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Successful fabrication of white light emitting diodes by using extremely high external quantum efficiency blue chips
Author(s) -
Narukawa Yukio,
Sano Masahiko,
Sakamoto Takahiko,
Yamada Takao,
Mukai Takashi
Publication year - 2008
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200778428
Subject(s) - luminous flux , quantum efficiency , phosphor , luminous efficacy , light emitting diode , incandescent light bulb , materials science , diode , optoelectronics , optics , fabrication , green light , physics , blue light , layer (electronics) , light source , nanotechnology , medicine , alternative medicine , pathology
We fabricated three types of high luminous efficiency white light emitting diodes (LEDs). The first is the white LED, which had a high luminous efficiency ( η L ) of 161 lm/W with the high luminous flux ( ϕ v ) of 9.89 lm at a forwardbias current of 20 mA. The blue LED had a high power ( ϕ e ) of 42.2 mW and high external quantum efficiency ( η ex ) of 75.5%. The second is the high luminous efficiency white LED with a low voltage ( V f ) of 2.80 V, which was almost equal to the theoretical limit. η L and wall‐plug efficiency (WPE) is 169 lm/W and 50.8%, respectively, at 20 mA. They are approximately twice higher than those of a tri‐phosphor fluorescent lamp (90 lm/W and 25%). The third is the high power white LED fabricated from the high power blue LED with high ϕ e of 651 mW at 350 mA. ϕ v , η L and WPE of the high power white LED are 145 lm, 134 lm/W and 39.6% at 350 mA, respectively. Moreover, at 1 A, ϕ v and η L were 361 lm and 97 lm/W, respectively. Thus ϕ v is equivalent to that of a 30 W‐class incandescent lamp. And, η L is slightly higher than that of a tri‐phosphor fluorescent lamp. Moreover, we fabricated the high power near ultra‐violet, bluish‐green and green LEDs, whose ϕ e at 350 mA were 675 mA, 325 mW, and 236 mW, respectively. ϕ v of the green LED was 128 lm at 350 mA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)