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The rapid development of low bandgap polymer acceptors has promoted the efficiency up to ≈17% for all‐polymer solar cells (all‐PSCs). Nevertheless, the polymeric blend film, core to the photoelectric conversion of all‐PSCs, has not been thoroughly understood in terms of the influence and regulatory factors of mechanical properties, which hinders the advances in flexible and wearable applications. Herein, a range of characterization methods is combined to investigate the mechanical properties, miscibility, and film microstructure of the blends based on several representative polymer donors (PTzBI‐Si, PTVT‐T, PM6 and PTQ10) and a benchmark polymer acceptor N2200, and to further reveal the miscibility‐property relationships of the miscibility property. The results stress that fracture behaviors and elastic moduli of these blends with varied compositions show different changing trends, which are affected by molecular interactions and aggregated structure of the blends. The elastic moduli of the four all‐polymer blends can be nicely predicted by different models that are deduced from macromolecular mechanics. Most crucially, the correlations between elastic modulus, morphology, and miscibility of all‐polymer blends are elucidated for the first time. The derived relationships is validated with another high‐efficiency blend and will be the key to the successful fabrication of mechanically robust and stretchable all‐PSCs with high efficiency. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Record‐breaking organic solar cells (OSCs) based on blends of polymer donors and small molecule acceptors often show undesirable degradation, which severely precludes their practical use. Herein, we demonstrate a facile and cost‐effective approach to construct thermally stable OSCs at 150 oC by incorporating a small amount of a polymer insulator polyacenaphthylene (PAC) with high glass‐transition temperature over 230 oC into polymer:acceptor blends. The model PTB7‐Th:EH‐IDTBR blend with 10 wt% PAC maintained above 85% of its initial efficiency upon continuous heating at 150 oC for over 800 h, while the efficiency of the blend without PAC sharply dropped by 70% after ~300 h. Owing to high miscibility with acceptors, PAC confines the motion of the acceptor molecules and suppresses the acceptor crystallization at elevated temperatures, leading to significantly improved stability. Importantly, the effectiveness of this blending approach was also validated in many other OSC systems, showing great potential for achieving high‐performance thermally stable electronics. [ABSTRACT FROM AUTHOR]

Intrinsically stretchable organic photovoltaic cells (OPVs) have garnered significant attention as crucial devices for powering next‐generation wearable electronics. Despite the rapid power conversion efficiency gains in champion OPVs, their brittle stretchability has failed to meet the demands of the Internet of Things era, severely hindering further development and practical applications. In this regard, a new dual‐donor polymer blending strategy is demonstrated for constructing intrinsically stretchable OPVs by designing a novel high‐molecular–weight conjugated polymer PM6‐HD. This PM6 derivative featuring long alkyl chains can reach a sufficiently high molecular weight and thus exhibits a high fracture strain exceeding 90%, which is ≈12 times higher than the benchmark PM6. Synergistic optimization of mechanical properties and photovoltaic performance in polymer:small molecule and all‐polymer systems constructed from the physical blends of PM6 and PM6‐HD is achieved. Crucially, the resulting intrinsically stretchable OPV demonstrates excellent stretchability and stability, with a record PCE80% strain of 50.3% and the efficiency retention of above 80% even after 1000 cycles of cyclic stretching at high strains. This work contributes to the advancement of intrinsically stretchable OPV technology and opens up new possibilities for its integration into wearable electronic devices. [ABSTRACT FROM AUTHOR]