Chlorinated Polypropylene Enables Stress-Dissipative Networks and High Efficiency in Intrinsically Stretchable Organic Photovoltaics

Abstract

Intrinsically stretchable organic photovoltaics (IS-OPVs) demand both high power conversion efficiency (PCE) and robust mechanical deformability, yet these requirements are often difficult to reconcile in state-of-the-art donor:acceptor blends. Existing toughening strategies typically rely on complicated synthesis and compromise the device PCE. Here, we report a synthesis-free toughening strategy based on commercially available chlorinated polyolefin (PP-Cl), which is low-cost, scalable, solution-processable, and broadly compatible with diverse high-performance donor:acceptor blends. This strategy enables mechanically resilient IS-OPVs without sacrificing photovoltaic performance. At an optimal loading, rigid PM6:BTP-eC9 devices show a reproducible increase in PCE, while the corresponding stretchable devices deliver an initial PCE of over 15% and still possess over 60% efficiency retention at 40% strain. In contrast, undoped controls undergo severe degradation at 20% strain. The same strategy is further extended to a ternary rigid D18:BTP-eC9:L8-BO system, delivering PCEs up to 20.5%, while the corresponding intrinsically stretchable devices deliver an initial PCE of 16.1%, ranking as the highest reported for IS-OPVs. Assisted by a mechanical framework and the Coran-Patel model, multiscale characterization suggests that chlorine-involved reversible weak interactions act as sacrificial stress-dissipation pathways. These results establish commodity chlorinated polyolefins as practical toughening additives for high-efficiency stretchable organic photovoltaics.