How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery

Nikhil Kalasariya; Paria Forozi Sowmeeh; Francisco Pena-camargo; Francesco Vanin; Tino Lukas; Yuxin Dong; Qifan Feng; Ziwei Liu; Waqar Ali Memon; Danpeng Gao; Jianqiu Gong; Xin Wu; Andres Felipe Castro Mendez; Jan Hagenberg; Zahra Abadi; Thomas Hultzsch; Xinyi Zhao; Sahil Shah; Hui Yu; Varun Srivastava; Jianbin Xu; Ni Zhao; Felix Lang; Zonglong Zhu; Martin Stolterfoht

doi:10.1002/aenm.202503866

How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery

Nikhil Kalasariya
, Paria Forozi Sowmeeh
, Francisco Pena-camargo
, Francesco Vanin
, Tino Lukas
, Yuxin Dong
, Qifan Feng
, Ziwei Liu
, Waqar Ali Memon
, Danpeng Gao
, Jianqiu Gong
, Xin Wu
, Andres Felipe Castro Mendez
, Jan Hagenberg
, Zahra Abadi
, Thomas Hultzsch
, Xinyi Zhao
, Sahil Shah
, Hui Yu
, Varun Srivastava

Jianbin Xu, Ni Zhao, Felix Lang, Zonglong Zhu, Martin Stolterfoht^*

^*Corresponding author for this work

Department of Chemistry

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

Abstract

Halide segregation (HS) is considered to be one of the most significant hurdles for the commercialization of tandem solar cells. However, despite significant research on this matter, the exact impact of HS on the performance degradation and the ion density evolution is yet to be established. In this work, we investigate the intriguing correlation between HS, ion-induced efficiency losses, and ion density evolution in wide-bandgap (WBG) triple cation perovskite cells. Our results highlight that all three phenomena evolve on similar timescales and follow the same trend across all studied bandgaps. This implies that the poor energy-lifetime product observed for devices prone to halide segregation is a result of enhanced ionic losses rather than, for instance, charge carrier funneling. Furthermore, reminiscent of the recovery of HS observed previously, we demonstrate that ionic losses also recover after light exposure and dark storage, which occurs along with a receding ion density. However, we also observe irreversible ionic losses, especially after prolonged illumination, which are critical for device operation. These findings present an important new understanding of the interplay between halide segregation and ionic processes and provide a rational explanation for the performance and stability of mixed halide WBG perovskites.
© 2026 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH

Original language	English
Article number	e03866
Number of pages	9
Journal	Advanced Energy Materials
Volume	16
Issue number	15
Online published	4 Feb 2026
DOIs	https://doi.org/10.1002/aenm.202503866
Publication status	Published - 15 Apr 2026

Funding

M.S. acknowledges funding support from The Chinese University of Hong Kong (CUHK) through the Vice-Chancellor Early Career Professorship Scheme, the Research Grants Council (RGC) under the NSCF/RGC Joint Research Scheme (N_CUHK414/24), and the Innovation and Technology Commission (ITC) via the ITF Seed Fund (ITS/239/23). This research is further supported in part by project RNE-p4-25 of the Shun Hing Institute of Advanced Engineering, The Chinese University of Hong Kong.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 7 Affordable and Clean Energy

Research Keywords

halide segregation timescale
ionic loss timescale
mobile ions and ionic losses
wide-bandgap (WBG) perovskites

Publisher's Copyright Statement

This full text is made available under CC-BY 4.0. https://creativecommons.org/licenses/by/4.0/

RGC Funding Information

RGC-funded

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Kalasariya, N., Sowmeeh, P. F., Pena-camargo, F., Vanin, F., Lukas, T., Dong, Y., Feng, Q., Liu, Z., Memon, W. A., Gao, D., Gong, J., Wu, X., Mendez, A. F. C., Hagenberg, J., Abadi, Z., Hultzsch, T., Zhao, X., Shah, S., Yu, H., ... Stolterfoht, M. (2026). How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery. Advanced Energy Materials, 16(15), Article e03866. https://doi.org/10.1002/aenm.202503866

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title = "How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery",

abstract = "Halide segregation (HS) is considered to be one of the most significant hurdles for the commercialization of tandem solar cells. However, despite significant research on this matter, the exact impact of HS on the performance degradation and the ion density evolution is yet to be established. In this work, we investigate the intriguing correlation between HS, ion-induced efficiency losses, and ion density evolution in wide-bandgap (WBG) triple cation perovskite cells. Our results highlight that all three phenomena evolve on similar timescales and follow the same trend across all studied bandgaps. This implies that the poor energy-lifetime product observed for devices prone to halide segregation is a result of enhanced ionic losses rather than, for instance, charge carrier funneling. Furthermore, reminiscent of the recovery of HS observed previously, we demonstrate that ionic losses also recover after light exposure and dark storage, which occurs along with a receding ion density. However, we also observe irreversible ionic losses, especially after prolonged illumination, which are critical for device operation. These findings present an important new understanding of the interplay between halide segregation and ionic processes and provide a rational explanation for the performance and stability of mixed halide WBG perovskites. {\textcopyright} 2026 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH",

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author = "Nikhil Kalasariya and Sowmeeh, \{Paria Forozi\} and Francisco Pena-camargo and Francesco Vanin and Tino Lukas and Yuxin Dong and Qifan Feng and Ziwei Liu and Memon, \{Waqar Ali\} and Danpeng Gao and Jianqiu Gong and Xin Wu and Mendez, \{Andres Felipe Castro\} and Jan Hagenberg and Zahra Abadi and Thomas Hultzsch and Xinyi Zhao and Sahil Shah and Hui Yu and Varun Srivastava and Jianbin Xu and Ni Zhao and Felix Lang and Zonglong Zhu and Martin Stolterfoht",

year = "2026",

month = apr,

day = "15",

doi = "10.1002/aenm.202503866",

language = "English",

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Kalasariya, N, Sowmeeh, PF, Pena-camargo, F, Vanin, F, Lukas, T, Dong, Y, Feng, Q, Liu, Z, Memon, WA, Gao, D , Gong, J , Wu, X, Mendez, AFC, Hagenberg, J, Abadi, Z, Hultzsch, T, Zhao, X, Shah, S, Yu, H, Srivastava, V, Xu, J, Zhao, N, Lang, F, Zhu, Z & Stolterfoht, M 2026, 'How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery', Advanced Energy Materials, vol. 16, no. 15, e03866. https://doi.org/10.1002/aenm.202503866

How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery. / Kalasariya, Nikhil; Sowmeeh, Paria Forozi; Pena-camargo, Francisco et al.
In: Advanced Energy Materials, Vol. 16, No. 15, e03866, 15.04.2026.

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

TY - JOUR

T1 - How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses

T2 - From Degradation to Recovery

AU - Kalasariya, Nikhil

AU - Sowmeeh, Paria Forozi

AU - Pena-camargo, Francisco

AU - Vanin, Francesco

AU - Lukas, Tino

AU - Dong, Yuxin

AU - Feng, Qifan

AU - Liu, Ziwei

AU - Memon, Waqar Ali

AU - Gao, Danpeng

AU - Gong, Jianqiu

AU - Wu, Xin

AU - Mendez, Andres Felipe Castro

AU - Hagenberg, Jan

AU - Abadi, Zahra

AU - Hultzsch, Thomas

AU - Zhao, Xinyi

AU - Shah, Sahil

AU - Yu, Hui

AU - Srivastava, Varun

AU - Xu, Jianbin

AU - Zhao, Ni

AU - Lang, Felix

AU - Zhu, Zonglong

AU - Stolterfoht, Martin

PY - 2026/4/15

Y1 - 2026/4/15

N2 - Halide segregation (HS) is considered to be one of the most significant hurdles for the commercialization of tandem solar cells. However, despite significant research on this matter, the exact impact of HS on the performance degradation and the ion density evolution is yet to be established. In this work, we investigate the intriguing correlation between HS, ion-induced efficiency losses, and ion density evolution in wide-bandgap (WBG) triple cation perovskite cells. Our results highlight that all three phenomena evolve on similar timescales and follow the same trend across all studied bandgaps. This implies that the poor energy-lifetime product observed for devices prone to halide segregation is a result of enhanced ionic losses rather than, for instance, charge carrier funneling. Furthermore, reminiscent of the recovery of HS observed previously, we demonstrate that ionic losses also recover after light exposure and dark storage, which occurs along with a receding ion density. However, we also observe irreversible ionic losses, especially after prolonged illumination, which are critical for device operation. These findings present an important new understanding of the interplay between halide segregation and ionic processes and provide a rational explanation for the performance and stability of mixed halide WBG perovskites. © 2026 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH

AB - Halide segregation (HS) is considered to be one of the most significant hurdles for the commercialization of tandem solar cells. However, despite significant research on this matter, the exact impact of HS on the performance degradation and the ion density evolution is yet to be established. In this work, we investigate the intriguing correlation between HS, ion-induced efficiency losses, and ion density evolution in wide-bandgap (WBG) triple cation perovskite cells. Our results highlight that all three phenomena evolve on similar timescales and follow the same trend across all studied bandgaps. This implies that the poor energy-lifetime product observed for devices prone to halide segregation is a result of enhanced ionic losses rather than, for instance, charge carrier funneling. Furthermore, reminiscent of the recovery of HS observed previously, we demonstrate that ionic losses also recover after light exposure and dark storage, which occurs along with a receding ion density. However, we also observe irreversible ionic losses, especially after prolonged illumination, which are critical for device operation. These findings present an important new understanding of the interplay between halide segregation and ionic processes and provide a rational explanation for the performance and stability of mixed halide WBG perovskites. © 2026 The Author(s). Advanced Energy Materials published by Wiley-VCH GmbH

KW - halide segregation timescale

KW - ionic loss timescale

KW - mobile ions and ionic losses

KW - wide-bandgap (WBG) perovskites

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DO - 10.1002/aenm.202503866

M3 - RGC 21 - Publication in refereed journal

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JO - Advanced Energy Materials

JF - Advanced Energy Materials

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How Halide Segregation Governs the Ion Density Evolution and Ionic Performance Losses: From Degradation to Recovery

Abstract

Funding

UN SDGs

Research Keywords

Publisher's Copyright Statement

RGC Funding Information

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