Light emission of organic luminogens: Generation, mechanism and application

Light has been, and continues to be, one of the most fundamental and indispensable elements to life and society. Generally, it can be produced in the process from a higher energy quantum mechanical state of a particle to a lower one through the emission of a photon, and the excitation can be from a variety of sources, including photoluminescence, electroluminescence, mechanoluminescence, chemiluminescence and so on, which are emitted from luminophores with different compositions. The development of luminescent materials has allowed us to gain enormous knowledge that has undoubtedly promoted high-tech innovations, such as organic light-emitting diodes (OLEDs), biological probes, chemical sensing, stimuli responses, security painting, and so on. This review makes a detailed introduction of the generation, mechanism and application of light emissions, especially for those in aggregate or solid state. With the classification of emissions with different types of excited states, we attempt to draw the whole map of these light emitting processes, thus summarizing the relationship between the molecular structure/packing and emission property. Also, their applications are highlighted with the exploration of novel materials and technologies.