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Issue 24, 2014
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Pseudo-direct bandgap transitions in silicon nanocrystals: effects on optoelectronics and thermoelectrics

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Abstract

While silicon nanostructures are extensively used in electronics, the indirect bandgap of silicon poses challenges for optoelectronic applications like photovoltaics and light emitting diodes (LEDs). Here, we show that size-dependent pseudo-direct bandgap transitions in silicon nanocrystals dominate the interactions between (photoexcited) charge carriers and phonons, and hence the optoelectronic properties of silicon nanocrystals. Direct measurements of the electronic density of states (DOS) for different sized silicon nanocrystals reveal that these pseudo-direct transitions, likely arising from the nanocrystal surface, can couple with the quantum-confined silicon states. Moreover, we demonstrate that since these transitions determine the interactions of charge carriers with phonons, they change the light emission, absorption, charge carrier diffusion and phonon drag (Seebeck coefficient) in nanoscaled silicon semiconductors. Therefore, these results can have important implications for the design of optoelectronics and thermoelectric devices based on nanostructured silicon.

Graphical abstract: Pseudo-direct bandgap transitions in silicon nanocrystals: effects on optoelectronics and thermoelectrics

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Article information


Submitted
14 Aug 2014
Accepted
12 Oct 2014
First published
13 Oct 2014

Nanoscale, 2014,6, 14643-14647
Article type
Communication

Pseudo-direct bandgap transitions in silicon nanocrystals: effects on optoelectronics and thermoelectrics

V. Singh, Y. Yu, Qi-C. Sun, B. Korgel and P. Nagpal, Nanoscale, 2014, 6, 14643
DOI: 10.1039/C4NR04688A

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