Effect of acceptor on efficiencies of exciplex-type organic light emitting diodes

The relationship between the electroluminescent (EL) efficiencies of interfacial exciplex emission and the lowest unoccupied molecular orbital (LUMO) of the acceptors systematically investigated. A nearly linear relationship was observed between LUMOs of acceptors and exciplex efficiency for a fixed donor of 4,4('),4(')-tris[3-methyl-phenyl(phenyl)amino]-triphenylamine in exciplex-type devices. This result indicates that the lower the LUMO of the acceptor is, the higher the EL efficiency of the exciplex is. The effect of acceptor on the efficiencies of exciplex-type devices is attributable to the interactions between the donor and acceptor molecules, which were closely related to the matched LUMOs and intermolecular conformations overlap between donor and acceptor molecules. (C) 2007 American Institute of Physics.