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

Abstract

A codoping strategy is advanced to improve luminescence efficiency, emission color tuning, and thermal stability of LED phosphors.

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