Interaction of excitons with charge carriers in organic solids: charged excitonic complexes

The coupled states of molecular excitons with charge carriers are considered. In centrosymmetric crystals the attraction of excitons to charge carriers arises mainly from the increase of molecular polarizability on electronic excitation, so that the exciton energy decreases in the electric field of the charge. In noncentrosymmetric crystals, the main contribution to the energy of exciton-charge interaction comes from the change of the static dipole moment of the molecule on excitation. Some physical consequences and possible experimental observations of the above-mentioned coupled states are discussed.