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 et al. · Sci Adv · 2019

basic_science · Level V

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Abstract

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 NaAlSiO<sub>4</sub>:Eu system enables the simultaneous fulfillment of the three criteria. The Li substitution at Al sites beside Na sites in NaAlSiO<sub>4</sub>:Eu leads to an enhanced emission intensity/efficiency owing to an effective Eu<sup>3+</sup> to Eu<sup>2+</sup> 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 NaAlSiO<sub>4</sub>:Eu as a green component exhibits improved performance. The phosphors with multiple activator sites can facilitate the positive synergistic effect on luminescence properties.