Green and Stable Processing of Organic Light-Emitting Diodes from Aqueous Nanodispersion

摘要： An imminent show-stopper for up-scaled production of printed thin-film electronics are the flammable and environmentally hazardous solvents used to dissolve the organic semiconductors. Especially in the case of wide-web large-area coating the development of toxic and flammable vapour during coating and drying poses serious health and safety risks. Processing the active materials from aqueous nanodispersion therefore offers a highly attractive alternative. In contrast to thin-film organic photovoltaics (OPV), nanoparticle-based organic light-emitting diodes (OLEDs) have so far received only little attention. The very high electrical field (~0.1 GV/m) poses rather “unforgiving” requirements regarding the topology, integrity and chemistry of the active layer, seemingly difficult to achieve using aqueous nanodispersions. In this work we show that it can be done. We present polymer light-emitting diodes (PLEDs) with active layers processed from nanodispersion. Through thorough optimization of the particle preparation and casting procedures, we obtain smooth, dense and intergral light-emitting nanoparticle films compatible with stable PLED operation. The performance of the nanoparticle PLEDs is on par with that of solution-cast reference devices. The devices exhibit low leakage current and turn-on voltage, no sign of degradation through voltage cycling, no current hysteresis and similar efficiencies.