Helically Chiral Donor–Acceptor Double Hetero[4]helicenes with Circularly Polarized Thermally Activated Delayed Fluorescence.

Although helically chiral heterohelicenes are widely adopted in chiroptical studies, those with circularly polarized thermally activated delayed fluorescence (CP‐TADF), which are highly valuable for circularly polarized organic light‐emitting diodes (CP‐OLEDs), are rarely realized. Moreover, the core skeletons of known CP‐TADF heterohelicenes are limited to the p‐ and n‐doped structures with multiresonance effect. In this study, a new type of helically chiral CP‐TADF heterohelicenes featuring a fused donor–acceptor core skeleton is successfully designed and constructed. Enantiomers possessing high configurational stability are achieved and separated, and they efficiently emit CP light with dissymmetry factors reaching 3.1 × 10−3 in doped films. Owing to the excellent photophysical properties, a high‐performance CP‐OLED with the maximum external quantum efficiency of up to 20.0% and an electroluminescence dissymmetry factor reaching 2.9 × 10−3 is obtained. This new type of CP‐TADF heterohelicenes provides a large space for the development of high‐performance CP‐TADF materials for various applications. [ABSTRACT FROM AUTHOR]