Strongly Luminescent Tungsten Emitters with Emission Quantum Yields of up to 84 %: TADF and High-Efficiency Molecular Tungsten OLEDs.

ABSTRACT

Metal-TADF (thermally activated delayed fluorescence) emitters hold promise in the development of next generation light-emitting materials for display and lighting applications, examples of which are, however, largely confined to CuI and recently AuI , AgI , and AuIII emitters. Herein is described the design strategy for an unprecedented type of metal-TADF emitter based on inexpensive tungsten metal chelated with Schiff base ligand that exhibit high emission quantum yields of up to 56 % in solutions and 84 % in thin-film (5 wt % in 1,3-bis(N-carbazolyl)benzene, mCP) at room temperature. Femtosecond time-resolved emission (fs-TRE) spectroscopy and DFT calculations were undertaken to decipher the TADF properties. Solution-processed OLEDs fabricated with the W-TADF emitter demonstrated external quantum efficiency (EQE) and luminance of up to 15.6 % and 16890 cd m-2 , respectively.