Relaxation and Energy Transfer in Ensembles of Si Nanocrystals

Radiative and nonradiative relaxation and migration processes are considered and then simulated in dense ensembles of Si nanocrystals. We have discussed, and adopted for the subsequent modeling, the rates of the interband radiative transitions, Auger recombination, capture on dangling bonds, Förster's exciton transfer, and tunneling of excited carriers between the nanocrystals. Computational simulation of the photoluminescence and migration in the ensemble was performed for ensembles with different volume fill. It was revealed that the migration processes essentially contribute to common relaxation dynamics of the ensemble and strongly influence the photoluminescence. This is due to a high migration efficiency that considerably exceeds an efficiency of the radiative relaxation channel in closely packed ensembles of Si crystallites.