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Berkeley Lab Develops Technology To Make Photovoltaics Out of Any Semiconductor
First time accepted submitter bigvibes writes "A technology that would enable low-cost, high efficiency solar cells to be made from virtually any semiconductor material has been developed by researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley. This technology allows for plentiful, relatively inexpensive semiconductors, such as metal oxides, sulfides and phosphides that had previously been considered unsuitable for solar cells because of the difficulty in tailoring their properties by chemical means."
as usual :-)
Perl Programmer for hire
progress marches on
To offset political mods, replace Flamebait with Insightful.
call me when I can buy it in rolls or sheets at Home Depot.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
“screening-engineered field-effect photovoltaics,” or SFPV
The two hyphenated pairs get a single letter. The single compound word gets two letter. Stop the madness!
That's about when I'll be building a house from scratch.
Lacking <sarcasm> tags,
for once, anyway.
Occasionally living proof of the Ballmer peak.
The issue was always a low output but if you can make them dirt cheap who cares if they are 5%? If you can cheaply replace the shingles on your house with cheap solar cells I'd call it a win even if you have to cover the whole roof instead of one part. Cheap and practical will always win over efficient and expensive. Even when over the long term you are better off with the more efficient cells people will actually buy the cheaper ones. It's what keeps Ikea and stores like it in business. Pressboard furniture falls apart after a couple of years but it's less than half the price of decent furniture. A good piece may last 50 years and out live 10 cheapie pieces so the cheap furniture costs 5X as much in the long run but people still go for cheap. If people could cover their roofs for $2,500 to $5,000 instead of $15,000 to $35,000 most roofs would have solar cells even if they last half as long.
It's really hard to picture what is described in the article. Here's a link to an article with a diagram.
I read the article (I know! But there were no comments yet, so what am I to do?) and, not having understood much of it, did some reading to try and understand what's going on here. I think I've more or less figured it out, so I'm attempting a simple explanation here. Semiconducting physics nerds, please fix this for me as appropriate.
Atoms consist of a positively charged nucleus, surrounded by one or more shells of electrons. Electrons farther away from the nucleus have more energy than ones closer in. Put a bunch of those atoms together, and there are two things that can happen. In some materials, the electrons in the higher energy states are so "far away" from the nucleus in energetic terms, that they can easily move from one atom to the next. These materials are conductors. In other materials, there is a big gap (the band gap) between the highest "bound" (valence band) energy state, and the minimum energy state (the conduction band) needed to move between atoms. So, the electrons can't move away from their nuclei, and these materials are electrical insulators. Then there are some materials that have an intermediate sized gap between stuck valence states and free-to-move conduction states, and these are called semiconductors.
A solar cell works by the photoelectric effect: when an incoming photon (e.g. sunlight) hits an electron in a semiconductor, the electron absorbs the photon and its energy increases. If the photon is energetic enough, this will move the electron from the valence band to the conduction band. This also creates a positively charged "hole", where the electron was before. The electron and the hole attract each other because they have opposite charge. Left to their own devices, they'll just recombine, so in a solar cell, an electric field is applied. This moves the electron in one direction, and the hole in the opposite direction (because of the opposite charge). This moving electrical charge is otherwise known as current flow, and so we have a working solar cell.
So how do we make an electric field? In normal photovoltaic cells, this is done by doping (adding small impurities, typically boron and phosphorus to) the semiconductor. Since these have less or more electrons in their outer shells, they create areas in the semiconductor with more electrons or more holes, which creates a charge difference between them (a P-N junction). This charge difference creates an electric field, which will whisk away any electrons and holes created within it. Apparently, this doping process only works for relatively expensive semiconductors however.
So, if I understand correctly, what these researchers have done is to apply an external electric field, by applying a small voltage across the whole thing. This puts a charge on the contacts on each side of the cell, which draws electrons in the semiconductor one way and holes the other way, thus creating a P-N junction without doping. The problem is that normally the construction of the contacts keeps their electric field from propagating into the semiconductor, so that it doesn't generate a good P-N junction. Apparently they've overcome this by changing the geometry of one of them, in two different ways for two different alternative semiconductors. And then they have a version in which the external voltage is supplied by the cell itself, making it self-contained.
So is this useful? Well, conspicuously absent from the article is any mention of efficiency. So I'd speculate that this mainly allows the production of low-efficiency solar cells at lower prices than before, rather than getting more output from your roof. But if this makes solar cells cheap enough to just blanket anything and everything with them, that could still be useful of course.
To quote Bart Simpson: "I can't believe it! You actually found a practical use for geometry!"
Have we forgotten the term 'vaporware'? Has it evaporated along with the products we used to laugh at?
I've been reading about 'exciting new developments' in photovoltaics for forty years, along with the flying car that's just around the corner and similar fantasies perpetuated by Popular Science & Popular Mechanics magazines.
Show me the cheap efficient PV product I can buy today or just shut up.
...omphaloskepsis often...
Solar panels are already cheap enough for me. In NYC, Con Ed charges $0.20+ per KWh, so installed panels at about $3:Wp pay off in under 7 years: a 14% ROI, better than the stock market ever gets (so I almost wish they cost more :).
My problem is that my roof is largely covered by trees, so I get only about 20% of the sunshine past them. So I've been considering building a platform above the roof, above the trees, though that's going to be something like 10m above the roof, which is about 7m above the ground. I don't know if it will be stable, or how many years of solar power it will cost to pay back the extra infrastructure costs. We don't have enough wind to make turbines on the platform worth their investment.
Where can I research whether a raised platform is feasible?
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make install -not war