Improving the light extraction efficiency of polymeric light emitting diodes using two-dimensional photonic crystals

We have fabricated light emitting diodes based on a conjugated polymer, in which a planarized two-dimensional photonic crystal (PC) was inserted between the glass substrate and the ITO anode. Planarized PCs were fabricated into a high-index layer via interference lithography, followed by dry-etching and the spin-casting of a low-index glass. We characterize the electroluminescence (EL) emission from devices containing a PC, and compare this with photoluminescence (PL) generated from within the same structure. We show that LEDs incorporating the PC have an increased EL external quantum efficiency of (2.3 ± 1.0) times compared to a standard non-patterned control. This efficiency increase is in excellent agreement with PL measurements on similar structures, which also demonstrate relative increases in external emission intensity of 2.3 times.