摘要： The utilization of localized surface plasmon (LSPR) to improve the yield of organic light emitting diode (OLED), has been subject of numerous publications and reports. Several enhancement mechanisms have been highlighted such as the increase of F?rster energy transfer, the enhancement of the OLED electroluminescence as well as the increase of the current I and the decrease of the turn-on voltage V [1,2]. Nevertheless, these mechanisms are still not completely studied and understood. One major problem of using metallic NPs is the inherent losses associated with their conductivity. Another important issue concerns the evaluation of their electrical and optical effects on the total yield enhancement. Besides, the LSPR wavelength and the distance of the metallic NPs from the OLED emitting layer (EML) are very important parameters for a maximum enhancement of the near-field-induced energy transfer between excitons and NPs LSPR. In fact, LSPR modifies the radiative and the non-radiative decay rates of adjacent emitters resulting in two competitive processes: the fluorophores radiation intensity enhancement and the non-radiative quenching of activated fluorophores on the NP metal surface. To obtain an overall enhancement, the resonance energy of the fluorophore and the LSPR should be carefully adjusted with an appropriate distance between the metal NPs and the emitter. In this work, we report a thorough investigation of Ag NPs randomly dispersed into a standard guest-host OLED (Alq3:DCM) by thermal evaporation during the OLED fabrication process. Mainly, we follow-up the interaction between the Ag-thin layer and the excitons by varying the position of Ag-NPs within the OLED stack (fig. 1). At each position of Ag-NPs, we compare the plasmonic-OLED performances to those of the reference one without NPs (zero line) and we bring a general analysis of the electroluminescence efficiency variation as a function of the position of Ag-NPs related to the excitons distribution within the OLED emitting layer. The experimental results allow us to draw the balance between the amplification and quenching due to the Ag-NPs. By considering the spatial distribution of the emission sites in the EML, we particularly, highlighted two competing effects: the LSPR amplification for large distances between the Ag-NPs and the emissive sites, and the quenching effect by metallic NPs for short distances between the Ag-NPs and the emissive sites. Nevertheless, other phenomena such as the influence of Ag-NPs on the charge carriers injection and transport as well as extraction effect should be also taken into account in order to thoroughly understand the effect of plasmonic nanoparticles on the OLED structure performance. Our study enable us to suggest a figure of merit giving the total yield as following (cid:75) (cid:97) σ. (cid:69)a. (cid:69)q. (cid:75)ex, where (cid:86) accounts for the electrical effects, (cid:69)a and (cid:69)b are LSPR amplification and plasmonic quenching, respectively and (cid:75)ex is related to the extraction effect. The weight of the previous parameters depends on the distance NPs-EML with three zones of interest: anode side, cathode side and nearby the EML. Two different physical phenomena are also to be considered on the side of the cathode and the anode (blue and green lines in fig.1), as well as the correlation between near and far field. These results are of a great interest in order to develop new generation of highly efficient OLED-based devices.