Enhanced light extraction in organic light-emitting devices: Using conductive low-index layers and micropatterned indium tin oxide electrodes with optimal taper angle

We present our study on organic light-emitting diodes (OLEDs) in which outcoupling is enhanced based on a bilayer electrode consisting of a conductive low-index layer and micro-patterned indium tin oxide (ITO) layers. Optical simulation reveals that the taper angle of an ITO pattern is among the most critical parameters influencing the outcoupling efficiency in the proposed structure. A fabrication method based on a lift-off process is then employed to control the taper angle of the ITO pattern to be in the optimal range. OLEDs with the proposed electrode structure exhibit 50%-70% enhancement in external quantum efficiency over reference devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4724306]