Abstract
We report on the quantum yield, photoluminescence (PL) lifetime, and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from the fractions, and we use a combination of measurement, simulation, and modeling to link this 'brightening' to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7389-7396 |
| Number of pages | 8 |
| Journal | ACS nano |
| Volume | 6 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 28 2012 |
Keywords
- nanocrystalline silicon
- photoluminescent stability
- polydispersity
- quantum yield