Multiple exciton generation in Ag and Ag–Cu quantum clusters by visible wavelength excitation

摘要

We investigated the single exciton and multiple exciton generation (MEG) behavior in Ag_7 and single Cu atom-doped Ag_7 quantum clusters using ab initio. MEG is observed for the first time in metal clusters. The results indicate that multiple excitons appear in the visible and near ultraviolet light ranges. Single excitations are main contribution for the optical spectra, while the multiple excitons merely contribute for some peaks at the higher energies. However, occurrence of MEG enhances the optical absorption in Ag_7 cluster. The optical spectrum of pure Ag_7 cluster obtained using the symmetry-adapted cluster theory with configuration interaction, and time-dependent density functional theory is in excellent agreement with experiment spectrum. As observed in both single Cu atom-doped Ag_7 clusters, redshifts and suppressions of the MEG-related absorption peaks are observed compared with pure Ag_7 cluster.