Highly Efficient Near‐Infrared Thermally Activated Delayed Fluorescent Emitters in Non‐Doped Electroluminescent Devices

Abstract

Constructing organic near‐infrared (NIR) luminescent materials to confront the formidable barrier of “energy gap law” remains challenging. Herein, two NIR thermally activated delayed fluorescence (TADF) molecules named T‐β‐IQD and TIQD were developed by connecting N,N‐diphenylnaphthalen‐2‐amine and triphenylamine with a novel electron withdrawing unit 6‐(4‐(tert‐butyl)phenyl)‐6H‐indolo[2,3‐b]quinoxaline‐2,3‐dicarbonitrile. It is confirmed NIR‐TADF emitters concurrent with aggregation‐induced emission effect, J‐aggregate with intra‐ and intermolecular CN⋅⋅⋅H−C and C−H⋅⋅⋅π interactions, and large center‐to‐center distance in solid states can boost the emissive efficiencies both in thin films and non‐doped organic light‐emitting diodes (OLEDs). Consequently, the T‐β‐IQD‐based non‐doped NIR‐OLED achieved the maximum external quantum efficiency (EQEmax) of 9.44 % with emission peak at 711 nm, which is one of the highest efficiencies reported to date for non‐doped NIR‐OLEDs.