Intermolecular interactions in condensed phases often lead to pronounced modulation of the excited‐state properties of organic emitters, yet controlled dimerization—either through covalent linkage or supramolecular association—has only recently been recognized as a distinct and powerful molecular‐engineering strategy. Despite the rapidly growing interest, comprehensive understanding of how dimer formation governs electronic coupling and excited‐state relaxation remains limited, although the phenomenon is of great significance in photophysics, photochemistry, materials science, and optoelectronic device engineering. Dimerization not only produces diverse emissive behaviors, such as excimer‐type broad emission, thermally activated delayed fluorescence, and room‐temperature phosphorescence, but also holds great potential for the development of multifunctional organic photonic systems with tunable color purity, extended lifetimes, and responsive characteristics. In this concept, we first summarize representative classes of purely organic luminescent dimers that have been reported to date. Second, the underlying mechanisms of dimer‐induced excited‐state pathways are discussed, with emphasis on the relationship between dimer geometry, electronic coupling, and emission characteristics. Moreover, perspectives on rationally exploiting molecular dimerization for advanced optoelectronic applications are presented, aiming to inspire future design of high‐performance organic photofunctional materials.
Zhu et al. (Sun,) studied this question.