Suppression of Eu²⁺ Luminescence Loss

Abstract Owing to the intriguing luminescence properties, Eu²⁺ is one of the most desirable activators for next‐generation lighting devices. Yet the application of Eu²⁺‐doped phosphors is limited because of the drawback of inferior luminescence efficiency. Understanding of this issue is generally from perspectives of frame structural rigidity and electronic band structure, while the lack of persuasiveness of this paradigm is frequently noticed. Herein, the analysis is conducted from a fresh view to investigate the outstanding luminescence properties of Eu²⁺‐doped SrMgP₂O₇ owning the narrow‐band emission and near‐unity quantum yield. The structural rigidity of materials is elaborately evaluated, and the influence of ionization on the luminescence efficiency of material is carefully discussed. Efforts are also made to assess the effect of vibronic coupling on 4f−5d transition of Eu²⁺ and clarify the excitation energy transfer route by using X‐ray spectroscopy. Based on these discussions, the synergy of weak electron−vibration interaction and inactive ionization causes the suppression of Eu²⁺ luminescence loss, which is associated with highly rigid local coordination and strong binding of Eu²⁺ to its valence electrons in the system, respectively. This work provides insight into the luminescence mechanism of Eu²⁺, which benefits the exploration of novel phosphors with superior luminescence features.