White LEDs for solid state lighting

Abstract

We show recent results of GaN based LEDs, the high efficiency blue LED, the high efficacy white LED, the high color rendering LED, the warm white LED, and the high output power 365-nm UV LED. The output power and the external efficiency of the high efficiency blue LED at 20 mA were 19.3 mW and 35.8%, respectively. Moreover, the lifetime of the molded this lamp was improved. For the high efficacy white LED using this high efficiency blue LED, the correlated color temperature (CCT) and the luminous efficacy (ηL) at 20 mA were 5470 K and 61.4 lm/W, respectively. This luminous efficacy is close to that of a fluorescent lamp. When the high color rendering LED using new red phosphor and shorter-YAG was operated at 20 mA, the CCT, ηL and the general color rendering index (Ra) were 4670 K, 28.3 lm/W and 87.7, respectively. In particular, the red color reproduction was improved. For the warm white, the CCT, ηL and Ra at 20 mA were 2830 K, 18.9 lm/W and 87.5, respectively. It can be used as a replacement for incandescent bulbs. When the high output power 365-nm UV LED was operated at a forward bias direct current (DC) of 500 mA, Po and ηex were 210 mW and 12.4%, respectively.