(Invited) Photon Management Using Si Nanocrystals and Er3+ Ions: Generation of Hot Carries upon Absorption of Low-Energy Photons

The most important limitation for efficiency of photovoltaic energy conversion appears due to the enormous  mismatch between the broad-band character of the solar radiation and the discrete operation mode of solar devices, as determined by the specific bandgap energy of the active medium. One remedy for that would be the spectral transformation of the solar radiation before it enters a photovoltaic device. Specifically, such a “solar shaper” should split the large energy photons into smaller ones, whose conversion efficiency is optimal.

In my presentation, I will discuss how shaping of the solar spectrum can be achieved using layers of Si nanocrystals with and without Er doping. In such systems efficient photon transformation can be realized by quantum cutting [1] and/or emission from Er³⁺ ions sensitized by Si nanocrystals [2]. Also the recently identified [3] ultra-efficient colloidal Si nanocrystals can be used for the purpose. I will present evaluation of external quantum efficiency of emission from thin layers of Si nanocrystals in SiO₂ and its evolution upon introduction of Er³⁺ ions. Using differently prepared materials I will evaluate how this can be maximized. I will also discuss energy efficiency of solar shapers based on Si nanocrystals and Er³⁺ ions.

[1] M.T. Trinh et al., Nature Photonics 6, 316-321 (2012).

[2] S. Saeed  et al., under consideration

[3] K. Dohnalova et al., Light: Science and Applications  2, e47 (2013)