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Intrinsic constraints on efficient photoluminescence (PL) from smaller alkene-capped silicon nanocrystals (SiNCs) put limits on potential applications, but the root cause of such effects remains elusive. Here, plasma-synthesized colloidal SiNCs separated into monodisperse fractions reveal an abrupt size-dependent partitioning of multilevel PL relaxation, which we study as a function of temperature. Guided by theory and simulation, we explore the potential role of resonant phonon interactions with "minigaps" that emerge in the electronic density of states (DOS) under strong quantum confinement. Such higher-order structures can be very sensitive to SiNC surface chemistry, which we suggest might explain the common implication of surface effects in both the emergence of multimodal PL relaxation and the loss of quantum yield with decreasing nanocrystal size. Our results have potentially profound implications for optimizing the radiative recombination kinetics and quantum yield of smaller ligand-passivated SiNCs.
Bibliographical noteFunding Information:
E.K.H. acknowledges the support of the National Science Foundation (NSF) through CBET-1133135 and the US Department of Energy (DOE) through DE-FG36-08GO88160. R.J.A. and U.R.K. acknowledge primary support through the NSF under MRSEC Grant Nos. DMR-0819885 and DMR-1420013. A.K. acknowledges use of computational resources of the Center for Computationally Assisted Science and Technology (CCAST) at North Dakota State University and NERSC DE-AC02-05CH11231 for computational resources and financial support for method development from the NSF (Grant No. CHE-1413614).
© 2017 American Chemical Society.
- quantum confinement
- silicon nanocrystals
- surface effects
How much support was provided by MRSEC?
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.
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