Affiliation:
1. Faculty of Chemistry Warsaw University of Technology Noakowskiego 3 00-664 Warsaw Poland
2. Department of Physics Durham University South Road Durham DH1 3LE UK
3. Faculty of Chemistry Silesian University of Technology Strzody 9 44-100 Gliwice Poland
Abstract
Abstract10H‐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.
Funder
European Social Fund
Narodowa Agencja Wymiany Akademickiej
Engineering and Physical Sciences Research Council
Wroclawskie Centrum Sieciowo-Superkomputerowe, Politechnika Wroclawska
Subject
General Chemistry,Catalysis
Cited by
11 articles.
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