Photoluminescence of Molecular Aggregates

Luminescence is a valuable gift that nature gives to us. Because of its existence, our world has become more colorful. To realize luminescence from a matter, excitation is needed. Photoluminescence, excited by another short-wavelength light, is one of the most studied luminescence phenomena for its easy access. Thanks to the enthusiasm of scientists, a relatively complete theoretical system of photoluminescence has been established. However, the corresponding studies were mainly carried out based on single molecules, while the aggregation of molecules often led to distinct luminescent behaviors. In this chapter, we mainly discussed the typical luminescent behaviors in the solid state, focusing on the molecular packing-property relationship and aiming to further improve the theoretical mechanism of photoluminescence.