In:
Journal of Materials Chemistry C, Royal Society of Chemistry (RSC), Vol. 11, No. 36 ( 2023), p. 12174-12184
Abstract:
Nitrogen-containing polycyclic aromatic hydrocarbons (N-PAH) have been widely used as deep lowest unoccupied molecular orbital (LUMO) acceptors in donor–acceptor (D–A) red thermally activated delayed fluorescence (TADF) emitters and in organic light-emitting diodes (OLEDs). However, most of the studies have focused disparately on donor/acceptor combinations to yield efficient emitters, while a methodological study investigating the influence of nitrogen (N) doping ratios on the ground and excited states of PAH acceptors is rare. Here, we report a family of four different N-PAH acceptors containing different numbers of nitrogen atoms within the N-PAH and their use in D–A TADF emitters, DMACBP, DMACPyBP, DMACBPN and DMACPyBPN, when coupled to the same donor, 9,9-dimethyl-9,10-dihydroacridine (DMAC). As the nitrogen content in the acceptor increases the LUMO becomes progressively more stabilized while the singlet–triplet energy gap (Δ E ST ) decreases and the rate constant for reverse intersystem crossing ( k RISC ) increases. In particular, introducing nitrogen at the 10-position of dibenzo[ a , c ]phenazine (BP) leads to a more than ten-fold enhancement in k RISC in DMACPyBP and DMACPyBPN compared to DMACBP and DMACBPN. Among the OLEDs with all four emitters that with DMACBPN demonstrates the highest EQE max of 19.4% at an emission peak of 588 nm, while the deepest red emitting device employed DMACPyBPN ( λ EL = 640 nm) with an EQE max of 5.4%.
Type of Medium:
Online Resource
ISSN:
2050-7526
,
2050-7534
Language:
English
Publisher:
Royal Society of Chemistry (RSC)
Publication Date:
2023
detail.hit.zdb_id:
2702245-6
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