Unraveling the Formation Process of an Organic Photovoltaic Active Layer During High‐Speed Coating Via a Synergistic Concentration‐Temperature Gradient Control Strategy

Abstract The Layer‐by‐Layer (LbL) strategy has emerged as a highly effective approach for enhancing the performance of organic photovoltaics (OPVs), notably boosting light harvesting and fill factor through spectral complementarity and morphology optimization. Crucially, the LbL processing strategy has been found to mitigate or overcome the decline in power conversion efficiency (PCE) during high‐speed blade coating. Despite these advancements, there remains a scarcity of research into the film‐formation process and the corresponding control strategies in high‐speed printing. A novel synergistic concentration‐temperature gradient control (SCTGC) strategy aimed at achieving high‐performance LbL‐type active layers at ultra‐fast coating speeds. This investigation reveals that both baseplate temperature and solution concentration exert a nonmonotonic regulatory influence on PCEs. Fine‐tuning the concentration gradient proves instrumental in balancing microfluidic competition within the wet film, thereby facilitating stable mass transport during the film formation process, and enhancing the high‐speed processability of the relevant OPV system. Additionally, the variations in crystallization kinetics under different temperatures are monitored. This work sheds light on the coating mechanism and film formation in high‐speed coating, highlighting the efficiency of the SCTGC method.