Efficient phosphorescent red iridium(iii) complexes containing a four-membered Ir–S–C–S ring backbone and large hindered spacers for high-performance OLEDs†
Abstract
Two efficient red iridium(III) complexes, (4tfmpq)2Ir(tBudpdtc) and (4tfmpq)2Ir(tBuCzdtc), containing a unique four-membered ring Ir–S–C–S backbone with flexible dithiocarbamate derivatives (tBudpdtc = N,N-bis(4-(tert-butyl)phenyl)dithiocarbamate and tBuCzdtc = N-3,6-di-tert-butyl-9H-carbazole dithiocarbamate) with large hindered spacers as ancillary ligands, respectively, and 4-(4-(trifluoromethyl)phenyl)quinazoline (4tfmpq) as the main ligand were synthesized at room temperature in 10 min and investigated in detail. Due to the electron-deficient 4tfmpq main ligand and two ancillary ligands with bulky electron-donating substituents, the photophysical properties of two complexes can be effectively regulated (λpeak = 630 nm, ΦP = 75.0% for (4tfmpq)2Ir(tBudpdtc), and 614 nm and 85.0% for (4tfmpq)2Ir(tBuCzdtc), respectively). Employing the two complexes as emitters, organic light emitting diodes (OLEDs) with double emissive layers exhibit superior performances with a maximum current efficiency of 34.72 cd A−1, a maximum external quantum efficiency (EQEmax) of 26.66% with low efficiency roll-off and an EQE of 24.62% was still obtained at a practical luminance of 1000 cd m−2. These results suggest that Ir(III) complexes with a four-membered ring Ir–S–C–S backbone containing flexible dithiocarbamate derivatives have potential application in OLEDs.
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