence spectroscopy measures to understand the kinetics of ion migration, which demonstrated suppressed ion migration in Pb-Sn devices compared to their Pb-only analogues. By linking those experimental observations to first-principles calculations on mixed Pb-Sn perovskites, the authors reveal the role played by Sn vacancies in increasing the iodide ion migration barrier due to local structural distortions. The results highlight the beneficial effect of Sn substitution in mitigating undesirable ion migration in halide perovskites, with potential implications for future device development.
