Multiple‐Resonance‐Induced Thermally Activated Delayed Fluorescence Materials Based on Indolo[3,2,1‐ jk ]carbazole with an Efficient Narrowband Pure‐Green Electroluminescence

Herein, we report two multiple-resonance thermally activated delayed fluorescence emitters (VTCzBN and TCz-VTCzBN) based on indolo[3,2,1-jk]carbazole unit and boron-nitrogen skeletons, whose emissions peaking at 496 and 521 nm with full width at half maximum of 34 and 29 nm, respectively. Meanwhile, fast rate constants of reverse intersystem crossing of above 10