AVS 47th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF+EL+SS-WeM

Invited Paper OF+EL+SS-WeM7
White-Light-Emitting Organic EL Devices Based on Vacuum Deposited Thin Films

Wednesday, October 4, 2000, 10:20 am, Room 313

Session: Transport and Device Issues in Organic Thin Films
Presenter: J. Kido, Yamagata University, Japan
Correspondent: Click to Email

In this paper, we describe the design and fabrication of bright and high efficiency white-light-emitting EL devices based on vacuum deposited organic thin films. In order to archive high quantum efficiency, multilayer structures are employed. White light can be generated by using two emitter layers composed of blue and yellow emitters. For the blue emitter layer, distyrylbiphenyl derivative is doped with a few percent of distyrylarylene derivative with carbazolyl groups. For the yellow emitter layer, rubrene was doped into hole-transporting arylamine derivative (NPD). Reduction of drive voltage was realized by using metal-doped electron injection layer,@footnote 1@ which is composed of electron-transporting bathophenantroline (Bphen) doped with Cs metal. Cs-doping to Bphen reduces resistivity of the Bphen film, and the contact between cathode and the Bphen layer becomes ohmic, which results in the low drive voltage. The typical device structure is ITO/NPD/yellow-emitting layer/blue-emitting/Bphen doped with Cs/Al. By optimizing the thickness of each layer and dopant concentration, the white EL devices exhibited extremely high luminous efficiency of 15 lm/W and external quantum efficiency of 4% which are the highest values reported for white organic EL devices. @FootnoteText@@footnote 1@J.Kido and T.Matsumoto, Apply. Phys. Lett, 73, 2868(1998).