The color of the TADF emitter depends on the choice of the donor and acceptor moieties. Approximately, the choice of the donor dictates the HOMO, while the acceptor dictates the LUMO. The energetic difference between HOMO and LUMO is the bandgap, which is closely connected to the emission color of the emitter. Roughly, a bandgap of ca. 2.8 eV (450 nm) relates to blue emission, while 1.9 eV (650 nm) gives red emission.23 In Sec. 1, () was introduced as the most crucial parameter for TADF. This parameter is highly dependent of the localization of the Frontier orbitals HOMO and LUMO.69,70 The better the separation (or the smaller the overlap between HOMO and LUMO), the smaller (), which facilitates efficient ISC and rISC. From a design point of view, the overlap of HOMO and LUMO can be manipulated by the way in which the donor and acceptor moieties are connected. This is emphasized by analyzing the properties of different combinations of triphenyltriazine-type acceptors (Trz) with carbazole-type donors (Cz and mCz or ), which have been published by Lee et al.71,72 This work lead to the TADF emitters DCzTrz, TCzTrz, DCzmCzTrz, and TmCzTrz, which are shown in Fig. 6. Addition of an additional carbazole or dimethylcarbazole to DCzTrz changes the triplet energy () from 0.23 to 0.16 and 0.07 eV, respectively, in TCtTrz and DCzmCzTrz.