Research Promises Full-Spectrum Solar Cell

nphillips writes "As is being here reported here, a serendipitous discovery was made that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current. For if solar cells can be made with this alloy, they promise to be rugged, relatively inexpensive -- and the most efficient ever created. Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth."

Comments

Re:UV during nighttime...

[Christopher Thomas]

As I understand it, UV light hits the earth at all hours.

Does anyone know how much UV hits the earth during the night?

Almost none. Virtually all of the light that strikes Earth comes from the sun.

As another poster pointed out, you may be confusing this with the mid-IR glow that warm objects (including the ground and the air) give off. The amounts of energy involved are very low, and room-temperature thermal IR is difficult to convert to electricity efficiently.

Any solar power scheme (and so any photovoltaic scheme) has to have enough storage capacity to power the load overnight. Ideally, it should be able to provide power for several days, in case of cloud cover/rain/whatever. This is why most home-powering schemes involve large battery arrays. A city-powering solar plant would probably use fuel cells (energy density is much higher, and there are off-the-shelf models of power-plant scale already available and in use).

Defect Densities, People...

[clark625]

What the article doesn't happen to mention is that InAs (Indium Arsenide) was believed to have a bandgap around 1.6eV (not sure the exact number) and it's now known to be somewhere in the range of ~0.6eV. The article also don't mention phosphide compounds, which are far bigger in research and industry right now.

Fact is, nitrides are bastards to grow. You have to use gas-sources (instead of solid sources that most MBE-ers prefer). There's also no current way to make a nitride-based substrate, which means growing (typically) on sapphire or other lattice mis-matched substrates (GaAs, InP, etc). These lead to HUGE dislocation densities that greatly impact performace.

Now, that doesn't mean this can't be done. And in fact, magic is being done all the time in the world of research. But nitrides aren't going to be realized for some time. Not at least until other technologies pan out first (phosphides and the like). Those are cheaper to grow and allow for much lower defect densities.

Just so you folk's know I'm not just talking out of my ars--do some research and look up some papers. Authors to look for are Steve Ringel (OSU), Gene Fitzgerald (MIT), John Carlin (OSU), Sumitomo (Japan, somewhere), and by-far Yamaguchi (Toyota Technological Institute). Read up on these folks' work and those around them--they know space-based photovoltaics better than most, and very, very, very, very few are working with nitrides right now. Not that it's not going to eventually happen--but until defect densities get low enough, there's simply no way to make a good solar cell (read up on the previous authors' works if you want the theoretical calculations as to why).