Flexible All‐Solution‐Processed Organic Solar Cells with High‐Performance Nonfullerene Active Layers

Abstract

All-solution-processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low-cost and ubiquitous applications. However, it is still challenging to fabricate efficient all-solution-processed organic solar cells with a high-performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all-solution-processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (H_X MoO₃ ) between the active layer and the PEDOT:PSS. The dual functions of H_X MoO₃ include: 1) its deep Fermi level of -5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the H_X MoO₃ composition during the synthesis is critical in obtaining processing orthogonality between H_X MoO₃ and the PEDOT:PSS. Flexible all-solution-processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm² , respectively.