From analysis above, BT-BT crossings are clearly the most efficient path for interchain charge transport (as also hypothesised elsewhere ) due to the π-π interactions. Therefore, we calculated the chain IDs which share at least one BT-BT crossing and then recognised the cluster of chains in contact by BT-BT crossings for all three polymer models. In Figure , the chains belong to each cluster are coloured similarly and the individual chains (which do not belong to any cluster) are removed. As shown, by increasing molecular weight, large clusters of polymer chains in contact through BT-BT crossings appear, an observation consistent with the experimental increase of mobility with increasing molecular weight . Note that considering great intrachain transport of IDTBT and considerable orbital overlaps at BT-BT crossings, each colour in Figure could represent an efficient path for charge transport. To provide a link between classical simulation and the electronic properties of IDTBT and, by extension, other SCPs, we adopt a method to approximate the bulk electronic structure of a polymer by averaging over the properties of numerous single-chain conformations extracted from MD simulation, with consideration of the chain environment (Figure ) . We compute three properties for IDTBT chains: (i) the density of states (DOS), (ii) its projection on IDT and BT fragments (PDOS), and (iii) an energy-dependent inverse participation ratio (IPRa measure of delocalisation).