Electroluminescence.

An overview is presented of research based on the observation by Arnold and Azzi (1971) (Photochem Photobiol 14: 233-240), that an electric field induces charge-recombination luminescence in a suspension of photosynthetic membrane vesicles. The 'electroluminescence' signals from Photosystems I and II are discussed in relation to the shape of the vesicles and the membrane potentials generated by the externally applied electric field. The use of the electroluminescence amplitude as a probe to study the kinetics and energetics of charge separation, and of its kinetics to monitor the electric-field induced charge recombination process are reviewed. Currently unresolved issues regarding the emission yield of electroluminescence are briefly discussed and the properties are summarized of the unexplained Photosystem II luminescence which is not sensitive to the membrane potential.