Control of molecular aggregation structures towards flexible organic photovoltaics

Flexible organic photovoltaics (OPVs) utilizing conjugated polymers have shown considerable promise in the field of wearable electronic devices. Although active-layer materials featuring extensive conjugated structures demonstrate good electron and optical properties, they often suffer from brittleness, which poses a significant challenge to the advancement of flexible OPVs. The aggregation structure of molecules within the active layer is pivotal in determining its mechanical properties, particularly its stretchability. Recently, researchers have employed a variety of strategies to manipulate the molecular aggregation structure within the active layer to enhance its tensile properties. This review first categorizes the aggregation structures of molecules across different scales, ranging from small to large (including molecular arrangement, chain entanglement, crystallization, phase separation, and semi-interpenetrating networks) and elucidates the mechanisms by which tensile performance can be improved. Subsequently, it summarizes the methodologies for regulating the molecular aggregation structures at various scales. Finally, the review discusses the ongoing development of flexible OPVs to provide valuable insights for researchers in the field.