Tracking ion migration in perovskite solar cells during degradation tests: improving performance or masking degradation?

Pilar Lopez Varo^a

^aIPVF, Institut Photovoltaïque d’Ile-de-France (IPVF), 18 boulevard Thomas Gobert, 91120 Palaiseau, France

Proceedings of MATSUS Spring 2026 Conference (MATSUSSpring26)

G2 Monitoring the degradation mechanisms of photovoltaic devices by optoelectronic characterization

Barcelona, Spain, 2026 March 23rd - 27th

Organizers: Enrique H. Balaguera and Emilio J. Juarez-Perez

Invited Speaker, Pilar Lopez Varo, presentation 602
Publication date: 15th December 2025

Perovskite photovoltaics have reached early stage of commercial deployment in a remarkably short period of maturation, driven by rapid advances in power conversion efficiency over the past decade. Despite these impressive achievements, the long-term reliability and stability of perovskite solar cells (PSCs) remain major challenges, largely due to ion migration. Ion motion affects the performance and operational stability of PSCs, as well as tandem and multijunction device architectures. Different transient experimental techniques have been used to better understand the puzzling performance of ion migration in PSCs [1,2].

In this work, we first investigate ion migration using two complementary spectroscopic techniques [3-6]: operando X-ray photoelectron spectroscopy (op-XPS) and impedance spectroscopy (IS). Op-XPS on lateral PSCs enables probing of device performance and interfacial electronic structure changes induced by ionic motion [4,5]. Second, IS measurements are combined with drift–diffusion (DD) simulations to provide a detailed characterization of device operation and ionic transport. This coupled IS–DD framework is applied to NiOx-based PSCs with different interfacial passivation schemes [6]. The simulations allow the interpretation of IS spectra under varying illumination intensities and during bias-stress tests, revealing that interfacial modification can reduce electron mobility in NiOx and ion mobility within the perovskite absorber.

Together, these combined results enhance our understanding of ion migration and its impact on PSC performance and operational stability.

References:

[1] López-Varo, P; Jiménez-Tejada, J.A.; García-Rosell, M.; Ravishankar, S.; Garcia-Belmonte, G.; Bisquert, J.; and Almora O. Device Physics of Hybrid Perovskite Solar cells: Theory and Experiment. Adv. Energy Mater. 2018, 8, 1702772.

[2] Messmer, C.; Parion, J; Meza, C.-V; Ramesh, S.; Bivour, M.; Heydarian, M.; Schön, J.; Radhakrishnan, H.-S.; Schubert, M.C.; and Glunz, S.-W. Understanding Ion-Related Performance Losses in Perovskite-Based Solar Cells by Capacitance Measurements and Simulation. Solar RRL 8(24) 2024

[3] Jun, H.; Tondelier, D.; Geffroy, B.; Bouree, J.E.; Lopez-Varo, P.; Schulz, P.; Bonnassieux, Y.; Swaraj, S. Electrochemical and Spectro-Microscopic Analyses of Charge Accumulation and Ion Migration in Dry Processed Perovskite Solar Cells under Electrical Biasing. The Journal of Physical Chemistry Letters 16(3):835-847, 2025

[4] Regaldo, D.; Bojar, A.; Dunfield, S.; Lopez-Varo, P.; Frégnaux, M.; Dufoulon, V.; Zhang, S.-T.; Alvarez, J.; Berry, J.-J. et al. On the equilibrium electrostatic potential and light-induced charge redistribution in halide perovskite structures. Progress in Photovoltaic. 2022. 30, 994-1002

[5] Lopez-Varo, P.; Frégnaux, M.; Regaldo, D.; Philip et al. Characterization of the Performance of Perovskite Solar Cells by Operando X-Ray Photoemission Spectroscopy. IEEE 52nd Photovoltaic Specialist Conference (PVSC), 1156-1156 (2024).

[6] Almora, O.; López-Varo, P.; Escalante, R.; Mohanraj, J.; Marsal; Olthof. S.; Anta, J. A.; Instability analysis of perovskite solar cells via short-circuit impedance spectroscopy: A case study on NiOx passivation. J. Appl. Phys. 2024. 136, 094502.

Acknowledgements:

This work was partially supported by the French Government in the frame of the program of investment for the future (Programme d’Investissement d'Avenir, No. ANR-IEED-002-01) and the European Union through the Horizon Europe project Triumph under the number 101075725. In the work of Impedance Spectroscopy, special thanks to Osbel Almora, Juan Pablo Flechas Medina and Raj Patel. In the work of Op-XPS, special thanks to Philip Schulz, Mathieu Frégnaux, Davide Regaldo, Solène Béchu, Jean-Paul Kleider and Jean-Baptiste Puel.

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