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High performance blue emitters with nice color purity are highly desired in the commercialization of organic light-emitting diodes (OLEDs). Herein, two blue-emissive hybridized local and charge-transfer (HLCT) phenanthroimidazole (PPI) derivatives were designed and synthesized. Comparing to the 9,9-dimethyl-9,10-dihydroacridine (DMAC) substituted DPCN , the 10H-spiro[acridine-9,9′-fluorene] (SAF) substituted SPCN demonstrates higher photoluminescence quantum yield (PLQY) and improved radiative transition rate (k r). With the same device structure, despite that SPCN and DPCN show similar electroluminescence (EL) spectra, the EL efficiency of SPCN is about 1.5 times that of DPCN. Especially the non-doped OLED based on SPCN , the maximum external quantum efficiency (EQE) is 7.1%, which is a competitive result among the conventional blue-emissive fluorescent emitters. More importantly, this work provides a general strategy to achieve high performance blue/deep-blue OLED by rational donor optimization. In this work, we report two blue-emissive hybridized local and charge-transfer (HLCT) materials (DPCN and SPCN) with different donor substitution. Comparing to the 9,9-dimethyl-9,10-dihydroacridine (DMAC) substituted DPCN , the 10H-spiro[acridine-9,9′-fluorene] (SAF) substituted SPCN displays an improved EL efficiency and blue purity, which provides an ideal molecular design strategy for efficient blue/deep-blue EL materials. [Display omitted] • Two blue-emissive HLCT materials with different donor substitution were designed and synthesized. • The relationship of structure-physical property as well as OLED performance are comprehensively explored. • Comparing to DPCN, the SAF substituted SPCN achieved a better OLED performance. [ABSTRACT FROM AUTHOR]

Two highly-efficient deep-blue materials DP and SP were synthesized, in which the more rigid SP performs even better photoluminescence quantum yield (PLQY) and horizontal dipole orientation (Θ //). As a result, the SP -based OLED achieves an extremely high external quantum efficiency (EQE) of over 11%, which is one of the best results among the non-doped, non-delayed deep-blue fluorescent OLEDs. [Display omitted] • Highly efficient HLCT deep-blue and near-ultraviolet emissions are realized. • Non-destructive C-H···π interactions decide a regular stacking for 89.5% Θ // of SP. • Non-doped, non-delayed deep-blue fluorescent OLED with EQE max of 11.3% is obtained. 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 (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. [ABSTRACT FROM AUTHOR]