Synthesis And Optoelectronic Properties Of The Multi-nuclear Cyclometalated Iridium Complexes With The D-A-D And D Linked Core

In this context, the recent progresses in cyclometalated iridium complexes andorganic light-emitting devices (OLEDs) have been described. In order to address thecurrent problems for the iridium complex-based single-molecules white emissionmaterials, such as relatively few types, poor color stability and low luminescentefficiency, two classes of multi-nuclear cyclometalated iridium complexes, whichcontains the linkage units of the donor-acceptor-donor (D-A-D) anddonor-donor-donor (D-D1-D) structure between the phosphorescent chromophore,were designed and synthesized. Their molecular structures were characterized by1HNMR,13CNMR, elemental analysis and MALDI-TOF MS. The effect of bridged unitsand linkage mode on the thermal stability, photophysical and electroluminescentproperties was studied. Single-dopant white organic light emitting diodes (WOLEDs)based on multi-nuclear cyclometalated iridium complexes were achieved.Main contents of this dissertation are summarized as follows:1. A class of dinuclear cyclometalated iridium complexes of (C8TPAFIrpic)2BT,(C8TPAFIrpic)2PZ and (C8TPAFIrpic)2AN linkaged via the conjugatedD-A-D/D-D1-D bridged unit were obtained, in which D and D1are triphenylamine(TPA) and anthracene (AN), respectively, as well as A are benzothiadiazole (BT) andphenazine (PZ) units. For comparision, another dinuclear cyclometalated iridiumcomplex of (C8TPA-PhOC2FIrpic)2BT linkaged by non-conjugated D-A-D bridgedunit was synthesized. All of these dinuclear cyclometalated iridium complexesexhibited good thermal stability with a decomposition temperature more than340°Cat5%weight loss. The D-A-D-based complexes of (C8TPAFIrpic)2BT,C8TPAFIrpic)2PZ and (C8TPAPhOC2FIrpic)2BT showed a stable red emission in thesingle-dopant and single-emissive-layer polymer light-emitting devices (PLEDs) atdifferent concentrations and voltage. The maximum luminance of6118cd/m2and themaximum current efficiency of1.20cd/A were obtained in the(C8TPAFIrpic)2PZ-doped devices. However, The D-D1-D-based complexe of (C8TPA-FIrpic)2AN displayed a stable white emission with a CIEx,yof (0.33,0.33) in thePLEDs at the doping concentration of1wt%to2wt%.2. A series of dinuclear cyclometalated iridium complexes of C8TPA-(FIrpic)2and FL(FIrpic)2linkaged via conjugated D bridged unit of triphenylamine (TPA) andfluorene (FL) were sucessfully prepared. Another trinuclear cyclometalated iridiumcomplexes of (FIrpic)OC6TPA(FIrpic)2was also synthesized with the non-conjugated D bridged unit of TPA. All these multi-nuclear cyclometalated iridium complexesexhibited good thermal stability with a decomposition temperature more than355°Cat a5%weight loss. Furthermore, these complexes revealed a stable white emission inthe single-dopant and single-emissive-layer at the doping concentrations of1wt%and2wt%. However, a yellow-green emission was observed in the devices withincreasing the doping concentrations. Importantly, the FL(FIrpic)2-doped devicesdisplayed the stable-white emission with a CIEx,y(0.34,0.35) in the dopingconcentration of2wt%. The maximum luminance of1420cd/m2and the maximumcurrent efficiency of4.18cd/A were obtained at this situation.