Stretchable and Transparent Conductive PEDOT:PSS-Based Electrodes for Organic Photovoltaics and Strain Sensors Applications

The development of transparent, conducting, and stretchable poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based electrodes using a combination of a polyethylene oxide (PEO) polymer network and the surfactant Zonyl is reported. The latter improves the ductility of PEDOT:PSS and enables its deposition on hydrophobic surfaces such as polydimethylsiloxane (PDMS) elastomers, while the presence of a 3D matrix offers high electrical conductivity, elasticity, and mechanical recoverability. The resulting electrode exhibits attractive properties such as high electrical conductivity of up to 1230 S cm−1 while maintaining high transparency of 95% at 550 nm. The potential of the electrode technology is demonstrated in indium-tin-oxide (ITO)-free solar cells using the PBDB-T-2F:IT-4F blend with a power conversion efficiency of 12.5%. The impact of repeated stretch-and-release cycles on the electrical resistance is also examined in the effort to evaluate the properties of the electrodes. The interpenetrated morphology of the PEDOT:PSS and polyethylene oxide network is found to exhibit beneficial synergetic effects resulting in excellent mechanical stretchability and high electrical conductivity. By carefully tuning the amount of additives, the ability to detect small changes in electrical resistance as a function of mechanical deformation is demonstrated, which enables the demonstration of stretchable and resilient on-skin strain sensors capable of detecting small motions of the finger.