

UCLA scientists double efficiency of novel solar cell - m_class
http://phys.org/news/2013-07-ucla-scientists-efficiency-solar-cell.html

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ChuckMcM
I was thinking about this the other day, in that since the photovoltaic effect
is a probabilistic thing (you need your photon to be absorbed so that you can
spit off an exciton), if you had transparent cells you might be able to boost
your efficiency by creating a light trap with mirrors to bounce them through
the cells 10 - 20 times and thus increase the chance that they generate an
exciton by that much.

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Osmium
Indeed; I believe they currently do that in some solar cells. I personal
favourite are "distributed Bragg reflectors" – they're mirrors, but don't work
in the traditional sense:

[http://en.wikipedia.org/wiki/Distributed_Bragg_reflector](http://en.wikipedia.org/wiki/Distributed_Bragg_reflector)

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ChuckMcM
Ok, that is just too cool. Thanks for that link.

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jcfrei
it's important to mention that they doubled the efficiency of their own
previous solar cell, clocking in at 7.3%. a mass produced amorphous silicon
cell achieves around 8%. however the advantage of polymer solar cells might be
much lower production costs.

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neltnerb
So put a regular cell immediately behind the transparent cell? It'd be
equivalent to a multi-junction standard cell, just one that goes out into the
infrared instead of stopping at red.

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dbecker
Can anyone here comment on whether there is enough energy in the infrared
spectrum to make this useful?

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neltnerb
This shows the solar spectrum:

[https://en.wikipedia.org/wiki/File:Solar_Spectrum.png](https://en.wikipedia.org/wiki/File:Solar_Spectrum.png)

Visible light ends at about 700nm, so it looks to me (doing an approximate
area comparison) as if there is about twice the total power in the spectrum
available in the infrared as compared to in the visible.

The article (sorry, it's behind a journal subscription) doesn't say outright
in words what frequencies are most absorbed, but from looking at their
absorption spectra I would assume that the band gap is between about 650nm and
850nm. I am a materials scientist, but I don't know enough of the acronyms
they're using to say more than that. The only other major part I understand
and knew to look for is that those efficiencies are measured under one sun of
illumination (a lot of the really good looking numbers are done under tens or
hundreds of suns).

Convoluting those absorbance spectra with the solar spectrum to get an
approximate maximum power input looks to me like something along the lines of
1/2-2/3rds of the total power as is in the visible spectrum. Definitely not
negligible.

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DamnYuppie
Is anyone looking into manufacturing this? I think it would be awesome to have
this as a film that could be put on windows. Of course the main issue there is
getting that energy back into the home and power grid.

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aidenn0
This is totally uninteresting for anything other than PR unless it is cheap.
Land for solar-cells is not the primary cost of solar energy and won't be for
quite some time.

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hyperbovine
But isn't the idea to decentralize power generation?

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aidenn0
I don't see big advantages to a slightly decentralized power generated system,
and a fully decentralized system won't be feasible at a minimum until we have
much better energy storage (and even then, there is insufficient insolation
for most tall buildings to be self-sufficient with solar).

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DamnYuppie
I see a huge benefit in that if this is in my house then my power consumption
off the grid, in aggregate, is less.

You say land isn't the issue, but access to it for the average person still
is. Yet if I can coat the windows of my own domicile I consider that a net
positive.

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shawkinaw
Seems pretty silly to not absorb visible light, given that that's where solar
energy is peaked. I don't really see the point of this.

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sp332
Did you see this part? _placed on windows, sunroofs, smartphone displays and
other surfaces to harvest energy from the sun._ It can turn surfaces that need
to be transparent into solar cells. And for windows, the visible energy is
already being put to good use, reducing the need for interior lighting.

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shawkinaw
Yes, I understand. I'm just questioning whether it's worth the effort trying
to collect solar energy in these scenarios.

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mitchty
It will provide power that never existed, additionally it makes things like
windows be a less of a heat source for things like air conditioners to pump
back out.

I don't know if its economical yet (nothing product wise available) so it is
somewhat premature to even speculate if it is or isn't worth the effort. The
idea is sound however to take advantage of unproductive real estate.

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mapt
"Economical" is the sum total of the problem with solar.

"Lack of space to put the panels" is not a problem at all - even in densely
populated city centers there are rooftops galore; everywhere else, the cost of
panels far exceeds the cost of land.

So it's a solution to a problem that doesn't exist.

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D9u
I'd say that the cost of efficient PV array systems is a real issue which
currently exists.

Unfortunately the article doesn't say much about the costs of these new cells.

In my area (Latitude 20 deg. N.) solar begins paying for itself after only a
couple, or more, years depending on the type of system.

Obviously, one wouldn't choose to power heavy inductive load appliances with
solar power, but for small items such as electronics and lighting, even
refrigeration, solar makes more sense than paying $0.47 per KWh.

Then there are reliability issues inherent to municipal power grids...

When my neighbors experience a power outage my home is not affected, and to me
this alone is worth the price I paid for my stand-alone solar power system.

