LAUSR

Five heteroleptic, cyclometalated (C$$^{\wedge }$$∧N) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline (piq) derivatives, Ir(acac)(piq)$$_{2}$$2, Ir(acac)(2,4-difluoro-piq)$$_{2}$$2, Ir(acac)(4-trifluoromethyl-piq)$$_{2}$$2, Ir(acac)(4-N,N-dimethyl-piq)$$_{2}$$2, Ir(acac)(4-acetyl-piq)$$_{2}$$2, were synthesized and characterized. The ($$\text {C}^{{\wedge }}\text {N})_{2}$$C∧N)2Ir(acac) complexes in toluene showed phosphorescence ($$\uplambda _{\max }= 598$$λmax=598 nm to 658 nm) with quantum yields (0.1 to 0.32) and microsecond lifetimes (0.43 to 1.9 $$\upmu $$μs). The complexes were non-luminescent in thin films due to self-quenching but luminescent when lightly doped (5%) in a host organic material, 4,4$$^\prime $$′-Bis(N-carbazolyl)-1,1$$^\prime $$′-biphenyl (CBP). The HOMO levels determined using cyclic voltammetric oxidation potentials were in the range −5.48 to −5.80 eV. Electroluminescence properties and performance of the Ir complexes doped in CBP (active layer) were studied in a multilayer (ITO/F4TCNQ/TPD/doped CBP/BCP/LiF/Al) organic light emitting device (OLED). The electroluminescense (EL) spectra of the device matched with the phosphorescent spectra of the Ir complexes. The turn-on voltage at $$\sim $$∼4.5 V, maximum brightness of 7600 cd/$$\hbox {m}^{2}$$m2 and current efficiency of $$\sim $$∼7.0 cd/A at a brightness of $$\sim $$∼100 cd/$$\hbox {m}^{2}$$m2 indicate that these are promising OLED materials.GRAPHICAL ABSTRACTSynopsis. Heteroleptic, cyclometalated (C$$^{\wedge }$$∧N) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline were synthesized and their photophysical, electrochemical and electroluminescence properties were studied. The OLED of Ir complex as emitting material showed turn-on voltage at $$\sim $$∼4.5 V, maximum brightness of 7600 cd/$$\hbox {m}^{2}$$m2 and current efficiency of $$\sim $$∼7.0 cd/A at a brightness of $$\sim $$∼100 cd/$$\hbox {m}^{2}$$m2.