Highly efficient solution-processed deep-red emitting heteroleptic thiophene-phenylquinoline based Ir(III) complexes for phosphorescent organic light-emitting diodes

New series of cyclometalated iridium(III) complexes [(TPQ)(2)Ir(pic), (TPQ)(2)Ir(pic-N-O) and (TPQ)(2)Ir(acac)] based on thiophene containing phenylquinoline main ligand (C<^>N) and three different ancillary ligands (picolinic acid, picolinic acid-N-oxide and acetylacetone) have been synthesized. Synthesized Will) complexes were characterized by H-1 NMR, C-13 NMR, mass spectroscopy and their absorption, emission, cyclic voltammetry and electroluminescence properties were steadily investigated. Herein, (TPQ)(2)Ir(pic-N-O) complex showed smaller singlet-triplet splitting energy and higher transition dipole moment from ground to excited state, thus making (TPQ)(2)Ir(pic-N-O) complex, a good candidate as a phosphorescent emitter. Phosphorescent organic light-emitting diodes (PhOLEDs) were fabricated using the Will) complexes, [(TPQ)(2)Ir(Pic), (TPQ)(2)Ir(pic-N-O) and (TPQ)(2)Ir(acac)], as deep-red emitters and devices using (TPQ)(2)Ir(-pic-N-O) achieved a maximum external quantum efficiency (EQE) of 15.42% and a current efficiency of 13.94 cd/A, whereas devices using (TPQ)(2)Ir(acac) showed a more saturated/deep-red emission with a maximum EQE of 11.45%. (C) 2017 Elsevier Ltd. All rights reserved.