Indium-oxide thin films deposited by using an oxygen-ion-beam-assisted deposition technique for top-emitting organic light-emitting diodes

To fabricate a top-emitting organic light-emitting diode (TEOLED) with a high aperture ratio and high resolution, we deposited an n-type indium oxide (IO) as a transparent conducting electrode, by using oxygen-ion-beam-assisted deposition (IBAD), on a device of glass/ITO/NPB (60 nm)/Alq ₃ (60 nm)/LiF (1 nm)/Al (2 nm)/Ag (20 nm), and we investigated its characteristics. To minimize the damage to the organic layers and the oxidation of the Ag layer during the oxygen IBAD, we required a two-step processing of IBAD composed of argon IBAD followed by oxygen IBAD. By the two-step processing of the IO thin film deposition using IBAD, TEOLED devices having emission on both sides could be formed successfully with an external quantum efficiency of 0.47 % and a luminous efficiency of 0.22 Im/W at a luminance of about 100 Cd/m ². With this device, a maximum luminance of 12,500 Cd/m ² was obtained at the glass surface of the device. Even though the overall quantum efficiency of this device was very low, we believe that it can be improved by optimizing oxygen-ion-beam processing used to fabricate the IO thin films and by optimizing the thickness of the semitransparent conducting protecting layer to reduce ion-beam-induced damage.