Characterisation of Sm²⁺-doped CsYbBr₃, CsYbI₃ and YbCl₂ for near-infrared scintillator application

Fast energy transfer from Yb²⁺ to Sm²⁺ is a requirement when using Yb²⁺ as a sensitiser for Sm²⁺ emission for near-infrared scintillator applications. This cannot be achieved through dipole-dipole interactions due to the spin-forbidden nature of the involved Yb²⁺ transition, making the rate of energy transfer too slow for application. This work explores whether exploiting the exchange interaction by increasing the Yb²⁺ concentration to 99% is an effective way to increase the rate at which energy is transferred from Yb²⁺ to Sm²⁺. The scintillation characteristics of CsYbBr₃:1%Sm, CsYbI₃:1%Sm and YbCl₂:1%Sm single crystals were studied through ¹³⁷Cs excited pulse height spectra, X-ray excited decay and X-ray excited luminescence spectra. An energy resolution of 7% and a light yield of 30,000 ph/MeV was achieved with CsYbI₃:1%Sm. Photoluminescence spectroscopy and decay studies were performed to study the band structure and relaxation dynamics.