2021/06/22 by Umamahesh Balijapalli, Yi‐Ting Lee, Buddhika S. B. Karunathilaka +5
Chemistry · Engineering · Materials Science · #Atomic physics #Chemistry #Dipole #Excited state #Exciton #Fluorescence #Intersystem crossing #Intramolecular force #Luminescence and Fluorescent Materials #Materials science #Optics #Optoelectronics #Organic Electronics and Photovoltaics #Organic Light-Emitting Diodes Research #Phenazine #Phenoxazine #Photochemistry #Photoluminescence #Physics #Singlet state #Stereochemistry #Transition dipole moment
paper · doi:10.1002/ange.202106570
openalex publication_date 2021/06/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Abstract Three thermally activated delayed fluorescence (TADF) molecules, namely PQ1 , PQ2 , and PQ3 , are composed of electron‐accepting (A) tetrabenzo[ a , c ]phenazine (TBPZ) and electron‐donating (D) phenoxazine (PXZ) units are designed and characterized. The combined effects of planar acceptor manipulation and high steric hindrance between D and A units endow high molecular rigidity that suppresses nonradiative decay of the excitons with improved photoluminescence quantum yields (PLQYs). Particularly, the well‐aligned excited states involving a singlet and a triplet charge‐transfer excited states and a localized excited triplet state in PQ3 enhances the reverse intersystem crossing rate constant ( k RISC ) with a short delay lifetime ( τ d ). The orange–red OLED based on PQ3 displays a maximum external EL quantum efficiency (EQE) of 27.4 % with a well‐suppressed EL efficiency roll‐off owing to a completely horizontal orientation of the transition dipole moment in the film state.