In recent years, Yn-based molecules (e.g., Y6) have emerged as the most efficient non-fullerene acceptors for organic solar cells. Thus, it is of significant interest to investigate the underlining factors responsible for their superior properties. In this work, we compare Y6 to prior-generation high-performance acceptors, ITIC and IT-4F. We exploit a combination of density functional theory (DFT) calculations and molecular dynamics (MD) simulations to probe the molecular packing in neat films and the various factors that control their charge and exciton transport rates. We demonstrate that the differences in molecular packing are drastic between these acceptors in terms of their directional stacking, number of <i>face-on</i> interactions, and network connectivity. The distinct molecular packing in Y6 consistently leads to higher electronic couplings for LUMOs, HOMOs, and local excitations than in ITIC-type acceptors, which translates into faster transport rates for electrons, holes, and excitons. The Y6 configurations in neat films are more diverse than in ITIC-type acceptors, with many similarities to the configurations found in the crystal structure. Many of these Y6 configurations possess strong binding interactions, large electronic couplings, and high transport rates.

Non-fullerene acceptors: Impact of the molecular architecture of Y6 vs. ITIC derivatives on the local morphologies and transport rates

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.