Enhanced Luminescent Stability through Particle Interactions in Silicon Nanocrystal Aggregates.
Close-packed assemblies of ligand-passivated colloidal nanocrystals can exhibit enhanced photoluminescent stability, but the origin of this effect is unclear. Here, we use experiment, simulation, and ab initio computation to examine the influence of interparticle interactions on the photoluminescent stability of silicon nanocrystal aggregates. The time-dependent photoluminescence emitted by structures ranging in size from a single quantum dot to agglomerates of more than a thousand is compared with Monte Carlo simulations of noninteracting ensembles using measured single-particle blinking data as input. In contrast to the behavior typically exhibited by the metal chalcogenides, the measured photoluminescent stability shows an enhancement with respect to the noninteracting scenario with increasing aggregate size. We model this behavior using time-dependent density functional theory calculations of energy transfer between neighboring nanocrystals as a function of nanocrystal size, separation, and the presence of charge and/or surface-passivation defects. Our results suggest that rapid exciton transfer from "bright" nanocrystals to surface trap states in nearest-neighbors can efficiently fill such traps and enhance the stability of emission by promoting the radiative recombination of slowly diffusing excited electrons.
North Dakota State University , Fargo, North Dakota 58108, United States.
Joseph B
JB
Miller
North Dakota State University , Fargo, North Dakota 58108, United States.
Naveen
N
Dandu
Theoretical Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
Kirill A
KA
Velizhanin
University of Minnesota , Minneapolis, Minnesota 55455, United States.
Rebecca J
RJ
Anthony
University of Minnesota , Minneapolis, Minnesota 55455, United States.
Uwe R
UR
Kortshagen
North Dakota State University , Fargo, North Dakota 58108, United States.
Daniel M
DM
Kroll
North Dakota State University , Fargo, North Dakota 58108, United States.
Svetlana
S
Kilina
North Dakota State University , Fargo, North Dakota 58108, United States.
Erik K
EK
Hobbie
energy transfer; fluorescence intermittency; nanocrystal interactions; silicon nanocrystals