Superior Illuminant Characteristics of Color Rendering and Luminous Efficacy in Multilayered Phosphor Conversion White Light Sources Excited by Near-Ultraviolet Light-Emitting Diodes

We have demonstrated that a phosphor conversion (PC) white light-emitting diode (LED) light source composed of multi-layered (ML) red, green, and blue (RGB) phosphors with a near-ultraviolet (n-UV) LED as an excitation source shows excellent color rendering. luminous efficacy, and luminous flux The ML-phosphor structure consists of vertically stacked layers and could significantly reduce cascade excitation loss compared with a mixed RGB PC white LED. A high luminous efficacy of 82 lm/W with a high color-rendering index (CRI) of over 90 was achieved using a ML-RGB PC white LED. The ML-RGB stricture also enables a white LED with an ultrahigh CRI of 99 and a high luminous efficacy comparable to that of a high CRI fluorescent lamp We have also fabricated a high-power ML-PC white LED excited by an n-UV LED In one package. a high luminous flux of 61 lm at a high CRI of 94 was obtained (C) 2009 The Japan Society of Applied Physics