| Abstract: | Thin‐film polymer solar cell consisting of 6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) and poly4,8‐bis(2‐ethylhexyl)oxy]benzo1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl]3‐fluoro‐2‐(2‐ethylhexyl)carbonyl]thieno3,4‐b]thiophenediyl]] (PTB7) demonstrates elastic stretchability with the aid of a high boiling point additive, 1,8‐diiodooctane (DIO). The usage of DIO not only helps to form uniformly distributed nanocrystalline grains, but may also create free volumes between the nano‐grains that allow for relative sliding between the nano‐grains. The relative sliding can accommodate large external deformation. Large dichroic ratios of the optical absorption of both PC71BM and PTB7 were observed under large‐strain deformation, indicating reorientation of the nanocrystalline PC71BM and PTB7 polymer chains along stretching direction. The dichroic ratio decreases to nearly 1.0 as the blend was relaxed to 0% strain. Therefore, the nanometer‐size grain blending morphology provides an approach to impart stretchability to organic semiconductors that are otherwise un‐stretchable. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 814–820 |
