Multifunctional Materials Serving as Efficient Non-Doped Violet-Blue Emitters and Host Materials for Phosphorescence.

Efficient multifunctional materials acting as violet-blue emitters, as well as host materials for phosphorescent OLEDs, are crucial but rare due to demand that they should have high first singlet state (S1 ) energy and first triplet state (T1 ) energy simultaneously. In this study, two new violet-blue bipolar fluorophores, TPA-PI-SBF and SBF-PI-SBF, were designed and synthesized by introducing the hole transporting moiety triphenylamine (TPA) and spirobifluorene (SBF) unit that has high T1 into high deep blue emission quantum yield group phenanthroimidazole (PI). As the results, the non-doped OLEDs based on TPA-PI-SBF exhibited excellent EL performance with a maximum external quantum efficiency (EQEmax ) of 6.76 % and a violet-blue emission with Commission Internationale de L'Eclairage (CIE) of (0.152, 0.059). The device based on SBF-PI-SBF displayed EQEmax of 6.19 % with CIE of (0.159, 0.049), which nearly matches the CIE coordinates of the violet-blue emitters standard of (0.131, 0.046). These EL performances are comparable to the best reported non-doped deep or violet-blue emissive OLEDs with CIEy<0.06 in recent years. Additionally, the green, yellow and red phosphorescent OLEDs with TPA-PI-SBF and SBF-PI-SBF as host materials achieved a high EQEmax of about 20 % and low efficiency roll-off at the ultra-high luminance of 10 000 cd m-2 . These results provided a new construction strategy for designing high-performance violet-blue emitters, as well as efficient host materials for phosphorescent OLEDs.