High-Performance WOLED Based On Phosphor Host-phosphor Guest System

White organic light-emitting diodes?WOLED?have attracted more and more attention due to its wide application value in the filed of panel display and solid state lighting.At present,the performance of WOLED have reached a high level,and most index have been able to meet the requirements of commercialization.To sum up,there are mainly two types of high-performance WOLEDs reported in the literature:one is the fluorescence-phosphorescence hybrid type,which is the combination of blue fluorescent materials and other-color phosphorescence materials.The other is fully phosphorescent type,that is,all luminaries employ phosphorescent materials.All the above white light devices need to be introduced extra fluorescent molecules as luminaries or host materials,and exhibit white colour emitting through energy transfer from the fluorescent host to the phosphor guest.However,the inherent different characters between the fluorescent materials and phosphorescent materials,would lead to a certain degree of the excited energy loss causing the driving voltage increase and electro-luminescence efficiency decrease as well as the lowering white color stability and quality.In terms of these issues,we would like to synthesize some phosphorescent complexes with superior charge-transporting ability and lighting performance to achieve high-performance WOLED without fluorescent materials.In addition,combining proper phosphors and designing optimal device structure is another major point.Some high-performance WOLEDs based on phosphor host-phosphor guest system have been fabricated.There are three main contents in this paper as followings:In chapter ?,a four-color warm-white organic light-emitting diode employing a simple adjacent two-emitting-layer structure as a blue host-orange dopant/green host-red dopant has been fabricated,and blue fluorescent material Bepp₂ and three phosphorescent materials FPPCA,BZQPG and BTIPG have been employed.This WOLED exhibited a stable high electroluminescent performance:an external quantum efficiency of 23.3%and a power efficiency of 63.2 lm/W at an illumination-relevant luminance of 1000 cd/m² with a high color-rendering index?CRI?of 92 and maintained high levels of 21.6%and 48.8 lm/W with a CRI value of93 at the extremely high luminance of 5000 cd/m².In chapter ?,we have synthesised two novel iridium complexes FPYPCA and FMPYPCA based on dfpypy as the first ligand and dipcca as the second ligand.Two non-doped monochrome devices have been fabricated at first with peak external quantum efficiency of 11.7%/9.1%and peak power efficiency of 36.4 lm/W/22.8lm/W and maintained high levels at high luminance.According to the well performance of FPYPCA and FMPYPCA,two warm white OLEDs were fabricated with peak external quantum efficiency of 23.6%/22.8%and peak power efficiency of69.3 lm/W/65.4 lm/W and maintained high levels at an illumination-relevant luminance.This is the first report of high-performance WOLED based on phosphor-only system.In chapter ?,two WOLEDs based on novel/efficient phosphor-only emitting systems consisting of simple double emitting layers have been fabricated,which exhibited stable high electroluminescence performance including the peak efficiencies of 25.0%for external quantum efficiency and 71.3 lm/W for power efficiency,which maintained quite high levels of 21.7%and 44.8 lm/W at an illumination-relevant luminance of 1000 cd/m² with desirable color rendering index values of⁹0.This is a kind of OLED being called the“candle light-style”case,and is a potential healthier lighting source being advocated strongly by medical experts for safeguarding our eyesight and even promoting human health.Therefore,this work indeed provides a practical strategy for the applications in low-cost energy-saving and high-quality light source in future.