We have developed green phosphorescent organic light-emitting devices (OLEDs) with high quantum and luminous efficiencies. A green phosphorescent metal complex, fac-tris(2-phenylpyridine) iridium [Ir(ppy)3], was used as an emitter material. Wide-energy-gap materials with high triplet excited energy levels were used as host materials for Ir(ppy)3 and as carrier transport materials. Hole injection and electron injection from the electrodes were balanced by placing chemically doped layers at the interface between the electrodes and the organic layers. In addition, a highly reflective Ag cathode was employed as an anode, instead of a conventional Al cathode to enhance the reflectivity of the cathode metal. An optimized device exhibited an external quantum efficiency (EQE) of 27% (95 cd/A) and a high power efficiency of 97 lm/W at 100 cd/m2 at 3.1 V.
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.
White OLEDs with high efficiency (over 30 lm/W) and high quality emission characteristics (e.g., CRI of over 90, very small variation of chromaticity in different directions and chromaticity just on the black-body radiation curve) applicable to "Lighting" were realized by a two-unit structure with a fluorescent deep blue emissive unit and a phosphorescent green and red emissive unit. A new deposition source with a hot-wall and a rate controllable valve was developed. Thickness uniformity within +/-3% at high deposition rate of over 8 nm/s, high material utilization of over 70 %, and repeatable deposition rate controllability were confirmed.
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