ABSTRACT: New technologies will require more and more compliant materials capable of conforming to curved surfaces, i.e., able to stretch and mechanically resist body motions for wearable and on-skin applications. In this regard, this work discusses strategies to induce stretchability in materials. We focused our attention on improving the elasticity of transparent conducting electrodes (TCE) based on PEDOT:PSS and semiconductors (active layer) for organic solar cells.
Firstly, the introduction of DMSO and Zonyl as additives into PEDOT:PSS was shown to produce highly transparent conducting electrodes (FoM > 35) with low Young's modulus and high carrier density. We investigated the relationship between the transport properties of PEDOT:PSS and the morphology and microstructure of its films. The combination of the two additives enhances the fibrillary nature and the aggregations of both PEDOT and PSS components of the films.
Secondly, stretchable TCEs based on PEDOT:PSS were fabricated using an innovative approach that combines an interpenetrated polymer network-based on polyethylene oxide and Zonyl. The presence of three-dimensional matrix provided high electrical conductivity, elasticity, and mechanical recoverability. The potential of this electrode was demonstrated with indium-tin-oxide (ITO)-free solar cells with a power conversion efficiency similar to ITO.
Finally, the research was completed by integrating a cross-linker or an elastomer into the active layer to enhance its stretchability while maintaining excellent photovoltaic performance. In particular, SEBS elastomer exhibited a tailored elasticity with various fullerene and non-fullerene blends: P3HT:PC61BM, PCE10:PC71BM and PCE13:IT-4F. This versatile approach highlights the ease of manufacturing and scalability achieved by the solution casting processes along with a high compatibility of acceptor and donor blends.