Efficient electroluminescence of bluish green iridium complexes with 2-(3,5-bis(trifluoromethyl)phenyl)pyrimidine and 2-(3,5-bis(trifluoromethyl)phenyl)-5-fluoropyrimidine as the main ligands?

Inorganic Chemistry Frontiers Pub Date: 2018-04-25 DOI: 10.1039/C8QI00294K

Abstract

We thoroughly investigated four iridium(III) complexes (Ir(tfmphpm)2(acac), Ir(f-tfmphpm)2(acac), Ir(tfmphpm)2(tpip), and Ir(f-tfmphpm)2(tpip)) using 2-(3,5-bis(trifluoromethyl)phenyl)pyrimidine (tfmphpm) and 2-(3,5-bis(trifluoromethyl)phenyl)-5-fluoropyrimidine (f-tfmphpm) as the main ligands and 2,4-pentanedionate (acac) and tetraphenylimidodiphosphinate (tpip) as the ancillary ligands. All complexes showed bluish green emissions peaking at 473–480 nm with very high photoluminescence quantum efficiencies in the range of 85–95%. The organic light-emitting diodes (OLEDs) using these emitters exhibited good performances. Especially, the device using Ir(tfmphpm)2(tpip) with the structure of ITO (indium-tin-oxide)/MoO3 (molybdenum oxide, 3 nm)/TAPC (di-[4-(N,N-ditolyl-amino)phenyl]cyclohexane, 50 nm)/mCP (1,3-bis(9H-carbazol-9-yl) benzene, 5 nm)/Ir(tfmphpm)2(tpip) (6 wt%)?:?PPO21 (3-(diphenylphosphoryl)-9-(4-(diphenylphosphoryl)phenyl)-9H-carbazole, 10 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl) benzene, 50 nm)/LiF (1 nm)/Al (100 nm) displayed the best performances with a maximum luminance of 28?194 cd m?2, a maximum current efficiency of 74.70 cd A?1, and a maximum external quantum efficiency up to 35.0%, and the efficiency roll-off ratio was small. The current efficiency of the device remained as high as 66.46 cd A?1 at the brightness of 1000 cd m?2, suggesting that they are potential materials for applications in OLEDs.

Graphical abstract: Efficient electroluminescence of bluish green iridium complexes with 2-(3,5-bis(trifluoromethyl)phenyl)pyrimidine and 2-(3,5-bis(trifluoromethyl)phenyl)-5-fluoropyrimidine as the main ligands
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