Enhanced Light Outcoupling in Organic Light-Emitting Diodes Using Phase Separated Polymer Films

We report high performance internal light outcoupling films based on phase separation polymer for indium tin oxide-free organic light emitting diodes (OLEDs). The two immiscible polymers of poly(amic acid) and polyimide in a blend film result in nanoporous structures after spin-coating by self-assembly process. The OLEDs are prepared by solution process including phase separation films and transparent electrodes, allowing for low-cost and high-speed manufacturing. The phase separation films prepared between the glass substrate and the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) transparent electrode remarkably improve the outcoupling performance of OLEDs. The poly(methyl methacrylate) (PMMA)-assisted phase separation films significantly improve the external quantum efficiency and power efficiency of OLEDs by a factor 1.88 and 1.87, respectively, compared to the reference device without any outcoupling structure. Our results demonstrate that phase separation films developed here offer new opportunities in improving the outcoupling efficiency in OLEDs. Graphic Abstract