Phosphorescent organic light-emitting devices (PhOLEDs) based on 1-methyl-3-propyl-5-(2,4,5-trifluorophenyl)-1H-1,2,4-triazole as the cyclometalated ligand: Influence of the ancillary ligand on the emissive properties

Two heteroleptic iridium complexes have been designed with 1-methyl-3-propyl-5-(2,4,5-trifluorophenyl)-1H-1,2,4-triazole as the cyclometalated ligand and acetylacetone (acac) or dibenzoylmethane (dbm) as the ancillary ligands. Interestingly, when tested as emitters for phosphorescent OLEDs (PhOLEDs), these two isostructural complexes that only have varying ancillary ligands exhibited completely different behaviors in devices. Notably, highly efficient PhOLEDs were only obtained with the complex bearing dbm as the ancillary ligand. To get a deeper insight in this unexpected behavior, TD-DFT calculations were carried out. The optical properties of the two complexes (UV–vis absorption and photoluminescence) and their electrochemical behaviors were also studied.