Synthesis And Photoelectric Properties Of Novel Iridium (?) Complexes

Organic light-emitting diodes(OLEDs)have been attracted widely attention due to various colours,wide viewing angle and flexible displays.Phosphorescence iridium(?)complexes are widely used in OLEDs owing to their high efficiency,stable chemical properties and tunable emission colours.In this thesis,we synthesized a series of new green,blue-green and red Ir(?)complexes by developing a series of novel ancillary ligands with five-or four-membered chelating rings,and investigated their photophysical and OLEDs performances.We further studied the effects of substituent groups on the properties of Ir(?)complexes by introducing different units into ancillary ligands.The specific research contents are as follows:1.New auxiliary ligands pyrazolylpyridine derivatives with the structure of nitrogen heterocycles were developed,which would improve the electronic mobility and device performances of Ir(?)complexes.Four novel pure green Ir(?)complexes(Ir-me,Ir-cf3,Ir-py and Ir-ph)were obtained with 2-(4-trifluoromethyl)phenylpyridine(tfmppy)as main ligand and 2-(3-methyl-1H-pyrazol-5-yl)pyridine(mepzpy),2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine(cf3pzpy),2,2'-(1H-pyrazole-3,5-diyl)dipyridine(pypzpy)and 2-(3-2-(3-phenyl-1H-pyrazol-5-yl)pyridine(phpzpy)as the ancillary ligands,respectively.Among four green Ir(?)complexes,the device based on Ir-me complex achieves the best device performances with the highest current efficiency of 92 cd A-1 and the maximum external quantum efficiency of 28.90%,even at the brightness of 1000 cd m-2,the efficiency values still keep at 79.97 cd A-1 and 25.16%.Two novel blue-green Ir(?)complexes Ir(BTBP)2mepzpy and Ir(BTBP)2phpzpy were obtained,in which 2',6'-bis(trifluoromethyl)-2,4'-bipyridine(BTBP)was used as main ligand,2-(3-methyl-1H-pyrazol-5-yl)pyridine(mepzpy)and 2-(3-2-(3-phenyl-1H-pyrazol-5-yl)pyridine(phpzpy)were introduced as the ancillary ligands,respectively.And the device using Ir(BTBP)2mepzpy complex as dopant achieves better performances with a maximum current efficiency of 58.17 cd A-1,a maximum power efficiency of 25.33 lm W-1 and CIE color coordinates at(0.19,0.43).Four red Ir(?)complexes PIQ-Irl-me,PIQ-Ir2-cf3,PQZ-Ir3-me and PQZ-Ir4-cf3 were synthesized,in which 1-(4-(trifluoromethyl)phenyl)isoquinoline(tfmpiq)and 4-(4-(trifluoromethyl)phenyl)quinazoline(tfmpqz)were used as the main ligands,2-(3-methyl-1H-pyrazol-5-yl)pyridine(mepzpy)and 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine(cf3pzpy)were applied as the ancillary ligands,respectively.Among them,the device using PQZ-Ir4-cf3 complex achieves the best performances with the maximum current efficiency of 40.04 cd A-1 and the maximum power efficiency of 33.98 1m W-1,respectively.Especially,PQZrIr3-me complex shows the most red-shifted emission with the maximum external quantum efficiency of 22.3%and CIE coordinates at(0.64,0.34).2.It is found that the ligands of thiocarbonic acid derivatives can help to synthesize Ir(?)complexes rapidly and show good device performances due to sulfur element.Three novel four-membered Ir(?)complexes(tfmpqz)2Ir(dpdtc),(tfmpqz)2Ir(medtc)and(tfmpqz)2Ir(cf3dtc)were rapidly synthesized at room temperature,in which 4-(4-(trifluoromethyl)phenyl)quinazoline(tfmpqz)was used as main ligand and thiocarbonic acid derivatives lithium salts formed from diphenylamine,di-p-tolylamine,bis(4-(trifluoromethyl)phenyl)amine,respectively,n-butyl lithium and carbon disulfide were applied as ancillary ligands(dpdtc,medtc,cf3dtc),respectively.The Ir(?I)complexes show emission peaks at 617-629 nm with quantum yields of 0.60-0.83 Particularly,the device based on(tfmpqz)2Ir(cf3dtc)complex achieves the best device performances with a maximum luminance of 30 740 cd m-2,a maximum current efficiency of 46.86 cd A-1,a maximum power efficiency of 37.73 Im W-1,a maximum external quantum efficiency of 26.10%and CIE color coordinates at(0.61,0.36).3.A new type of sulfur-containing ancillary ligands triethylamine salts of diphenylphosphinodithioic acid(dpss)and its derivatives(di-p-tolylphosphinodithioic acid(mess),di(naphthalen-1-yl)phosphinodithioic acid(nmss),bis(4-methoxyphenyl)phosphinodithioic acid(omess),bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphinodithioic acid(tbuss),0,0-diphenyl S-hydrogen phosphorodithioate(opss)and 0,0-di(naphthalen-l-yl)S-hydrogen phosphorodithioate(onss))were developed for eight novel four-membered Ir(?)complexes(tfmpiq)2Ir(dpss),(tfmpqz)2Ir(dpss),(tfmpqz)2Ir(mess),(tfmpqz)2Ir(niss),(tfmpqz)2Ir(omess),(tfmpqz)2Ir(tbuss),(tfmpqz)2Ir(opss)and(tfmpqz)2Ir(onss),in which 1-(4-(trifluoromethyl)phenyl)isoquinoline(tfmpiq)and 4-(4-(trifluoromethyl)phenyl)quinazoline(tfmpqz)were used as the main ligands,respectively,and aboved triethylamine salts were applied as ancillary ligands,respectively,these Ir(?)complexes were rapidly synthesized at room temperature.Gibbs free energy changes(?G)calculations of these reactions further prove that they are exothermic and thermodynamically favorable processes.Especially,the device using(tfmpqz)2Ir(onss)complex achieves the best device performances with a maximum luminance of 52 030 cd m-2,a maximum current efficiency of 57.98 cd A-1,a maximum power efficiency of 44.40 lm W-1,a maximum external quantum efficiency of 24.90%and CIE color coordinates at(0.59,0.39).