High-performance perovskite/perovskite tandem solar cells require high-efficiency and stable low-bandgap perovskite subcells. State-of-the-art low-bandgap mixed tin–lead iodide perovskite solar cells exhibit either a high power-conversion efficiency or improved stability, but not both. Here we report a two-step bilayer interdiffusion growth process to simultaneously meet both requirements for formamidinium-based low-bandgap mixed tin–lead iodide perovskite solar cells. The bilayer interdiffusion growth process allows for the formation of high-quality and large-grained perovskite films with only 10 mol% volatile methylammonium. Additionally, one-dimensional pyrrolidinium perovskite was applied to passivate the perovskite film and improve the junction quality, which resulted in a carrier lifetime of 1.1 μs and an open circuit voltage of 0.865 V for our perovskite film and device with a bandgap of 1.28 eV. Our strategies enabled a power-conversion efficiency of 20.4% for low-bandgap perovskite solar cells under AM 1.5G illumination. More importantly, an encapsulated device can retain 92% of its initial efficiency after 450 h of continuous 1 sun illumination.
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All data generated or analysed during this study are included in the published article and its Supplementary Information.
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This material is based on work supported by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Solar Energy Technologies Office Award no. DE-EE0008753. The TPD-MS study was supported by the National Science Foundation under contract no. DMR-1807818. K.K.S. and R.J.E. were supported by the US Air Force Research Laboratory under agreement no. FA9453-18-2-0037, and N.S., B.S., N.J.P. and R.J.E. were supported by the US Air Force Research Laboratory under agreement no. FA9453-19-C-1002. The US Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.
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Li, C., Song, Z., Chen, C. et al. Low-bandgap mixed tin–lead iodide perovskites with reduced methylammonium for simultaneous enhancement of solar cell efficiency and stability. Nat Energy 5, 768–776 (2020). https://doi.org/10.1038/s41560-020-00692-7