Insight into the Phosphorescent Process of Cyclometalated Ir(III) Complexes: Combination of the Substituents on Primary and Ancillary Ligands Controls the Emission Rule and Quantum Yield

Abstract

Rare high-efficiency deep blue organometallic phosphors are one of the major roadblocks to develop the white organic light-emitting diodes (OLEDs). In this article, the phosphorescent properties of four potential blue-emitting cyclometalated (C^N) Ir(III) complexes (two experimental reported and two theoretical novel designed) are investigated by the density functional theory/time-dependent density functional theory (DFT/TDDFT) method to explore the cooperative effect of the electron-withdrawing substituent on the primary ligand associated with different ancillary ligands. The origins of emission are identified by means of DFT and TDDFT calculations including spin–orbit coupling (SOC). The theoretical results indicate that emissions from the higher-lying triplet state also have a contribution. The radiative rate constant (kr) is quantitatively determined. To further elucidate the phosphorescent decay process, the SOC matrix elements, singlet–triplet splitting energies, and transition dipole moments are ca...