The Effect of Intrinsic Defects in Grain Boundaries on Non-Radiative Recombination in CsPbI3 and CsPbBr3

Lotte Kortstee^a, Noam Veber^b^,^c, Betty Shamaev^b^,^c, Yehonadav Bekenstein^b^,^c, Juan María García-Lastra^a, Ivano E. Castelli^a

^aDepartment of Energy Conversion and Storage (DTU Energy), Technical University of Denmark, Agnes Nielsens Vej 301, DK-2800 Kongens Lyngby, Denmark

^bDepartment of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel

^cThe Solid-State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel

Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV26)

Uppsala, Sweden, 2026 May 18th - 20th

Organizers: Gerrit Boschloo, Ellen Moons, Feng Gao and Anders Hagfeldt

Oral, Lotte Kortstee, presentation 130
Publication date: 11th March 2026

Halide perovskites hold great potential for high‑efficiency photovoltaic technologies, yet understanding and overcoming their material instabilities remains a major obstacle to commercialization [1-3]. A key challenge lies in understanding the behaviour of these materials at grain boundaries, which can greatly affect the overal material characteristics. Grain boundaries are frequently linked to both enhanced non‑radiative recombination [4,5], as well as regions of photobrigthening [6,7].

Here, we combine first‑principles defect calculations within Density Functional Theory with high‑resolution cathodoluminescence mapping to establish a link between atomic structure, defect physics, and recombination activity at grain boundaries in γ‑CsPbBr₃ and γ‑CsPbI₃. By comparing bulk with two representative grain boundary geometries, we show that the local environment of the grain boundaries can act as thermodynamic sinks for defects, significantly increasing their concentrations around grain boundary edges. Besides grain boundaries being able to accumulate defects, we observe a modified electronic behavior of some defects when present in the local grain boundary environment. The Pb interstitial, which is largely benign in the bulk, becomes electronically ‘activated’ at grain boundaries, with its charge‑transition level shifting into the mid‑gap region. This activation transforms Pb interstitials into dominant non‑radiative recombination centers specifically at grain boundaries. The strong sensitivity of this effect to local boundary geometry contributes as an explanation for the widely reported yet seemingly contradictory photoluminescence signatures in polycrystalline perovskite films.

References:

[1] Kore, B. P., Jamshidi, M. & Gardner, J. M. The impact of moisture on the stability and degradation of perovskites in solar cells. Materials Advances vol. 5 2200–2217, (2024).

[2] Ma, L. et al. Temperature-dependent thermal decomposition pathway of organic-inorganic halide perovskite materials. Chemistry of Materials 31, 8515–8522 (2019).

[3] Abdelmageed, G. et al. Mechanisms for light induced degradation in MAPbI3 perovskite thin films and solar cells. Appl Phys Lett 109, (2016).

[4] deQuilettes, D. W. et al. Impact of microsctructure on local carrier lifetime in perovskite solar cells. Science (1979) 348, 683–686 (2015).

[5] Ni, Z. et al. High Grain Boundary Recombination Velocity in Polycrystalline Metal Halide Perovskites. Sci. Adv vol. 8 p. 8345 (2022).

[6] Adhyaksa, G. W. P. et al. Understanding Detrimental and Beneficial Grain Boundary Effects in Halide Perovskites. Advanced Materials 30, (2018).

[7] Halpati, J. S., Samuel, A. K., Robert, T. M. & Chandiran, A. K. Real-Time Visualization of Photobrightening in Lead Halide Perovskites Using Confocal Laser Scanning Microscopy. Journal of Physical Chemistry C 127, 3256–3267 (2023).

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