Effect of multiple exciton generation on ultraviolet–visible absorption of Ag–Cu clusters: Ab initio study

• Ag7, Cu7, doping Ag6Cu1 clusters produce the multiple excitons in the visible and near ultraviolet light wavelength.
• The occurrence of MEG enhances the optical absorption in 7-atom Ag–Cu clusters.
• Doping can tune MEG-related optical spectra by redshifting and suppressing the optical peak.

We demonstrate the effect of multiple exciton generation on the Ultraviolet–visible absorption of 7-atom Ag–Cu clusters using symmetry adapted cluster theory with configuration interaction. Multiple exciton generation (MEG) behavior is for the first time observed in metal clusters. The results indicate that multiple excitons appear in the visible and near ultraviolet light ranges. Single excitations are mainly contributions 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–Cu clusters. The optical spectra of pure Ag7 and Cu7 clusters obtained using SAC–CI is in excellent agreement with experiment spectra. As observed in AgnCu7−n (n = 1–6) clusters, doping can tune MEG–related optical spectra by redshifting and suppressing the absorption peak.