Anomalous concentration anti-quenching of Eu3+ red luminescence based on novel rare-earth borate K7SrLu2B15O30

Trivalent europium ion (Eu 3+ )-based phosphors have emerged as promising candidates for advancing the performance of white light-emitting-diodes (WLEDs) due to their characteristic narrow-band red emission from 5 D 0 → 7 F 1,2 transitions. High Eu 3+ concentration could optimize absorption efficiency but also trigger emission attenuation owing to the concentration quenching effect. Herein, we develop a unique class of efficient red-emitting phosphors without occurring concentration quenching, K 7 SrLu 2(1- x ) B 15 O 30 : x Eu 3+ (0≤x ≤ 1), exhibiting sharp red emission peaking at 619 nm upon excitation with a 393 nm. The increasing proportion of Eu 3+ in the K 7 SrLu 2 B 15 O 30 host can raise the emission intensity monotonously until the Eu 3+ concentration comes to 100%, while no distortion has been observed in the nature of the crystal structure. The concentration anti-quenching effect can be ascribed to the limitation of energy transfer due to the effective separation of neighboring [LuO 6 ] octahedral in crystal lattice. Consequently, the optimal K 7 SrEu 2 B 15 O 30 (KSEBO) phosphor achieves a high internal quantum efficiency (IQE) of 80.62%, excellent color purity of 92.69%, and retains 74% of the initial intensity at 423 K. The WLEDs device fabricated with the K 7 SrEu 2 B 15 O 30 phosphor presents a high general color rendering index (CRI) of 85.2 and low correlated color temperature (CCT) of 4409 K, demonstrating the developed phosphor applicable as a red component in warm WLEDs.