Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition

Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials. The discovery of cyan-emitting (470–500 nm) phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light. Na 0.5 K 0.5 Li 3 SiO 4 :Eu 2+ (NKLSO:Eu 2+ ) phosphor was developed with impressive properties, providing cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C. The ultra-narrow-band cyan emission results from the high-symmetry cation sites, leading to almost ideal cubic coordination for UCr 4 C 4 -type compounds. NKLSO:Eu 2+ phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled, and the color-rendering index can be enhanced from 86 to 95.2, suggesting great applications in full-spectrum white LEDs. Lighting: Shining in the cyan valley Luminescent crystals that efficiently emit light in the narrow cyan color wavelength range, from 470 to 500 nanometers, could be used to fill a gap or “valley” in light-emitting diodes (LEDs) intended to mimic the full spectrum of daylight. There is great interest in developing more efficient and cost-effective full daylight spectrum LED lighting sources. These can create more natural indoor lighting conditions that are also believed to be more beneficial for health. Researchers in China and Russia, led by Zhiguo Xia at the University of Science and Technology Beijing, developed a suitable inorganic crystalline compound showing narrow cyan emission, with the formula Na 0.5 K 0.5 Li 3 SiO 4 :Eu 2+ . The many possible applications include LEDs for daylight spectrum lamps used to treat the low mood and depression associated with Seasonal Affective Disorder (SAD).