Simple and Efficient Synthesis of Novel Tetramers with Enhanced Glass Transition Temperature for High-Performance and Stable Organic Solar Cells

Oligomer acceptors in organic solar cells (OSCs) have garnered substantial attention owing to their impressive power conversion efficiency (PCE) and long-term stability. However, the simple and efficient synthesis of oligomer acceptors with higher glass transition temperatures (T_g) remains a formidable challenge. In this study, we propose an innovative strategy for the synthesis of tetramers, denoted as Tet-n, with elevated T_gs, achieved through only two consecutive Stille coupling reactions. Importantly, our strategy significantly reduces the redundancy in reaction steps compared to conventional methods for linear tetramer synthesis, thereby improving both reaction efficiency and yield. Furthermore, the OSC based on PM6:Tet-1 attains a high PCE of 17.32 %, and the PM6:L8-BO:Tet-1 ternary device achieves an even more higher PCE of 19.31 %. Remarkably, the binary device based on the Tet-1 tetramer demonstrates outstanding operational stability, retaining 80 % of the initial efficiency (T₈₀) even after 1706 h of continuous illumination, which is primarily attributed to the enhanced T_g (247 °C) and lower diffusion coefficient (1.56×10⁻²⁷ cm² s⁻¹). This work demonstrates the effectiveness of our proposed approach in the straightforward and efficient synthesis of tetramers materials with higher T_gs, thus offering a viable pathway for developing high-efficiency and stable OSCs.