Effects of the morphologies and structures of light-emitting layers on theperformance of organic electroluminescent devices

Organic electroluminescent devices with a structure of ITO/ploy (9-vinylcar bazole)/tris (8-hydroxyquinoline) aluminum (Alq3)/Mg:Ag are fabricated at d ifferent substrate temperatures (77, 298, and 438 K) during Alq3 deposition . It is found that the surface morphologies of Alq3 thin films greatly affe ct the I-V characteristics of the devices by the contact area between metal cathode and light-emitting layer. There is an increase in the luminous eff iciency of the devices in the order 77 K < 298 K < 438 K. We attribute this trend to different structures of Alq3 thin films. (C) 2001 American Instit ute of Physics.