Organic molecular aggregates have attracted widespread attention over the past decade owing to their unique optoelectronic properties in the aggregate state, which mainly involves the effects of aggregation structure as well as molecular packing mode. Although many examples of H‐ and J‐aggregates defined by molecular exciton model have been found, there are also other types of unconventional aggregates, especially for aggregation‐induced emission (AIE) system. In this review, the recent progress of some examples of basic and novel aggregate forms, as well as coassembled forms, presenting distinctive optical features, such as optical waveguide and polarization emission, polymorph‐dependent emission and stimuli‐responsive luminescence are presented. The systematic insight into the relationship between the aggregation structure and emission property is discussed. Guidelines are therefore anticipated and will direct the future preprogramming molecular design so as to fine‐tune the emission feature through a specific aggregation model for developing organic molecular aggregates with desirable optoelectronic properties.

Organic cocrystals whose unique polymorphic feature can provide a feasible way to investigate and understand the relationship between luminescence properties and aggregate structures have attracted increasing attention in the area of organic optoelectronics. Herein, we prepare polymorphic cocrystals (C1, C2) by using 9,10-bis­((E)-2-(pyridin-3-yl)­vinyl)­anthracene (BP3VA) as chromophore and 1,3,5-trifluoro-2,4,6-triiodobenzene (FIB) as conformer. Both C1 and C2 stack with segregated stacking form, but different intermolecular interactions promote the formation of sheet cocrystals C1 and needle cocrystals C2. C1 exhibits anisotropic optical waveguide property and photoluminescent polarization, while C2 only exhibits the quasi-one-dimensional optical waveguide property. The different optical properties originate from the varieties of molecular packing modes and directions of the optical transition dipole in the two polymorphic cocrystals, which can be clarified through the structure analysis and theoretical calculation. The study can provide a deep understanding of the structure–property relationship of cocrystals and benefit the rational design of novel functional materials.

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