Correlation between Morphology, Mechanics, and Electricity of PEDOT:PSS-Based Stretchable Electrodes Fabricated by the Prestrain Transfer Method

The recent advancement of stretchable photoelectronics has catalyzed revolutionary transformations in various cutting-edge fields. However, the stretchable transparent electrodes (STEs), which are vital components ensuring signal conduction in stretchable photoelectronics, pose a challenge due to the rigid and fragile nature of conventional conductive materials. In this study, we demonstrated a prestrain transfer technique for fabricating STEs using PEDOT:PSS. The resulting STEs achieved a sheet resistance of approximately 50 Ω/sq by leveraging the benefits of methanesulfonic acid treatment and incorporating a carbon-nanotube blend in PEDOT:PSS. The fabricated STEs exhibited exceptional transparency exceeding 90% and remarkable stability over 1000 stretching cycles without degradation in conductance. An in situ investigation was conducted to visualize the deformation of the PEDOT:PSS film and its association with the electrical ductility of the STEs. The prestrain transfer was found to induce kirigami-type cracks and out-of-plane microwrinkles in the PEDOT:PSS film. These structures effectively alleviate stress concentration and compensate for strain during stretching loading, thereby imparting enhanced stretchability and electrical ductility to the STEs. However, once the stretching strain exceeded the prestrain threshold, numerous microcracks emerged on the PEDOT:PSS film, leading to electrical failure of the STEs due to a significant rise in resistance. The incorporation of carbon nanotubes was demonstrated to modulate crack structures, thereby enhancing both the mechanical and electrical ductility of STEs. Additionally, a theoretical model was proposed to quantitatively analyze the morphological evolutions in the PEDOT:PSS film while establishing its correlation with the mechanical and electrical properties of the STEs. The parameters associated with crack structures, sensitivity of resistance to cracks, and tensile limit of PEDOT:PSS were extracted to elucidate the underlying mechanisms of prestrain engineering on the electrical ductility and failure of the STEs. The present results offer guidance for experimental and theoretical approaches for optimizing the fabrication process of stretchable electronics.