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Other questions.
(female speaker). In these multi junction,
multi layered ones, like the typical ones
that a house would use now absorb mainly the red part
of the spectrum, is that right?
(Dr. Bailey). You absorb, the silicon solar
cells absorb more towards the red, towards the middle
of the spectrum and into the red.
The new multi-junction cells absorb from the UV into the red.
So they are much more efficient.
They are also much more expensive.
(female speaker). Like the Mars rover,
is that, it was a multi junction cell?
(Dr. Bailey). It is a multi-junction cell.
It is a gallium indium phosphide on gallium arsenide on germanium
solar cell.
(female speaker). [unclear audio].
(Dr. Bailey). Yes, it is.
And it's done very well.
I didn't get to Mars rovers, we really ran out of time.
There was another question over here.
(male speaker). [unclear audio].
(Dr. Bailey). Well, the motivation
for quantum dots is that if you make a single
intermediate band structure, which is actually a P-I-N cell,
it's almost twice the efficiency of a single junction,
multi-junction cell.
And you've not introduced any new materials, anything other
than a little more complicated process which is mostly
programming the computer for the reactor.
So the idea is that you're making a more complicated cell
but you're making it with the same processes that you used
to make a regular cell and you're just getting a more
highly efficient cell, eventually.
Because it isn't there yet.
(male speaker). [unclear audio].
(Dr. Bailey). I'm sorry, I missed that.
(male speaker). [unclear audio].
(Dr. Bailey). Oh, well, the solar cell
people really don't look at it that way.
They look at it as the quantum dots being a different
energy band gap.
Okay, so that's really how they view a quantum dot solar cell.
By controlling the diameter of the dot, you control the band
gap of the material.
You can always make it longer than the base material.
You can never make it shorter than the base material.
Other questions.
(male speaker). Well, thank you very much
for coming.
In the interest of time, you probably have other things to do
to wrap up the day.
Thank you very much, Dr. Bailey, for the presentation.
(Dr. Bailey). You're welcome.
♪ [music playing-- no dialogue] ♪♪.