Selective doping of multilayer organic light emitting devices

Doping of organic light emitting diodes (OLEDs) has well-established benefits such as tuning emission wavelengths, as well as enhancing device lifetime and quantum efficiency. The use of low percentage doping within the emissive layer is an established tool for the study of energy transfer processes in OLEDs, allowing one to trace electron and hole movement and exciton formation. Delta doping, in which a thin layer of the dopant material alone is incorporated in the device, has the added advantage of a thinner sensing layer and an electroluminescence spectrum distinct from that of the host material. In an ongoing effort to further our understanding of electroluminescent emission processes, we have fabricated multilayer OLEDs which incorporate a narrow (<1 nm) delta-doped DCM region within the emissive layer. The devices studied were deposited on indium tin oxide (ITO) on glass substrates using thermal evaporation, with a structure of ITO, TPD (40 nm)/selectively doped Alq3 (40 nm)/Al (100 nm). The relationship between the doping profile and the emission characteristics will be discussed.