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Ion Migration and Redox Reactions in Axial Heterojunction Perovskite CsPb(Br1-xClx)3 Nanowire Devices Revealed by Operando Nanofocused X-ray Photoelectron Spectroscopy

Liu, Yen Po LU ; Lamers, Nils LU ; Zhang, Zhaojun LU ; Zaiats, Nelia LU orcid ; Mikkelsen, Anders LU ; Wallentin, Jesper LU ; Dittmann, Regina LU and Timm, Rainer LU orcid (2024) In ACS Nano 18(51). p.34763-34775
Abstract

Metal-halide perovskites (MHPs) have gained substantial interest in the energy and optoelectronics field. MHPs in nanostructure forms, such as nanocrystals and nanowires (NWs), have further expanded the horizons for perovskite nanodevices in geometry and properties. A partial anion exchange within the nanostructure, creating axial heterojunctions, has significantly augmented the potential applications. However, surface degradation and halide ion migration are deteriorating device performance. Quantitative analysis of halide metal concentration and mapping of the electrical surface potential along the operating NW device are needed to better understand ion transportation, band structure, and chemical states, which have not been... (More)

Metal-halide perovskites (MHPs) have gained substantial interest in the energy and optoelectronics field. MHPs in nanostructure forms, such as nanocrystals and nanowires (NWs), have further expanded the horizons for perovskite nanodevices in geometry and properties. A partial anion exchange within the nanostructure, creating axial heterojunctions, has significantly augmented the potential applications. However, surface degradation and halide ion migration are deteriorating device performance. Quantitative analysis of halide metal concentration and mapping of the electrical surface potential along the operating NW device are needed to better understand ion transportation, band structure, and chemical states, which have not been experimentally reported yet. This requires a characterization approach that is capable to provide surface-sensitive chemical and electrical information at the subμm scale. Here, we used operando nanofocused X-ray photoelectron spectroscopy (nano-XPS) to study CsPbBr3/CsPb(Br1-xClx)3 heterojunction NW devices with a spatial resolution of 120 nm. We monitored Br- and Cl- ion migration and comprehended the potential drop along the device during operation. Ion migration and healing of defects and vacancies are found for applied voltages of as low as 1 V. We present a model delineating band bending along the device based on precise XPS peak positions. Notably, a reversible redox reaction of Pb was observed, that reveals the interaction of migrating halide ions, vacancies, and biased metal electrodes under electrical operation. We further demonstrate how X-ray-induced surface modification can be avoided, by limiting exposure times to less than 100 ms. The results facilitate the understanding of halide ion migration in MHP nanodevices under operation.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ion migration, metal halide perovskite, nanowire, operando device, redox reaction, SPEM, XPS
in
ACS Nano
volume
18
issue
51
pages
13 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:39659190
  • scopus:85213003628
ISSN
1936-0851
DOI
10.1021/acsnano.4c11458
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.
id
ba1412e1-d5c5-40cc-8a0e-3491272c6516
date added to LUP
2025-01-07 09:45:35
date last changed
2025-07-09 01:12:06
@article{ba1412e1-d5c5-40cc-8a0e-3491272c6516,
  abstract     = {{<p>Metal-halide perovskites (MHPs) have gained substantial interest in the energy and optoelectronics field. MHPs in nanostructure forms, such as nanocrystals and nanowires (NWs), have further expanded the horizons for perovskite nanodevices in geometry and properties. A partial anion exchange within the nanostructure, creating axial heterojunctions, has significantly augmented the potential applications. However, surface degradation and halide ion migration are deteriorating device performance. Quantitative analysis of halide metal concentration and mapping of the electrical surface potential along the operating NW device are needed to better understand ion transportation, band structure, and chemical states, which have not been experimentally reported yet. This requires a characterization approach that is capable to provide surface-sensitive chemical and electrical information at the subμm scale. Here, we used operando nanofocused X-ray photoelectron spectroscopy (nano-XPS) to study CsPbBr<sub>3</sub>/CsPb(Br<sub>1-x</sub>Cl<sub>x</sub>)<sub>3</sub> heterojunction NW devices with a spatial resolution of 120 nm. We monitored Br<sup>-</sup> and Cl<sup>-</sup> ion migration and comprehended the potential drop along the device during operation. Ion migration and healing of defects and vacancies are found for applied voltages of as low as 1 V. We present a model delineating band bending along the device based on precise XPS peak positions. Notably, a reversible redox reaction of Pb was observed, that reveals the interaction of migrating halide ions, vacancies, and biased metal electrodes under electrical operation. We further demonstrate how X-ray-induced surface modification can be avoided, by limiting exposure times to less than 100 ms. The results facilitate the understanding of halide ion migration in MHP nanodevices under operation.</p>}},
  author       = {{Liu, Yen Po and Lamers, Nils and Zhang, Zhaojun and Zaiats, Nelia and Mikkelsen, Anders and Wallentin, Jesper and Dittmann, Regina and Timm, Rainer}},
  issn         = {{1936-0851}},
  keywords     = {{ion migration; metal halide perovskite; nanowire; operando device; redox reaction; SPEM; XPS}},
  language     = {{eng}},
  month        = {{12}},
  number       = {{51}},
  pages        = {{34763--34775}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{ACS Nano}},
  title        = {{Ion Migration and Redox Reactions in Axial Heterojunction Perovskite CsPb(Br<sub>1-x</sub>Clx)<sub>3</sub> Nanowire Devices Revealed by Operando Nanofocused X-ray Photoelectron Spectroscopy}},
  url          = {{http://dx.doi.org/10.1021/acsnano.4c11458}},
  doi          = {{10.1021/acsnano.4c11458}},
  volume       = {{18}},
  year         = {{2024}},
}