Overall, multi-chain aggregation, resulting in the formation of extended rod-like aggregates, is expected to occur under conditions in which (1) partially overlapping chains are inseparable over sufficiently long time scales that they do not rearrange to the energetically favourable fully-overlapped chains before becoming trapped, and (2) single-chain folding occurs slowly enough that it is not expected to occur before multi-chain aggregation prevents further folding. The relative rates of the single-and multi-chain pathways that control the second of these conditions depend on the polymer concentration, chain length, and backbone flexibility. Although we have assumed these processes to be independent, they are likely to show a complex interdependence, with the progress along the single-chain folding pathway affecting the aggregation rate. A more complex model that accounts for these processes more completely, as well as explicitly including the effects of hydrodynamics, will further improve understanding of the solution-phase behaviour of semiflexible polymers. Finally, we have studied this behaviour using a coarse-grained model systematically parameterised to accurately represent P(NDI2OD-T2). However, these results are not expected to be specific to this molecule, with the reported dependence of the solution-phase morphology on solvent quality, backbone flexibility, concentration, chain length, and solvent viscosity expected to be applicable more generally to any semiflexible polymer.