HF‐Free Microwave‐Assisted Synthesis of Nano‐Micro‐Sized K₂SiF₆:Mn⁴⁺ for MicroLED Color Conversion

Abstract

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, K2SiF6: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.

Synthesis and photoluminescence properties of high-quality reddish-orange emitting Ca4Nb2O9:Eu3+ phosphors for WLEDs and anti-counterfeiting

“…Interestingly, the full width at half maximum (FWHM) of the Ca 4 Nb 2 O 9 :0.15Eu 3+ phosphor was approximately 8 nm, which was much narrower than those of typical red-emitting phosphors used in displays such as Sr 2 Si 5 N 8 :Eu 2+ (FWHM = 86 nm), CaAlSiN 3 :Eu 2+ (FWHM = 94 nm), and KSF:Mn 4+ (FWHM = 30 nm). 53–55 This performance is attributed to the hypersensitive 5 D 0 → 7 F 2 transition. 56…”

Unusual red luminescence and super thermal stability of a new narrow-band emission phosphor for backlight display application

“…6 Although the phosphors SiAlON:Eu 2+ and K 2 SiF 6 :Mn 4+ both exhibit narrow-band emission, the nitride or fluoride host materials SiAlON and K 2 SiF 6 are difficult to synthesize and have poor chemical stability. 7,8 The excessively sharp emission of red phosphors such as Y 2 O 3 :Eu 3+ and K 2 SiF 6 :Mn 4+ hinder their application prospects. Thus, it is urgent to develop new narrow-band emission phosphors based on oxygenated host materials to obtain the advantages of a broad band gap, structural diversity, simple preparation methods and good chemical stability.…”

Bright white light emission from lanthanide oxide LaGdO3 for LED lighting by Bi3+ to Eu3+ energy transfer

“…Also, the composition of the matrix should be as simple as possible to meet the developing demand for small-sized phosphors for mini- or micro-LEDs, because matrixes with simple compositions are more easy to synthesize as small particles. 12,13…”