ANALYZING FATIGUE DUE TO CYCLIC LOADING IN POLY(3-ALKYLTHIOPHENE)-THIN FILMS WITH THE WEAKLY INTERACTING H-AGGREGATE MODEL
Shang-Chun Chiang, Adam Printz, Darren Lipomi.
University of California, San Diego, La Jolla, CA.
Organic semiconductors are promising materials for applications that require mechanical compliance and robustness such as wearable and implantable biomedical devices and stretchable organic photovoltaics. However, even highly compliant devices experience failure when repetitively strained. This failure (or fatigue), which is likely due to disruption in the quantity and quality of polymer aggregates that dominate charge transport in poly(3-alkylthiophene)s, can be measured using UV-vis spectroscopy and the weakly interacting H-aggregate model. The polymer films were transferred to stretchable substrates, strained cyclically, and measured periodically to determine the quantity and quality of high-charge transport aggregates. Preliminary data showed a critical number of cycles dependent on the strain percentage before the destruction of polymer aggregates began to occur. Understanding the degradation mechanisms and loading limits of conjugated polymer films undergoing cyclic strain will inform scientists and engineers and allow for the intelligent design and selection of polymers for applications requiring repetitive strains such as portable and wearable stretchable or flexible electronic devices.