Simply Structured Near-Infrared Emitters with a Multicyano Linear Acceptor for Solution-Processed Organic...

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.