Publication date: 22nd July 2026
Metal halide perovskites have emerged as promising materials for solar cells, LEDs and other optoelectronic devices, due to their outstanding optical and electronic properties. To optimize the performance and minimize degradation effects under operation, a detailed understanding of the optoelectronic and structural properties at the micro- and nanoscale is required.
In this study, we use cathodoluminescence spectroscopy (CL) to probe these properties. CL involves scanning a high-energy electron beam (5–30 keV) across the sample surface in a scanning electron microscope (SEM) and collecting the resulting light emission. We study polycrystalline CsPbBr₃ films and correlate high-resolution 2D CL maps with nanoscale surface morphology. We observe that CL intensity drops at grain boundaries, hinting at reduced optical quality in these regions. Interestingly, we also find a ring-like emission pattern in samples with larger grains.
We then utilise optical near-field simulations with electric dipole sources to simulate the CL emission intensity across the surface, considering the surface morphology around the grain boundaries and the electron-sample interaction volume. The simulated CL profiles match the experimental data closely, indicating that the nano- and microscale surface morphology strongly impacts light outcoupling from grains and grain boundaries. We further show that the ring patterns arise from interference between dipole radiation and reflected waves (both propagating and evanescent), linking the observed emission patterns directly to surface morphology and substrate effects. Extending this analysis to the limiting cases of IQE = 0 and IQE = 1 reveals that surface morphology dominates the CL response irrespective of internal quantum efficiency.
Our results demonstrate that CL spectroscopy is a powerful method for exploring nanoscale optoelectronic behaviour in perovskites. At the conference, we will further discuss the role of the local density of optical states (LDOS) in shaping CL emission maps. By comparing simulated radiative decay-rate variations with far-field outcoupling, we disentangle changes in local emission probability from purely optical collection effects. Finally, we will discuss an outlook toward inverse CL-based metrology, exploring whether CL emission maps can be used to retrieve information on the underlying surface morphology.
The authors acknowledge Daphne Dekker for conducting the time-resolved PL measurements. This work is part of the research program of the Dutch Research Counsil (NWO) and SolarLab within SolarNL, a national research, innovation and industrial development program funded by The Netherlands National Growth Fund. It is financed by the European Research Council (ERC) under Grant Agreement No. 101019932 (QEWS), the European Innovation Counsel (EIC) under Grant Agreements No. 101017720 (EBEAM), No. 101151994 (EXPLEIN), and No. 947221 (SHAPE) under the European Union’s Horizon 2020 Research and Innovation Program, and the Engineering and Physical Sciences Research Council (EPSRC) for funding (EP/S030638/1, EP/V06164X/1). S.D.S. acknowledges the Royal Society and Tata Group (UF150033, URF\R\221026). This work was supported by the Henry Royce Institute for advanced materials through the Equipment Access Scheme enabling access to Ambient Cluster Tool facilities at Cambridge [the EPSRC (EP/R00661X/1) and Cambridge Royce facilities grant EP/P024947/1]. This work used the Dutch national e-infrastructure with the support of the SURF Cooperative using grant no. EINF-11575.
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