Synchrotron-Based Photoelectron Spectroscopy of Halide Perovskite Single Crystals: From Clean Surfaces to Buried Interfaces

Alberto García-Fernández^a^,^b, Karen Radetzky^b^,^c, Birgit Kammlander^b, Håkan Rensmo^b^,^c, Ute B. Cappel^b^,^c

^aCICA (Interdisciplinary Center for Chemistry and Biology), Department of Chemistry, Faculty of Science, Universidade da Coruña, As Carballeiras, s/n, Campus de Elviña 15071, A Coruña, Spain

^bDivision of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Box 534, 751 20 Uppsala, Sweden

^cWallenberg Initiative Materials Science for Sustainability, Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden

Proceedings of MATSUS Fall 2026 Conference (MATSUSFall26)

A3 Single-Crystal Halide Perovskites: From Growth to Device Applications

Palma, Spain, 2026 October 26th - 30th

Organizer: Daniela Marongiu

Oral, Alberto García-Fernández, presentation 201
Publication date: 22nd July 2026

Single-crystal halide perovskites provide an excellent platform for investigating the intrinsic electronic properties of metal halide semiconductors while eliminating many of the complexities associated with polycrystalline films. However, translating these materials into high-performance devices requires a detailed understanding of their surfaces, buried interfaces, and their response to intense X-ray irradiation during advanced characterization.[1]

In this contribution, we present a methodology based on synchrotron soft- and hard X-ray photoelectron spectroscopy to investigate the electronic structure of clean single-crystal halide perovskites.[2] By combining in situ crystal cleavage with the sequential evaporation of charge-transport materials and metallic contacts under ultra-high vacuum, we have developed a platform to fabricate clean interfaces and monitor their formation in real time. This approach enables direct observation of energy-level alignment, band bending, electronic structure evolution, and interfacial chemical reactions during interface formation, including buried interfaces relevant to photovoltaic and optoelectronic devices.[3,4] We also discuss the influence of X-ray exposure on the electronic structure and chemical stability of single crystals, highlighting practical considerations for obtaining reliable spectroscopic data.[5] Together, these studies demonstrate how advanced synchrotron characterization can provide unique insight into the fundamental mechanisms governing charge extraction, interface formation, and device performance in single-crystal halide perovskites, while establishing experimental guidelines for the characterization of these beam-sensitive materials.

References:

[1] Cho, Y., Jung, H. R., & Jo, W. (2022). Halide perovskite single crystals: growth, characterization, and stability for optoelectronic applications. Nanoscale, 14(26), 9248-9277.

[2] García‐Fernández, A., Svanström, S., Sterling, C. M., Gangan, A., Erbing, A., Kamal, C., ... & Cappel, U. B. (2022). Experimental and theoretical core level and valence band analysis of clean perovskite single crystal surfaces. Small, 18(13), 2106450

[3] Garcia-Fernandez, A., Kammlander, B., Riva, S., Kühn, D., Svanstrom, S., Rensmo, H., & Cappel, U. B. (2023). Interface energy alignment between lead halide perovskite single crystals and TIPS-pentacene. Inorganic Chemistry, 62(38), 15412-15420.

[4] Radetzky, K., Garcia-Fernandez, A., Kammlander, B., Johannesson, E., Rydgren, B., Varma, R. M., ... & Cappel, U. B. (2026). Energetics and chemistry at the electron selective interfaces for pin perovskite solar cells: an in situ investigation. EES Solar, Advance Article.

[5] García-Fernández, A., Kammlander, B., Riva, S., Rensmo, H., & Cappel, U. B. (2024). Composition dependence of X-ray stability and degradation mechanisms at lead halide perovskite single crystal surfaces. Physical Chemistry Chemical Physics, 26(2), 1000-1010.

Acknowledgements:

The authors acknowledge MAX IV Laboratory for time on Beamline FlexPES and the Helmholtz-Zentrum Berlin fur Materialien und Energie for the allocation of synchrotron radiation beamtime. A. G.-F. acknowledges support from a Beatriz Galindo junior fellowship (BG23/00033) from the Spanish Ministry of Science and Innovation.We acknowledge funding from the Swedish Research Council (Grant No. VR 2022-03168), the Carl Tryggers foundation the Göran Gustafsson foundation and Xunta de Galicia. This work was partially supported by the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation

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