Successful fabrication of white light emitting diodes by using extremely high external quantum efficiency blue chips

摘要

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 Im/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 highrnpower 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_v,at 350 mA were 675 mA, 325 mW, and 236 mW, respectively. φ_v of the green LED was 128 lm at 350 mA.