Zero-dimensional Cs₄EuX₆ (X = Br, I) all-inorganic perovskite single crystals for gamma-ray spectroscopy

Organic-inorganic and all-inorganic halide perovskites have become leading candidates toward high-performance optoelectronic devices and radiation detectors. In this work, we report novel zero-dimensional Cs₄EuX₆ (X = Br, I) perovskite single crystals as self-activated scintillators with superior performance for gamma-ray spectroscopy. Both Cs₄EuBr₆ and Cs₄EuI₆ single crystals grown by the Bridgman method were determined to have the trigonal crystal structure with the R3c space group, and have a melting point of approximately 540 °C. Cs₄EuBr₆ and Cs₄EuI₆ exhibit blue emission under UV excitation and high light yields of 78:000 ± 4000 photons per MeV and 53:000 ± 3000 photons per MeV under ¹³⁷Cs gamma-ray irradiation, respectively. In particular, the former represents the best result achieved for self-activated scintillators thus far. Thermally stimulated luminescence studies and density functional theory calculations elucidate the correlation between halogen vacancies and long-lived emission (afterglow) at room temperature in Cs₄EuX₆ (X = Br, I) single crystals. Our findings not only demonstrate the high gamma-ray detection efficiency in Cs₄EuX₆ (X = Br, I), but will further promote the development of 0D metal halide-based novel luminescent and radiation detection materials.