What is the Solubility of PCBM?
Results show that approximately 9-10 mg can at maximum be dissolved per mL of toluene at room temperature, when stirring the solution for a long time (several days). After that time, the dark red-brown solution is (almost) clear/transparent, meaning that the material has fully dissolved. We can, however, not exclude that some of it is still present as un-dissolved nanoparticles, which are not seen by the eye, nor can be easily filtered out. Sonification may lead to a higher solubility, however, may also lead to more of these nanoparticles. When heated, e.g. at 50 degrees C, more PCBM can be dissolved in toluene. Upon cooling to room temperature, the PCBM does not precipitate directly, but stays in solution for at least several hours. Thus, a supersaturated solution can be obtained. PCBM is better soluble in so-called good fullerene solvents, such as chlorobenzene and ODCB. In the latter solvent, 50 mg/mL solutions can be made without too much trouble.
