TADF Invariant of Host Polarity and Ultralong Fluorescence Lifetimes in a Donor‐Acceptor Emitter Featuring a Hybrid Sulfone‐Triarylboron Acceptor

Urban, Mateusz; Marek‐Urban, Paulina H.; Durka, Krzysztof; Luliński, Sergiusz; Pander, Piotr; Monkman, Andrew P.

Abstract

10H-Dibenzo[b,e][1,4]thiaborinine 5,5-dioxide (SO2B)—a high triplet (T1=3.05 eV) strongly electron-accepting boracycle was successfully utilised in thermally activated delayed fluorescence (TADF) emitters PXZ-Dipp-SO2B and CZ-Dipp-SO2B. We demonstrate the near-complete separation of highest occupied and lowest unoccupied molecular orbitals leading to a low oscillator strength of the S1→S0 CT transition, resulting in very long ca. 83 ns and 400 ns prompt fluorescence lifetimes for CZ-Dipp-SO2B and PXZ-Dipp-SO2B, respectively, but retaining near unity photoluminescence quantum yield. OLEDs using CZ-Dipp-SO2B as the luminescent dopant display high external quantum efficiency (EQE) of 23.3 % and maximum luminance of 18600 cd m−2 with low efficiency roll off at high brightness. For CZ-Dipp-SO2B, reverse intersystem crossing (rISC) is mediated through the vibronic coupling of two charge transfer (CT) states, without involving the triplet local excited state (3LE), resulting in remarkable rISC rate invariance to environmental polarity and polarisability whilst giving high organic light-emitting diode (OLED) efficiency. This new form of rISC allows stable OLED performance to be achieved in different host environments.

Citation

Urban, M., Marek‐Urban, P. H., Durka, K., Luliński, S., Pander, P., & Monkman, A. P. (2023). TADF Invariant of Host Polarity and Ultralong Fluorescence Lifetimes in a Donor‐Acceptor Emitter Featuring a Hybrid Sulfone‐Triarylboron Acceptor. Angewandte Chemie International Edition, 62(9), https://doi.org/10.1002/anie.202217530

• Journal Article Type: Article
• Acceptance Date: Jan 9, 2023
• Online Publication Date: Jan 24, 2023
• Publication Date: Feb 20, 2023
• Deposit Date: Sep 18, 2023
• Publicly Available Date: Sep 18, 2023
• Journal: Angewandte Chemie International Edition
• Print ISSN: 1433-7851
• Electronic ISSN: 1521-3773
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 62
• Issue: 9
• DOI: https://doi.org/10.1002/anie.202217530
• Keywords: General Chemistry; Catalysis
• Public URL: https://durham-repository.worktribe.com/output/1741275