Multilength‐Scale Morphological Engineering for Stable Organic Solar Cells

Abstract Organic solar cells (OSCs) have garnered significant attention owing to the light weight, flexibility, and low cost. Continuous improvement in molecular design, morphology control, and device fabrication has propelled the power conversion efficiency of OSCs beyond 20%. While obtaining long‐term device stability is still a critical obstacle for the commercialization of OSCs. The nano‐ and microstructural characteristics of the active layer morphology—including molecular stacking, phase separation, and domain sizes—play a pivotal role in determining device performance. Consequently, a comprehensive understanding of how film structure impacting device stability and the methods to control film morphology are vital for improving device lifetime. This review seeks to elucidate the structure–performance relationship between active layer morphology from the nanoscale to microscale and device stability. It can provide rational guidance to enhance device stability from morphology control, accelerating the commercialization of OSCs.