Synthesis And Device Properties Of Some Organic Functional Materials

In recent years,the developers have carried out in-depth research on OLEDs.Smart gadgets featuring OLEDs display have already made to market and in solid lighting industry,OLEDs lighting panels are in the dawn of mass production.As the research hot area in organic electronics,the development of organic functional materials for OLEDs also attacted many researchers.In the thesis,we mainly focus on the design of novel organic functional materials such as hole-transporting materials,hole-transporting type host materials,bipolar host materials type host materials,phosphine-oxide host materials and phosphorescent iridium complexes.Using the N-phenyl-l-naphthylamine as the basic unit,a series of materials were designed and synthesized by conjugating different electron-acceptor unit,and the relationships between molecular structures and devices performance were studied.Therefore,some new strategies were harvested for designing high performance materials for OLEDs.1.Two hole transport materials,N-(4-carbazol-9-yl-phenyl)-N'-naphthalen-1-yl-N,N'-diphenyl-naphthalene-1,4-diamine(CZ-NPNA2)and N-(4-carbazol-9-yl-phenyl)-N'-(4-N,N-phenyl-naphthalene-naphthalen-1-yl)-N,N'-diphenyl-naphthalene-1,4-diamine(CZ-NPNA3),were synthesized by the addition of a carbazole moiety on to the dimer or trimer of N-phenyl-1-naphthylamine.Both of these hole-transporting materials have high glass transition temperatures of 135 and 167 ?,respectively.The green phosphorescent organic light-emitting diodes(PHOLEDs)of ITO(indium tin oxide)/new hole transport material(50 nm)/Ir(tfinppy)2(tpip)(tfinppy =4-trifluoromethylphenyl-pyridine,tpip = tetraphenylimidodiphosphinate,8 wt%):mCP(N,N'-dicarbazolyl-3,5-benzene,25 nm)/TmPyPB(1,3,5-trim-pyrid-3-yl-phenyl)benzene,50 nm)/LiF(1 nm)/Al(100 nm)exhibit high efficiency(maximum current efficiency(?c,max)of 113.9 and 108.8 cd A-1,maximum external quantum efficiency(EQE)of 29.8%and 28.5%,respectively)with low efficiency roll-off.Even at 3000 cd m-2 brightness,the ?c values still remain as high as 109.3 and 105.3 cd A-1,respectively.The device performances proved that these new materials derived from N-phenyl-1-naphthylamine would be promising hole transport materials for PHOLEDs.2.Two novel host materials,N1-(naphthalen-1-yl)-N1,N4-diphenyl-NB4-(4-(triphenylsilyl)phenyl)naphthalene-1,4-diamine(SiP)and N1-(naphthalen-l-yl)-N1,N4-diphenyl-N4-(3-(triphenylsilyl)phenyl)naphthalene-1,4-diamine(SiM),were synthesised by incorporating a hole-transporting moiety,N1-(naphthalen-l-yl)-N1,N4-diphenylnaphthalene-1,4-diamine(NPNA2)and typical electron-transporting tetraphenylsilane moiety.SiP and SiM materials exhibit high thermal and morphological stability with high glass transition temperature higher than 110 ? and decomposition temperature above 350 ?.Using Ir(bt)2(acac)(bis(2-phenylbenzothiozolato-N,C2')iridium(acetylacetonate))as emitter,yellow phosphorescent organic light-emitting diodes of ITO/TAPC(4,4'-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline,40 nm)/host:Ir(bt)2(acac)(15 wt%,20 nm)/TmPyPB(40 nm)/LiF(1 nm)/Al(100 nm)show maximum current and power efficiency of 40.81 cd A-1 and 33.60 lm W-1,respectively,with low efficiency roll-off.The current efficiency of 40.10 cd A-1 is still observed at the practically useful brightness value of 1000 cd m-2.3.Two novel bipolar host materials,N1-(naphthalen-l-yl)-N1,N4-diphenyl-N4-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl)naphthalene-1,4-diamine(NONP)and N1?(naphthalen-1-yl)-N1,N4-diphenyl-N4-(3-(5-phenyl-1,3,4-oxadiazol-2yl)phenyl)naphthalene-1,4-diamine(NONM),were synthesised by incorporating a hole-transporting moiety NPNA2 and a typical electron-transporting 1,3,4-oxadiazole moiety.Both the host materials have the high thermal stabilities(Tg>100 ?).For the hole-only and electron-only devices,two host materials exhibit excellent bipolar charge-transporting properties.The PHOLEDs using two compounds doped with the yellow phosphor Ir(bt)2(acac)as the emitting layer were fabricated.A maximum current efficiency(?c,max)of 43.22 cd A-1 and a maximum power efficiency(?p,max)of 35.71 lm W-1 based on the NONP as the host were achieved,and the maximum current efficiency(?c,max)and maximum power efficiency(?p,max)of the device based-on NONM were 44.42 cd A-1 and 35.94 lm W-1.4.The hole-transporting unit NPNA2 and electron-transporting phosphine oxide(PO)moiety,which both meet the requirements for host materials,were selected for the construction of two new compounds,(4-((4-(naphthalen-1-yl(phenyl)amino)naphthalen-1-yl)(phenyl)amino)phenyl)diphenylphosphine oxide(PO-p-NPNA2)and(3-((4-(naphthalen-1-yl(phenyl)amino)naphthalen-1-yl)(phenyl)amino)phenyl)diphenylphosphine oxide(PO-m-NPNA2),through adjusting the linkage mode between two moieties.Both two host materials exhibited good thermal ability and device performance.The PHOLEDs using two compounds doped with the yellow phosphor Ir(bt)2(acac)as the emitting layer were fabricated.A maximum current efficiency(?c,max)of 68.28 cd A-1 and a maximum power efficiency(?p,max)of 50.90 lm W-1 based on the PO-p-NPNA2 as the host were achieved,and the maximum current efficiency(?c,max)and maximum power efficiency(?p,max)of the device based-on PO-m-NPNA2 were 44.95 cd A-1 and 34.37 lm W-1.5.Three green phosphorescent iridium complexes,Ir1,Ir2 and Ir3,were synthesized by using pyrimidine-based structures as the main ligand and tpip as the ancillary ligand.All of them exhibited good thermal ability and strong green phosphorescent emission.The PHOLEDs using three complexes doped in the host mCP as the emitting layer were fabricated:ITO/TAPC(40 nm)/mCP:guest(10 wt%)(20 nm)/TmPyPB(30 nm)/LiF(1 nm)/Al(100 nm).And the OLED based on Ir1 showed excellent performance with the maximum current efficiency of 81.91 cd A-1 and the maximum luminance of 70986 cd m-2,respectively.