Recent progress of high efficiency white LEDs

✍ Scribed by Narukawa, Yukio ;Narita, Junya ;Sakamoto, Takahiko ;Yamada, Takao ;Narimatsu, Hiroki ;Sano, Masahiko ;Mukai, Takashi

• Book ID: 105364245
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 266 KB
• Volume: 204
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200674782

✦ Synopsis

Abstract

We fabricated three types of white light emitting diodes (LEDs). The first is the white LED, which has a high general color rendering index (R~a~) of 97 and CRI‐No. 9 of 96. The CRI‐No. 9 denotes the color reproduction in the red region. These values are higher than those of a tri‐phosphor fluorescent lamp (R~a~ = 85 and CRI‐No. 9 = 8). The second is the high efficiency white LED fabricated from the small‐size high efficiency blue LED chip. The output power (P~o~), the external quantum efficiency (η~ex~) and wall‐plug efficiency (WPE) of the small‐size blue LED were 35.0 mW, 63.3% and 56.3%, respectively, at a forward‐bias current of 20 mA. The luminous flux (Φ), luminous efficiency (η~L~) and WPE of the second white LED are 8.6 lm, 138 lm/W and 41.7%, respectively. The luminous efficiency is 1.5 times greater than that of a tri‐phosphor fluorescent lamp (90 lm/W). The third is the high power white LED fabricated from the larger‐size blue LED chip. Po, η~ex~ and W.P.E. are 458 mW, 47.2% and 39.7%, respectively, at 350 mA. Φ, η~L~ and WPE of the third white LED are 106 lm, 91.7 lm/W and 27.7% at 350 mA, respectively. Moreover, Φ of 247 lm and 402 lm at 1 A and 2 A are obtained, respectively. Φ at 2 A is equivalent to the total flux of a 30 W incandescent lamp. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)