To quantify the solubility in chloroform, a solvent often used for device fabrication, we initially used a stepwise solvent addition approach (see Supporting Information section 8.1). Using this approach, the solubility limit was determined to be approx. 143 mg/mL for poly(PCT-T) and 67 mg/mL for poly(PCT-2T), significantly higher than the polymer concentrations of around 20 mg/mL that are commonly used for optoelectronic device fabrication. As expected, the solubility limit was found to be lower for poly(PCT-2T), as the copolymerization with bithiophene instead of thiophene derivatives results in a lower number of solubilizing units per molecular weight. Similar effects have been observed for polymers incorporating aliphatic side chains. As an alternative independent evaluation of the polymer solubility, we also employed a previously reported method based on UV/vis absorbance values (see Supporting Information section 8.2), obtaining a solubility limit of 176 mg/mL for poly(PCT-T), in good agreement with the results of the stepwise solvent addition approach.