Luminescence Study and Energy Transfer from Ce³⁺ to Yb³⁺ in Sr₅(BO₃)₃Cl Phosphor

A new phosphor Sr₅(BO₃)₃Cl:Ce³⁺,Yb³⁺, which enables near-infrared (NIR) quantum cutting, was prepared using traditional solid-state reaction methods. Its properties were examined using X-ray diffraction, photoluminescence emission, excitation spectra, and measurements of fluorescence decay. Upon excitation of Ce³⁺ with an ultraviolent (UV) photon at 350 nm, broadband emission at 415 nm and an intense NIR emission at 982 nm were observed. Emission at 415 nm corresponds to 5d→4f transition of Ce³⁺ ions, whereas the NIR emission at 982 nm is ascribed to the characteristic ²F_5/2 → ²F_7/2 transition of Yb³⁺ ions. Thorough investigation delved into how the concentration of Ce³⁺ affects visible and NIR emissions, decay lifetime, and energy transfer efficiency (η_ETE). Detailed analysis of photoluminescence excitation, emission spectra, and fluorescence decay measurements revealed a proficient energy transfer from Ce³⁺ to Yb³⁺ ions. This transfer was demonstrated as a cooperative energy transfer (CET) process, showcasing a CET efficiency of 71.2% and a total theoretical quantum efficiency of 171.2%.