Critical Role of High-Lying Triplet States for Efficient Excitons Utilization in High-Performance Non-Doped Deep-Blue Fluorescent and Hybrid White Organic Light-Emitting Diodes

作者：Li, Baoxi; Li, Ganggang; Zhang, Han; Wu, Haozhong; Chen, Kongqi; Wang, Zhiming^*; Tang, Ben Zhong^*

来源：Advanced Optical Materials, 2022, 10(4): 2101724.

DOI：10.1002/adom.202101724

• deep-blue OLEDs
• high-lying triplet state
• hot excitons
• two-color hybrid WOLEDs

For organic light-emitting diodes (OLEDs), the characteristics of high-lying excited states of pure organic materials significantly affect the utilization of triplet excitons, which are critical in the process of electroluminescence. Herein, two novel molecules, PT-1 and PT-2, with deep-blue emission are obtained, which exhibit nearly identical photophysical behavior in the photoluminescence process. However, the remarkable distinction in the characteristics of the high-lying triplet excited states between PT-1 and PT-2 leads to a significant difference in the electroluminescence performance. Moreover, the non-doped OLED based on PT-1 exhibits maximum external quantum efficiency (eta(ext)) of 6.63% with a low efficiency roll-off. In addition, the authors employ PT-1 as the phosphorescent host materials to fabricate two-color hybrid white OLEDs (WOLEDs), from which they can realize the transformation from warm-white to quasi-white light by tuning the thickness of emission layer, with maximum eta(ext) and power efficiency (eta(p)) of 23.93%/84.37 lm W-1 and 10.49%/33.96 lm W-1, respectively. These results deeply demonstrate the effects of high-lying excited states on electroluminescence and facilitate the preparation of functional OLEDs.