Design of highly efficient phosphor-converted white light-emitting diodes with color rendering indices (R-1 - R-15) >= 95 for artificial lighting

Abstract

Phosphor-converted white light-emitting diodes (pc-WLEDs) are excellent energy-efficient light sources for artificial lighting applications. One goal of artificial lighting is to make objects/images look natural - as they look under the sunlight. The ability of a light source to accurately render the natural color of an object is gauged by the parameter - color rendering index (CRI). A conventional pc-WLED has an average CRI similar to 80, which is very low for accurate color reproduction. To utilize the pc-WLEDs for artificial lighting applications, all the CRI points (R-1 - R-15) should be above 95. However, there is a tradeoff between CRI and luminous efficacy (LER), and it is challenging to increase both CRI and LER. Herein we propose a novel LED package (PKG) design to achieve CRI points >= 95 and efficiency similar to 100 lm/W by introducing two blue LEDs and a UV LED in combination with green and red phosphors. The silicone encapsulant, the current through the LEDs, and the green/red phosphor ratio were optimized for achieving high CRI and LER. Our re-designed LED PKG will find applications in stadium lighting as well as for ultra-high-definition television production where high CRI points are required for the artificial light source.