Abstract
In non-fullerene organic solar cells (OSCs), the long-range structure ordering induced by end group π–π stacking of fused-ring non-fullerene acceptors is considered as the critical factor in realizing efficient charge transport and high power conversion efficiency. Here, we demonstrate that side-chain engineering of non-fullerene acceptors could drive the fused-ring backbone assembly from a π–π stacking mode to an intermixed packing mode, and to a non-stacking mode to refine its solid-state properties. Different from the above-mentioned understanding, we find that close atom contacts in a non-stacking mode can form efficient charge transport pathway through close side atom interactions. The intermixed solid-state packing motif in active layers could enable OSCs with superior efficiency and reduced non-radiative recombination loss compared with devices based on molecules with the classic end-group π–π stacking mode. Our observations provide new insights into the influence of non-fullerene acceptor molecular packing on exciton dissociation, charge transport, and recombination losses, and open a new avenue in material design that endows better photovoltaic performance.
Device and morphological engineering of organic solar cells for enhanced charge transport and photovoltaic performance
