Near-Unity Internal Quantum Efficiency of Luminescent Silicon Nanocrystals with Ligand Passivation

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• 作者：Fatemeh Sangghaleh ; Ilya Sychugov ; Zhenyu Yang ; Jonathan G. C. Veinot ; Jan Linnros
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：July 28, 2015
• 年：2015
• 卷：9
• 期：7
• 页码：7097-7104
• 全文大小：508K
• ISSN：1936-086X

文摘

Spectrally resolved photoluminescence (PL) decays were measured for samples of colloidal, ligand-passivated silicon nanocrystals. These samples have PL emission energies with peak positions in the range 鈭?.4鈥?.8 eV and quantum yields of 鈭?0鈥?0%. Their ensemble PL decays are characterized by a stretched-exponential decay with a dispersion factor of 鈭?.8, which changes to an almost monoexponential character at fixed detection energies. The dispersion factors and decay rates for various detection energies were extracted from spectrally resolved curves using a mathematical approach that excluded the effect of homogeneous line width broadening. Since nonradiative recombination would introduce a random lifetime variation, leading to a stretched-exponential decay for an ensemble, we conclude that the observed monoexponential decay in size-selected ensembles signifies negligible nonradiative transitions of a similar strength to the radiative one. This conjecture is further supported as extracted decay rates agree with radiative rates reported in the literature, suggesting 100% internal quantum efficiency over a broad range of emission wavelengths. The apparent differences in the quantum yields can then be explained by a varying fraction of 鈥渄ark鈥?or blinking nanocrystals.