Disentangling Conformational and Electronic Effects in Polymerized Acceptors for All-Polymer Solar Cells

We carry out first-principles simulations to investigate how common linker functionalization strategies affect the optoelectronic properties of polymerized small molecule acceptors (PSMAs), which are promising materials for all-polymer solar cells. While enhancing planarity via linker substitution improves conformational order and morphology, the role of thermally accessible molecular torsions in tuning the optoelectronic properties of PSMAs remains largely unexplored. Furthermore, the impact, on electronic properties, of restricting these torsions compared to the incorporation of electron-donating or electron-withdrawing moieties along the PSMA backbone is yet unclear. We show that restricting thermally accessible torsions along the polymer backbone has a negligible effect on key optoelectronic properties, whereas the chemical nature of the functional groups plays a dominant role in tuning the optical and fundamental gaps and electron affinity of PSMAs. These findings pave the way to targeted synthetic strategies to simultaneously improve the conformational and optoelectronic properties of PSMAs for all-polymer solar cells.