Volume compensation directed enhanced photoluminescence in Li+ Co-doped Y4Al2O9:Eu3+ phosphors for solid state lighting applications

Abstract

Rare-earth activated red phosphors have become the indispensable component for the generation of warm white light from phosphor converted white light emitting diodes (PC WLEDs). Eu³⁺ doped Yittrium based hosts are considered as the highly promising red phosphors and thus have widely been investigated in the last few years. However, The mismatch in the size of Eu³⁺ and Y³⁺ restricts their PL enhancement below the desired limit. Herein, Li⁺ co-activated Y₄Al₂O₉:Eu³⁺ phosphors have been synthesized via facile solvothermal technique. All the phosphors exhibit characteristic ⁵D₀ → ⁷F_j (j=1–4) transitions of Eu³⁺ and introduction of Li⁺ co-activator results in nearly 2.5 fold enhancement of PL intensity as compared to pristine Y₄Al₂O₉:Eu³⁺ phosphors. Moreover, both the excited state lifetime and thermal stability of the phosphors are remarkably improved upon Li⁺ co-activation. The enhancement in PL efficiency has been explained in light of volume compensation induced lattice relaxation mechanism. Strong red emission was achieved by the red LED fabricated by employing Li⁺ co-activated Y₄Al₂O₉ : Eu³⁺ phosphors under 3 Volt driving potential. The demonstrated volume compensation technique possesses great promise to play the pivotal role in designing highly luminescent phosphors for LED applications.