Efficient and Versatile Interconnection Layer by Solvent Treatment of PEDOT: PSS Interlayer for Air-Processed Organic Tandem Solar Cells

A robust and efficient interconnection layer (ICL) based on low conductive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and ZnO nanoparticles is implemented in a solution-air-processed, blade coated inverted polymer tandem solar cell. The commercial PEDOT:PSS (Heraeus Clevios P VP Al 4083) is modified with a fluorosurfactant to allow its deposi- tion onto any hydrophobic active layer surface. However, this method alters the electrical and energetic properties of the PEDOT:PSS thus affecting the interface with the ZnO layer, responsible for an inefficient ICL and poorly performing tandem devices. The ohmic contact at the PEDOT:PSS/ZnO interface is successfully optimized through a simple solvent treatment of the PEDOT:PSS film surface, leading to tandem devices with power conversion efficiencies (PCEs) improved by more than 50% compared to the untreated reference system. The reported method is an easy and versatile approach to optimize the functionality of the PEDOT:PSS/ZnO ICL of inverted multijunc- tion devices, applicable onto any organic active layer and compatible with a roll-to-roll production line.