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

Abstract

AbstractThe “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.