Enhancement of Two-Photon Absorption via Oligomerization. A Route for the Engineering of Two-Photon Absorbers in the Visible Range

Abstract

In this paper, we develop a new strategy for designing organic molecules exhibiting at the same time a strong two-photon absorption and a good transparency in the visible region: the oligomeric strategy. At the present time, these two properties are hardly simultaneously fulfilled only by a few existing organic molecules. This approach does not involve any charge transfer and then contrasts with the donor−acceptor strategy. The one- and two-photon absorption properties of 9,9-dihexylfluorene oligomers are first presented and then analyzed thanks to a simple three-level excitonic coupling model. This model, which succeeds in reproducing the experimental data, is then used as a prospective tool, and a set of simple rules is extracted for improving the optical properties of this family of molecules.