Exploring interface tension as a tool to control the morphology of binary organic semiconductor nanoparticles prepared by nanoprecipitation.

The ability to control the morphology of organic semiconductor nanoparticles is of paramount importance for applications in organic photovoltaics, photocatalysis, and photo-triggered biological applications. In this paper, we demonstrate that nanoprecipitation is a powerful technique to provide a variety of morphologies in binary blends of organic semiconductors. By investigating seven different donor : acceptor couples we demonstrate that the resulting morphology is primarily governed by the interfacial tension between the two photo-active components. The structure of the particles is also influenced by the interactions between the medium and the materials. Indeed, we show that the medium should not be considered solely as water; rather, the surfactant employed and the organic solvent in which the materials are dissolved also play crucial roles. By manipulating these parameters, P3HT : PCBM nanoparticles were produced nanoprecipitation, exhibiting either intermixed, Janus, or core-shell morphologies depending on the dispersive medium. Cryo-TEM and STEM-EDX were utilized to image the internal structure of the particles for couples involving PCBM and non-fullerene acceptors (NFA) such as Y6 and a polymer P(DTS-DAP). The increased surface tension between the donors and PCBM generally results in the formation of Janus nanoparticles. Conversely, the NFAs used in this study exhibit a higher compatibility with the donor, thereby promoting in some cases an intermixed structure.