Organic light-emitting diodes based on a cohost electron transporting composite

The efficiency of green organic electroluminescent devices have been improved by cohosting the electron dominant complex, 4,7-diphenyl-1,10-phenanthroline into the traditional electron transporting layer of tris (8-hydroxyquinoline) aluminum. In this cohost strategy, we demonstrate that the luminous efficiency is enhanced by > 20% while the driving voltage can be reduced by similar to 30% in a uniformly mixed composition as compared to the traditional device configuration. The corresponding device lifetime under atmospheric condition is extended by a factor of similar to 1.8, attributed to the reduction of the accumulated positive charges near the electron-hole recombination regime. Results indicate that the knowledge of bulk conductivity engineering of organic n-type transporters is essential in enhancing organic light-emitting devices. (c) 2006 American Institute of Physics.