23.3: Distinguished Paper: High-Efficiency Tandem Blue OLEDs

Abstract

Tandem blue OLEDs using different fluorescent dopants have achieved 20 cd/A (CIEx,y = 0.14, 0.18) and 38 cd/A (CIEx,y = 0.15, 0.42) with external quantum efficiencies higher than 11%. The tandem blue OLEDs include two electroluminescent units that are connected in series with an organic intermediate connector. At an initial brightness of 1,000 cd/m2, the drive voltage of the devices can be less than 6.5 V, and the operational lifetime (T 50) of the devices is estimated to be greater than 10,000 h. We also demonstrate that the selection of electron‐transporting material and an intermediate connector have significant impact on the electroluminescence performance of the tandem blue OLEDs.

36.2: High‐Performing Organic Electron‐Injecting and Transporting Layers for Red, Green, Blue, and White OLED Devices

“…At this concentration, the drive voltage is 5.4 V, and the luminance efficiency is 5.44 cd/A. Similar observations have been reported earlier with the mixture of Alq 3 and Bphen, which exhibits concentration dependent electron transporting properties [4]. It has been speculated that the Alq 3 :Bphen mixture is more conducting with an increased ability to supply electrons to the LEL.…”

“…The full potential of this new mixed ETL in combination with the new class of EIMs can also be seen in Table 2. The data in Table 2 is a summary of the performance characteristics of blue devices incorporating the blue dopant OP31 and BH3 host [3]. With LiF the luminance efficiency is a respectable 12.5 cd/A and a drive voltage of 7.2 V. However, upon simply replacing the LiF with EK-ET703, the luminance efficiency increases to 21.1 cd/A and the drive voltage drops to 4.2 V, a remarkable enhancement in performance.…”

“…In this paper, we report the development of a new class of organic electron-injecting materials (EIMs) that, in combination with a previously described ETL [3] and a newly developed ETL, simultaneously reduce the device drive voltage while increasing the luminance and quantum efficiency of R, G, B and white devices. The performances of these devices with the new materials surpass our previously described best positions [1].…”