Study On Illumination Mechanism Of Phosphorescent Organic Electro Luminescent Devices Based On PVK

Organic light-emitting diodes (OLEDs) have received increasing attention in the development of advanced flat panel display technology because of its low weight, broad visual angle, low cost, fast response speed, active emitting, high brightness, high efficiency and the capability to support full color display. Although the production of OLEDs has been commercialized, much work remains to enhance the product performance and achieve market advantage. In this dissertation, we have made some meaningful works relating to the improving efficiency and color stability of OLEDs, It includes the following items:1) The excitons need to be effective used to improve the efficiency of light-emitting-devices, so it should be tied as many as possible in the light-emitting layer to avoid quenching by the electrodes when it spreads to the outer region of the light-emitting layer. In this paper, the dynamics of exciton quenching in a polymer PVK doped with phosphorescent guest materials FirPic,Ir(piq)2(acac),Ir(ppy)3, respectively, which due to the presence of metal films is analyzed using time-resolved photoluminescence. The decay of the luminescence for various polymer layer thicknesses is described by a one-dimensional diffusion model which has been proved to be correct. The energy transfer distance and exciton diffusion length derived for PVK doped with phosphorescent guest materials is 10nm, 9nm, 15nm and 29.3nm,30.1nm,30.9nm . This can disentangle the contributions from direct energy transfer to the metal and exciton migration, to the exciton quenching process. The width of the exciton quenching region of the doping system is 39.3nm,39.1nm and 45.9nm. It can provide guidance on preparation of the device. The diffusion parameters derived in this work are also valuable for modeling other polymer-based optoelectronic devices with the same layer heterostructure geometry.2) Many methods to improve the color stability have been reported in the literature. These include the control of the exciton recombination zone by introducing a carrier blocking layer and the fabrication of a single-emitting-layer device. The single-emitting-layer and double-emitting-layer white organic device which doped with phosphorescent guest materials are fabricated using the result of above research. The CIE coordinate of the single-emitting-layer device achieve (0.35,0.36) by adjusting the doped proportion of red and blue material. The double-emitting-layer device use the material BCP as the carrier blocking device is keeps in the white region under all voltage when the doped proportion of red material is 8wt% and the optimum value of CIE coordinate is (0.339,0.336). This paper fabricate the white organic device using three basic color of blue, red and green, it also achieve good white light emission.