HF-Free Microwave-Assisted Synthesis of Nano-Micro-Sized K₂ SiF₆ :Mn⁴⁺ for MicroLED Color Conversion

Micro-light-emitting diodes (MicroLED) are considered to be the next generation of ideal display devices, with chip size requirements of less than 50 µm. To meet its micron-scale pixel size, submicron luminescent materials are needed. Mn⁴⁺ doped fluoride phosphor, K₂ SiF₆ :Mn⁴⁺ (KSFM) as a red luminescent material with excellent narrow-band emission sensitivity to human eyes, has great potential as a color conversion material for full-color MicroLED. However, it is difficult to obtain small-size KSFM efficiently by conventional synthesis methods. Here, a simple HF-free strategy for the rapid batch synthesis of nano-micro-sized KSFM based on a microwave-assisted method is reported. The synthesized KSFM shows uniform morphology, average particle size is less than 0.2 µm, and has 89.3% internal quantum efficiency under 455 nm excitation. It exhibits excellent thermal stability (97.4%@423 K of the integrated emission intensity at 298 K) and prominent moisture resistance (81.9% of its initial relative emission intensity after immersing in water for 30 min). By employing it as a red emitter, the authors fabricate high-performance white LEDs with high luminous efficacy of 116.1 lm W^-1 and wide color gamut of 130.4% NTSC. In addition, self-luminous red-emitting arrays with a pixel size of 20 × 40 µm are constructed by nanoimprinting as-synthesized KSFM.