Magnetic field effects on electro-photoluminescence of photoinduced electron transfer systems in a polymer film

Magnetic field effects on photoluminescence (PL) in the presence of external electric fields have been examined for a variety of electron donor and acceptor pairs, either linked with methylene chain or randomly distributed in polymethyl methacrylate (PMMA) films, which show intermolecular photoinduced electron transfer (PIET). Application of electric fields changes the energy separation among different electronic states, because the electric dipole moment at the state under consideration is usually different from the others. The energy levels within the same spin multiplicity are also shifted or splitted by application of magnetic field. Then, simultaneous application of electric field and magnetic field induces interesting effects on PL which cannot be observed when only electric field or magnetic field is applied to molecules. In this article, experimental results of the magnetic field effect of the electric field effect both on LE fluorescence and on exciplex fluorescence resulting from PIET are presented, and the mechanism of the synergy effects of the electric and magnetic fields on PL are discussed. The hyperfine interaction of the various radical-ion pairs produced by PIET has been also determined on the basis of the synergy effects on PL, and the results are compared with the calculated values. (C) 2011 Elsevier B.V. All rights reserved.