114% quantum efficient solar cell - in the lab

techntrek

NREL has tested a solar cell in the lab which outputs more electrons than photons going in. The additional output is captured from high-energy photons creating more than one electron-hole in some cases. Took over 10 years to go from theory to a working model in the lab, so don't expect this on your roof any time soon.

http://www.physorg.com/news/2011-12-scientists-solar-cell-electrons-photocurrent.html

niel

Re: 114% quantum efficient solar cell - in the lab

unless i'm misreading this, you can't get more out than what is put in. there is only a certain amount of solar energy that hits the earth and you won't be able to get all of that energy let alone more.

techntrek

Re: 114% quantum efficient solar cell - in the lab

From the article:

Quantum dots, by confining charge carriers within their tiny volumes, can harvest excess energy that otherwise would be lost as heat – and therefore greatly increase the efficiency of converting photons into usable free energy.

niel

Re: 114% quantum efficient solar cell - in the lab

techntrek wrote: »

From the article:

Quantum dots, by confining charge carriers within their tiny volumes, can harvest excess energy that otherwise would be lost as heat – and therefore greatly increase the efficiency of converting photons into usable free energy.

that's wonderful, but there is still only 1000w/m^2 on average of solar energy that hits the earth in all forms and you can't get 114% of 1000w/m^2. now maybe they are getting 114% over some of the present solar cells which is more within the realm of possibility, but i'd still be skeptical.

nsaspook

Re: 114% quantum efficient solar cell - in the lab

What they are getting is 114% of a single photon -> electron energy transfer. The process produces a photon -> two electrons with each ~1/2 the power transfer from the photon. A single electron can only receive so much power (less than 50% , close to 40%) so in theory two at half power could transfer 80% of the total power from the photon. I'm skeptical it will ever be cost effective.

mike95490

Re: 114% quantum efficient solar cell - in the lab

I'm always concerned when someone uses numbers over 100%. "101%" is just 4 randon digits, AFIC.

It would earn you an F in a math class. I know. I remember.

westbranch

Re: 114% quantum efficient solar cell - in the lab

this one is far more realistic vis a vis making it to the market

http://forum.solar-electric.com/showthread.php?14072-Chemistry-Professor-Sheds-New-Light-on-Solar-Efficiency

nsaspook

Re: 114% quantum efficient solar cell - in the lab

westbranch wrote: »

this one is far more realistic vis a vis making it to the market

http://forum.solar-electric.com/showthread.php?14072-Chemistry-Professor-Sheds-New-Light-on-Solar-Efficiency

The other way is direct conversion of photon energy by tiny light-wave antenna/rectifiers on a chip.
http://www.coolcadelectronics.com/DARPA_Energy_Harvesting.html

A real device, like with most of these things is a long way off.
http://en.wikipedia.org/wiki/Nantenna

niel

Re: 114% quantum efficient solar cell - in the lab

what you guys may be missing here is that an antenna is a narrow band device, aka resonant. when it becomes a working development it may only work well in a narrow part of the spectrum. many see this type of curve already on pvs where it rises toward the smallest wavelength of infrared spectrum where it just about enters into visible light and then may start back down again in its response from there. what this may do is just allow a pv to be made for the lower and mid infrared ranges that will not respond as well to visible light. in essence, it's a trade off on wavelength and will not necessarily collect any more power than present technology.

john p

Re: 114% quantum efficient solar cell - in the lab

mike90045 wrote: »

I'm always concerned when someone uses numbers over 100%. "101%" is just 4 randon digits, AFIC.

It would earn you an F in a math class. I know. I remember.

Mike if you lent out money at 10% per month what is the per annum rate??

techntrek

Re: 114% quantum efficient solar cell - in the lab

john p wrote: »

Mike if you lent out money at 10% per month what is the per annum rate??

Simple or compound?

john p

Re: 114% quantum efficient solar cell - in the lab

Its not relevant to the question. .As there is no amount of money given .therefor its only the percentage figure asked.

techntrek

Re: 114% quantum efficient solar cell - in the lab

Completely relevant, thus the difference between rate and effective annual percentage rate on loan documents.

bmet

Re: 114% quantum efficient solar cell - in the lab

niel wrote: »

what this may do is just allow a pv to be made for the lower and mid infrared ranges that will not respond as well to visible light. in essence, it's a trade off on wavelength and will not necessarily collect any more power than present technology.

And what happens to the glare study? Would these panels reflect low and mid infrared waves to a degree that they would confuse insects who see in these ranges? Is reflected infrared going to cause sunburn, interfere with security cameras, assist night-vision glasses, or screw with remote controllers in it's footprint? There are so many infrared devices in the general public, that panels may inadvertently cause electronic dead spots instead of warped vinyl siding.

Joe_B

Re: 114% quantum efficient solar cell - in the lab

Do they get colder when the sun shines on them?

niel

Re: 114% quantum efficient solar cell - in the lab

nobody said the panels would reflect the infrared and they do that now anyway to one degree or another like most things that are shiny or reflective. it's irrelevant.

as to insects, well i just haven't asked any of them lately if they are getting confused. have you asked them and if so please tell us what they said?:roll::p

it is true that reflected infrared can warm you up, but the tans are from the other side of the light spectrum called uv.

all of the items you list take advantage of ir at night and wouldn't affect them detrimentally regardless.

nsaspook

Re: 114% quantum efficient solar cell - in the lab

niel wrote: »

what you guys may be missing here is that an antenna is a narrow band device, aka resonant. when it becomes a working development it may only work well in a narrow part of the spectrum. many see this type of curve already on pvs where it rises toward the smallest wavelength of infrared spectrum where it just about enters into visible light and then may start back down again in its response from there. what this may do is just allow a pv to be made for the lower and mid infrared ranges that will not respond as well to visible light. in essence, it's a trade off on wavelength and will not necessarily collect any more power than present technology.

It's pretty easy to make wide-band (~10:1) unity gain antennas with at normal RF frequencies. The same principle can be used with light with shaped feed elements.
http://en.wikipedia.org/wiki/Discone_antenna
http://classes.yale.edu/fractals/panorama/ManuFractals/FractalAntennas/FractalAntennas.html

niel

Re: 114% quantum efficient solar cell - in the lab

yes, i'll agree that some antenna designs may work well enough to overcome the narrowbandedness to some degree, but it will still be a resonant type thing. remember the multi-layered pvs that responded to various wavelengths? that was a similar idea.

nsaspook

Re: 114% quantum efficient solar cell - in the lab

Yes, Tandem PV junction cells are one way to bypass the http://en.wikipedia.org/wiki/Shockley–Queisser_limit

The problem with direct photon conversion is not really the antenna system, it's the (quantum
mechanical tunneling) diode needing to work at 150Thz with high efficiency that's the tough nut to crack.