Spectroscopic Performance of CsPbBr₃ Perovskite γ-Ray Detectors Despite Grain Boundaries

The CsPbBr₃ perovskite has emerged as a promising material for next-generation γ-ray detection owing to its high stopping power, wide bandgap, and excellent charge-transport properties. Unlike conventional semiconductors, in which grain boundaries (GBs) degrade response, we observed that CsPbBr₃ retains functional spectroscopic performance in their presence, demonstrating remarkable defect tolerance. We systematically investigate the impact of GBs on the performance and stability of CsPbBr₃-based detectors. Detectors containing GBs exhibit measurable spectroscopic performance at room temperature, including resolved photopeaks at 59.5 keV (²⁴¹Am) and 122 keV (⁵⁷Co), along with hole mobility-lifetime products (µτ)_h on the order of ∼10^-4 cm²·V^-1, highlighting the defect-tolerant nature of CsPbBr₃. Two-photon excitation PL microscopy shows asymmetric carrier diffusion near GBs (under zero field bias), indicative of impeded charge transport, while transient waveform analysis captures field-assisted detrapping that recovers charge collection on application-relevant timescales. Our measurements indicate that device engineering choices, pixel placement/size, guard rings, field shaping, and electrode work-function design can help drift paths and electric fields away from defects, and may reduce GB impacts.