Broadened and enhanced blue emission of interstitial Eu2+ in α-cristobalite via Al3+ codoping for high color rendering white LEDs

Abstract

The interstitial site engineering that purposely creates interstitial luminescent centers in suitable hosts has become an intriguing strategy in designing novel inorganic phosphors. However, effectively tuning the photoluminescence of interstitial activators remains tough challenging at this stage. Here, we demonstrate the effective modulation of interstitial luminescence in inorganic phosphor. In detail, the blue emission band (λ_em = 446 nm) of interstitial Eu²⁺ doped α-cristobalite (SiO₂:Eu²⁺) is largely enhanced and broadened via a partial, aliovalent substitution of Si⁴⁺ by Al³⁺. After introducing Al³⁺ ions into SiO₂ lattice, the full width at half maximum of the blue emission band increase from 59 to 76 nm with a triple growth in quantum efficiency (10.82% → 35.56%). Moreover, the thermal stability improves significantly with a high emission retention of 60% at 325 °C (SiO₂:0.06Al³⁺,0.005Eu²⁺), far higher than that of the parent SiO₂:0.005Eu²⁺ (30%). Encapsulating blue-emitting SiO₂:Al³⁺,Eu²⁺ along with two commercial green and red phosphors on an ultraviolet LED chip (λ_em = 375 nm), a white LED device with high color rendering index (Ra > 90) was successful fabricated, showing the great potential of this phosphor for achieving high-quality white LED lighting. This study not only provides a promising bule emitter but also sheds light on modulating interstitial luminescence properties in inorganic phosphors.