Transparent organic light-emitting devices with CsCl capping layers on semitransparent Ca/Ag cathodes

We have developed transparent organic light-emitting devices (TOLEDs) with CsCl capping layers deposited on top of semitransparent Ca/Ag cathodes. The CsCl layer was deposited by the thermal evaporation method which does not result in any damage to the underlying organic layers. The transmittance was enhanced by depositing the CsCl layer on the Ca/Ag cathode. The current efficiency measured at the cathode side increased by the enhanced transmittance of the cathode, whereas the anode-side current efficiency was determined by the reflectance of the cathode. In a TOLED with semitransparent Ca/Ag/CsCl layer, the microcavity effect was not profound so that the electroluminescence spectrum was not seriously changed by the CsCl capping layer.