Highly efficient ⁶ Li-doped copper halide scintillators toward neutron and gamma detection

Neutron detection materials are critical and irreplaceable in the fields of nuclear security monitoring, radioactive waste management, and particle physics research. The development of efficient neutron-gamma multimode scintillators that simultaneously offer high light yield, decent energy resolution, and efficient neutron-gamma discrimination capability remains a grand challenge. In this work, we report a neutron-gamma discrimination strategy by introducing ${}^{6}\mathrm{Li}$-enriched $\mathrm{Li}\mathrm{I}$ dopants, which has a high thermal neutron absorption cross section, into the highly efficient ${\mathrm{Cs}}_{3}{\mathrm{Cu}}_{2}{\mathrm{I}}_{5}:\mathrm{Tl}$ single crystals. The Bridgman-grown ${\mathrm{Cs}}_{3}{\mathrm{Cu}}_{2}{\mathrm{I}}_{5}:\mathrm{Tl},\mathrm{Li}$ single crystals demonstrate superior light yield of 81 000 photons/MeV under gamma irradiation and 200 000 photons/neutron under thermal neutron irradiation, respectively, higher than any reported multimode scintillators. Moreover, ${\mathrm{Cs}}_{3}{\mathrm{Cu}}_{2}{\mathrm{I}}_{5}:\mathrm{Tl},\mathrm{Li}$ single crystals possess a superior energy resolution of 4.2% at 662 keV, a decent neutron-gamma discrimination figure of merit of 2.35, and an intrinsic absence of radioactive background. By combining the density-functional-theory calculations, nuclear magnetic resonance, positron annihilation, and thermoluminescence measurements, the effects of ${}^{6}\mathrm{Li}$ codoping on the defect structure and scintillation performance were clarified. This work provides an alternative horizon for designing highly efficient neutron-gamma multimode scintillators.