Journal ArticleThe hole in the bucky: structure-property mapping of closed- vs. open-cage fullerene solar-cell blends via temperature/composition phase diagramsStingelin, Natalie; Matrone, Giovanni Maria; Gutierrez-Meza, Elizabeth; Balzer, Alex H.; Khirbat, Aditi; Levitski, Artem; Sieval, Alexander B.; Frey, Gitti L.; Richter, Lee; Silva, CarlosnullThe morphology development of polymer-based blends, such as those used in organic photovoltaic (OPV) systems, typically arrests in a state away from equilibrium – how far from equilibrium this is will depend on the materials chemistry and the selected assembly parameters/environment. As a consequence, small changes during the blend assembly alters the solid-structure development from solution and, in turn, the final device performance. Comparing an open-cage ketolactam fullerene with the prototypical [6,6]-phenyl-C₆₁-butyric acid methyl ester in blends with poly[2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT), we demonstrate that experimentally established, non-equilibrium temperature/composition phase diagrams can be useful beyond rationalization of optimum blend composition for OPV device performance. Indeed, they can be exploited as tools for rapid, qualitative structure-property mapping, providing insights into why apparent similar donor:acceptor blends display different optoelectronic processes resulting from changes in the phase-morphology formation induced by the different chemistries of the fullerenes.2021-01-0110296337Journal of Materials Chemistry C2050-7526https://doi.org/10.1039/D1TC03082E1729737; 1905901National Science Foundation