Side-Chain-Engineered Insulating Polymer Distribution Enables High-performance Intrinsically Stretchable Organic Photovoltaics.

Intrinsically stretchable organic photovoltaics (is-OPVs) face a critical efficiency-stretchability trade-off that limits wearable applications. Here, a breakthrough molecular design strategy employing side-chain-engineered insulating polymers-poly(methyl methacrylate) (PMMA) and poly(benzyl methacrylate) (PBMA)-as multifunctional additives to simultaneously enhance electronic and mechanical properties is presented. Through synergistic control of compatibility, chain diffusivity, and docking position with PM6/Y6 components, PMMA selectively distributes in the amorphous regions of the PM6 donor while promoting molecular packing in crystalline regions, enabling dual stress-dissipation networks and efficient charge transport pathways. As a result, the rigid 10PMMA (with 10 wt.% PMMA) devices achieve a record 19.01% power conversion efficiency (PCE), while maintaining 18.53% PCE (only 2% loss) for the rigid 20PMMA (with 20 wt.% PMMA) devices. More remarkably, the stretchable 20PMMA devices exhibit exceptional mechanical robustness with 10.8% fracture strain (2.2-fold improvement) and 87% PCE retention after 100 stretching cycles (10% strain), far surpassing the control devices (50% retention). The work establishes fundamental design principles for insulating polymer additives in is-OPVs, demonstrating how molecular control over micro-/nanoscale distribution can simultaneously optimize electronic and mechanical properties. These findings provide a universal materials platform for high-performance stretchable electronics, particularly for next-generation wearable energy technologies where both efficiency and durability are paramount.