LAUSR

The success of non-fullerene acceptor (NFA) solar cells lies in their unique physical properties beyond the extended absorption and suitable energy levels. The current study investigates the morphology and photo physical behavior of PM6 donor blending with ITIC, 4TIC, and 6TIC acceptors. Single crystal study shows that the pi-pi stacking and side-chain interaction dictate molecular assembly, which can be carried to blended films, forming a multi-length-scale morphology. Spontaneous carrier generation is seen in ITIC, 4TIC and 6TIC neat films and their blended thin films using PBDB-T donor, providing a new avenue of zero energy loss carrier formation. The molecular packing associated with specific contacts and geometry is key in influencing the photo physics, as demonstrated by the charge transfer and carrier lifetime results. We see the 2D layer of 6TIC that facilitates the exciton to polaron conversion and obtains the largest photo-generated polaron yield. The new mechanism in together with the highly efficient blending region carrier generation prospect the fundamental advantage for NFA solar cells, from molecular assembly to thin film morphology. This article is protected by copyright. All rights reserved.