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Carrier Multiplication in Si-NCs: ab-initio results

Giovedì 11 gennaio 2018 alle ore 11:00, aula Seminari, III piano, edificio Fisica, Dipartimento FIM, Modena

Relatore: Ivan Marri

Abstract:   An important challenge of the scientific research is promoting the establishment of clean, cheap and renewable energy sources. One of the most appealing and promising technology is solar based, i.e. photovoltaics. For optimal energy conversion in photovoltaic devices one important requirement is that the full energy of the photons is used. However, in solar cells, a single electron-hole pair of specific energy is generated only when the incoming photon energy is above a certain threshold, with the excess energy being lost to heat. Efficiency bottleneck caused by heat generation induced by phonon-assisted carrier relaxation processes can be partially reduced promoting fast and non-dissipative mechanisms that impede or strongly reduce the occurrence of thermalization processes.
In this context Carrier Multiplication seems one of the most promising way to minimise thermalisation loss factors and thus to significantly increase the solar cell power conversion [1-4]. Carrier multiplication is a non-radiative recombination mechanism that results in the generation of two or more electron-hole pairs after absorption of a single high-energy photon.
In this talk we analyse results obtained in the study of carrier multiplication processes in silicon nanocrystals. After a brief analysis of carrier multiplication in isolated silicon nanocrystals, we investigate effects induced by nanocrystals interplay on carrier multiplication dynamics [5-6]. A comparison with experimental results is finally carried out.
1) R.J. Ellison et al., Nano Lett. 5, 865 (2005)
2) R. D. Schaller et al., Phys. Rev. Lett. 92, 186601 (2004)
3) O.E. Semonin et al., Science 334, 1530 (2011)
4) D. Timmerman et al., Nat. Phot. 2, 105 (2008)
5) M. Govoni et al. Nature Photonics 6, 672 (2012)
6) I. Marri et al. J. Am. Chem. Soc., 136, 3257 (2014)

Ospiti: F. Taddei, M. Rontani.

[Ultimo aggiornamento: 08/01/2018 14:38:01]