Organic molecular aggregates: From aggregation structure to emission property

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. In this review, a brief introduction of molecular stacking modes such as H‐, J‐, X‐aggregates, and aggregation‐induced emission (AIE) is summarized. Particularly, the recent progress of some examples of basic aggregate forms, as well as coassembled forms based on organic molecular crystals are presented, with the aim to systematically discuss the relationship between the aggregation structure and emission property.