Figure 5: Which is first: phase separation or polymer aggregation?
From: A real-time study of the benefits of co-solvents in polymer solar cell processing

(a) Total solvent content (concentration in vol%) at the onset of scattering (pink stars) and at the change in transmission (blue circles at 50% change) versus concentration of oDCB in the initial chloroform solution (error bars for scattering arise from the time-uncertainty in the scattering onset; thickness uncertainty from back-calculating the interference signals is not included. The transmission error bars indicate 20–80% transmission change). (b) Same for DIO instead of oDCB. (c) Schematic phase diagram revealing the role of co-solvent in inducing polymer aggregation at higher solvent contents which, in turn, prevents large-scale liquid–liquid phase separation during drying and results in optimized morphologies.