PL spectra of all samples: the two top spectra [(a) and (b)] are the samples annealed in and Ar. The lower two spectra [(c) and (d)] refer to the samples postannealed in . Only the size controlled samples (A2 and A5) show sharp, intense, and symmetric peaks. The PL blueshift by annealing is only pronounced for sample A2 with 2 nm NCs.
Results of the PL analysis (peak intensity and position). The blueshift induced by annealing compared to Ar is most distinct for small NCs (sample A2). Generally, Ar annealing results in considerably less PL intensity than , which remains unaltered after passivation.
Normalized ratios of the paramagnetic defect densities measured by ESR compared to PL intensities of passivated and unpassivated samples. The correlation between PL intensity increase and density decrease by passivation is clearly evident.
Summary of the PL results of all samples studied. The redshift by is highest for the sample with the broadest size distribution (B), while the blueshift by is much stronger for the small NC (A2) than for the larger ones (A5). The given average FWHM values are almost constant for both Ar and annealing and are hardly affected by passivation.
Comparison of the paramagnetic defect densities (in units of ) measured by ESR. Generally, annealing results in fewer defects than Ar and the defect ratio (Ar over ) is independent on passivation. The not size controlled sample B has always much more defects than the size controlled NC samples (A2 and A5).
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