Systematic characterization of excited states in π-conjugated polymers

Exact finite chain calculations within a diagrammatic exciton basis give pictorial descriptions of all excited states of pi-conjugated polymers. In linear chain polymers the 1B(u) is an exciton, and the fundamental two-photon states can be broadly classified into triplet-triplet, charge-transfer and singlet-singlet excitations. The mA(g), a two-photon state that plays a strong role in nonlinear optics, is a correlated charge-transfer state. The singlet-singlet states occur higher in energy and split into bound biexcitons and a continuum of free two-exciton states. (C) 1997 Elsevier Science B.V.