Spiro[Acridine‐Indoloacridine] Donor Based TADF Emitter with Near‐Unity PLQY and Horizontal Dipole Orientation toward High‐Efficiency OLEDs with Low Efficiency Roll‐Off

• Published in: Advanced optical materials 2024-03, Vol.12 (9), p.n/a
• Main Authors: Wu, Yaxun, Li, Nengquan, Ni, Fan, Ning, Weimin, Ying, Ao, Zhang, He, Gao, Xiang, Gong, Shaolong, Yang, Chuluo
• Format: Article
• Language: English
• Subjects: Conjugation; Dipoles; Emitters; Excitons; horizontal dipole orientation; Horizontal orientation; Organic light emitting diodes; Photoluminescence; Quantum efficiency; thermally activated delayed fluorescence
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202301954

Designing thermally activated delayed fluorescence (TADF) emitters with excellent photoluminescence quantum yield (PLQY), preferential horizontal emitting dipole orientation (Θ//), and fascinating ability to rapidly utilize both singlet and triplet excitons for radiation is crucial for high‐performance organic light‐emitting diodes (OLEDs) with both high efficiency and relieved efficiency roll‐off. Integrating these advantages into a single TADF emitter is a formidable challenge. In this work, a spiro[acridine‐indoloacridine]‐based rigid donor, named AIA, is designed to establish a cooperatively long‐axis extended and conjugation expanded donor–acceptor type TADF emitter (AIA‐TRZ). The proof‐of‐the‐concept emitter simultaneously achieves an excellent PLQY of 99%, a near‐unity Θ// of 99%, and balanced excited state dynamic parameters. OLEDs based on AIA‐TRZ realize remarkable performance with an emission peak at around 480 nm, including doping concentration insensitivity, a maximum external quantum efficiency (EQEmax) of 37.3%, extremely low efficiency roll‐off, and over 20% EQE even at 14000 cd m−2. A donor of spiro[acridine‐indoloacridine] enables a superior D–A type thermally activated delayed fluorescence emitter of AIA‐TRZ with near‐unity photoluminescence quantum yield and horizontal emitting dipole orientation, as well as fast but balanced kr, kISC, and kRISC rates. The AIA‐TRZ‐based organic light‐emitting diodes achieve excellent performance with a high maximum external quantum efficiency of 37.3% and low efficiency roll‐off of 11.2% at 1000 cd·m−2.