Enhanced light out-coupling from surface plasmonic loss minimized transparent organic light-emitting diodes

We report extremely high light out-coupling efficiency from a transparent organic light-emitting diode (OLED) integrated with microstructures on both sides of the device.[1] The OLED having a metal free structure offers dramatically reduced surface plasmonic loss and absorption loss. To extract the confined light inside the device, a high refractive index light extraction pattern was directly fabricated on the top side transparent conducting oxide electrode using a simple evaporation method, and a micro lens array sheet was simultaneously attached on the bottom side of the glass substrate. As a result, the external quantum efficiency of the device increased from 18.2% to 47.3% by using the microstructures, and was additionally enhanced to 62.9% by attaching an index-matched hemisphere lens instead of the micro lens array on the glass side in order to reduce additional light guiding loss inside of the device. These values showed very good agreement with the simulation performed by a combination of the dipole model and a 3-dimensional geometrical simulation.