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 (Theta(//)) of them are both superior to the isotropic emitters (66.7%), especially the Theta(//) 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 (EQE(max)) 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 EQE(max) of 7.5%, which is also a competitive result in the materials with comparable NUV OLED applications.

Automated summary

This study reports two deep-blue emitters (DP, SP) with high photoluminescence quantum yield and good color purity. The horizontal dipole orientation of these emitters is superior to isotropic emitters, especially for SP. This improvement greatly enhances the OLED performance.