Study On The Enhanced Performances Of Organic Light-emitting Diodes Using Nanoparticles

Organic light emitting diodes(OLED) have attracted much attention because of properties of self-luminous, wide viewing angle, short response time, high luminous efficiency and fabricated large-size and flexible faceplate. Although the internal quantum efficiency can be achieved up to 100% by the use of phosphorescence material, the external quantum efficiency remains unsatisfactory for the optical effect enhancement such as: internal reflection, refraction and surface plasmon. The effect of surface plasmon enhanced effect is widely applied in OLED research areas because of the simple fabrication process. Meanwhile, the luminous efficiency can be enhanced by the light scattering effect caused by nanoparticles which will change the path of photons.In this paper, we fabricated single nanoparticles and the complex nano-structures, and then doped them into the anodic buffer layers. The performances of nanoparticles based device were increased significantly. My work is as detailed follows:1. Solution-processed MoOx:Au NPs buffer layer is incorporated into OLED by spin-coating methods. The device structure is simple sandwich of ITO/Au NPs:MoO3 /NPB/Alq3/LiF/Al, and the device properties realized low turn-on voltage, high efficiency and good stability, which should be attributed to work function(WF) of MoOx and surface plasmonic effect of Au nanoparticles.2. Based on our preliminary work, we construct the complex nano-structures by incorporating the SPP properties of Au NPs and the anodic modification of Fe3O4 NPs. We also fabricated green light OLED with Fe3O4@Au doped PEDOT:PSS buffer layer, and the fluorescence efficiency was nearly enhanced up to 100% y optimizing parameters and structures.All in all, I systemically studied the effect of single NPs and complex NPs on OLED properties, and I also demonstrated that the improved performances is mainly due to the small hole-injection barrier and the increased internal efficiency induced by LSPP and the increased light extraction efficiency related to light scattering effect.Our research provides some optimized process foundation for obtaining the high-efficiency and low cost OLEDs.