Search

Device simplification is of practical significance for organic light emitting diodes (OLEDs), and remains the great challenge for deep‐red emitters. Herein, a deep‐red thermally activated delayed fluorescence molecule (pTPA‐DPPZ) is reported which features a T shaped structure containing two triphenylamine (TPA) donors, one either side of a planar dipyridophenazine (DPPZ) acceptor. The rational spatial arrangement of the functional groups leads to limited but sufficient molecular packing for effective carrier transport. The neat pTPA‐DPPZ film achieves an around 90‐fold improved radiation rate constant of 107 s−1 and the nearly unitary reverse intersystem crossing (RISC) efficiency, as well as accelerated emission decays for quenching suppression. The high radiation and RISC result in a photoluminescence quantum yield of 87 %. The bilayer OLED based on the pTPA‐DPPZ emissive layer achieved the record external quantum efficiencies of 12.3 % for maximum and 10.4 % at 1000 nits, accompanied by the deep‐red electroluminescence with the excellent color purity. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) organic light‐emitting diodes (OLEDs) show great potential in a variety of applications including sensors, night vision, and information security. Despite the superiority of thermally activated delayed fluorescence (TADF) in 100 % exciton harvesting, the development of NIR TADF OLEDs is still a great challenge, especially in terms of solution‐processing technology. In this work, a multicyano acceptor of 2‐dicyanomethylene‐3‐cyano‐4,5,5‐trimethyl‐2,5‐dihydrofurance (TCF) with strong electron‐withdrawing ability was employed to construct solution‐processible NIR emitters, CzTCF and tBCzTCF, with the feature of donor–π–acceptor (D–π–A) structure. The significantly enhanced intermolecular charge transfer effects not only render the deep‐red and NIR emissions of CzTCF and tBCzTCF films, respectively, but also lead to their typical TADF characteristics. Consequently, the nondoped solution‐processed NIR OLED based on tBCzTCF was successfully demonstrated with the peak wavelength of 715 nm, which paves the way for developing NIR emitters without polycyclic aromatic cores and heavy‐metal ions. A multicyano‐substituted acceptor and styryl π‐conjugate linker were both optimized to realize efficient NIR thermally activated delayed fluorescence (TADF) emitters (CzTCF and tBCzTCF) with simple D–π–A structure. The three linearly distributed cyano groups in TCF and the longer conjugation in the styryl π‐linker effectively regulated the D–A interactions and the frontier molecular orbital distributions (see scheme). [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials have great potential for applications in many fields. However, it is more challenging for such kinds of materials to achieve efficient NIR emission in comparison to visible light. Herein, as a proof of concept, three acceptors are regularly aligned to optimize intramolecular charge transfer (ICT) interactions in donor‐π‐acceptor molecules to improve bathochromic shift and TADF performance, which successfully supports the application in NIR OLEDs. More information can be found in the Full Paper by C. Han, H. Xu, et al. on page 1010. [ABSTRACT FROM AUTHOR]