Publication date: 11th March 2026
Mobile ions in metal halide perovskites are found to degrade perovskite solar cells (PSCs). Therefore, characterizing their density and mobility is crucial for improving the long-term performance of PSCs. A common method to characterize PSCs is impedance spectroscopy.
In the literature, the low-frequency (LF) feature of the PSC impedance response is related to ion dynamics and the high-frequency feature to electronic processes. Yet, why these features can vary over orders of magnitude in terms of frequency and impedance is unclear.
In this work, we identify the specific ion dynamics that drive the LF feature. We derive two seperate analytical expressions that directly relate the frequency and magnitude of the LF feature to the ion density and ion mobility, respectively. The validity of both analytical expressions are confirmed through extensive drift-diffusion simulations, varying over 35 parameters to ensure that they are applicable to a wide range of perovskite solar cells.
Alternative formulas from the literature are also tested, but are found to be suboptimal. After the validation, we experimentally determine the ion density and mobility of a methylammonium lead iodide PSC. They are 2 × 1022 m-3 and 4 × 10-10 m2 V-1 s-1, respectively.
This new method, which depends on the low-frequency feature of the impedance spectrum, facilitates the precise and straightforward determination of the ion density and ion mobility in PSCs.
Funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not
necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. VALHALLA project has received funding from Horizon Europe Research and Innovation Action programme under Grant Agreement No. 101082176. Authors also acknowledge support by the Ministry of Science and Innovation (MCIN) and the Spanish State Research Agency (AEI), project PID2021-126444OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”.
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