In Situ Morphology Control for Solution‐Printable Organic Photovoltaics

The morphology of the photoactive layer plays an important role in both the photoelectric effect and device performance of solution‐processed organic solar cells (OSCs). Optimizing the morphology requires precise control over the complex film formation kinetics, which are influenced by a range of factors from the solution state to the solid‐film state. This review delves into the in situ characterization technologies employed to understand the active layer formation process and explores strategies for controlling film formation during key stages, including solution aggregation, nucleation, crystal growth, and phase separation. Special attention is given to the mechanism by which these strategies enable real‐time morphology control during the printing process and their potential to facilitate direct printing of active layers with optimized morphology. The goal is to offer valuable insights and guidance for managing film formation kinetics in solution‐processed OSCs, ultimately addressing the challenges of real‐time morphology control in scale‐up printing and paving the way for high‐throughput production of post‐processing‐free devices. Recent research progress on the in situ morphology control (e.g., control of solution aggregation, nucleation, crystal growth, and phase separation processes) of active layers for improved solid‐film morphology and organic solar cells performance are comprehensively summarized. Future perspectives on challenges and opportunities for real‐time morphology control during up‐scaling production of active layers are also presented.