Highly Efficient Solid-State Near-Infrared Emitting Material Based on Triphenylamine and Diphenylfumaronitrile with an EQE of 2.58% in Nondoped Organic Light-Emitting Diode

The development of efficient near-infrared (NIR) emitting material is of current focus. Donor-acceptor (D-A) architecture has been proved to be an effective strategy to obtain narrow energy gap. Herein, a D-A-type NIR fluorescent compound 2,3-bis(4-(diphenylamino)-[1,1-biphenyl]-4-yl)fumaronitrile (TPATCN) is synthesized and fully characterized. As revealed by theoretical calculations and photophysical experiments, TPATCN exerts the advantages of the relatively large dipole moment of the charge transfer state and a certain degree of orbital overlap of the local excited state. A highly mixed or hybrid local and charge transfer excited state might occur to simultaneously achieve both a large fraction of singlet formation and a high quantum efficiency in D-A system. TPATCN exhibits strong NIR fluorescence with the corresponding thin film quantum efficiency of 33% and the crystal efficiency of 72%. Remarkably, the external quantum efficiency of nondoped NIR organic light-emitting diode (OLED) reaches 2.58% and remains fairly constant over a range of 100-300 mA cm(-2), which is among the best results for NIR OLEDs reported so far.