Supplementary material from "Does 1,8-diiodooctane affect the aggregation state of PC 71 BM in solution?"

We have critically re-examined this finding in a series of scattering measurements using both X-rays and neutrons. With SAXS, we find that the form of the background solvent scattering is influenced by the presence of DIO, that there is substantial attenuation of the X-rays by the background solvent and that there appears to be beam-induced aggregation.

All three factors call into question the suitability of SAXS for measurements on these samples. By contrast, small-angle neutron scattering (SANS) measurements, performed at concentrations of 15 mg ml −1 up to and including 40 mg ml −1 , show no difference in the aggregation state for PC 71 BM in chlorobenzene with and without 3% DIO; we find PC 71 BM to be molecularly dissolved in all solvent cases. In situ film thinning measurements of spin-coated PC 71 BM solution with the DIO additive dry much slower.