| Iridium complexes can harvest both the singlet and the triplet excitons and render the internal quantum efficiency reach100%in organic light-emitting diode (OLED), which have been attracted great attention in the development of highly efficient OLED. There are categories of homoleptic and heteroleptic iridium complexes. Cyclometalated iridium complexes have a lot of advantages, such as high thermal stability and the possibility to tune the color of emission from blue to red. Heteroleptic iridium complexes also have many advantages, such as low synthesis temperature and the ability of turing material energy levels. A certain amount of homoleptic iridium complexes with CAN=N structure have been studied which exhibited excellent performances (e.g. high efficiency and low roll-off). While the study of heteroleptic iridium complexes with CAN=N structure are rare.Seven homoleptic/heteroleptic iridium complexes with CAN=N structure were synthesized and structurally characterized in this work. Based on these materials, photophysical and electrochemical features, quantumchemistry simulation as well as electroluminescence properties of some materials were systematically investigated. The study show that the photoluminescent quantum yield (PLQY) can be significantly improved via introducing ancillary ligand of pic. Based on theoretical calculation it was found that the electron cloud of the lowest unoccupied molecular orbital locates on one of the main ligand, which is the direct reason for the increase of PLQY. On the study of device performance, based on Ir(mdfppya)2pic, a maximum current efficiency of40.96cd A-1and a maximum power efficiency of33.86lm W"1were achieved. The maximum efficiencies are11.44cd A-1and8.45lm W-1for the homoleptic complex of Ir(mdfppya)3. The reason for obtaining the highest efficiency based on Ir(mdfppya)2pic is that besides its high PLQY, its energy levels are the most matched with CBP host. |
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