Thioxanthone-containing blue thermally activated delayed fluorescent emitter

Abstract

Accelerating reverse intersystem crossing (RISC) without sacrificing fast radiative decay is effective in suppressing efficiency roll‐off (eRO) in thermally activated delayed fluorescence (TADF)‐based organic light‐emitting diodes. We here report a TADF emitter, CC‐TXO‐I, combining a bicarbazole donor (CC) and a sulfur‐containing acceptor (TXO). The CC is used to accelerate radiative decay via moderate donor‐acceptor torsion angle, and the TXO is expected to provide fast RISC by the heavy atom effect. We realized very large rate constants of RISC (k RISCs) of ~107 s−1. Both k RISCs and rate constants of radiative decay of CC‐TXO‐I increased with increasing doping concentration, attributing improved eRO.

Peripheral halogen atoms in multi-resonant thermally activated delayed fluorescence emitters: the role of heavy atoms in intermolecular interactions and spin orbit coupling

“…19,20 Further examples of HAE investigations of D–A TADF materials are summarised in the (ESI†). 21–31…”

“…19,20 Further examples of HAE investigations of D-A TADF materials are summarised in the (ESI †). [21][22][23][24][25][26][27][28][29][30][31] In contrast to D-A TADF materials, multi-resonant TADF emitters (MR-TADF) are rigid polycyclic aromatic compounds containing a combination of p-and n-dopants, which usually show larger DE ST (40.10 eV) and slower k RISC (B10 4 s À1 ). 32 RISC is typically enabled through an upper-state crossing mechanism rather than the vibronic coupling of the lower energy triplet states in D-A TADF emitters.…”