Improved color rendering and luminous efficacy in phosphor-converted white light-emitting diodes by use of dual-blue emitting active regions

Roya Mirhosseini,Jong Kyu Kim,Sameer Chhajed,Martin F Schubert,Jaehee Cho,E Fred Schubert

doi:10.1364/oe.17.010806

Abstract

Conventional white-light sources suffer from a fundamental trade-off between color rendering index and the luminous efficacy; increasing one generally comes at the expense of the other. We demonstrate through simulation that dual-wavelength blue-emitting active regions in phosphor-converted white light sources maximize the output luminous flux while significantly increasing the color rendering ability. Our results indicate that such improvements can be achieved over a broad range of correlated color temperatures.

Highlights

Semiconductor white light-emitting diodes (LEDs) have attracted a great deal of attention in solid-state lighting applications
White LEDs based on cerium-doped yttrium aluminum garnet (YAG:Ce) yellow phosphor have been used in various markets
While high color rendering ability is best attained by broad spectral distribution of the emission band throughout the visible region, the luminous efficacy of radiation (LER) of a source is highest for monochromatic light sources radiating at 555 nm

Summary

Introduction

Semiconductor white light-emitting diodes (LEDs) have attracted a great deal of attention in solid-state lighting applications Due to their potential for substantial energy savings, high efficiency, small size, and long lifetime, it has been projected that LEDs will broadly replace conventional incandescent and fluorescent lamps for general lighting in the future [1,2,3,4]. While high color rendering ability is best attained by broad spectral distribution of the emission band throughout the visible region, the LER of a source is highest for monochromatic light sources radiating at 555 nm. A key element associated with the future penetration of LEDs into the solid-state lighting market is LER, and this parameter is reduced with increasing LED quantity In this investigation, we analyze single-chip phosphor-converted white-light sources with single-wavelength blue-emitting active regions and dual-wavelength blue-emitting active regions. We show that dual-blue emitting active regions broaden the emission spectrum, and result in higher CRI values

LED-based white light source comprised of dual-color emitting active regions

Phosphor-converted white light source consisting of dual-blue emitting MQWs

Findings

Conclusion