wherein the central DMAC donor is decorated with two aryl groups containing at the 4-position differing electron-donating or withdrawing groups. The effect of donor decoration on the colour tuning of the emitters, their triplet exciton harvesting, and PL efficiencies is demonstrated. Further, using angle resolved photoluminescence spectroscopy we explore how the increased molecular weight and length of the emitter (depending on the nature of the peripheral substituent on the donor), affects the orientation of its TDM. Using light outcoupling simulations, the effect of TDM orientation on the light outcoupling efficiency is explored, showing a small improvement in outcoupling efficiency in most cases, compared to DMAC-TRZ.