Deep-red iridium complex with alkyl-functionalized ligands for high-performance phosphorescent organic light-emitting diodes

In this work, a novel deep-red (638 nm) iridium complex, Ir(bp3b)(2)(dend), is developed. This compound exhibits suitable physical properties for a phosphorescent emitter. First, Ir(bp3b)(2)(dend) and its doped film exhibit balanced charge-transporting ability. Second, methyl and pentyl groups in ligands weaken the intermolecular interaction and endow Ir(bp3b)(2)(dend) with good film-formation property and low concentration sensitivity. Third, short phosphorescence lifetime (1073.2 ns) indicates that it is relatively easy for triplet exciton to return to the ground state in the form of phosphorescence. Therefore, Ir(bp3b)(2)(dend)-doped device displays high efficiencies (8.93 cd A(-1), 11.57 lm W-1, 15.63%), low roll-off of efficiencies, relatively low concentration sensitivity (from 5 to 10%), long device lifetime (T-75: 11,166 h at 100 cd m(-2)) and very stable electroluminescent spectra (from 1 cd m(-2) to maximum luminance). This performance is comparable to those of previous record deep-red (635-645 nm) phosphorescent emitters. More importantly, compared with previous record emitters, Ir(bp3b)(2)(dend) reports more kinds of excellent parameters. Such comprehensive deep-red phosphorescent emitter is rare at present.