Assembly of PCBM and tn-ZnPc Molecular Domains and Phase Separation of Molecular Mixtures from Liquid Solution on Si(111).

We present the results of investigations aimed at understanding the mechanisms by which small, mutually immiscible organic molecules self-assemble into domains during phase separation from liquid solutions in the presence of a solid substrate. As an example system, we investigated molecular mixtures of tetranitro zinc-phthalocyanine (tn-ZnPc), an electron donor, and [6,6]-phenyl-C-butyric acid methyl ester (PCBM), an electron acceptor, in chloroform solution, deposited onto native oxide-covered Si(111) substrates. We found qualitatively different behavior in the formation of domains of the two types of molecules, seemingly because of a large difference in their solubilities in the solvent.