On the relationship between emission color and Ce concentration in garnet phosphors

It is known that the emission color of Ce³⁺ doped garnets is strongly redshifted at higher Ce³⁺ concentrations. In this report, we study the cause of this redshift in Lu₃Al₅O₁₂:Ce³⁺ (LuAG:Ce) phosphors. These changes in emission color with Ce³⁺ concentration are mainly attributed to a combination of inhomogenous broadening for Ce³⁺ in LuAG and energy transfer from high energy Ce³⁺ ions to low energy Ce³⁺ ions. Evidence for inhomogenous broadening and energy transfer is given through time resolved measurements. Potential reasons for inhomogenous broadening of Ce³⁺ in these phosphors are also discussed.