Intermolecular interactions in molecular crystals and their effect on thermally activated delayed fluorescence of helicene-based emitters

Here, we discuss the influence of the crystal structure on the photophysical properties of two new TADF emitters containing a non-planar helical moiety. The presence of solvent in the crystal lattice of a diaza[5]helicene-based compound alters molecular packing significantly and suppresses aggregation. This results in more intense TADF emission and an increase in PLQY. Solution-processed OLED devices gave a maximum external quantum efficiency of 7.1%.