Theoretical study of injection, transport, absorption and phosphorescence properties of a series of heteroleptic iridium(III) complexes in OLEDs

We report a quantum-chemistry analysis of four heteroleptic iridium(III) complexes (tfmppy)2Ir(tpip) [tfmppy = 4-trifluoromethylphenylpyridine, tpip = tetraphenylimido-diphosphinate] (1), (tfmpyN3)2Ir(tpip) [tfmpyN3 = 4-trifluoromethylphenyl-[1,2,3]-triazole] (2), (CN-pyN3)2Ir(tpip) [CN-pyN3 = 4-cyanophenyl-[1,2,3]-triazole] (3) (ph-pta)2Ir(tpip) [ph-pta = 2-(5-phenyl-[1,2,4]-triazol-3-yl)-pyridine] (4), which have been studied by using density functional theory (DFT) and time-dependent DFT (TDDFT) methods, to investigate their electronic structures, injection and transport properties, absorption and phosphorescence mechanism. The results reveal the different cyclometalated ligands have a large impact on the charge transfer performances of the studied complexes. The complex 4 possess better charge transfer abilities and balanced charge transfer rates, which is a potential candidate as blue-emitting material.