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Keywords:

  • Bragg gratings;
  • Light extraction;
  • Light-emitting diodes, organic;
  • Soft lithography

Abstract

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 %.