Spatial extent of the recombination zone in a PPV/polymer blend light-emitting diode

Double-layer LEDs containing poly(phenylenevinylene) (PPV) and a tris(stilbene)amine (TSA)/polysulfone (PSu) blend as active components were prepared in order to determine the spatial extent of the recombination zone. By monitoring the electroluminescence spectra as a function of the thickness of the TSA layer the fraction of the electrons that reach the PPV layer can be estimated. The electron range s decreases with increasing cell current. For E = 2 × 106 V/cm, s = 55 ± 10 mm is found. Arguments are presented in favor of the notion that s is limited by recombination with majority carriers (holes).