A theoretical study on blue-green phosphorescent iridium (III) complexes with low-efficiency roll-off properties

Here, eight phosphorescent heteroleptic cyclometalated Ir (III) complexes were theoretically designed to identify some suitable organic light-emitting diode materials. (F-2-PYBPY)(2)Ir (acac) (marked 1), (F-2-PYBPY)(2)Ir (tpip) (marked 2), (PYBPY)(2)Ir (acac) (marked 3), (PYBPY)(2)Ir (tpip) (marked 4), (F-2-PYPY)(2)Ir (acac) (marked 5), (F-2-PYPY)(2)Ir (tpip) (marked 6), (PYPY)(2)Ir (acac) (marked 7), and (PYPY)(2)Ir (tpip) (marked 8) were studied via density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Here, acac denotes acetylacetonate, tpip denotes tetraphenylimido-diphosphinate, F-2-PYBPY denotes 3-(4-tert-butylpyridin-2-yl)-2,6-difluoropyridine, PYBPY denotes 4-tert-butyl-2-(pyridin-3-yl) pyridine, F-2-PYPY denotes 2,6-difluoro-3-(pyridin-2-yl) pyridine, and PYPY denotes 2-(pyridin-3-yl) pyridine. Further, we discuss the value of these materials from the electronic structure, spectral properties, ionization potentials, electron affinities, and application prospects of the complexes. We hope that these light-emitting materials contribute to the organic light-emitting diode sector. This theoretical study included the energy transfer mechanism of the complexes with acac and tpip substituents as auxiliary ligands: We analyzed the possibilities and inevitability of the results in the experiments as well as evaluated the underlying mechanism for these materials' low-efficiency roll-off.