A quinoxaline–benzothiadiazole heterotrimer for organic solar cells with extraordinary efficiency and stability

Abstract

Organic solar cells (OSCs) based on oligomer acceptors have garnered significant interest due to their notable power conversion efficiency (PCE) and enduring stability. Despite their great potential, the development of oligomer acceptors remains behind traditional small molecule acceptor (SMA)-based systems, primarily due to the scarcity of effective oligomer materials. To address this gap, our study introduces a novel hybrid synthesis strategy for oligomer acceptors, integrating two distinct acceptor units. We synthesize the heterotrimer acceptor TQT and the single-acceptor-unit oligomers Tri-BT and Tri-Qx to assess the impact of our approach on OSC performance and durability. Notably, the crystallinity of the hybrid molecule TQT is obviously enhanced compared to the other two molecules. Consequently, the PCE of the PM6:TQT-based OSC reached 18.52%, representing the highest efficiency observed among OSCs composed of linear-shaped trimer acceptors to date. Meanwhile, the PM6:L8-BO:TQT ternary system surpassed this with a PCE of 19.15%. Moreover, our oligomer acceptor-based binary device demonstrated exceptional photostability and thermal stability. The top-performing trimer TQT retained 80% of its initial efficiency (T₈₀) after 1330 hours of continuous exposure. Our findings highlight the potential of hybridizing various acceptor units as a strategic approach to developing stable and efficient oligomers for OSCs.