Bidirectional energy transfer in yellow-emitting Gd2WTiO8:Er3+,Sm3+ phosphors for white and NIR LEDs applications

• Published in: Ceramics international 2024-04, Vol.50 (8), p.13770-13781
• Main Authors: Hao, Run, Yang, Xiongfeng, Liang, Zhiping, Sheng, Zhixin, Fan, Xing, Su, Liumei, Cai, Gemei
• Format: Article
• Language: English
• Subjects: Bidirectional energy transfer; LEDs applications; Luminous properties; Phosphors: solid state reaction
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2024.01.291

Energy transfer between rare earth ions is a well-established strategy for achieving controlled and tunable emission in phosphors. Previous researches have reported tunable photoluminescence in Er3+ and Sm3+ co-doped phosphors by altering their concentration ratio. However, whether there is energy transfer between Er3+ and Sm3+ is still controversial. Hence, it is of great significant to reveal the underlying mechanism of energy transfer between Er3+ and Sm3+, which is conducive to the development of rare-earth activated phosphors. In this work, we employ the scheelite compound of Gd2WTiO8 as the host, Er3+ and Sm3+ as the activators to prepare color-tunable Gd2WTiO8:Er3+,Sm3+ phosphors and comprehensively study the energy transfer process between Er3+ and Sm3+. Though analysis of photoluminescence excitation, emission spectra, and decay curves, a bidirectional energy transfer process involving four cross-relaxation events between Er3+ and Sm3+ is uncovered. Due to this bidirectional energy transfer, Er3+ and Sm3+ mutually quench each other's luminescence. Excitation peaks of Sm3+ are specifically quenched at 378, 489, and 520 nm, ascribed to the distinct differences in absorption and energy transfer efficiency between Er3+ and Sm3+. Tunable emission from green to orange-red is obtained in Gd2WTiO8:Er3+,Sm3+ phosphors by adjusting the co-doped concentration of Er3+ and Sm3+. The phosphor has excellent thermal stability, retaining 82.33 % of its integral intensity for visible light emission at 423 K compared to room temperature. A phosphor-converted light-emitting diode (pc-LED) using Gd2WTiO8:Er3+,Sm3+ as a yellow-emitting component has been fabricated. This white pc-LED achieves a color rendering index of 87.5 for lighting and emits infrared emission for night vision applications. This study will offer crucial backing in the advancement of phosphors doped with rare earth elements. [Display omitted] •Bidirectional energy transfer involving four cross-relaxation processes between Er3+ and Sm3+ is elucidated.•Effects of bidirectional energy transfer on emission quenching, and thermal emission of Gd2WTiO8:Er3+,Sm3+ are studied.•Gd2WTiO8:Er3+,Sm3+ exhibit tunable emission, excellent thermal and chemical stability, promising for pc-LEDs application.•A white pc-LED using Gd2WTiO8:Er3+,Sm3+ as a yellow component is fabricated for lighting and night-vision applications.