Effects Of Doping Concentration And Hole Blocking Material On The Performance Of Phosphorescent OLEDs

Organic light-emitting device(OLED) is a promising candidate for the next generation display due to their merits of portability,flexibility and high contrast.Phosphorescence boosts efficiency by 4 times compared to that of the normal fluorescence OLED(PhOLED),by harvesting the normally spin-forbidden triplet state which accounts for three quarters of all excitons formed in the device.Based on the challenges in electrophosphorescent devices,this thesis consists of two aspects:First, based on the tested the electroluminescent characteristics of electrophosphorescent devices with two kinds of phosphorescent materials,Ir(ppy)₃ or Ir(piq)₃,we analyze the energy transfer situation in the polymer doped system.Second,the influence of the electron injection barrier on the performance of the devices is also investigated.The possible processes of electron injection in the device are proposed.This thesis consists of five chapters.In the first chapter,the development and the mechanism of organic light-emitting devices are introduced.The second Chapter is aimed at the materials,the manufacture and measurement of the electrophosphorescent devices.The following two chapters study the above mentioned aspects by experiments and theory.The fifth Chapter is the conclusion.(1) In this thesis,we use two iridium complexes as the Phosphorescence guest, and study the electroluminescent characteristics of these two kinds of iridium complexes and the energy transfer situation in the polymer doped system.We analyze the source of electroluminescent in devices.(2) Based on(1),we use Ir(ppy)₃ material as phosphorescence gust,PVK and PBD as the host material,and fabricate two series of devices with different hole-blocking layer.We investigate the mode of electron injection in the system by the electrical properties.Furthermore,by comparing of the two different structural devices,we study the influence of doping concentration and electron injection modes the structure on the photometric efficiency of the device in this paper.