A mature approach: Allowing solutions of poly[(4,4-didodecyldithieno[3,2-b: 2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl] (P1) to stand in a solvent of marginal quality leads to interchain aggregation. These supramolecular structures lead to thin films with higher charge carrier mobilities and internal order, as determined by the fabrication of thin film transistors and grazing-incidence wide angle X-ray scattering (GIWAXS) measurements, respectively. Aging of solutions is therefore a very straightforward method to modify the optoelectronic properties of solution-processable organic semiconductors.