The isoindigo-bithiophene-based polymer (PII-2T) and thieno-isoindigo-bithiophenebased polymer (PTII-2T) were synthesized as previously reported . A low MW PII-2T (Mn = 19,883, Mw = 61,700, PDI = 3.1) and a high MW PII-2T (Mn = 30,645, Mw = 76,809, PDI = 2.5) batch were characterized using high temperature gel permeation chromatography at 150 °C in trichlorobenzene. The full molecular weight distributions of PII-2T are shown in Figure . PTII-2T molecular weight could not be measured due to strong interaction with the column material, even at high temperature. The polymer solutions were prepared by dissolving the polymer in either chlorobenzene (anhydrous, 99.8%; Sigma-Aldrich Inc.), decane (anhydrous, ≥99%; Sigma-Aldrich Inc.), or a mixture of both. The solutions were then stirred at 80 °C for at least 12 hours prior to characterization. After heating, the solutions were removed to room temperature for 15 minutes prior to being used in all experiments.