Improve OLED Light Outcoupling Efficiency by Eliminating Waveguide Mode using Ultrathin Metal Electrode

Abstract

Extracting light from the waveguide mode in organic light-emitting diodes (OLED) is most challenging as such optical mode is intrinsic in traditional OLED due to materials and layered structure used in the device. This work intends to address the root cause of the light trapping problem. We systematically analyzed OLEDs made with an ultrathin Ag anode and found that waveguide modes can be completely eliminated by designing a structure to below the cutoff thickness of waveguide modes. We also experimentally verified the waveguide mode elimination in organic waveguides. In principle such a scheme can be extended to tandem cells, and in making transparent OLED. A further benefit is the ductility of the ultrathin metal allows foldable OLED to be realized.