Spectral Dependencies of the Stretched Exponential Dispersion Factor and Photoluminescence Quantum Yield as a Common Feature of Nanocrystalline Si

Herein, the spectral dependencies of the dispersion factor β (from the stretched exponential function) and photoluminescence (PL) quantum yield (QY) of silicon nanocrystals (Si NCs) are thoroughly studied. Spectrally resolved PL decay kinetics of Si NCs in both liquid and solid samples are measured and their corresponding distributions of rates are retrieved by means of the hybrid maximum-entropy method. This enables us to demonstrate a direct correlation of dispersion factor β with the width of rate distribution. Here, the evidence of the same step-like spectral dependence of rate distribution widths (dispersion factor) for different forms of nanocrystalline silicon (including porous silicon and chemically synthesized Si NCs) is presented suggesting intrinsic (core-related) origin of rate distributions. Spectral dependence of normalized QY of Si NCs reveals two characteristic peaks with spectral positions at ≈1.42 and ≈1.68 eV. A similar peak in QY spectral dependence of CdSe quantum dots (QDs) is found, which suggests its common origin regardless the material of semiconductor QDs.