The realization of efficient polymeric light emitting diode (PLEDs) in a double-layered configuration was investigated. The devices are composed by transparent conductive oxide (ITO)/MoO3/organic layers/aluminum/selenium, conformed by thin film sandwich structures obtained by vacuum evaporation. Two organic layers were developed. First a n-type organic layer of composite based on polymethylmethacrylate (PMMA)/polyacrilic acid (PAA)/Er(AP)(6)Cl-3 complex and second a n-type organic semiconductor, N,N'-didodecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C12H25). The rare earth complex composites and the perilenic compound were synthesized and characterized using UV-Visible absorption, XPS, and NMR techniques, respectively. Driving voltage of devices was lowered by applying MoO3 thin film as buffer layer and high current intensity efficiency was obtained applying a perilenic film. The effect of MoO3 and PTCDI-C12H25 thin films, on the optical and the physical properties of the electroluminescent devices were discussed. I-V measurements have shown that the structures exhibit diode characteristics and the electroluminescent signal increases when PTCDI-C12H25 thin layer is introduced between the anode and the holes transporting layer. The morphology of the thin films with and without buffer layer indicates that introduction of this layer allows to obtain a homogeneous surface morphology. The results indicate that carrier injection ability and optimized charge balance is obtained to the lowest driving voltage and highest intensities efficiency among the referenced devices.