Publications by Pabitra Nayak


Synthesis, photophysical, electrochemical and electroluminescence studies of red emitting phosphorescent Ir(III) heteroleptic complexes

Journal of Chemical Sciences 129 (2017) 1391-1398

F Ali, PK Nayak, N Periasamy, N Agarwal

© 2017, Indian Academy of Sciences. Abstract: Five heteroleptic, cyclometalated (C∧N) Iridium(III) complexes of acetylacetone (acac) and 1-phenyl-isoquinoline (piq) derivatives, Ir(acac)(piq)2, Ir(acac)(2,4-difluoro-piq)2, Ir(acac)(4-trifluoromethyl-piq)2, Ir(acac)(4-N,N-dimethyl-piq)2, Ir(acac)(4-acetyl-piq)2, were synthesized and characterized. The (C ∧N ) 2Ir(acac) complexes in toluene showed phosphorescence (λ max= 598 nm to 658 nm) with quantum yields (0.1 to 0.32) and microsecond lifetimes (0.43 to 1.9 μ s). 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′-Bis(N-carbazolyl)-1,1′-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 ∼ 4.5 V, maximum brightness of 7600 cd/m 2 and current efficiency of ∼ 7.0 cd/A at a brightness of ∼ 100 cd/m 2 indicate that these are promising OLED materials. GRAPHICAL ABSTRACT: Synopsis. Heteroleptic, cyclometalated (C∧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 ∼ 4.5 V, maximum brightness of 7600 cd/m 2 and current efficiency of ∼ 7.0 cd/A at a brightness of ∼ 100 cd/m 2.[Figure not available: see fulltext.].


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