Extracting Light from Polymer Light‐Emitting Diodes Using Stamped Bragg Gratings

In this paper, we describe a method for increasing the external efficiency of polymer light-emitting diodes (LEDs) by coupling out waveguided light with Bragg gratings. We numerically model the waveguide modes in a typical LED structure and demonstrate how optimizing layer thicknesses and reducing waveguide absorption can enhance the grating outcoupling. The gratings were created by a soft-lithography technique that minimizes changes to the conventional LED structure. Using one-dimensional and two-dimensional gratings, we were able to increase the forward-directed emission by 47 % and 70 %, respectively, and the external quantum efficiency by 15 % and 25 %.