Efficient yellow electroluminescence of four iridium(iii) complexes with benzo[d]thiazole derivatives as main ligands?

Dalton Transactions Pub Date: 2018-05-21 DOI: 10.1039/C8DT01479E

Abstract

Four bis-cyclometalated iridium(III) complexes, (bt)2Ir(tpip), (fbt)2Ir(tpip), (cf3bt)2Ir(tpip) and (dfbt)2Ir(tpip) (bt = 2-phenylbenzo[d]thiazole, fbt = 6-fluoro-2-phenylbenzo[d]thiazole, cf3bt = 2-phenyl-6-(trifluoromethyl)benzo[d]thiazole, dfbt = 5,7-difluoro-2-phenylbenzo[d]thiazole, tpip = tetraphenylimidodiphosphinate) have been synthesized and investigated. All complexes emit yellow light peaks at 564–574 nm with quantum efficiencies (Φem) of 27.1–48.4% and excited state lifetimes of 2.40–2.81 μs in degassed CH2Cl2 solution at room temperature. Correspondingly, organic light-emitting diodes (OLEDs) using these complexes as emitters achieve yellow electrophosphorescence with good device characteristics. Due to its highest photoluminescence quantum yield (48.4%), the device based on (dfbt)2Ir(tpip) displays the best device performance with a maximum current efficiency (ηc, max) of up to 69.8 cd A?1 and a maximum external quantum efficiency (EQEmax) of up to 24.3%. Furthermore, all devices showed low efficiency roll-off ratios. The EQE could still be retained at 17.7%, 16.4%, 18.3% and 20.6% for four devices at a luminance of 1000 cd m?2. These results suggest that these materials have potential application in efficient OLEDs.

Graphical abstract: Efficient yellow electroluminescence of four iridium(iii) complexes with benzo[d]thiazole derivatives as main ligands
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