B‐N Covalent Bond Embedded Double Hetero‐[n]helicenes for Pure Red Narrowband Circularly Polarized Electroluminescence with High Efficiency and Stability
Guoyun Meng, Jianping Zhou, Xu‐Shuang Han, Wenlong Zhao, Yuewei Zhang, Meng Li, Chuan‐Feng Chen, Dongdong Zhang, Lian Duan
Abstract
Abstract Chiral B/N embedded multi‐resonance (MR) emitters open a new paradigm of circularly polarized (CP) organic light‐emitting diodes (OLEDs) owing to their unique narrowband spectra. However, pure‐red CP‐MR emitters and devices remain exclusive in literature. Herein, by introducing a B‐N covalent bond to lower the electron‐withdrawing ability of the para‐positioned B‐π‐B motif, the first pair of pure‐red double hetero‐[n]helicenes (n = 6 and 7) CP‐MR emitter peaking 617 nm with a small full‐width at half‐maximum of 38 nm and a high photoluminescence quantum yield of ≈100% in toluene is developed. The intense mirror‐image CP light produced by the enantiomers is characterized by high photoluminescence dissymmetry factors (g PL ) of +1.40/−1.41 × 10 −3 from their stable helicenes configuration. The corresponding devices using these enantiomers afford impressive CP electroluminescence dissymmetry factors (g EL ) of +1.91/−1.77 × 10 −3 , maximum external quantum efficiencies of 36.6%/34.4% and Commission Internationale de I’Éclairage coordinates of (0.67, 0.33), exactly satisfying the red‐color requirement specified by National Television Standards Committee (NTSC) standard. Notably a remarkable long LT95 (operational time to 95% of the initial luminance) of ≈400 h at an initial brightness of 10,000 cd m −2 is also observed for the same device, representing the most stable CP‐OLED up to date.