?Doped thin films of two organic molecules for light emitting diodes.?

The photoluminescence and electroluminescence of doped organic materials are reported for thin films prepared by ultra high vacuum co-evaporation and by spin-coating from solution of two emitting molecules. For both the films efficient energy transfer from the donor to the acceptor molecules is observed without relevant dopant segregation for molar concentrations up to 10%. In spin-coated films the energy transfer from the matrix to the dopant is due to purely resonant energy transfer processes while the co-sublimated films show the presence of additional thermally activated hopping processes. Light emitting diodes fabricated with co-evaporated films yield electroluminescence with higher efficiency and stability.