[seminar] Sajeev John, Photonic Crystals Solar Cells: Prospects for World Record Efficiencies

[Hrvoje Buljan]

Reminder for today's seminar!

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Dear colleagues,
I am glad to announce a seminar within the QuantiXLie Center of
Excellence, that will be given next Monday,

Time: Ponedjeljak, 18. 6. 2018., 15:15 sati
Place: Fizički odsjek, prostorija F-201

by one of the pioneers in the field of photonic crystals, Sajeev John.
The title and the abstract of the talk are attached and below.
Hrvoje Buljan

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Photonic Crystals Solar Cells:
Prospects for World Record Efficiencies

Sajeev John
Dept. of Physics, University of Toronto, Ontario, Canada

Photonic crystals are widely known for their light-trapping capabilities.
This is often associated with the occurrence of a
photonic band gap or other suppression in the electromagnetic density of
states [1,2]. This enables guiding of light on an
optical micro-chip and unprecedented forms of strong-coupling between
light and matter. In the past, practical
applications of these effects have focused on information technology. More
recently, an important opportunity has emerged
in the area of energy technology. This arises from light-trapping in the
higher bands of a photonic crystal, where the
electromagnetic density of states is enhanced rather than suppressed. This
enables unprecedented strong absorption of
sunlight in a thin-film material with weak intrinsic absorption [3-10].
We describe designs of photonic crystal solar cells consisting of less
than ten micron thickness of silicon that enable
the absorption of 98% of all available sunlight in the wavelength range
from 300 nm to 1100 nm. These 3D photonic crystals
exhibit an enhanced electromagnetic density of states, consisting of slow
group velocity modes, in which the flow of energy is
transverse to the depth of a thin film of material. The ability to absorb
nearly all sunlight, using light-trapping, in a flexible 10
micron sheet of silicon, enables considerable reduction of carrier Auger
recombination losses in the bulk. Coupled with
recent advances in surface passivation near electrical contacts, it is
possible to reach a power conversion efficiency of
30%, well above the current world record for any silicon solar cell.
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