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

Abstract

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.

Highly Efficient Organic Blue‐and White‐Light‐Emitting Devices Having a Carrier‐ and Exciton‐Confining Structure for Reduced Efficiency Roll‐Off

“…Utilization of phosphorescent emitters may solve the problem of achieving efficient emissions, and several white OLEDs with a single or multiple emissive layers have been reported. [7][8][9]13,14] As one of the three primary colors, the corresponding blue-light-emitting devices exhibit maximum external quantum efficiencies of (12 AE 1)% [7] and (10.8 AE 0.6)%, [9] much lower than those reported for green-light-emitting devices, [17][18][19][20] and thus limiting the efficiency of white OLEDs.…”

“…Second, a double-emission layer and a bipolar host were employed to broaden the exciton-formation zone, and thus reduce efficiency roll-off compared to conventional single-emission-layer OLEDs. [17][18][19] Third, HTMs and ETMs with wide energy gaps and high-lying LUMO and lowlying HOMO energy levels, respectively, were employed adjacent to the emissive layers to confine carriers and triplet excitons. Blue OLEDs were fabricated with a commercially available blue-phosphorescence emitter based on FIrpic.…”

Rubidium-Carbonate-Doped 4,7-Diphenyl-1,10-phenanthroline Electron Transporting Layer for High-Efficiency p-i-n Organic Light Emitting Diodes

“…This fact suggests that heavy doping may cause a significant diffusion of the dopant into the undoped Bphen layer, indicating that the dopant can diffuse into an EML of real OLEDs to degrade the device efficiency and stability if the doped layer is in contact with an EML. 6,18 Based on the J-V characteristics, we selected 15% doping ratio of Rb 2 CO 3 in the Bphen layer as the optimum condition of n-ETL. The J-V characteristics can be further controlled by the adjustment of thicknesses of the doped and undoped Bphen layer.…”

Pyridoindole Derivative as Electron Transporting Host Material for Efficient Deep‐blue Phosphorescent Organic Light‐emitting Diodes

“…[ 4 ] By using phosphorescent dyes, red and green POLEDs with higher power effi ciencies have already been reported. [4][5][6] Compared to the higher power effi ciency of red and green POLEDs previously reported, the power effi ciency of blue POLEDs is poor, especially in deep-blue POLEDs. Blue light is not only one of the three primary colors from which white light can be obtained, [ 7 ] but it can also generate other low-energy emissions, such as green and red, by using a color-change medium.…”