Thermally Activated Delayed Fluorescent Materials Combining Intra- and Intermolecular Charge Transfers

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Abstract
A novel thermally activated delayed fluorescent (TADF) compound, 9-(3-((4,6-diphenyl-1,3,5-triazin-2-yl)oxy)phenyl)-3,6-diphenyl-9H-carbazole (PhCz-o-Trz), with donor-σ-acceptor (D-σ-A) motif is developed. A flexible small space σ-junction is adopted to partly suppress the intramolecular charge transfer (intra-CT) while inversely enhancing the intermolecular CT (inter-CT) between D/A moieties, realizing the coexistence of both intra- and inter-CT in an amorphous aggregate. The coexistence of dual CTs increases the complexity of the singlet and triplet states mixing, enhancing the triplet-to-singlet spin-flip transition and thereby the TADF emission. Additionally, PhCz-o-Trz is evaluated not only as an emitter but also a sensitizing host for fluorescent and phosphorescent dopants, all realizing high efficiencies with alleviated efficiency roll-offs. These results shed light on the development of new TADF materials with dual CTs and may further deepen our understanding about TADF mechanisms.
Funding Information
  • Japan Society for the Promotion of Science (17H01231, 17J09631)

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