Synthesis of red-emitting Mn4+ doped metal-oxide solutions for improving heat dissipation, color rendering and quantum efficiency of nanowire InGaN-LED (>100 micrometers in size).

- Theoretical results: The possibility of combining nanowire-InGaN blue-LEDs with down-converted nanophosphor has been studied. Red-emitting Al2O3:Mn4+,Mg2+ (~32 nm) nanosheets and Mg2(Ti/Si)O4:Mn4+ nanoparticles (~14 nm) are preapred. The calcined phosphors at 500-1300 °C exhibited high emission intensity, low thermal quenching and excellent water resistance. A warm white LED with a high colour rendering index (CRI ~95) and a low CCT ~5000-3000 K is fabricated using the nanophosphors and a nanowire–InGaN-based LED emitting blue and yellow light. Moreover, the current-voltage characteristic of the nanowire LEDs could be improved using Al2O3:Mn4+,Mg2+ nanophosphors which is attributed to the increased heat dissipation in the nanowire LEDs. This study demonstrates a promising approach for improving the color reproducibility of WLEDs that can be suitable for practical applications that may include micro-displays, and AR/VR devices.
- Applied results: The enhanced demand for smart optoelctronic devices is one of significant factor driving the smart display market growth. The research results are high-efficient and cost-effective mini/microLED products based on nanowire-InGaN and red-emitting nanomaterials. The global smart-display market is growing very fast and is expected to reach millions of USD by 2025, so mini/microLED will be a potential and high-tech product that is promoting economic development.

Since the invention of high-brightness InGaN-blue light-emitting diode (LEDs), most WLEDs have been fabricated using a combination of blue-LED chips and yellow-emitting phosphors. Interest to develop high quantum yield (QY) nanostructure emitters is considerable to extend light-emitting diodes (LED) usage to other types of applications, such as wearable displays, curved or flexible television screens, biomedical devices and future lighting sources. Display technology using LEDs in size of 10-300 µm2 (mini/microLED display) with high CRI, ultra-wide viewing angle, fast response time, high brightness and impressive luminous efficiency, will be the next-generation display of LCD and OLED screens.
The cost-effective and high-color quality μWLEDs with a hybrid structure of blue-yellow InGaN/AlGaN nanowire LED combining with red-emitting nanomaterials Al2O3:Mn4+,Mg2+ and Mg2(Ti/Si)O4:Mn4+ have been fabricated. The WLED shows a stable warm white emission with high CRI of ~95 và CCT ~5000-3000 K. Moreover, the hybrid WLEDs exhibits improved current-voltage characteristics which are attributed to the increased heat dissipation in the nanowire LEDs.

- Scientific papers in referred journals (list):
H.-D. Nguyen el al., Highly stable white light emission from III-nitride nanowire LEDs utilizing nanostructured alumina doped Mn4+ and Mg2+, 8, 2501-2507, 2023.
H.-D. Nguyen el al., High-efficiency InGaN blue LEDs with reduced positive sheet polarization, Applied Optics, 61, 4967-4970, 2022.
H.-D. Nguyen el al., Positron annihilation study of lattice defects and nanoporous structures in Mn4+ doped K2SiF6 nanophosphors exhibiting high quantum yield, Radiation Physics and Chemistry, 195, 110064, 2022.
H.-D. Nguyen el al., Fabrication of ultra‐thin alumina membranes utilizing waste aluminum cans, Vietnam Journal of Chemistry, 60, 84-91, 2022.
- Technological products (describe in details: technical characteristics, place):
White powder Al2O3:Mn4+,Mg2+ with average particle size ~32 nm and Al2O3:Mn4+,Mg2+ white powder with average particle size ~190 nm show red emission at 678 nm at room temperature.
Light-yellow powder Mg2TiO4:Mn4+ with average particle size ~63 nm and Mg2(Ti/Si)O4:Mn4+ with average particle size ~14 nm show red emission at 665 nm at room temperature.
LED in size of 300´300 mm2 including nanowire-InGaN and Al2O3:Mn4+,Mg2+ or Mg2TiO4:Mn4+ show warm white-light emission with CRI ~95, correlated color temperature (CCT) ~5000-3000 K and good current-voltage (I-V) characteristic