Quantum Dots Could Double Solar Energy Efficiency 112
dptalia notes the recent publication in Science of research demonstrating a way to use hot electrons in solar cells, resulting in an overall energy conversion efficiency of 66%. Here is the abstract in Science; access to the full article requires a subscription. "A team of University of Minnesota-led researchers has cleared a major hurdle in the drive to build solar cells with potential efficiencies up to twice as high as current levels, which rarely exceed 30 percent. ... Tisdale and his colleagues demonstrated that quantum dots — made not of silicon but of another semiconductor called lead selenide — could indeed be made to surrender their 'hot' electrons before they cooled. The electrons were pulled away by titanium dioxide, another common inexpensive and abundant semiconductor material that behaves like a wire."
Re:Econuts will be torn over this one (Score:3, Interesting)
Not a problem; lead's not nearly as bad as the arsenic in some panels!
Re:Could, might, may... (Score:4, Interesting)
I think you mean;
Give me more Grant money!
Fund my Startup company!
You can't get the money to do the engineering to make these things a reality if nobody knows about your research in the first place. Shameless self-promotion (in this case publishing in Science) therefore becomes a necessary evil.
Re:Could, might, may... (Score:5, Interesting)
Read the damn paper, or at least the abstract, ok? The horsepucky all comes from the university PR flacks, amplified by the Slashdot editors.
That's how research works (Score:4, Interesting)
It's messy.
If you're lucky, you have a clear goal, and that goal is reachable though no one knew it beforehand of course. Also far from assured is that no one else has already done it. Not at all easy to find it out either, as others may have approached some problem from a completely different direction, and you will not be looking in the right places when you try to find out what others have done. And you could discover something entirely unrelated while in pursuit of your objectives, something worth taking a massive detour to pursue. Reporting on science skips over the difficulties to the point that it's like the joke about how to put an elephant in a refrigerator. You open the door, put the elephant in, and close the door, duh! Even scientific journals omit "extraneous" details about wrong turns taken, because "thinking is vulgar". Researchers naturally don't want to look dumb, and neither do journals. Plus, journals are always trying to save space and time. Streamlining articles to talk of only the successful experiments is an obvious cut to make. There's a STNG episode that touches on the problem. Lore mocks Dr. Noonien Soong, calling him "Often Wrong", but there it is clear that Lore's criticism is unfair. Science is all about doing things that will probably turn out to be mistakes, and learning from them.
Most people think science is about finding answers. That's only half of it. More important is asking good questions. Finding out which questions to ask and hopefully answer. Yes there are bad questions, don't believe that dogma about there being no such thing as a dumb question. They're still worth asking if you don't know or can't know they're bad. What they aren't is worth answering, and discovering that is the problem. There are questions that turn out to make no sense, or are too simple, or too complicated, or pointless, or misleading, or are based upon or arise from inferior modelings or from misunderstandings, or are predicated on assumptions that actually aren't valid, or are unanswerable. Math is full of shifts in representation to avoid such problems.
For instance, how do you deal with infinity in, say, the slope of a line? Vertical lines have infinite slope. You could pull out calculus and limits to handle these infinities, but if you do, you've just been sucked into doing things in a much harder way, been pulled down a rabbit hole to figure out all kinds of problems with working with infinities and division by 0. So much easier to use vector representations from linear algebra and avoid those infinities. All those questions about handling infinities turn out to be pointless for this problem. Mind you, infinites crop up in plenty of other places, so having ways to handle them is still useful, it just isn't necessary for this problem of representing a line. That's an old, well known problem for which we've known good answers for a long time now. There are also things like the famous Fourier Transform, and Lagrangian basis, not to mention Calculus itself to handle problems that are very nasty in classical geometry. But in new, unexplored territory it's not so easy to tell which questions will turn out to be bad.
Most things that scientists try turn out to be wrong. History has a few famous ones, such as "Squaring the Circle". The public hears little more than the 1% that turned out right.
Re:Econuts will be torn over this one (Score:5, Interesting)
Re:How much energy are we talking about? (Score:2, Interesting)
The only thing that I'm unsure of is whether you can concentrate the light in nano-confined cells as much as you can in bulk material cells.
I would think that quantum dots might be ideal for use in a grid array of something like the dye-sensitized collectors that have recently been developed. I don't think that current saturation would be an issue, as the leads will be distributed evenly at each quantum dot. The problem I see is that increasing the area used for contact wiring will mean increased non-radiative losses. The article states that the wire contacts will be made of semi-conductor material as well, and semi-conductors typically have lower conductivity/higher loss than conductors. Supposedly they are trying to overcome those losses by using a partially generative material as an intermediate between the conducting leads and PbSe cells?
price not efficiency (Score:3, Interesting)
who cares about efficiency?
If you make a solar cell that is 100% efficient but costs $10billion / watt to make, who cares?
On the other hand if you make one that is only 1% efficient but only cost .01c / watt to make, that would change the world.
potential 66%? In your dreams... (Score:3, Interesting)
This is good, solid condensed matter physics research, and it is important. But, the 66% efficiency they're quoting comes from an old calculation of what is effectively a perfect solar thermal converter where the electrons are "hot" and the temperature of the crystal doesn't really matter because there's no interaction between the electrons (or photons) and the crystal. This theory has been the motivation for the hot electron transfer work on quantum dots, but at some point it should come up that they can't get hot electron transfer to work at much above around 100 K. That's kind-of really important (not to mention impractical). The device they're *trying* to make shouldn't need to be cooled at all. That's a giant clue that the theory they're basing this amazing 66% on is more than a little oversimplified for what they actually have. It's annoying that people are using an out of date 28 year old paper to sell the direction of their research; it makes life hard on their competition using more honest efficiencies.
Re:Lead (Score:1, Interesting)
I've got more than plenty of batteries with lead and electronics composed of parts containing much nastier chemicals. As long as it's contained and the goo or magic smoke stays inside, it's all good.