Boosting red-emitting 5D0→7F2 transition in KSrBP2O8:Eu3+ phosphors via Si4+/Gd3+ Co-doping and charge compensation

Abstract

Eu³⁺ doped KSrBP₂O₈ phosphors exhibits great potential for red-emitting boosting in light-emitting diodes owing to high color purity and low correlated color temperature. However, phosphors solely doped with Eu³⁺ suffer from insufficient red-light emission and low luminescence intensity limiting the practical application. Herein, a series of KSrBP₂O₈:Eu³⁺ phosphors doped by Si⁴⁺ and Gd³⁺ were prepared via a facile high-temperature solid-state reaction method. The as-synthesized phosphors possess outstanding luminescence performances, including high emission intensity and favorable color purity. Enhancement of the ⁵D₀→⁷F₂ transition was achieved through co-doping with Si⁴⁺ and Gd³⁺ ions, together with the introduction of charge compensators (Li⁺, Na⁺, K⁺, and Cs⁺). Continuous tuning of luminescent color was realized by modifying the local symmetry of the Eu³⁺ luminescent centers, thereby simultaneously improving red color purity and luminescence intensity. Specifically, the sample co-doped with Si⁴⁺ exhibited a 1.51-fold increase in luminescence intensity compared with the sample doped only with Eu³⁺, achieving chromaticity coordinates closest to those of standard red light. The sample co-doped with Gd³⁺ effectively sensitized the Eu³⁺ emission, with a 1.21-fold increase in luminescence intensity. Among the charge-compensated samples, Na⁺ doping produced the most significant improvement, increasing the luminescence intensity by 1.63 times. These co-doping strategies provide a reliable and versatile approach for enhancing the designability of the host lattice and the luminescent properties of KSrBP₂O₈:Eu³⁺ phosphors.