4. Outlook and development

It is clear from all these results that GEB cannot be linked to a single phenomenon, but that several phenomena need to be considered, clearly highlighting the complexity of the interpretation. Whether observed in PL or EL, GEB can have at least three origins. It may come from :

• excimer emissions due to system stacking $\pi$ ;

• exciplex emission when the exciton is confined in a donor-acceptor environment;

• and finally, in the majority of cases, excimer emissions due to the presence of ketonic defects (dipole/dipole interactions). The formation of ketonic defects can result from chemical, photochemical or thermal oxidation, or from interaction with...