Compatibilizer Effects of Strategically Designed Donor–Acceptor Block Copolymers to Enhance the Performance, Stability, and Mechanical Durability of Inverted Organic Solar Cells

Abstract A strategically designed donor–acceptor (D‐A) block copolymer (PM6‐b‐PYIT) is introduced, as a compatibilizer to enhance the performance and stability of inverted organic solar cells (OSCs) consisting of a bulk heterojunction (BHJ) of PM6 and L8‐BO. The PM6‐b‐PYIT compatibilizer not only significantly boosts the power conversion efficiency from 16.32% to 18.02%, but also further modulates the molecular arrangement and improves the compatibility between donor and acceptor materials. This stems from the structural similarity between the copolymer and the host materials, which facilitates ordered molecular stacking and superior charge‐transporting properties, thereby improving the dielectric constant and built‐in voltage and mitigating excessive charge recombination. More importantly, the role of the compatibilizer in stabilizing the BHJ morphology under long‐term aging conditions is highlighted, ascribed to the improved miscibility between different components in the BHJ composite. This in turn renders the photoactive layer more mechanically durable, making it suitable for stretchable applications.