Exciton Recovery Strategy in Hot Exciton Emitter toward High-Performance Non-Doped Deep-Blue and Host-Sensitized Organic Light-Emitting Diodes

The hot exciton mechanism based on high-lying reverse intersystem crossing process has great advantages in achieving high-performance deep-blue organic light-emitting diodes (OLEDs). Nevertheless, how to solve the loss of high-lying excitons to improve device performance further is a pressing and challenging issue. To break through this shackle, a novel deep-blue emitter based on exciton recovery strategy is successfully design, namely CAT. By combining the transient absorption spectrum, theoretical calculation, magneto-electroluminescence, and transient-electroluminescence measurements, the multi-channeled pathways of excitons utilization via hot exciton and triplet-triplet annihilation processes is comprehensively demonstrated, and the proportion of singlet excitons by each channel. Finally, a high exciton utilization efficiency is successfully achieved, and the non-doped OLED based on CAT exhibit an excellent external quantum efficiency of 10.39% with the CIE coordinates of (0.15, 0.087). Furthermore, the sensitized blue fluorescent OLED by CAT as host also achieves excellent performance. More importantly, the operational lifetime of the multi-channel sensitized device is evaluated for the first time, performing the remarkable LT50 (lifetime to 50% of the initial luminance) of 320 h at 540 cd m(-2). These results fully reveal the significance of the exciton recovery strategy and give new inspiration for exploring high-performance blue OLEDs.

Automated summary

The hot exciton mechanism based on high-lying reverse intersystem crossing process is advantageous in achieving high-performance deep-blue OLEDs. To further improve device performance, a deep-blue emitter based on exciton recovery strategy, named CAT, is successfully designed. Through various measurements, the multi-channeled pathways of exciton utilization and the proportion of singlet excitons are comprehensively demonstrated. By achieving high exciton utilization efficiency, CAT-based non-doped OLEDs exhibit excellent external quantum efficiency and sensitized blue fluorescent OLEDs also achieve remarkable performance. The operational lifetime of the multi-channel sensitized device is evaluated for the first time, highlighting the significance of the exciton recovery strategy.