Highly efficient hybridized local and Charge-transfer (HLCT) Deep-blue electroluminescence with excellent molecular horizontal orientation

Efficient deep-blue emitters with nice color purity are fundamental in organic light-emitting diode (OLED) applications. Herein, we report two phenanthroimidazole (PPI) derivative deep-blue emitters (DP, SP) with hybrid local and charge-transfer (HLCT) properties of high photoluminescence quantum yield (PLQY) and nice color purity. More importantly, the horizontal dipole orientation (Θ//) of them are both superior to the isotropic emitters (66.7%), especially the Θ// of SP is 89.5%, which can greatly improve its OLED performance. As a result, non-doped OLED of SP exhibits deep-blue emission with Commission Internationale de lEclairage (CIE) coordinate of (0.158, 0.068) and maximum external quantum efficiency (EQEmax) of 11.3%, which is nearly twice that of DP and is one of the best results among the non-delayed, non-doped deep-blue fluorescent OLEDs. Furthermore, SP-based doped OLED displays an excellent performance of near ultraviolet (NUV) emission at 406 nm with CIE coordinate of (0.157, 0.046) and EQEmax of 7.5%, which is also a competitive result in the materials with comparable NUV OLED applications.