Light extraction of trapped optical modes in polymer light-emitting diodes with nanoimprinted double-pattern gratings.

Despite the rapid development of polymer light-emitting diodes (PLEDs), the overall device efficiency is still limited because ∼80% of the generated light is trapped in a conventional device architecture by the high refractive index of organic materials and the optical confinement and internal reflection. The implementation of the energy dissipation compensation techniques is urgently required for further enhancement in the efficiency of PLEDs. Here, we demonstrate that incorporating the double-pattern Bragg gratings in the organic layers with soft nanoimprinting lithography can dramatically enhance the light extraction of trapped optical modes in PLEDs. The resulting efficiency is 1.35 times that of a conventional device with a flat architecture used as a comparison. The experimental and theoretical analyses indicate that the enhanced out-coupling efficiency is attributed to the combination of the ordinary Bragg scattering, the guided-mode resonance (GMR), surface plasmon polariton (SPP) modes, and the hybrid anticross coupling between GMR and SPP, leading to the extraordinary efficient photo flux that can transfer in direction of the leaky modes. We anticipate that our method provides a new pathway for precisely manipulating nanoscale optical fields and could enable the integration of different optical modes in PLEDs for the viable applications.