Blending fullerenes with a donor polymer for the
fabrication of organic solar cells often leads to at least partial
vitrification of one, if not both, components. For prototypical
poly(3-hexylthiophene):fullerene blend, we show
that the addition of a commercial nucleating agent, di(3,4-dimethyl benzylidene)sorbitol, to such binary blends accelerates
the crystallization of the donor, resulting in an
increase in its degree of crystallinity in as-cast structures.
This allows manipulation of the extent of intermixing/
phase separation of the donor and acceptor directly
from solution, offering a tool to improve device characteristics
such as power conversion efficiency.