Colored semi-transparent organic light-emitting diodes

Semi-transparent, colored organic light-emitting diodes (OLEDs) were demonstrated by comprising a microcavity-embedded structure that uses an organic layer sandwiched between thin metal layers as the cathode. Without bias, the colored OLEDs exhibited various colors depending on the metal/organic/metal cathode configuration, by means of internal interference effects under ambient illumination. By varying the thickness of the organic layer, the transmittance and reflectance of the colored OLEDs could be controlled. The influence of the microcavity cathode on the light-emitting performances of OLEDs, such as the efficiencies and the electroluminescence spectra, was also studied.