Enhanced Neutron and γ-Ray Detection via ⁶Li Substitution in Undoped and Tl-Doped Zero-Dimensional Perovskite Cs₃Cu₂I₅ Scintillators

Radiation detectors are crucial in a wide variety of research and commercial applications, such as oil and gas exploration, medical imaging, nuclear nonproliferation, and homeland security. Neutron and γ-ray detectors are fundamental components in portal monitors at ports and border crossings, bolstering national security against radiological threats. This study presents a dual-mode scintillator, undoped and Tl-doped 6Li–Cs3Cu2I5, and demonstrates its potential as a promising material for simultaneous thermal neutron and γ-ray detection. We explore the Bridgman growth of both undoped and thallium-doped Li → Cu and Li → Cs substitutional systems with various Li doping levels and assess their impact on scintillation properties. Under 662 keV γ-ray excitation, the undoped crystals had light yields up to 35,900 ph/MeV, with energy resolutions down to 4.5%. The Tl-doped crystals performed better than the undoped crystals, with light yields peaking at 65,900 ph/MeV and energy resolutions as low as 3.5%. When exposed to a moderated 252Cf excitation source, our crystals had light yields between 102,900 and 167,200 photons per thermal neutron capture, with a full energy thermal neutron peak reaching 3 MeV in γ equivalent energy. Pulse shape discrimination studies reveal well-separated γ and neutron events, resulting in a figure-of-merit (FOM) as high as 3.7. These findings highlight the potential of Li-doped Cs3Cu2I5 as a viable candidate for next-generation dual-mode scintillators.