Theoretical investigation of two-photon absorption properties of naphthalimide derivatives

In the process of photovoltaic energy conversion, photons with the energy below the band-gap cannot be absorbed and do not contribute to energy conversion. Frequency up-conversion describes the conversion of low energy incident photons towards higher energy photons via active materials. Two-photon absorption induced fluorescence is one of the approaches that convert low energy incident photons towards higher energy photons via active material. In this paper, quantum-chemical techniques were applied to investigate two-photon absorption properties of some new naphthalimide derivatives. One- and two-photon absorption cross sections of these derivatives were obtained using two-state and three-state model. Geometrical structure of molecule was optimized using Hartree-Fock Theory (HF) and properties of excited states of molecule were obtained based on Configuration Interaction with single excitations method (CIS). The theoretical findings of two-photon absorption cross sections of these derivatives were consistent with the experimental observations.