A novel red-emitting phosphor K2MgGeO4:Eu3+ for WLEDs: zero-thermal quenching induced by heterovalent substitution. Issue 42 (12th October 2022)

• Record Type: Journal Article
• Authors: Bai, Yuxing; Jia, Zhenwei; Gao, Jingyi; Wu, Li; Kong, Yongfa; Zhang, Yi; Xu, Jingjun
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 42(2022)
• Page Start: 15957
• Page End: 15966
• Publication Date: 2022-10-12
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc03500f
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The heterovalent substitution of Eu 3+ ions for K + sites introduces quantitative VK and Oi in the host lattice, which yields high IQE, induces zero-TQ, and promotes the fabrication of WLED with high R a . Abstract : The popularity of high-power LEDs drives mounting demands for thermal stability of luminescent materials, of which the satisfactory performance via subjective structural design is still a great challenge. Herein, we propose an effective defect-modulated strategy to fulfill the excellent performances of red-emitting phosphors K2 MgGeO4 :Eu 3+, including high quantum efficiency (94.98%) and zero-thermal quenching. The distribution of lattice defects was studied in detail through experimental investigations and first principles calculations. It is demonstrated that the heterovalent substitution process (Eu 3+ –K + ) creates quantitative potassium vacancies, and interstitial oxygen atoms are also observed in the host. Those defects form trap levels, and most of them are in the deep position of the forbidden band ( E = 1.30 eV). Under the stimulus of thermal activation, the electrons detrapped from the defect levels return to the luminescent center to realize radiative recombination and compensate for the energy loss caused by non-radiative transition at high temperatures. Correspondingly, a defect-assisted model was constructed to depict the whole photoluminescence process. Finally, a fabricated WLED with a good color rendering index ( R a = 91.7) manifests the prominent application potential of the as-prepared sample. This study not only deepens the understanding of the response mechanism between optical properties and defects, but also broadens the channel to explore novel functional materials with good thermal stability.