Substantial Improvement of Color-Rendering Properties of Conventional White LEDs Using Remote-Type Red Quantum-Dot Caps

Abstract

A new type of remote red quantum-dot (QD) component was designed and fabricated to improve the color-rendering properties of conventional white LED (light-emitting diode) lightings. Based on an optical simulation, the rectangular cavity-type QD cap was designed with an opening window on the top surface. Red QD caps were fabricated using a typical injection molding technique and CdSe/ZnS QDs with a core/shell structure whose average size was ~6 nm. Red QD caps were applied to conventional 6-inch, 15-W white LED downlighting consisting of 72 LEDs arrayed concentrically. The red QD caps placed over white LEDs enhanced the red components in the long-wavelength range resulting in the increase of the color rendering index (CRI) from 82.9 to 94.5. The correlated color temperature was tuned easily in a wide range by adopting various configurations consisting of different QD caps. The spatial and angular homogeneities were secured on the emitting area because QD caps placed over the white LEDs did not exhibit any substantial optical path length difference. The present study demonstrates that adopting QD caps in conventional LED lightings provides a flexible and efficient method to realize a high color-rendering property and to adjust correlated color temperature appropriately for a specific application.

Color Rendering Index over 95 Achieved by Using Light Recycling Process Based on Hybrid Remote-Type Red Quantum-Dot Components Applied to Conventional LED Lighting Devices

“…Two remote red QD components were used: QD films and QD caps. The detailed fabrication process of the red QD films and QD caps has been reported before [ 39 , 41 , 42 ]. QD particles were mixed with irregular hollow silica (SG-HS40, Sukgyung AT Co., Ansan, Korea) of a size of ~40 ± 10 nm for dispersion.…”

“…At the initial stage, a QD concentration of 5.0 wt% was also prepared and tested in the lighting. The QD caps (QD concentration of 5 wt%) with the outer dimensions of 7.4 × 5.3 × 4.2 mm 3 and two lateral thicknesses of 0.9 and 1.8 mm were fabricated by using a UV curing agent (Miracle UV Resin) and red QDs according to the method described in [ 41 ]. The upper surface has a rectangular opening with an area of 5.6 × 1.7 mm 2 .…”

“…In our previous studies, either QD films or QD caps have been incorporated into conventional white LED lighting devices to improve the color-rendering properties [ 39 , 40 , 41 , 42 ]. In particular, the position of each QD component has been optimized by evaluating the optical characteristics of the white LEDs.…”

Structural Optimization of Vertically-Stacked White LEDs with a Yellow Phosphor Plate and a Red Quantum-Dot Film

“…For example, QD particles were incorporated in polymers or glasses as composites in various forms [34][35][36][37][38][39][40][41][42][43][44][45][46][47]. In addition, large-size QD films or QD caps could be developed for practical applications in displays and illumination [48][49][50]. These designs could improve the efficiency, colorrendering characteristics, and long-term stability of W-LEDs successfully.…”