Enhanced performance of tris-(8-hydroxyquinoline)aluminum-based organic light-emitting devices with LiF/Mg:Ag/Ag cathode

The device characteristics of organic light-emitting devices based on tris-(8-hydroxyqunoline) aluminum devices with LiF/Mg:Ag/Ag cathodes were investigated. The devices with Mg:Ag/Ag,LiF/Al and Al-only cathodes were also fabricated in the same run for comparison. Similar to the LiF/Al cathodes, the LiF/Mg:Ag/Ag cathode greatly improved the performance of the device over the Mg:Ag/Ag cathode. A LiF layer of 0.5 nm significantly enhanced the electron injection and resulted in lower turn-on voltage and increased device efficiency. The turn-on voltage of the device with 0.5 nm LiF as buffered layer is as low as 2.8 V. At injection current density of 20 mA/cm(2), the current efficiency and power efficiency of the device is 5.56 cd/A and 1.94 lm/W, respectively. Compared to the device with Mg: Ag/Ag only cathode, the turn-on voltage is 1.6 V lower, the current efficiency improved by 75 %, and power efficiency is almost double. The performance of the device is also much improved over the device with LiF/Al cathode. (C) 2005 Optical Society of America.