Effect of Molecular Conformation on Intermolecular Interactions and Photovoltaic Performances of Giant Molecule Acceptors

The molecular conformation of giant molecule acceptors (GMAs) plays a significant role in regulating the intermolecular interactions and their photovoltaic performances in organic solar cells (OSCs). For the linear GMA GT-l, the stronger homo-molecular interaction causes its aggregation being weakly affected by the donor, thus forming an ordered molecular stacking and proper phase separation in its blend film. The star-shaped GMA GT-s-based blend film shows a dominant hetero-molecular interaction that suppresses the aggregation of the donor and acceptor, resulting in smaller phase separation and more uniform vertical phase distribution. While for another star-shaped GMA GTs, the weakest hetero-molecular interaction causes its blend film to form larger phase separation. Therefore, the GT-l based OSC with PM6 as donor shows the highest charge mobilities, the fastest charge transfer (CT) process, reduced energy loss and less charge recombination, contributing to a higher power conversion efficiency (PCE) of 19.03%. Comparatively, the PCEs of the OSCs based on GTs and GT-s are 18.05% and 17.58% respectively. Notably, all the three GMAs based OSCs show excellent thermal stability and long-term storage stability. This study provides a facile strategy by tuning the linking unit and its connecting mode for designing highly efficient and stable organic photovoltaic materials. Different molecular conformation of the giant molecule acceptors (GMAs) GT-l, GTs, and GT-s enables them possessing distinct homo/hetero-molecular interactions in their blend films, which synergistically affect the molecular packing, vertical phase distribution, and phase separation in the PM6:GMA-based blend films, resulting in different excition dissociation, charge transpot, and recombination properties and futher photovoltaic performances of these GMAs-based Organic solar cells (OSCs). image