Thermally Activated Delayed Fluorescence: An Extended Study of Peripherally Substituted DMAC‐TRZ Analogues

: A comprehensive experimental and theoretical study of a family of dyes of interest for organic light-emitting diode (OLED) applications is presented. Specifically, we compare the behavior of structurally related dyes obtained by peripheral substitution of a prototypical thermally activated delayed fluorescence (TADF) dye, DMAC-TRZ. Decorating the donor (DMAC) moiety with two phenyl groups, a blue-shift of the emission is obtained, as sought, and an increase of the spin-orbit coupling, suggesting amplified TADF. Quite surprisingly, subtle geometrical rearrangements of the two peripheral groups upon photoexcitation suppress again spin-orbit coupling, leading overall to a similar photophysics as DMAC-TRZ.