Research Of Organic Light-emitting Device Based On Novel Iridium Complexs

Organic light-emitting diodes （OLEDs） have drawn considerable attentions inrecent years due to their promising applications as full color displays, backlight forliquid crystal displays, and solid-state lighting sources. Especially, OLEDs employingphosphorescent materials have drawn extensive research interest in recent years sincethey could harness triplet excitons to great increase the internal quantum efficiency ofdevice. However, due to intensive concentration quench of most present materials, mostof these devices only display high performance on the basis of doping system within alow concentration ranging from5wt%to10wt%. For solving this problem, wefabricated heavily-doped and high performance device based on novel iridium complexs.Subsequently, systematic study about influence of the spectral variation, energy levelalignment, carrier injection, transport and balance on the device performance iscarefully discussed. The details are as following:（1） Highly efficient and heavily-doped phosphorescent organic light-emittingdevices had been fabricated using novel iridium complex,（tbpbt）₂Ir（acac） and（fbt）₂Ir（acac） as phosphors. Take the device utilizing （tbpbt）₂Ir（acac） as an example,With a high doping concentration of20wt%, the device achieved a high powerefficiency, current efficiency, and external quantum efficiency of35.9lm/W,46.8cd/A,17.8%, respectively, indicating an excellent quench-resistant property of（tbpbt）₂Ir（acac）. Meanwhile, as far as our knowledge, the performance of our red（fbt）₂Ir（acac） OLED achieved one of the best records in heavily-doped red OLED.（2） Based on the quench-resistant property, white OLEDs employing（tbpbt）₂Ir（acac） as a host-free layer are fabricated, providing us a simple manufacturingprocess without largely sacrificing device efficiency.（3） Concentration-insensitive property of （tbpbt）₂Ir（acac） was demonstrated byfabricating monochrome devices with different doping ratio. On the basis of theconcentration-insensitive characteristic, white OLEDs were fabricated by using（tbpbt）₂Ir（acac） as phosphor. It is worth mentioning that the concentration variationsdidn’t induce great alterations of device efficiency, which is very important because it will simplify the experimental process of concentration optimization.（4） Interlayer based white OLEDs were fabricated. By varying the interlayerthickness, the mechanisms of electroluminescent spectral alteration, energy transfer, andespecially, charge carrier transport and balance in the devices were investigated andrevealed in detail. Additionally, quantitative analysis and experimental method weresubsequently carried out, demonstrating that the enhancement of carrier recombinationefficiency was key factor relating to the optimization of device performance.