Layer‐by‐Layer Processed Pseudo‐Bilayer Heterojunctions Advance the Performance of Organic Solar Cells

Abstract Recent progress in organic (semiconductor) solar cells (OSCs) has led to power conversion efficiencies (PCEs) reaching 20%, with predictions that 25% may be possible. Additional to PCE improvements, significant efforts have been made to address the engineering challenges that have traditionally limited OSCs small area devices often with poor temporal stability. Layer‐by‐layer (LbL) processing of active layers has emerged as a promising approach to tackle these challenges, with numerous state‐of‐the‐art OSCs processed using LbL reported. In this Perspective, recent developments are developed in enhancing OSC efficiency and stability, with a particular focus on the working mechanisms of pseudo‐bilayer heterojunctions (P‐BHJ) and the practical aspects of fabricating high‐performance devices using LbL techniques. By providing insights into LbL processing and the resultant film morphology, it is hoped to contribute to the ongoing efforts to improve OSC efficiency, stability, and scalability and to explore their potential for broader applications such as for example for indoor light harvesting or agrivoltaics.