The Effects Of Substituent On C^N=N Type Iridium(Ⅲ) Complexes And OLED Study

Organic light-emitting diodes (OLEDs) are currently attracting a lot of attentions due to theirpotenial application in low-cost full color displays. Phosphorescent OLEDs (PhOLEDs) areparticularly promising because they can emit light from both singlet and triplet states, enabling100%internal quantum effieieney. In this work, focusing on the effects of substitution tophosphorescent emitters of iridum complexes with C^N=N structure, we have done:Firstly, three homoleptic iridium complexes with C^N=N type ligand containing differentnumber of fluorine atoms were synthesized. Compared to the nonfluorinated Ir complex, blue-shiftof photoluminescence spectra and absorption spectra at long wavelength were observed. PLQY(photoluminescence quantum yield)(0.290.84) and phosphoresces lifetime (0.681.31μs)increased obviously after fluorinating ligand. Oppositely, thermal stability of the iridium complexesdecreased regularly (Td:439408°C). In the density functional theory (DFT) calculations,orientational differences among the complexes were observed. In PhOLEDs, the Dexter energytransfer between the emission of host and the absorption of the dopand, and the resonanceback-energy transfer from triplet dopant to triplet host lead to the contrary trend between PLQY anddevice external quantum efficiency.Secondly, diphenylamine-or carbazole-containing triscyclometalated iridium complexes{IrNPPya [tris(N,N,6-triphenylpyridazin-3-amine)iridium], IrCzPPya[tris(9-(6-phenylpyridazin-3-yl)-9H-carbazole] iridium} based on a C^N=N type ligand of3-phenylpyridazine were synthesized.The link between molecular structures and material properties was studied via quantum chemistrycalculations. The more rigid structure of carbazole relative to diphenylamine results in an increasedavailable space for the penetration of environmental species, thus in IrCzPPya the channel foraccessing the core part of the complex is larger, leading to more deactivation of MLCT processhence reducing ФPLandph.Finally, the orange emitter Ir(CzPPya)3and the blue emitter FIrpic [Bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium] were chosen to prepare phosphorescent WOLED. Afterregulating the structure of the light-emitting layer, the WOLED with good CIE (0.32,0.44)(at1000cd/cm2) has been successfully constructed.