Ambipolar Charge Transport in Perovskite CsPbBr₃ γ‐Ray Detectors with Superior Uniformity and Spectral Resolution by Zone Refining Processing

Perovskite semiconductor cesium lead bromide (CsPbBr₃) has demonstrated great promise as a new-generation gamma-ray detector. However, substantial challenges still present in reproducibly achieving optimal spectroscopic performance. The specific strategy for producing spectroscopic-grade CsPbBr₃ crystals with high reproducibility and uniformity are still not clarified. Herein, efficient zone refining processing is developed for CsPbBr₃ crystals that facilitates impurity segregation to achieve an ultrahigh purity level of ≈1.42 ppm, therefore lowers trap density and balances charge transport. In a typical 30 mm diameter zone-refined CsPbBr₃ ingot, all wafers exhibited remarkable energy resolutions of 6-12% and 3-8% for ²⁴¹Am and ⁵⁷Co γ-rays under comparable electric fields. The crystals also exhibited an ambipolar charge transport characteristic, resemble to elemental semiconductors, with equivalent hole and electron mobility-lifetime products averaging 5.42 × 10^-3 and 2.27 × 10^-3 cm²∙V^-1, respectively. Consequently, over 95% of wafers achieved energy resolutions below 5% whereas 70% exceeded 3% for ¹³⁷Cs γ-rays, demonstrating exceptional reproducibility and uniformity. Notably, a champion energy resolution of 1.3% with an outstanding photopeak-to-Compton (P/C) ratio of ≈5.3 is attained in an ambipolar planar detector. It is anticipated that this work shall expedite scalable manufacturing and practical applications of CsPbBr₃ detectors.