3 years ago

Size-Dependent Photoluminescence Efficiency of Silicon Nanocrystal Quantum Dots

Size-Dependent Photoluminescence Efficiency of Silicon Nanocrystal Quantum Dots
Yixuan Yu, Detlef-M. Smilgies, Paola Ceroni, Vittorio Morandi, Raffaello Mazzaro, Gang Fan, Brian A. Korgel, Andrea Fermi
Photoluminescence (PL) spectra were measured for dodecene-capped Si nanocrystals with a wide range of average diameters, from 1.8 to 9.1 nm. Nanocrystals larger than 3 nm exhibited relatively high PL quantum yields of 30%–45%. Smaller nanocrystals exhibited lower quantum yields that decreased significantly with reduced size. Because smaller nanocrystals also have lower optical absorption there is a significant biasing of the PL spectra by the larger nanocrystals. We show that with proper accounting of polydispersity and size-dependent quantum yields and optical absorption the effective mass approximation (EMA) accurately estimates the average diameter of silicon (Si) nanocrystals from experimentally determined PL emission peak energies. A finite confinement model is presented that explains the decreased PL quantum yields of the smaller diameter nanocrystals.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b08054

DOI: 10.1021/acs.jpcc.7b08054

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