Nobuhiro Ide

High-Efficiency Green Phosphorescent Organic Light-Emitting Devices with Chemically Doped Layers

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.

Organic light-emitting diode (OLED) and its application to lighting devices

Organic Light Emitting Diode (OLED) is an emerging technology as one of the strong candidates for next generation solid state lighting with various advantages such as thin flat shape, no UV emission and environmental benefits. At this moment, OLED still has a lot of issues to be solved before widely used as lighting devices. Nonetheless, typical properties of OLED, such as efficiency and lifetime, have been recently made great progress. For example, a green phosphorescent OLED with over 100 lm/W and a red fluorescent OLED with an estimated half decay time of over 100,000 h at 1,000 cd/m2 were reported. Large area, white OLEDs with long lifetime were also demonstrated. In this way, some of the issues are going to be steadily overcome. In this publication, we will present a phosphorescent white OLED with a high luminous efficiency of 46 lm/W and an external quantum efficiency of 20.6 percent observed at 100 cd/m2. This device achieves a luminous efficiency of 62.8 lm/W with a light-outcoupling film attached on the glass substrate. This is one of the highest values so far reported for white OLEDs. And we will also show a color-tunable stacked OLED with improved emission characteristics. This device minimizes a viewing angle dependence of the emission spectra and has color tunability from white to reddish-white. These technologies will be applied to OLED lighting.

High‐performance white OLEDs with high color‐rendering index for next‐generation solid‐state lighting

Abstract— Several white-OLED structures with a high color-rendering index (CRI) were investigated for lighting applications. A two-unit fluorescent/phosphorescent hybrid white OLED achieved an excellent CRI of 95, high luminous efficacy of 37 lm/W, and long lifetime of over 40,000 hours at 1000 cd/m2. White-OLED lighting panels of 8 × 8 cm for high-luminance operation were fabricated, and a stable emission at 3000 cd/m2 was confirmed. Quite a small variation in chromaticity in a different directions was achieved by using an optimized optical device structure. With a light-outcoupling substrate, a higher efficacy of 56 lm/W, high CRI of 91, and longer half-decay lifetime of over 150,000 hours at 1000 cd/m2 was achieved. All-phosphorescent white OLEDs placed on the light-outcoupling substrate show a high CRI of 85 and higher efficacy of 65 lm/W with a fairly good half-decay lifetime of over 30,000 hours. With a further voltage reduction and a high-index spherical extractor, 128 lm/W at 1000 cd/m2 has been achieved.

White OLED devices and processes for lighting applications

In these days, the basic performances of white OLEDs are dramatically improved and application of OLEDs to Lighting is expected to be true in the near future. We have developed various technologies for OLED lighting with the aid of the Japanese governmental project, High-efficiency lighting based on the organic light-emitting mechanism. In this project, a white OLED with high efficiency (37 lm/W) and high quality emission characteristics (CRI of 95 with a small variation of chromaticity in different directions and chromaticity just on the black-body radiation curve) applicable to Lighting was realized by a two-unit structure with a fluorescent deep blue emissive unit and a phosphorescent green and red emissive unit. Half-decay lifetime of this white OLED at 1,000 cd/m2 was over 40,000 h. A heat radiative, thin encapsulation structure (less than 1 mm) realized a very stable emission at high luminance of over 3,000 cd/m2. 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.

72.1: Invited Paper: High Performance White OLEDs for Next Generation Solid State Lightings

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/m2. White OLED lighting panels of 8 cm × 8 cm for high luminance operation were fabricated and quite stable emission at 3,000 cd/m2 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/Wat 1,000 cd/m2 has been achieved.

66.4: Invited Paper: High-Quality White OLEDs and Resource Saving Fabrication Processes for Lighting Application

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.