Influence of electron-acceptor strength on the resonant two-photon absorption cross sections of diphenylaminofluorene-based chromophores

Resonant two-photon absorption (TPA) cross sections of a series of diphenylaminofluorene-based chromophores with various electron acceptors are predicted using the random phase approximation and using hybrid density functional theory implemented for a two-state model. A comparison of the two methods indicates that the two-state model is adequate for describing the TPA cross sections of all asymmetrical charge-transfer systems under investigation. It is demonstrated that the inclusion of electron correlation can drastically increase the absolute values of the TPA cross sections, but that it has negligible effects on the relative order of the TPA activity of the molecules.