Nano-Coprecipitation Route Synthesis of Highly-Efficient Submicron (Sr,Ba)2SiO4:Eu2+ Phosphors with Enhanced Thermal Stability for MicroLED Color Conversion

As the size of MicroLED chips shrinks below 50 μm, the emergence of quantum dots (QDs)-based color conversion with narrow-band emission and nanoscale size properties has become one of the powerful full-color solutions for MicroLED displays. However, the stability and toxicity of quantum dots limit their application in full-color MicroLEDs. The phosphor-based conversion has the prominent features of high thermal and chemical stability relative to those of QD-based conversion. Nevertheless, the particle size of phosphor prepared by a traditional high-temperature solid-state reaction (SSR) is equivalent to or even larger than that of the MicroLED chip. In this work, we propose a strategy to prepare (Sr,Ba)2SiO4:0.03Eu2+ (SBSO:0.03Eu2+) submicron phosphors via a nano-coprecipitation method (NCP) using nanoSi3N4 as the Si source materials, which enables the particle size to be reduced while maintaining the luminescence efficiency. The optimized SBSO:0.03Eu2+ has an average size of less than 2 μm, showing a narrow band green emission centered at 522 nm, with a full width at half-maximum of 60 nm and an external quantum efficiency of 40.2%. At 150 °C, its thermal stability is greatly enhanced to 80.2% of the emission at room temperature. Further, the mechanism for defect compensation thermal stability is investigated. By employing it as a green emitter, we fabricate a high-performance white LED device (WLED) with a wide color gamut of 86.7% NTSC. This work for the preparation of high-brightness and thermal stability enhancement SBSO:0.03Eu2+ phosphor not only provides a facile method but also helps to provide an alternative green fluorescent material for the realization of full color MicroLED.