Novel Long-Conjugated Backbone-Based Non-Fullerene Acceptors for Efficient and Eco-Friendly Ternary Organic Solar Cells

Organic solar cells (OSCs) are made from carbon-rich organic compounds with low environmental impacts, unlike the silicon in traditional solar panels. Some of these organic materials can be broken down and reprocessed, enabling the recovery of valuable components. Specifically, the active-layer materials that make up OSCs can be designed with sustainability in mind. However, it is important to note that practical active materials that can be used for the commercialization of OSCs are still an area of research and development due to their low efficiency/stability and processability. Herein, we designed and synthesized three A-D-A'-D-A-type long-conjugated non-fullerene acceptors (NFAs) by incorporating various electron-withdrawing groups into the benzothiadiazole-diindacenodithiophene core. These NFAs, by changing their end-capping groups, exhibit not only distinct physical, optical, and electrochemical properties, but also differences in crystallinity and exciton dissociation. As a result, they exhibited significant differences in photovoltaic performance in PM6 donor-based binary devices. The introduction of small amounts of NFAs as a third component in the PM6:BTP-eC9 blend significantly enhanced its photon harvesting capabilities and influenced its charge transfer dynamics. Finally, we achieved a remarkable power conversion efficiency of nearly 17% by utilizing an eco-friendly solvent. This study provides valuable insights for the development of NFAs in efficient and eco-friendly OSCs.