Powering the Wearable Era: The Quest for High‐Strain Stretchable Polymer Solar Cells

The rise of wearable electronics is driving demand for new forms of solar cells with both high power conversion efficiency (PCE) and high strain tolerance. However, these properties are often inherently conflicting: state‐of‐the‐art organic/polymeric photovoltaic materials often rely on rigid or highly fused conjugated backbones, yielding fracture strains below 10% in high‐efficiency systems with PCEs above 21%. This article critically examines mechanical optimization strategies for emerging high‐strain stretchable polymer solar cells (HS‐PSCs), comparing two common polymeric blend architectures: polymer:small‐molecule and all‐polymer systems. We benchmark mechanical characterization techniques, from elastomer‐based methods to free‐standing tensile testing, and dissect recent strategies to overcome the efficiency–stretchability trade‐off, including molecular engineering (flexible spacers and hydrogen‐bonding chains) and morphological control (ternary blending, layer‐by‐layer assembly, and cocontinuous networks). After surveying over 100 reported systems, several advanced all‐polymer and layer‐by‐layer systems have reached fracture strain >30% while maintaining PCE >15%. Finally, we offer a forward‐looking perspective on three priority routes (entanglement‐controlled polymer design, elastomer‐based networks, and crosslinked systems) that promise to simultaneously deliver >20% PCE and >50% fracture strain. This review provides a structured inventory of current achievements and a strategic roadmap toward stretchable, commercially viable solar cells.