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 recombinatio n zone. By monitoring the electroluminescence spectra as a function of the thickness of the TSA layer the fraction of the electrons that rea ch the PPV layer can be estimated. The electron range s decreases with increasing cell current, For E = 2 x 10(6) V/cm, s = 55 +/- 10 nm is found. Arguments are presented in favor of the notion that s is limite d by recombination with majority carriers (holes).