Benzobisoxazole-based electron transporting materials with high Tg and ambipolar property: high efficiency deep-red phosphorescent OLEDsElectronic supplementary information (ESI) available: Molecular packing of TPO-DBBO; TOF signal, EL and PL spectra, optimized molecular configuration of 3Py-DBBO and TPO-DBBO. CCDC 1062626. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5tc01353d

Two new benzobisoxazole-based compounds, namely, 4,8-bis(3,5-di(pyridin-3-yl)phenyl)-2,6-dimethylbenzo[1,2- d :4,5- d ′]bis(oxazole) ( 3Py-DBBO ) and 4,8-bis(4-yl-triphenylphosphine oxide)-2,6-dimethylbenzo[1,2- d :4,5- d ′]bis(oxazole) ( TPO-DBBO ), were synthesized and characterized. The steric effect of the ortho hydrogens on the phenyl ring at 4,8-positions of benzobisoxazole resulted in out-of-plane twisting, and consequently a decrease of the intermolecular π-π interaction. The two new compounds showed excellent thermal stabilities with high glass-transition temperatures ( T g ) of 248 °C for 3Py-DBBO and 142 °C for TPO-DBBO . The two compounds exhibited ambipolar transport properties, with both electron and hole mobilities of 10 −6 -10 −5 cm 2 V −1 s −1 . Using the compounds as electron-transport materials, the deep-red phosphorescent organic light-emitting devices achieved a maximum external quantum efficiency up to 19.3%. Deep-red PhOLEDs using two new benzobisoxazole-based compounds as electronic transporting materials achieved a maximum EQE of 19.3%.