Influence of sensitizer on organic electroluminescence

We synthesized a polymer, poly(N,N'-diphenyl-N,N'-bis(4-methylphenyl)-1,4-phenylenediamine1,3-diisopropenylbenzene) (PDAIPB), of which the energy of the highest occupied molecular orbital was measured to be 5.6 eV below vacuum level. In this article, PDAIPB was used as a hole transporter in a light emitting diode, with tri(8-hydroxyquinoline)-aluminum (Alq(3)) as an electron transporter and emitting layer to ameliorate the stability of the device, and fullerene doped in the hole transporting layer as a sensitizer to study the influence of sensitizer on organic electroluminescence (EL). Internal EL quantum efficiency as high as 7.8% was obtained under an applied electric field of 1.2 x 10(6) V/cm and doping fullerene concentration of 0.9 wt %. A function for EL quantum efficiency in terms of the dopant concentration is derived. The theoretical analysis is consistent with the experimental results. (C) 2001 American Institute of Physics.