We have fabricated light emitting devices based on sequentially adsorbed multilayers of an electrochemiluminescent active ruthenium (II) complex, Ru(bpy)(3)(2+) polyester, and various polyanions including a small molecule Ru(II) dye, sulfonated poly(p-phenylene), sulfonated polystyrene, poly(methacrylic acid) and poly(acrylic acid). Thicknesses per bilayer (polycation plus polyanion) ranging from 7 to 59 Angstrom were obtained by changing the nature of the polyanion. Our results revealed that the nature of the polyanion does not influence the optical transitions of the Ru(II) complex. Device performance, however, was dramatically dependent on the type of polyanion used. Symmetric behavior was exhibited from devices fabricated with polyanions containing weakly acidic carboxylic acid groups whereas more diode-like behavior was observed from the devices fabricated with polyanions containing the strongly acidic sulfonic acid group. Our best devices to date utilize poly(acrylic acid) as the polyanion and exhibit an external quantum efficiency of 3.2% (photons/electron) and a maximum light output of about 1350 nW (40 cd/m(2)).