Abstracts Book - IMRC 2018

• SA4-O007 Invited Talk
CARRIER MULTIPLICATIONS IN SI-NCS: AB-INITIO RESULTS
Ivan Marri 1
1 CNR, Institute of nanoscience CNR-NANO, Italy.
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 nondissipative
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 and germanium nanocrystals by underlining
the role played by size, passivation and doping. After a brief analysis of carrier
multiplication in isolated nanocrystals, we investigate effects induced by
nanocrystals interplay on carrier multiplication dynamics [5-6]. A comparison
with experimental results is finally carried out.
References
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)