Optimizing Conducting Polymer Top Electrodes for Nonfullerene Organic Solar Cells

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is a promising solution-processed electrode for printable organic solar cells (OSCs). PEDOT:PSS-based top electrode has been used in fullerene OSCs, but hasn't been successfully used in nonfullerene OSCs. The PEDOT:PSS electrode suffers energy level mismatch with emerging nonfullerene active layers and poor wettability on the top of those active layers. In this work, two types of PEDOT (alcohol-dispersed PEDOT:F and aqueous PEDOT:PSS PH1000) are combined to fabricate efficient top electrodes for nonfullerene OSCs. The alcohol-dispersed PEDOT:F solves the issues of the energy level mismatch and poor wetting. PEDOT:PSS is transfer-printed onto the PEDOT:F to obtain high electrical conductivity for hole collection. Nonfullerene OSCs with the PEDOT:F/PEDOT:PSS polymer top electrodes (vacuum-free processing) show power conversion efficiency of 12.46% based on PM6:Y6:PC71BM active layer.