Figure 6: Aggregation alone does not prevent liquid–liquid demixing.
From: A real-time study of the benefits of co-solvents in polymer solar cell processing

(a) AFM height image of the photoactive layer of a solar cell made from a PDPP5T:[70]PCBM solution in pure chloroform which had been left to preaggregate for 6 days. (b) AFM height image of a the photoactive layer of solar cell made from the same solution as in a that had been restirred at 90 °C for 20 min and left to cool down for 10 min to room temperature before spin coating. (c) EQE measurements of the solar cells in a and b reveal that the solar cell from the preaggregated solution has a more pronounced red-shifted response and a slightly lower photocurrent compared to the solar cell from the reheated solution. (d) In situ absorption spectra showing wet and dry film absorption spectra for both solar cells in a (preaggregated) and b (reheated). The measurements were vertically shifted such that the absorbance at 925 nm is set to zero. The thickness of the active layers of both solar cells was 100 nm.