Face-to-Face Type Giant Dimeric Donors Synergistically Improve the Stability and Efficiency of Organic Solar Cells

Abstract

With the development of organic solar cells (OSCs), maintaining the batch stability of photovoltaic donor materials and improving the device stability are becoming a new challenge. Given the successful application of giant oligomeric acceptors, increasing the molecular size while keeping precise molecular structure have been proven to be an effective method. However, the efficient giant oligomeric donors are still less due to a lack of design principles. Here, we innovatively designed and developed “face-to-face” type giant dimeric donors (GDDs), DZ-1 and DZ-2, by covalently tethering BTR-Cl monomer. Using the different rhodanine-based terminals significantly tuned their molecular interaction and thermal-driven assembly capability. Compare to DZ-1, DZ-2 had moderate molecular stacking and compatible miscibility in the blend film, thus realizing a higher PCE of 13.27%. Importantly, the GDDs with increasing molecular size not only improved the Tg, but also suppressed the molecular diffusion in blend films. Furthermore, the ternary OSCs based on PM6:DZ-2:L8-BO achieved an improved PCE of 19.07% and higher device stability, due to the establishment of 3D charge transport channel and suppression of the molecular diffusion. This study provides a new design strategy of giant molecule donors to develop high-performance and stable OSCs.