To visualize the interaction modes in these groups, we take the representative geometry of each group: C1, C2 and C3 (shown in Fig. and; also see Fig. , S7 and S8 in Supplementary Information for magnified representation). The C1 configuration shows that F 4 TCNQ anion is in close proximity to the hexyl side-chain of the polymer. This mode of dopant interaction with the side-chains of polymers has been postulated for molecular doped polymer films by various studies. Configuration C2 depicts the well known π-πstack configuration of dopant F 4 TCNQ anions with the thiophene unit of the polymer. In configuration C3, the F 4 TCNQ anions are slipped stacked to interact with two thiophene units in the polymer chain. Thus, our MD simulations reveal three major dopant-polymer interaction modes: side-chain, π-π-stack and slipped stack. These different interactions modes must result in different types of excitonic couplings between electronic levels of dopant and polymer ion-pairs. The Coulombic excitonic couplings between various ion-pairs are calculated using transition partial charges. The computational details can be found in the reference. Table : Computed excitonic couplings for different dopant-polymer interaction modes.