A series of red iridium(iii) complexes using flexible dithiocarbamate derivatives as ancillary ligands for highly efficient phosphorescent OLEDs?

Materials Chemistry Frontiers Pub Date: 2019-03-19 DOI: 10.1039/C9QM00088G

Abstract

Five red cyclometalated iridium(III) complexes containing the unique four-membered ring Ir–S–C–S backbone with different dithiocarbamate derivatives as ancillary ligands and 1-(4-(trifluoromethyl)phenyl)isoquinoline (4tfmpiq) as the main ligand were synthesized at room temperature within ten minutes. The emission color (λpeak = 607–619 nm) and photoluminescence quantum efficiency (PLQY) (ΦP = 36.6–63.0%) can be effectively tuned by introducing different electron – donating substituents such as diisopropylamine (dipdtc), diphenylamine (dpdtc), bis(4-(tert-butyl)phenyl)amine (tBudpdtc), carbazole (Czdtc) and 3,6-di-tert-butyl-9H-carbazole (tBuCzdtc) into the dithiocarbamate ancillary ligands. Employing (4tfmpiq)2Ir(dipdtc) as the emitter, the organic light emitting diodes (OLEDs) with double emitting layers exhibit good performances with a maximum current efficiency (ηc,max) of 18.67 cd A?1, an EQEmax of 20.69% and low efficiency roll-off with an EQE of 18.11% at the practical luminance of 1000 cd m?2. The Commision Internationale de L’Eclairage coordinates of (0.660, 0.337) are quite close to the National Television System Comittee (NTSC) standard red emission. These results demonstrate that by introducing different electron – donating substituents into the dithiocarbamate ligands, the diversity of the S–C–S ligands is greatly enriched for red Ir(III) complexes and the corresponding OLEDs.

Graphical abstract: A series of red iridium(iii) complexes using flexible dithiocarbamate derivatives as ancillary ligands for highly efficient phosphorescent OLEDs
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