Publication date: 15th December 2025
Halide perovskites have emerged as promising materials for next-generation radiation detectors, echoing their transformative impact on photovoltaics. Due to the long penetration depths of X-rays and γ-rays, thick single crystals are required to sufficiently attenuate the radiation, making bulk crystal quality critical for device performance. Photoluminescence properties, particularly long lifetimes and redshifted emission peaks, are commonly used as proxies for identifying high-quality CsPbBr3 crystals for high-performance detectors, yet the physical origin of this correlation remains unclear. Here, we combine complementary photoluminescence techniques with a full-spectrum fit to reveal the importance of vertical diffusion in governing photoluminescence response, ultimately shaping detector performance. High-quality crystals exhibit larger vertical diffusion coefficients (up to 0.65 cm2 s⁻¹) and lower recombination rates (down to 1.1×106 s⁻¹), leading to diffusion lengths up to 5 times greater than those in low-quality crystals. Using one- and two-photon photoluminescence microscopy, we further visualise microscale defects, with suppressed redshift and distributions throughout the bulk, in low-quality crystals. Two-photon diffusion mapping directly reveals how these defects hinder carrier transport. Our findings establish a direct link between photoluminescence and carrier diffusion, providing a quantitative framework that connects crystal quality to charge transport and device performance in perovskite radiation detectors.
The authors thank the Engineering and Physical Sciences Research Council (EPSRC) for support (EP/V027131/1) and for a Core Equipment Grant funding the radioluminescence setup. Z.W. acknowledges the Leverhulme Trust (Project No: RPG-2021-191). C.M. acknowledges funding from Connected Electronics and Photonics CDT (Project Code: EP/S022139/1) M.D. acknowledges UKRI guarantee funding for Marie Skłodowska-Curie Actions Postdoctoral Fellowships 2022 (EP/Y024648/1). S.D.S. acknowledges the Royal Society and Tata Group (grant no. UF150033, URF\R\221026). At Northwestern University, this work was supported by the Department of Energy under Contract No. DE-0024020 and by the Defense Threat Reduction Agency (DTRA) through the Interaction of Ionizing Radiation with Matter University Research Alliance (IIRM-URA) under Contract No. HDTRA1-20-2-0002. We thank Krzys Galkowski and Simon Kahmann for building the optics for two-photon excitation, and Cullen Chosy and Ganbaatar Tumen-Ulzii for fruitful discussions.
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