Elasticization Enables Strain‐Tolerant Microstructure and Enhanced Performance in Stretchable Polymer Solar Cells

The advancement of intrinsically stretchable photovoltaic films is essential for powering next-generation wearable electronics through all-polymer solar cells (APSCs). While blending with elastomeric materials has emerged as an effective strategy to enhance mechanical robustness, the fundamental microstructural evolution under strain remains poorly understood. Here we introduce and implement a synchrotron-based in situ stretching X-ray scattering technique to directly probe nanoscale morphological changes in real time. Incorporating a styrene-isoprene-styrene elastomer SIS induces enhanced π-π stacking intensity both parallel and perpendicular to the stretching direction. The resulting stretchable APSCs achieve a record-high efficiency over 16% and exceptional mechanical stability, retaining over 80% of initial efficiency at 60% strain and 81% after 1000 stretching cycles at 40% strain. Furthermore, power output remains stable under strains of up to 60%, and the mechancial parameters are well predicted by the Coral-Patel model. This study provides critical insights for elastomer selection and microstructure design in stretchable electronics.