Electrochemical processes leading to light emission are reviewed, with emph
asis on aspects of this subject relevant to the understanding and optimizat
ion of electrogenerated luminescence (EL) in organic thin-film materials. T
he basic energetic requirements of light emission from electrochemically in
itiated solution redox reactions [electrogenerated chemiluminescence (ECL)]
are reviewed first. This review is followed by a discussion of light-emitt
ing electrochemical processes that have been observed in hybrids of ionical
ly conducting polymers and electronically conducting polymers. Finally, the
features of EL in insulating polymers and molecular thin films are reviewe
d, along with recent electrochemical and ECL studies of the small-molecule
components of certain organic light-emitting diodes. These studies provide
a conceptual framework for understanding and optimizing these materials and
the EL process.