Organic Solvent-Based PEDOT:PSS Solution for Air-Processed Organic Photovoltaics.

PSS is one of the best hole transport materials in organic photovoltaics (OPV). However, due to poor wettability, the aqueous PEDOT:PSS (a-PEDOT) is not applicable for inverted structured OPV as a hole transport layer (HTL) on top of the active layer. In this work, organic solvent-based PEDOT:PSS (o-PEDOT) with improved wettability was prepared by the solvent-replacement method through centrifugal ultrafiltration, dialysis membrane, and thermal evaporation. Adopting o-PEDOT as the HTL on the top surface of the active layer, the inverted OPVs were successfully prepared through a solution process. Importantly, due to good conductivity and suitable work function, the o-PEDOT can also act as the interconnection layer (ICL) in air-processed tandem OPV devices. The tandem device achieved a champion PCE of 15%, among the best reports of solution-processed homotandem OPV under open-air conditions. The flexible tandem OPV using o-PEDOT as an ICL was also demonstrated, with an efficiency of over 14%.