The nature of the lowest-energy excited states can play a significant role in the color purity of the emitter. In particular, the narrowband of MR-TADF emitters is conserved when the S1 state possesses SRCT, whereas the emission can broaden in some cases when the MR-TADF core is decorated with donor groups due to the stabilization of the LRCT state that dominates in donoracceptor systems. To gain insight into the relative energies of these states and to rationalize the optoelectronic properties of the emitters, the FMOs were first modelled at the optimized ground state geometry in the gas-phase using the density functional theory (DFT) at the PBE0/6-31G(d,p) level of theory. In contrast to the planarities calculated from the X-ray structures, those calculated from the DFT-optimized structures show planarity differences between the two compounds (Figure ). 3TPA-DiKTa adopts a more planar conformation, with a planarity ratio of 74%, compared to 3DPA-DiKTa where the planarity ratio is 42%.