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

摘要

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