Li substituent tuning of LED phosphors with enhanced efficiency, tunable photoluminescence, and improved thermal stability

Zhao, Ming; Xia, Zhiguo; Huang, Xiaoxiao; Ning, Lixin; Gautier, Romain; Molokeev, Maxim S.; Zhou, Yayun; Chuang, Yu-Chun; Zhang, Qinyuan; Liu, Quanlin; Poeppelmeier, Kenneth R. Source: SCIENCE ADVANCES, 5 (1):10.1126/sciadv.aav0363 JAN 2019

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are currently revolutionizing the lighting industry. To advance the technology, phosphors with high efficiency, tunable photoluminescence, and high thermal stability are required. Here, we demonstrate that a simple lithium incorporation in NaAlSiO4:Eu system enables the simultaneous fulfillment of the three criteria. The Li substitution at Al sites beside Na sites in NaAlSiO4:Eu leads to an enhanced emission intensity/efficiency owing to an effective Eu3+ to Eu2+ reduction, an emission color tuning from yellow to green by tuning the occupation of different Eu sites, and an improvement of luminescence thermal stability as a result of the interplay with Li-related defects. A pc-WLED using the Li-codoped NaAlSiO4:Eu as a green component exhibits improved performance. The phosphors with multiple activator sites can facilitate the positive synergistic effect on luminescence properties.