Strongly-directed emission from microcavity structure in electroluminescent diodes with europium complex as an emitter

Multilayer electroluminescent (EL) diodes with sharp red emission were fabricated using an europium complex as an emitter. Microcavity structures were introduced into the EL diodes with sharp red emission. The device structures were composed of pairs of TiO2/SiO2 dielectric reflector, indium-tin-oxide electrode, hole transport layer (HTL), europium complex as an emission layer (EML), electron transport layer (ETL) and MgAg electrode. The dielectric reflector and the MgAg metal electrode constituted a planar microcavity. Sharply directed emission from europium complex was observed when operated under dc drive voltage at room temperature. In fabricating such EL diodes with optical microcavity made of dielectric reflector and a metal mirror, the best total thickness of the organic layers was found to depend on the stack structure of dielectric reflector.