Nonlinear plexcitons: excitons coupled with plasmons in two-photon absorption

The nonlinear optical properties of a D-A (donor-acceptor) conjugated organic molecule with polythiophene (PT) as the donor and indene-C-60 bisadduct (IC(60)BA) as the acceptor are theoretically investigated, which exhibits a large two-photon absorption (TPA) cross-section up to 8000 GM at the wavelength of 780 nm. Combining surface plasmon resonances (SPRs) with nonlinear optics, nonlinear properties can be strongly enhanced. In this paper, an appropriate nonlinear plexciton method by the coupling of Au@Ag nanorods and an Ag film is designed, in which the TPA properties of the PT:IC(60)BA complex can be increased by 10(6) times. The angle dependence on polarization and incidence is investigated to obtain the maximum of plasmonic enhancement. Our results emphasize the physical mechanism of nonlinear plexcitons and provide a feasible method to improve the nonlinear properties of organic solar cell materials.

Automated summary

This paper theoretically investigates the nonlinear optical properties of a D-A conjugated organic molecule and proposes a method to enhance its properties using surface plasmon resonances and nonlinear optics. The results show a significant improvement in two-photon absorption by 10(6) times using a nonlinear plexciton method.