Red-Shifted Carrier Multiplication Energy Threshold and Exciton Recycling Mechanisms in Strongly Interacting Silicon Nanocrystals

We
present density functional theory calculations of carrier multiplication
properties in a system of strongly coupled silicon nanocrystals. Our
results suggest that nanocrystal–nanocrystal interaction can
lead to a reduction of the carrier multiplication energy threshold
without altering the carrier multiplication efficiency at high energies,
in agreement with experiments. The time evolution of the number of
electron–hole pairs generated in a system of strongly interacting
nanocrystals upon absorption of high-energy photons is analyzed by
solving a system of coupled rate equations, where exciton recycling
mechanisms are implemented. We reconsider the role played by Auger
recombination which is here accounted also as an active, nondetrimental
process.