White light from polymer light-emitting diodes: Utilization of fluorenone defects and exciplex

A white light polymer light-emitting diode was demonstrated with a double layer configuration: poly[N,N-'-bis(4-butylphenyl)-N,N-'-bis(phenyl)benzidine] (poly-TPD) blended with poly(N-vinylcarbazole) as both hole-transporting layer and electron-blocking layer, blue-emissive poly(9,9-dihexylfluorene-alt-co-2,5-dioctyloxy-para-phenylene) (PDHFDOOP) blended with green-emissive poly[6,6(')-bi-(9,9(')-dihexylfluorene)-co-(9,9(')-dihexylfluorene-3-thiophene-5(')-yl)] as an emissive layer. By annealing the emissive layer at a relatively high temperature, fluorenone defects were generated into PDHFDOOP, which formed an exciplex with poly-TPD, as a red emitter. The devices exhibit a maximum brightness of similar to 4800 cd/m(2) and a maximum luminous efficiency of similar to 3 cd/A. Moreover, the Commission Internationale de L'Eclairage coordinates of the emitted light is close to that of pure white light and is insensitive to the applied voltages. (c) 2006 American Institute of Physics.