How Photogenerated I2 Induces I-Rich Phase Formation in Lead Mixed Halide Perovskites

Yang Zhou (Corresponding author), Simone C.W. van Laar, Daniele Meggiolaro (Corresponding author), Luca Gregori, Samuele Martani, Jia Yong Heng, Kunal Datta, Jesús Jiménez-López, Feng Wang, E. Laine Wong, Isabella Poli, Antonella Treglia, Daniele Cortecchia, Mirko Prato, Libor Kobera, Feng Gao, Ni Zhao, René A.J. Janssen, Filippo De Angelis, Annamaria Petrozza (Corresponding author)

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Bandgap tunability of lead mixed halide perovskites (LMHPs) is a crucial characteristic for versatile optoelectronic applications. Nevertheless, LMHPs show the formation of iodide-rich (I-rich) phase under illumination, which destabilizes the semiconductor bandgap and impedes their exploitation. Here, it is shown that how I2, photogenerated upon charge carrier trapping at iodine interstitials in LMHPs, can promote the formation of I-rich phase. I2 can react with bromide (Br) in the perovskite to form a trihalide ion I2Br (Iδ−-Iδ+-Brδ−), whose negatively charged iodide (Iδ−) can further exchange with another lattice Br to form the I-rich phase. Importantly, it is observed that the effectiveness of the process is dependent on the overall stability of the crystalline perovskite structure. Therefore, the bandgap instability in LMHPs is governed by two factors, i.e., the density of native defects leading to I2 production and the Br binding strength within the crystalline unit. Eventually, this study provides rules for the design of chemical composition in LMHPs to reach their full potential for optoelectronic devices.

Original languageEnglish
Article number2305567
Number of pages12
JournalAdvanced Materials
Issue number1
Publication statusPublished - 4 Jan 2024


The research has received funding from the ERC project SOPHY under grant agreement no. 771528, the European Union's Horizon 2020 research and innovation programme via the MSCA‐IF under grant agreement no.839480 (PERICLeS), via the MSCA‐IF under grant agreement no.101023689 (Bolla), via the MSCA‐ITN SMART‐X under grant agreement no.860553, via the European Union's HOrizon Europe reserach and innovation programme under grant agreement no. 101082176‐VALHALLA, the Netherlands Ministry of Education, Culture and Science (Gravity program 024.001.035) and the Netherlands Organization for Scientific Research via a Spinoza grant.

FundersFunder number
European Union 's Horizon 2020 - Research and Innovation Framework Programme101082176‐VALHALLA
European Union's H2020-MSCA-IF-2018839480, 101023689, 860553
European Research Council771528
Ministerie van Onderwijs, Cultuur en Wetenschap024.001.035
Nederlandse Organisatie voor Wetenschappelijk Onderzoek


    • defects
    • metal halide semiconductors
    • optoelectronics
    • solar cells
    • wide bandgap metal halide perovskites


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