Solubilizing core modifications on high-performing benzodithiophene-based molecular semiconductors and their influences on film nanostructure and photovoltaic performance

Sidechain engineering of the benzodithiophene-based high-performance organic solar cell (OSC) material BTR generated four novel p-type small-molecule semiconducting materials to investigate structure-property relationships in p-type organic semiconductors. Through depth-dependent grazing incidence wide-angle X-ray scattering (GIWAXS) studies, it is found that our best performing materials possess an active-layer morphology comprised of a vertically graded structure with different crystallite orientations. We further establish a correlation between a high solubility in the spin-coating deposition solution and the occurrence of this vertical distribution, whereas materials with lower solubility are found to possess a predominantly edge-on molecular orientation. These results further the understanding of this high-performing class of materials and suggest the importance of solubility considerations to OSC morphology.