Design And Synthesis Of Red/Blue Phosphorescent Iridium(?) Complexes For Highly Efficient Organic Light-emitting Diodes

Organic light-emitting diodes(OLEDs)are considered to be potential replacements in future full-color flat-panel displays and solid-state lighting techniques.The applications of phosphorescent transition metal complexes greatly improve the efficiency of organic electroluminescent devices.Among all kinds of transition-metal complexes,the cyclometalated iridium(?)complexes are considered as the most attractive candidates for electroluminescent devices owing to their easily tunable emission wavelength,high phosphorescence quantum efficiency,large Stokes shifts and rich excited state properties.Recent efforts have been devoted to the exploration of these complexes.At present,there are many reports on the tuning of photophysical properties of the iridium(?)complex,which mainly involves the synthesis of the main ligand with the new skeletal structure,and the chemical modification of the ligand and the selection of the ancillary ligand.In this thesis,we designed and synthesized a series of neutral red/blue light-emitting iridium(?)complexes with different ancillary ligands.The effects of ancillary ligands on their photophysical properties were investigated in detail.They were also applied in organic electroluminescent devices.The main research contents are as follows:Firstly,we designed and synthetized two novel highly efficient red iridium(?)complexes using4-methyl-2-(thiophen-2-yl)quinolone(HMTQ)as cyclometalated ligands and2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine(HTFTP)or picolinic acid(HPIC)as ancillary ligands.Via the variation of ancillary ligand,we can tune the photophysical properties of thienylquinoline-based complexes,especially in aspect of ?PL,FWHMs,etc.Furthermore,based on these highly efficient red light-emitting phosphors,high-performance red and three-color-based white OLEDs have been successfully fabricated.The maximum EQEs of red and white OLEDs can reach 16.2% and 15.1%,respectively.Especially,under wide operating voltage range,the designed WOLED exhibits excellent spectral stability,and the color rendering index(CRI)of white OLED is up to 77.Secondly,we designed and synthetized one homoleptic facial(fac)and five novel highly efficient blue light-emitting heteroleptic iridium(?)complexes using2-(4-fluoro-3-(trifluoromethyl)phenyl)pyridine(4F-3CF3ppyH)as cyclometalated ligands.Via the variation of ancillary ligand,we can tune the photophysical properties of phenylpyridine-based complexes,especially in aspect of wavelength,?PL,FWHMs,etc.The phosphors designed showbright emissions in blue region with very high absolute ?PL up to 0.98 in solution and relatively narrow FWHMs up to 52 nm.Furthermore,high-performance solution-processed blue organic light-emitting diodes(OLEDs)have been successfully fabricated based on these highly efficient blue phosphors.The electroluminescence peak,1931 Commission Internationale de L'Eclairage(CIE)coordinate and FWHM of the device based on Ir4 are all superior to the device based on FIrpic.The maximum luminance of the OLED based on Ir4 exceeds 20000 cd.m-2 and the efficiency of 14.6 cd.A-1 is very close to that of FIrpic-based device under the same conditions.