Aggregation of molecules is a multi-molecular phenomenon occurring when two or more molecules behave differently from discrete molecules due to their intermolecular interactions. Moving beyond single molecules, aggregation usually demonstrates evolutive or wholly emerging new functionalities relative to the molecular components. Conjugated small molecules and polymers interact with each other, resulting in complex solution-state aggregates and solid-state microstructures. Optoelectronic properties of conjugated small molecules and polymers are sensitively determined by their aggregation states across a broad range of spatial scales. This review focused on the aggregation ranging from molecular structure, intermolecular interactions, solution-state assemblies, and solid-state microstructures of conjugated small molecules and polymers. We addressed the importance of such aggregation in filling the gaps from the molecular level to device functions and highlighted the multi-scale structures and properties at different scales. From the view of multi-level aggregation behaviors, we divided the whole process from the molecule to devices into several parts: molecular design, solvation, solution-state aggregation, crystal engineering, and solid-state microstructures. We summarized the progress and challenges of relationships between optoelectronic properties and multi-level aggregation. We believe aggregation science will become an interdisciplinary research field and serves as a general platform to develop future materials with the desired functions.

分子的聚集是一种多分子现象，当两个或多个分子由于它们的分子间相互作用而表现出与离散分子不同的行为时发生。超越单个分子，聚集通常表现出相对于分子成分的进化或完全新兴的新功能。共轭小分子和聚合物相互作用，产生复杂的溶液态聚集体和固态微观结构。共轭小分子和聚合物的光电特性由它们在广泛空间尺度上的聚集状态敏感地决定。本综述重点关注共轭小分子和聚合物的分子结构、分子间相互作用、溶液状态组装和固态微观结构的聚集。我们强调了这种聚集在填补从分子水平到设备功能的空白方面的重要性，并强调了不同尺度的多尺度结构和特性。从多级聚集行为的角度，我们将分子到器件的整个过程分为几个部分：分子设计、溶剂化、溶液态聚集、晶体工程和固态微结构。我们总结了光电特性与多级聚合之间关系的进展和挑战。我们相信聚合科学将成为一个跨学科的研究领域，并作为开发具有所需功能的未来材料的通用平台。