Orange red iridium complexes with good electron mobility and mild OLED efficiency roll-off

Abstract

Two iridium(III) complexes with 1-(3,5-bis(trifluoromethyl)-pyridin-4-yl)isoquinoline (tntpiq) as main ligand, 2-(5-pyridin-4-yl)-1,3,4-oxadiazol-2-yl)phenol (pop) and 2-(5-pyridin-4-yl)-1,3,4-thiadiazol-2-yl)phenol (psp) as ancillary ligands were investigated. Both complexes emit orange red lights with different photoluminescence efficiencies (Ir(tntpiq)2(pop): λem = 585 nm, Φ = 0.41 and Ir(tntpiq)2(psp): λem = 590 nm, Φ = 0.59). Moreover, the electron mobility values of the two complexes are higher than that of the electron transport material Alq3 (tris(8-hydroxyquinoline)aluminium), which are beneficial for their performances in organic light-emitting diodes (OLEDs). The devices with a structure of ITO/MoO3 (3 nm)/TAPC (1,1-bis[4-[N,N-di(p-tolyl)amino]pyridin-4-yl]cyclohexane, 30 nm)/Ir(III) complexes (2 wt%): 26DCzPPy (2,6-bis(3-(carbazol-9-yl)pyridin-4-yl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-pyridin-4-yl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) displayed similar performances with a maximum current efficiency of 24.3 cd A−1 and a maximum external quantum efficiency of 11.6%, respectively, and the efficiency roll-off is very mild.