Approaches for achieving highly efficient exciplex-based organic light-emitting devices

We studied the performance of exciplex-based organic light-emitting devices (OLEDs) made of different electron transporting materials (ETMs) with similar electron affinities to minimize the effect of the lowest unoccupied molecular orbital levels. A strong correlation was observed between the intensity of exciplex emission and the choice of ETMs. The intensity of exciplex emission relied on interfacial charge accumulation densities at organic/organic contacts, which in turn determined device color and efficiency. Contrary to common belief, highly efficient exciplex-based OLEDs can be achieved, provided that the involved organic materials have high carrier mobility, high photoluminescence quantum yield, and suitable electron energy levels. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2993326]