Highly Efficient Phosphorescent Light-Emitting Diodes by Using an Electron-Transport Material with High Electron Affinity

Spin-coated polymer-based phosphorescent organic light-emitting diodes (PhOLEDs) were found to be substantially brighter and more efficient when 4,9-diphenylbisindenoanthorazoline (DADA) was used as an electron-transport material compared to widely used Alq 3 . Devices with fac -tris(2-phenylpyridine)iridium (Ir(ppy) 3 ) dispersed in poly( N -vinylcarbazole) as the emissive layer and DADA as the electron-transport layer showed a maximum brightness of 73 600 cd/m 2 and a maximum luminous efficiency of 48.1 cd/A at a brightness of 5640 cd/m 2 . The high electron affinity (3.67 eV) and electron mobility (3.1 × 10 −5 cm 2 /V·s) of DADA explain its effectiveness as an electron-transport material in PhOLEDs. These results demonstrate the use of an electron-transport material having a high electron affinity as a promising strategy for improving the charge injection and overall performance of PhOLEDs.