Highly efficient warm-white emission and energy transfer mechanism in apatite-like RbSr4(BO3)3: Dy3+,Eu3+ phosphors via heterovalent substitution engineering

Abstract

Based on the advantage of large structural inclusiveness, the apatite-like borate RbSr₄(BO₃)₃:Dy³⁺,Eu³⁺ warm-white fluorescent materials have been designed using a heterovalent substitution strategy. In RbSr₄(BO₃)₃:Dy³⁺,Eu³⁺, the trivalent dysprosium and europium cations occupy the crystallization sites of divalent strontium cations. The trivalent dysprosium doped RbSr₄(BO₃)₃ exhibits bluish fluorescence with CIE color coordinates of (0.306, 0.347) and correlated color temperature of 6714 K. This is due to the blue emission originating from the ⁴F_9/2 → ⁶H_15/2 electron transition being more intense than the yellow emission derived from the ⁴F_9/2 → ⁶H_13/2 transition. Accordingly, the trivalent europium cations were incorporated into RbSr₄(BO₃)₃:Dy³⁺ to complement for the insufficient red light. Ultimately, the single-matrix warm-white fluorescent material RbSr₄(BO₃)₃:Dy³⁺,Eu³⁺ was successfully synthesized. RbSr₄(BO₃)₃:0.6%Dy³⁺,0.8%Eu³⁺ shows CIE color coordinates of (0.395, 0.344), a correlated color temperature of 3340 K, and an enhanced photoluminescence quantum yield (PLQY) of up to approximately 95.9%. This work not only provides a design strategy for novel fluorescent materials, but also endows high-performance single-component warm-white phosphors suitable for solid-state lighting applications.