Triarylborane-based thermally activated delayed fluorescence materials with an efficient reverse intersystem crossing

• Published in: Applied physics express Vol. 17; no. 4; pp. 41003 - 41006
• Main Authors: Okumura, Ryosuke, Kusakabe, Yu, Rauch, Florian, Lubczyk, Lukas, Suzuki, Katsuaki, Marder, Todd B., Kaji, Hironori
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.04.2024
• Subjects: charge transfer excited states; locally excited states; organic light-emitting diodes; reverse intersystem crossing; thermally activated delayed fluorescence; triarylborane compounds
• ISSN: 1882-0778; 1882-0786
• DOI: 10.35848/1882-0786/ad392a

Abstract Efficient reverse intersystem crossing (RISC) is an important process for thermally activated delayed fluorescence (TADF) to suppress efficiency roll-off in organic LEDs (OLEDs). Enhancing spin–orbit coupling is effective for fast RISC and is achieved by mediating a locally excited triplet state when RISC occurs between charge transfer states. Here, we experimentally confirmed that efficient RISC occurred in triarylborane-based TADF emitters named Phox- Me π , Phox- MeO π , and MeO3 Ph- FMe π . The three emitters showed large RISC rate constants exceeding 10 6 s −1 . The Phox- Me π -based OLED exhibited higher maximum external quantum efficiency (EQE max = 10.0%) compared to the Phox- MeO π -based OLED (EQE max = 6.7%).