Design,Synthesisand Photoelectric Property Studies Of Carbazole And Diphenylphosphoryl-Functionalized Ir(?) Complexes

As time goes,the needs of light and electricity become higher.Owing to the peculiarity of light weight,self-emission,high efficiency,fast response times,energy saving and emission reduction in solid-state lighting and the characteristic of ultrathin and light,wide viewing angle,flexible display,anti-seismic performance in flat-panel displays,organic light-emiting diodes?OLEDs?become the new generation of display technology.Among the numerous electroluminescent?EL?materials used for OLEDs,iridium???complexes have attracted much attention because of their unique advantages such as appropriate excition lifetime,good photo-thermal and electrochemical stability,high photoluminescence quantum yield,tunable emission wavelength and so on.However,most iridium???complexes suffer the serious concentration quenching effect,which impede the development of materials.Meanwhile,from the perspective of the devices,OLEDs based on iridium???complexes show severe efficiency roll-offs and color drift phenomena.Therefore,it is necessary that we explore the structure of iridium???complexes to fabricate high-performance OLEDs.In this paper,considering the steric effect and favourable hole/electron transporting characteristics caused by carbazole and diphenylphosphine oxide moieties,we design and synthesize a series of phosphorescent iridium???materials which could be applied in solution-processable OLEDs.What's more,the photophysical properties and photoelectric properties are studied in detail.The specific research work is presented as follows:?1?To reduce the phenomenon of intermolecular self-quenching and severe efficiency roll-off,we design and synthesize four iridium???complexes possessing carbazole and diphenylphosphoryl groups simultaneously.Then,we fabricate multilayer doped OLEDs by solution process and explore the EL properties.The low efficiency roll-offs luminescent devices are obtained.The device based on POCzIrbiq achieves higher current efficiency and lower efficiency roll-off.When the doped concentration is 10 wt%,the maximum current efficiency is 21.3 cd A^-1,and the efficiency roll-off is 11.2%in 1000 cd m^-2.?2?In order to achieve the highly efficient single-layer red OLEDs,we design and synthesis cationic red metal iridium???complexes employing carbazole and diphenylphosphine oxide as functionalized groups,namely m-Cz and m-PO.The single-layer nodoped OLEDs are fabricated by solution process.The device based on m-PO exhibits superior EL performance with high brightness of 2256 cd m^-2 and maximum external quantum efficiency of 4.73%.