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CMP
Credit: Jack Hobhouse

Jarla Thiesbrummel

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Research theme

  • Photovoltaics and nanoscience

Sub department

  • Condensed Matter Physics
jarla.thiesbrummel@physics.ox.ac.uk
Robert Hooke Building, room G29
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  • About
  • Publications

Ion-induced field screening as a dominant factor in perovskite solar cell operational stability

Nature Energy Nature Research 9:6 (2024) 664-676

Authors:

Jarla Thiesbrummel, Sahil Shah, Emilio Gutierrez-Partida, Fengshuo Zu, Francisco Peña-Camargo, Stefan Zeiske, Jonas Diekmann, Fangyuan Ye, Karol P Peters, Kai O Brinkmann, Pietro Caprioglio, Akash Dasgupta, Seongrok Seo, Fatai A Adeleye, Jonathan Warby, Quentin Jeangros, Felix Lang, Shuo Zhang, Steve Albrecht, Thomas Riedl, Ardalan Armin, Dieter Neher, Norbert Koch, Yongzhen Wu, Henry Snaith

Abstract:

The presence of mobile ions in metal halide perovskites has been shown to adversely affect the intrinsic stability of perovskite solar cells (PSCs). However, the actual contribution of mobile ions to the total degradation loss compared with other factors such as trap-assisted recombination remains poorly understood. Here we reveal that mobile ion-induced internal field screening is the dominant factor in the degradation of PSCs under operational conditions. The increased field screening leads to a decrease in the steady-state efficiency, often owing to a large reduction in the current density. Instead, the efficiency at high scan speeds (>1,000 V s−1), where the ions are immobilized, is much less affected. We also show that the bulk and interface quality do not degrade upon ageing, yet the open-circuit voltage decreases owing to an increase in the mobile ion density. This work reveals the importance of ionic losses for intrinsic PSC degradation before chemical or extrinsic mechanical effects manifest.
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Improving interface quality for 1-cm2 all-perovskite tandem solar cells

Nature Springer Nature 618:7963 (2023) 80-86

Authors:

Rui He, Wanhai Wang, Zongjin Yi, Felix Lang, Cong Chen, Jincheng Luo, Jingwei Zhu, Jarla Thiesbrummel, Sahil Shah, Kun Wei, Yi Luo, Changlei Wang, Huagui Lai, Hao Huang, Jie Zhou, Bingsuo Zou, Xinxing Yin, Shengqiang Ren, Xia Hao, Lili Wu, Jingquan Zhang, Jinbao Zhang, Martin Stolterfoht, Fan Fu, Weihua Tang, Dewei Zhao
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Excitation Intervals Enhance Performance in Perovskite Solar Cells.

ACS applied materials & interfaces (2025)

Authors:

Sarah C Gillespie, Jarla Thiesbrummel, Veronique S Gevaerts, LJ Geerligs, Jeroen J de Boer, Gianluca Coletti, Erik C Garnett

Abstract:

Halide perovskites face intrinsic stability challenges primarily due to light- and bias-induced ion migration. To mitigate ion-mediated degradation on operationally relevant time scales, this work investigates how introducing brief periodic intervals of light and darkness (LD cycling) can stabilize the average efficiency of perovskite films and devices. Systematic photoluminescence (PL) studies reveal that dark intervals on the order of seconds significantly suppress nonradiative recombination and slow degradation. The extent of PL enhancement depends on the duration of the dark time, the material composition, and critically, the sample's age. Remarkably, LD cycling increases PL by more than 7-fold even in aged samples that would otherwise undergo photodarkening under continuous illumination. Moreover, the PL kinetics under LD cycling mirror the corresponding open-circuit voltage dynamics in full solar cells, showing that local emission changes provide a direct measure of device-level behavior. Device measurements similarly show that LD cycling enhances the power conversion efficiency compared to continuous illumination and mitigates deterioration over extended operation. This strategy highlights a potential pathway to dynamically preserve or even improve perovskite performance in future optoelectronic applications.
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Intensity-Modulated Photoluminescence Spectroscopy for Revealing Ionic Processes in Halide Perovskites.

ACS energy letters 10:7 (2025) 3122-3131

Authors:

Sarah C Gillespie, Agustin O Alvarez, Jarla Thiesbrummel, Veronique S Gevaerts, LJ Geerligs, Bruno Ehrler, Gianluca Coletti, Erik C Garnett

Abstract:

Mobile ions limit halide perovskite device performance, yet quantifying ionic properties remains challenging. Frequency-domain electrical techniques are restricted to operational devices, and the resulting signals are often dominated by interfacial recombination which obscures ionic contributions. Here, we introduce intensity-modulated photoluminescence spectroscopy (IMPLS) as a fully optical alternative, where the amplitude and phase of the photoluminescence intensity is measured as a function of excitation modulation frequency. IMPLS is demonstrated on a Cs0.07(FA0.83MA0.17)0.93Pb-(I0.83Br0.17)3 film. Fitting the data with an optical equivalent circuit model reveals two characteristic lifetimes: τchar = 2.1 ms and 77 s, likely corresponding to defect formation and ionic diffusion, respectively. The diffusion feature is consistent with intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) measurements on corresponding full devices. Importantly, IMPLS enables contact-free characterization of slow processes for all perovskite sample types, including films and devices, significantly expanding the techniques available for understanding mobile ions in these materials.
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Impact of Ion Migration on the Performance and Stability of Perovskite‐Based Tandem Solar Cells

Advanced Energy Materials Wiley (2024) 2400720

Authors:

Sahil Shah, Fengjiu Yang, Eike Köhnen, Esma Ugur, Mark Khenkin, Jarla Thiesbrummel, Bor Li, Lucas Holte, Sebastian Berwig, Florian Scherler, Paria Forozi, Jonas Diekmann, Francisco Peña‐Camargo, Marko Remec, Nikhil Kalasariya, Erkan Aydin, Felix Lang, Henry Snaith, Dieter Neher, Stefaan De Wolf, Carolin Ulbrich, Steve Albrecht, Martin Stolterfoht

Abstract:

The stability of perovskite‐based tandem solar cells (TSCs) is the last major scientific/technical challenge to be overcome before commercialization. Understanding the impact of mobile ions on the TSC performance is key to minimizing degradation. Here, a comprehensive study that combines an experimental analysis of ionic losses in Si/perovskite and all‐perovskite TSCs using scan‐rate‐dependent current–voltage (J–V) measurements with drift‐diffusion simulations is presented. The findings demonstrate that mobile ions have a significant influence on the tandem cell performance lowering the ion‐freeze power conversion efficiency from >31% for Si/perovskite and >30% for all‐perovskite tandems to ≈28% in steady‐state. Moreover, the ions cause a substantial hysteresis in Si/perovskite TSCs at high scan speeds (400 s−1), and significantly influence the performance degradation of both devices through internal field screening. Additionally, for all‐perovskite tandems, subcell‐dominated J–V characterization reveals more pronounced ionic losses in the wide‐bandgap subcell during aging, which is attributed to its tendency for halide segregation. This work provides valuable insights into ionic losses in perovskite‐based TSCs which helps to separate ion migration‐related degradation modes from other degradation mechanisms and guides targeted interventions for enhanced subcell efficiency and stability.
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