Crystal structure, photoluminescence and electroluminescence of three bluish green light-emitting iridium complexes

Abstract

Three bis-cyclometalated iridium complexes ((TPP)₂Ir(acac), (TPP)₂Ir(tpip) and (TPP)₂Ir(pic)) with 2-(2-trifluoromethyl)pyrimidine-pyridine (TPP) as the main ligand, 2,4-pentanedionate (acac), tetraphenylimidodiphosphinate (tpip) and picolinate (pic) as the ancillary ligands, respectively, were prepared. Their photoluminescence and electrochemistry properties were investigated in detail, and (TPP)₂Ir(tpip) was also examined by X-ray crystallography. These complexes show bluish green emission with a quantum efficiency of 11–14%. The organic light emitting diodes (OLEDs) with the structure of ITO/TAPC (1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane, 40 nm)/mCP (1,3-bis(9H-carbazol-9-yl)benzene, 10 nm)/Ir complex (8 wt%):PPO21 (3-(diphenylphosphoryl)-9-(4-(diphenylphosphoryl)phenyl)-9H-carbazole, 25 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) were fabricated to evaluate the potential application of these complexes. A (TPP)₂Ir(tpip) emitter based device showed the best performance of a maximum current efficiency (η_c) value of 37.61 cd A⁻¹ and a maximum external quantum efficiency (EQE) of 13.7% with low efficiency roll-off.