Giant Stokes Shifts in AgInS2 Nanocrystals with Trapped Charge Carriers

Nanocrystals of AgInS2 demonstrate giant Stokes shifts similar to 1 eV, the nature of which is still not clearly understood. We propose a theoretical model of this phenomenon, bringing together several different mechanisms previously considered only separately. We take into account the contribution of the electron-electron interaction with the hybrid density functional theory, as well as the renormalization of the energy spectrum due to the electron-phonon coupling. Furthermore, we consider the presence of at least one point defect responsible for hole trapping and the formation of a localized polaron state. Our numerical simulations show that photoluminescence due to the recombination of a nontrapped electron and a trapped hole results in the giant Stokes shift in AgInS2 nanocrystals, which is in close agreement with the recent experimental results.