Inverted top-emitting organic light-emitting diodes using sputter-deposited anodes

Abstract

We demonstrate vacuum-sublimed topside-emitting inverted organic light-emitting diodes (IOLEDs) employing low-power radio-frequency magnetron sputter-deposited indium tin oxide (ITO) anodes. The device introduces a two-step sputtering sequence to reduce damage incurred by the sputtering process, paired with a buffer- and hole-transporting material Pentacene. Systematic optimization of the organic growth sequence focused on device performance characterized by current and luminous efficiencies, suggest the incorporation of rather thick Pentacene layers. The optimized thickness is obtained as a trade-off between light absorption and protective properties of Pentacene. The optically and electrically undoped organic multilayer devices capped with 90-nm ITO exhibit high current efficiencies of 3.9 cd/A at a raised luminance level of 1.500 cd/m2, combined with luminous efficiencies of 0.7 lm/W. The inverted configuration allows for integration of organic light-emitting diodes (OLEDs) with preferentially used n-channel field-effect transistors for driver backplanes in active matrix OLED displays.