Optimization of Fabrication Process of Stretchable, Transparent PEDOT:PSS Electrodes for Optoelectronic Applications

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a conductive polymer, is one of the candidate materials for stretchable, transparent electrodes in wearable optoelectronic devices. The treatment of PEDOT:PSS films with organic solvents, e.g., methanol in this study, and acids improves the sheet conductance of the polymer film. This study presents a fabrication process to maximize the conductance of the PEDOT:PSS film, by optimizing the methanol treatment method. Two treatment methods, post-treatment and in-situ treatment, are compared. The in-situ treatment at the optimal methanol concentration is found to be slightly more effective than the post-treatment in reducing the resistance of the PEDOT:PSS films. Forming multilayers of the PEDOT:PSS film further reduces the sheet resistance. However, the multilayer structure also decreases the optical transmittance, which is undesirable in optoelectronic applications. As a result, two layers of the PEDOT:PSS film are selected as an optimal number of layers in terms of conductance and transmittance. The double-layered PEDOT:PSS film coated on a stretchable polydimethylsiloxane (PDMS) substrate demonstrates stable strain-dependent resistance up to 100% strain. Finally, the stretchable PEDOT:PSS electrode fabricated by the optimized process was used as the transparent electrode for a perovskite solar cell, exhibiting typical J-V characteristics with a power conversion efficiency of 1.65%.