To elucidate the mechanism underlying the full-color tunable TSCT emission of NDI polymers, we analyzed the electronic structures and transitions of isolated oligomers as well as the excited states of donor-acceptor pairs. First, we performed density functional theory (DFT) calculations to examine the impact of polycyclic aromatic structures on the molecular orbitals. To simplify the model, we considered a series of NDI oligomers containing 2 styrene and 2 PAM units (Table ). The spatial distribution and band diagrams of ground-state molecular orbitals were obtained for all types of oligomers using the Becke-3 Lee-Yong-Parr (B3LYP) functional, as shown in Figure .