Unraveling the Stretch-Induced Microstructural Evolution and Morphology-Stretchability Relationships of High-Performance Ternary Organic Photovoltaic Blends.

The stretchability and stretch-induced structural evolution of organic solar cells (OSCs) are pivotal for their collapsible, portable, and wearable applications, and they are mainly affected by the complex morphology of active layers. Herein, a highly ductile conjugated polymer P(NDI2OD-T2) is incorporated into the active layers of high-efficiency OSCs based on nonfullerene small molecule acceptors to simultaneously investigate the morphological, mechanical, and photovoltaic properties and structural evolution under stretching of ternary blend films with various acceptor contents. The structural robustness of the blend films is indicated by their stretch-induced structural evolution, which is monitored in real-time by a combination of in situ wide/small angle X-ray scattering. It is found that adding the soft P(NDI2OD-T2) can enhance the stretchability and structural robustness of ternary blend films by more entangled chains and tie chains to dissipate strain. Furthermore, the stretchability of the ternary blends can be superbly predicted by a 3D equivalent box model. This work provides instructive insight and guidance for designing stretchable electronics and predicting the stretchability of multicomponent blends.