Exploiting Bis‐Sulfonimide Featuring Multiple <i>d–p</i> π Bonds to Construct Interlayers for Organic Solar Cells

Abstract Herein, bis‐sulfonimide (BSI), characterized by multiple d ‐ p π bonds rather than typical p ‐ p π bonds, is unprecedently utilized as a general and extendable building block to develop a series of multifunctional cathode interlayer materials (CIMs) for organic solar cells (OSCs). An illustrative CIM, BSIz‐TT‐PDI, demonstrates favorable alcohol processability, superior work function tunability, appropriate energy levels, strong self‐doping effect, and decent crystallinity. These attributes contribute to its high conductivity exceeding 5×10 −3 S/cm, as well as precise optimization of the interfacial connection between the active layer and metal cathode. Therefore, BSIz‐TT‐PDI‐based OSCs delivers an outstanding efficiency of 18.08 % using PM6:Y6 active layer while retaining 84 % of its initial performance after tracking at the maximum power point under continuous illumination for 1100 hours. Additionally, the devices maintain over 94 % of the optimal performance across a film thickness range of BSIz‐TT‐PDI from 5 to 90 nm. Moreover, BSIz‐TT‐PDI exhibits high compatibility with various active layers, enabling a record efficiency of 19.80 % with the PM6:BTP‐eC9:L8‐BO active layer. This work not only introduces a new library of water/alcohol‐soluble n‐type semiconductors containing BSI, while also pioneers the creation of thickness‐insensitive CIMs for stable and efficient OSCs by integrating electron‐withdrawing components with d ‐ p π bonds.