Thermally Activated Delayed Fluorescent Donor–Acceptor–Donor–Acceptor π-Conjugated Macrocycle for Organic Light-Emitting Diodes

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Abstract
A new class of thermally activated delayed fluorescent donor–acceptor–donor–acceptor (D–A–D–A) π-conjugated macrocycle comprised of two U-shaped electron-acceptors (dibenzo[a,j]phenazine) and two electron-donors (N,N’-diphenyl-p-phenyelendiamine) has been rationally designed and successfully synthesized. The macrocyclic compound displayed polymorphs-dependent conformations and emission properties. Comparative studies on physicochemical properties of the macrocycle with a linear surrogate has revealed significant effects of the structural cyclization of D–A-repeating structure, including more efficient thermally activated delayed fluorescence (TADF). Furthermore, an organic light-emitting diode (OLED) device fabricated with the macrocycle compound as the emitter has achieved a high external quantum efficiency (EQE) up to 11.6%, far exceeding the theoretical maximum (5%) of conventional fluorescent emitters and that with linear analog (6.9%).
Funding Information
  • European Regional Development Fund (POIR.04.04.00-00- 4668/17-00)
  • Asahi Glass Foundation
  • H2020 Marie Skłodowska-Curie Actions (778158)
  • Japan Society for the Promotion of Science (JP17H05155, JP19H05716)
  • Fundacja na rzecz Nauki Polskiej

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