Organic semiconductors (OSCs) have a number of advantages over conventional inorganic semiconductors for the fabrication of lightweight, flexible, and low-cost electronic devices. These advantages stem to a large extent from their ability to be processed from solution using inexpensive printing methods. However, the final thin-film microstructure is difficult to predict, particularly for semiconducting polymers, and has been found to depend on many factors, including the monomer chemical structure, molecular weight, solvent, solution concentration, and dissolution temperature as well as non-equilibrium processes during or post deposition. Device performance is closely tied to this microstructure. Thus, the systematic design of molecules and processing conditions to achieve good performance is challenging.