A novel green-emitting phosphor NaLa9Ge6O26:xTb3+ with anti-thermal quenching for WLEDs

Abstract

The development of high-power WLEDs has driven higher requirements with respect to the thermal stability of luminescent materials. Herein, we propose an effective defect-modulation strategy to achieve excellent performance of green-emitting phosphors NaLa₉Ge₆O₂₆(NLGO):xTb³⁺ with anti-thermal quenching. The phosphor exhibits a remarkable increase in emission intensity up to 100 °C and retains 104% of its room-temperature intensity at a high temperature of 150 °C. This behavior is driven by deep defect levels (1.19 eV) originating from oxygen vacancies, which capture and subsequently release energy to the Tb³⁺ activators at higher temperatures. The optimal NLGO:0.2Tb³⁺ sample achieves a quantum yield of 63.43%. A fabricated WLED with a good color rendering index (R_a = 84.9) shows the prominent application potential of the as-prepared sample. This study validates defect modulation as an effective strategy for designing next-generation phosphors with superior thermal performance for solid-state lighting.