4 years ago

Giant Enhancement of Luminescence from Phosphors through Oxygen-Vacancy-Mediated Chemical Pressure Relaxation

Giant Enhancement of Luminescence from Phosphors through Oxygen-Vacancy-Mediated Chemical Pressure Relaxation
Li-Rong Zheng, Jing-Shan Hou, Chong-Geng Ma, Jia-Yue Xu, Kai Zhang, Shao-Qiang Guo, Yang Zhou, Yong-Zheng Fang, Bo-Mei Liu, Hong-Tao Sun, Jun-Ying Zhang
Relaxing chemical pressure in phosphors with large-size-mismatched dopants, aiming at attaining high-efficiency luminescence and a higher dopant concentration, remains a challenging subject of continuous research effort. Originally seen as undesirable and detrimental to the performance of luminescent systems, this study demonstrates that the formation of a tiny amount of oxygen vacancies favors chemical pressure relaxation (CPR), resulting in topotactic transformation of poorly luminescent parent phases to highly luminescent cousins, as exemplified by a model system of Bi3+-doped Lu2O3. The integration of experimental observations with theoretical calculations reveals that the emergence of oxygen vacancies adjacent to Bi3+ can expand its size of coordination geometry, thus releasing the chemical pressure and significantly influencing the emission characteristics. Importantly, it is illustrated that the concept of oxygen-vacancy-mediated CPR is sufficiently general to allow the optimization of luminescence from other classes of foreign-ion-doped phosphors plagued by size mismatch. It is suggested that this concept can be applied to an array of optical materials in various forms, and also provides unique opportunities for tuning other properties of functional materials that are sensitive to local coordination environments of dopants. Oxygen-vacancy-mediated chemical pressure relaxation is proposed and confirmed as a universal strategy to significantly enhance photoluminescence from phosphors with large-size-mismatched dopants. Experimental and theoretical results suggest that topotactic creation of oxygen vacancies favors the modification of local environment of dopant due to the expansion of coordination geometry, thus leading to the conversion of dark emitters into bright cousins.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adom.201700448

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