Local nanoscale phase impurities are degradation sites in halide perovskites.

Authors
Macpherson, Stuart 
Doherty, Tiarnan AS  ORCID logo  https://orcid.org/0000-0003-1150-4012
Winchester, Andrew J 
Kosar, Sofiia 
Johnstone, Duncan N 

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Article
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Abstract

Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7 per cent in single-junction and 29.8 per cent in tandem perovskite/silicon cells1,2, yet retaining such performance under continuous operation has remained elusive3. Here we develop a multimodal microscopy toolkit to reveal that in leading formamidinium-rich perovskite absorbers, nanoscale phase impurities, including hexagonal polytype and lead iodide inclusions, are not only traps for photoexcited carriers, which themselves reduce performance4,5, but also, through the same trapping process, are sites at which photochemical degradation of the absorber layer is seeded. We visualize illumination-induced structural changes at phase impurities associated with trap clusters, revealing that even trace amounts of these phases, otherwise undetected with bulk measurements, compromise device longevity. The type and distribution of these unwanted phase inclusions depends on the film composition and processing, with the presence of polytypes being most detrimental for film photo-stability. Importantly, we reveal that both performance losses and intrinsic degradation processes can be mitigated by modulating these defective phase impurities, and demonstrate that this requires careful tuning of local structural and chemical properties. This multimodal workflow to correlate the nanoscopic landscape of beam-sensitive energy materials will be applicable to a wide range of semiconductors for which a local picture of performance and operational stability has yet to be established.

Publication Date
2022-07
Online Publication Date
2022-05-24
Acceptance Date
2022-05-13
Keywords
3403 Macromolecular and Materials Chemistry, 40 Engineering, 34 Chemical Sciences, 3406 Physical Chemistry, 7 Affordable and Clean Energy
Journal Title
Nature
Journal ISSN
0028-0836
1476-4687
Volume Title
Publisher
Springer Science and Business Media LLC
Sponsorship
Royal Society (UF150033)
European Research Council (756962)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (841136)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (841386)
Engineering and Physical Sciences Research Council (EP/S030638/1)
EPSRC (EP/T02030X/1)
EPSRC (2127077)
EPSRC (EP/V012932/1)
Engineering and Physical Sciences Research Council (EP/R023980/1)
Engineering and Physical Sciences Research Council (EP/R008779/1)
European Commission Horizon 2020 (H2020) Research Infrastructures (RI) (823717)
EPSRC (EP/V007750/1)
Engineering and Physical Sciences Research Council (EP/P007767/1)
Engineering and Physical Sciences Research Council (EP/P024947/1)
Engineering and Physical Sciences Research Council (EP/R00661X/1)
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