Synergistic Optimization of Ternary Active Layer and Transparent Electrode for High‐Performance Flexible Organic Solar Cells

Abstract Organic solar cells (OSCs) are highly promising for flexible electronics due to their mechanical flexibility and light weight. The efficiency of flexible OSCs (F‐OSCs) has been limited by suboptimal active layer designs and underperforming flexible transparent electrode (FTE). Herein, a collaborative effort was made to improve F‐OSCs performance through rational design of ternary active layers and innovation in FTE. Specifically, a wide‐bandgap acceptor, F‐GS‐ISO, was synthesized and incorporated into D18:L8‐BO system to modulate energy levels, optimize molecular packing and morphology. The D18:L8‐BO:F‐GS‐ISO based rigid device yielded a high power conversion efficiency (PCE) of 19.91% (certified as 19.46%) alongside enhanced active layer mechanical properties. Concurrently, a highly conductive PEDOT:PSS ( h ‐PEDOT:PSS) was developed as FTE through a facile yet effective in‐situ doping method, which eliminates the need for complex post‐treatment and offers excellent conductivity, transparency, and compatibility with roll‐to‐roll processing. The synergistic effect of these two advancements enabled F‐OSCs to achieve a high PCE of 18.60% (certified as 18.28%) and robust mechanical properties: the h ‐PEDOT:PSS ensures favorable interfacial contact for efficient charge extraction, while the ternary active layer delivered high photoelectric conversion capability and mechanical robustness. This work provides deep insights into active layers design and electrode engineering for high‐performance F‐OSCs.