Understanding photophysical properties of iridium complexes with N-(5-phenyl-1,3,4-oxadiazol-2-yl)-diphenylphosphinic amide as the ancillary ligand
Understanding the physical nature behind the experimental phenomena is rather significant to further optimize performance of material. Now, density functional theory (DFT) has become a well-accepted tool for unveiling the origin of physical/chemical properties of materials and design new materials with desirable property. Recently, the two novel POXD-based (N-(5-phenyl-1,3,4-oxadiazol-2-yl)-diphenylphosphinic amide) iridium(III) complexes 1 and 4 with different cyclometalated ligands show significant performance differences. Herein, we employ the DFT calculations to investigate the electronic structures, absorption and emission spectra, as well as charge transportation properties of iridium(III) complexes 1 and 4. In comparison with 4, the good performance of 1 can be attributed to its favorable charge transport property. Based on complex 1, two new iridium complexes (2 and 3) were theoretically designed by substituting phenyl rings with tert-butyl group (-t-Bu) and methyl group (-CH3), respectively. The results clearly indicated that the -t-Bu and -CH3 groups enhance the hole and electron injection abilities and improve the charge balance. On the other hand, the designed complexes 2 and 3 also show a blue-shift in emission spectra with respect to complex 1. As a result, complexes 2 and 3 are expected to be promising phosphorescence emitters with good device performance.