TADF-emitting dendrimers for scalable bar-coating fabrication of light-emitting electrochemical cells

The light-emitting electrochemical cell (LEC) is a good fit for scalable ambient-air coating and printing, since it can deliver efficient emission from a robust three-layer architecture comprising solely air-stable and soluble materials. However, a drawback is that hitherto employed emitters for printed LECs are either conjugated polymers that are efficiency and purification limited or small molecules that are difficult to solution process into uniform thin films. The recent advent of dendrimers that emit by thermally activated delayed fluorescence (TADF) promises to address all these issues, since they can efficiently utilize all (both singlet and triplet) excitons for the light emission, be of high purity because of their well-defined structure, and feature high solubility and good film-forming capacity by the virtue of being equipped with branched dendrons. Herein, an asymmetric second-generation TADF-dendrimer, tBuCz2m2pTRZ, is combined with an ionic-liquid electrolyte for the formulation of a tuned ink, which is used for a bar-coating fabrication of uniform LEC active-material films featuring a high photoluminescence quantum yield of 84%. This opportunity is ultimately utilized for the pioneering demonstration of a bar-coated TADF-dendrimer-LEC, which delivers uniform and bright green luminance of 350 cd m⁻² at an external quantum efficiency of 1.2%.