High performance all phosphorescent white devices with single unit and two‐unit structures on a light outcoupling substrate were investigated. The single unit device showed high efficacy of 87 lm/W with a half decay lifetime of 10,000 h at the luminance of 1,000 cd/m2. The two‐unit device realized also high efficacy of 83 lm/W with much improved lifetime of over 100,000 h.

High‐performance all‐phosphorescent white devices on a light‐outcoupling substrate which comprised high‐index materials were studied. As a result of suitable optical and electrical design, the device showed an extremely high efficacy of 114 lm/W at 1,000 cd/m2 and 102 lm/W at 3,000 cd/m2.

A built-up outcoupling substrate with a micro-patterned high refractive index layer was developed in order to obtain both high efficiency and reliability for OLEDs. Light extraction efficiency of this substrate was about 47 %, and high efficacy of about 85 lm/W was achieved by the combination with an all phosphorescent white OLED.

Two-unit fluorescent/phosphorescent OLED system with a light outcoupling substrate gives high efficacy of over 55 lm/W and quite long half decay lifetime of over 150,000 h at 1,000 cd/m 2 . White OLED lighting panels of 8 cm x 8 cm for high luminance operation were fabricated and quite stable emission at 3,000 cd/m 2 was confirmed. All phosphorescent white OLEDs on the light outcoupling substrate show higher efficacy of about 70 lm/W and with a fairly good half decay lifetime of over 30,000 h. With a further voltage reduction and a high index spherical extractor, about 120 lm/W at 1,000 cd/m 2 has been achieved.

Non-radiation mode of OLED device was reduced by optimizing the distance between emissive layers to the metal cathode. Light distribution of OLED and optical properties of a light outcoupling substrate based on high refractive index microstructures were adjusted to achieve the better combination of the OLED device with the substrate. Those advanced optical design decreased non-radiative evanescent mode and waveguide mode, and realized a white OLED device with quite high light outcoupling efficiency of at least 56 % and outstandingly high efficacy of 133 lm/W at 1,000 cd/m 2 .