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Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells

Abstract

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)yCs1–yPb(IxBr1–x)3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 °C in air, under open-circuit conditions. This work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.

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Fig. 1: Impact of hydrohalic acids on the morphology, crystal quality and electronic disorder of the FA0.83Cs0.17Pb(I0.6Br0.4)3 perovskite film.
Fig. 2: Impact of DMACl on the intermediate phases of FA0.83Cs0.17Pb(Br0.2I0.8)3.
Fig. 3: The impact of excess amounts of DMACl on the crystal quality, orientation and electronic disorder of the FAyCs1–yPb(IxBr1–x)3 perovskite.
Fig. 4: Impact of solvent and fabrication method on thin-film humidity stability.
Fig. 5: Thin-film thermal stability.
Fig. 6: Stability comparison, aged in air under heat and light, of encapsulated perovskite solar cell devices prepared with DMF/DMSO or DMF/DMACl fabrication method.

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Data availability

The datasets used in this work are available in the Oxford University Research Archive repository.

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Acknowledgements

The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 763977 of the PerTPV project and the innovation programme under Marie Skłodowska-Curie grant agreement no. 764787. We acknowledge financial support from the Engineering and Physical Sciences Research Council (UK), grant EP/S004947/1. We also acknowledge the financial support from the Australian Research Council Centre of Excellence in Exciton Science (ACEx:CE170100026). D.P.M. acknowledges financial support from the Australian Centre for Advanced Photovoltaics, the Australian Renewable Energy Agency and the Marie Skłodowska-Curie grant agreement SAMA no. 101029896. The work by S.P.H. and L.T.S was supported by the De-Risking Halide Perovskite Solar Cells programme of the National Center for Photovoltaics, funded by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office under US Department of Energy contract no. DE-AC36-08GO28308 with Alliance for Sustainable Energy, LLC, the Manager and Operator of the National Renewable Energy Laboratory. Work by J.J.B. was supported by the Office of Naval Research. The views expressed in the article do not necessarily represent the views of the US Department of Energy or the US Government. We acknowledge F. Vollrath and the Oxford Silk Group for their help and equipment. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, was supported by the US Department of Energy, Office of Basic Energy Sciences under contract no. DE-AC02-76SF00515. We also acknowledge the Monash X-ray Platform.

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D.P.M. contributed to the conceptualization, investigation, methodology, analysis and original draft. P.H., S.O.F., S.P.H. and L.T.S. contributed to the investigation, methodology and analysis. J.M.B. contributed to the investigation. S.M. contributed to the analysis. S.S. contributed to the investigation and methodology. N.H. and J.L. contributed to the investigation. M.B.J. and J.J.B. supervised the research. U.B. contributed to funding acquisition, resources and supervision. H.J.S. contributed to the conceptualization, funding acquisition, resources, supervision and the original draft. All authors contributed to the writing of the paper.

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Correspondence to David P. McMeekin, Udo Bach or Henry J. Snaith.

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H.J.S. is founder and CSO of Oxford Photovoltaics Ltd. All other authors declare no competing interests.

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Supplementary Figs. 1–35, Discussion of halide segregation and characterization.

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McMeekin, D.P., Holzhey, P., Fürer, S.O. et al. Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells. Nat. Mater. 22, 73–83 (2023). https://doi.org/10.1038/s41563-022-01399-8

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