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

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-07, Vol.440, p.135911, Article 135911
• Main Authors: Xiao, Shengbing, Gao, Ying, Wang, Runze, Liu, Haichao, Li, Weijun, Zhou, Changjiang, Xue, Shanfeng, Zhang, Shi-Tong, Yang, Bing, Ma, Yuguang
• Format: Article
• Language: English
• Subjects: Deep-blue emitter; Horizontal dipole orientation; Hybridized local and charge-transfer state; Near ultraviolet emission; Organic light-emitting diode
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.135911

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 EQEmax 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 (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.