Size-dependent radiative relaxation in silicon quantum dots: Impact of targeted size
Phys. Rev. Materials 9, 076004 – Published 28 July, 2025
DOI: https://doi.org/10.1103/d6p5-jc18
Abstract
We measure radiative and nonradiative rates for two sets of size-purified colloidal silicon nanocrystals (SiNCs) with overlapping size distributions but different quantum yields (QYs). Plasma-synthesized SiNCs of two distinct targeted diameters are processed into monodisperse fractions through density-gradient ultracentrifugation in organic solvents, where the nanocrystals are shielded from air throughout synthesis, passivation, and purification. At a common nanocrystal diameter, fractions from the smaller, lower-QY parent exhibit lower QY and lower photoluminescence lifetime than fractions from the larger, higher-QY parent, and a simple scaling argument is used to link this effect to differences in the density of surface quenching sites. In contrast, both sets of fractions exhibit the same radiative rate, which we suggest is a strong signature of core emission. Our results reveal steep changes in the nonradiative rate with changes in nanocrystal size and surface chemistry.
