Australian scientists report breakthrough in solar cell efficiency

April 18, 2012
(L-R) Professor Tim Schmidt and his research partner Dr Klaus Lips at the Helmholtz Centre for Materials and Energy have made a breakthrough in solar cell technology.

( -- Low cost solar cells suitable for rooftop panels could reach a record-breaking 40 percent efficiency following an early stage breakthrough by a University of Sydney researcher and his German partners.

With Australian Solar Institute support, Professor Tim Schmidt from the University's School of Chemistry, together with the Helmholtz Centre for Materials and , has developed a "turbo for ", called photochemical upconversion that allows energy, normally lost in solar cells, to be turned into .

The finding has been published in the Energy & Environmental Science journal.

Professor Tim Schmidt said using the upconversion technique, a process which harvests the part of the solar spectrum currently unused by solar cells, eliminates the need for costly redevelopment of solar cells.

"We are able to boost by forcing two energy-poor red photons in the cell to join and make one energy-rich yellow photon that can capture light, which is then turned into electricity," Professor Schmidt said.

"We now have a benchmark for the performance of an upconverting solar cell. We need to improve this several times, but the pathway is now clear."

Australian Solar Institute Executive Director Mark Twidell said this is a great example of successful collaboration between leading Australian and German solar researchers.

"Together, Australia and Germany can accelerate the pace of commercialisation of solar technologies and drive down the cost of solar electricity," Mr Twidell said.

"That's why the Australian Solar Institute is supporting collaboration between the two countries through the Australia-Germany Collaborative Solar Research and Development Program."

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5 / 5 (8) Apr 18, 2012
Anyone have the paper? By what mechaism are the forcing the low power photons to 'join forces'?

If it's simple and cheap and can be applied to regular solar cells in an industrial process then this is pretty significant.
0.3 / 5 (23) Apr 18, 2012
Maybe some gold nanoparticle coating of some sort.
similar to lithography perhaps.
5 / 5 (5) Apr 18, 2012
The paper is actually linked in the artcle. Here is the direct link.

not rated yet Apr 18, 2012
5 / 5 (3) Apr 18, 2012
Thanks for the link. Seems like it's an organic compound,. so before we go 'Eureka' we should see how well it holds up to prolonged exposure to UV.

But if I interperte the image correctly then that layer is at the back of the solar cell - so UV will mostly already have been captured by the silicon layer. Clever.
3.4 / 5 (7) Apr 18, 2012
We need to improve this several times, but the pathway is now clear.

Translation: We're allllllmost kidding this time....HONEST....
4.7 / 5 (3) Apr 18, 2012
Combining this with techniques that get two electrons per photon from the UV end and cells would start approaching the theoretical maximum.
But the real challenge in the industry is decreasing installation costs. They can account for 60-80% of the process. Much of that is poorly conceived interconnects and support systems.
not rated yet Apr 18, 2012
A friend of mine installed solar panels for a while, and said it almost felt like stealing when people would pay him to install theirs because it was so easy. Granted, he was smarter than he gave himself credit for, but if anyone has actually installed panels before (probably more than one set, since the first is the hardest) your opinion would be welcome.
4.5 / 5 (2) Apr 18, 2012
Nobody wants cheap high-efficiency solar panels more than me. That said, I can't get too excited by the claim from the abstract:
A peak efficiency enhancement of (1.0 ± 0.2)% at 720 nm is measured under irradiation equivalent to (48 ± 3) suns (AM1.5).

I guess they speculate about %40 in the actual paper? I'm not holding my breath.
1.7 / 5 (3) Apr 18, 2012
This is a staggering achievement because while everyone else is focused on the physical shape of the solar cell or utilizing lost thermal energy, they've found a way to eradicate the fundamental flaw of the cell's absorption limits.
4 / 5 (1) Apr 18, 2012
It would actually be cheaper and easier to put a thermoelectric substance on the back of the panel and harvest an additional 10% that way...
3 / 5 (1) Apr 18, 2012
@dschlink: correct. Needed: flexible cells that can be put into solar shingles. The incremental cost of installing solar shingles over regular shingles is small---You need a roof anyway. That will be the big game changer.
3 / 5 (1) Apr 18, 2012
@Roland, I like that idea. How to link them together is a question though. Wiring from one to the next might be more complicated than needed. Perhaps contacts on the upper side on one end and the lower side on the next? Possibly on the sides in case one goes out energy can flow around the damaged shingle? Or just lay down some kind of conductive mat before putting the shingles on. I wonder what complications rain would cause that system, though, since with solar panels all of the critical connections are water sealed. I'd love to see a proof of concept.
4.5 / 5 (2) Apr 18, 2012
Needed: flexible cells that can be put into solar shingles

Google for 'solar shingles'. They have been on the market since 2005.
5 / 5 (3) Apr 18, 2012
@antialias - yes, the upconverting layer would be below the silicon (or other short-wavelength) layer(s). The longer wavelength photons pass right through the semiconductor layers with higher bandgaps (this is how a multi-junction cell works).

This would also work with today's triple-junction concentrator cells, converting IR photons that are normally wasted (or worse) as heat to productive photons. It could even exceed the performance boost of adding another layer.
2.3 / 5 (4) Apr 19, 2012
Oraganic thin film cells aren't new. As said above, they don't last long enough because they decompose when used. It's not just a problem with UV rays. It's exposure to heat, cold, oxygen, water, any wavelength of light (IR to UV), etc. You have to make them really thin in order to make them work as solar collectors. That doesn't leave much room for durability, especially since they decompose quickly. One of the best solutions I have seen involved a really cheap organic dye that could be painted or sprayed on periodically, like twice a year. It still wasn't a very good solution, but better than most.

Another problem with the organic dyes is that many of them are toxic to people, and/or they corrode the other parts of the cell.

As for the cost of hooking up solar cells, it's not too bad for a home install, but for an industrial scale array, you need to compensate for all the different volts/amps that each group of cells produce. It requires expensive equipment, lots of it.
1 / 5 (2) Apr 22, 2012
Systems would be cheaper if they would put even a small fraction of the effort that goes into improving solar cells into improving the inverters and other power conversion / conditioning electronics.
3 / 5 (3) Apr 23, 2012
Most of the comments cite the cost of mating the tech with existing wiring. Agree. Is why Edison made his lightbulbs to fit the sockets of the gas outlets. Is why so hard to move onto new energy as would require all new -from-the ground up tech. Even this little push for electric cars is problematic. Even with the electric wires everywhere.
BUT if the solution could be individual on-site apps, then not so much problem but that avoids just what the economy demands happen, the tech be wired INTO the existing net.
2 / 5 (2) Apr 24, 2012
Oraganic thin film cells aren't new. As said above, they don't last long enough because they decompose when used...
Another problem with the organic dyes is that many of them are toxic to people, and/or they corrode the other parts of the cell...

How about encasing the solar cells in in an tightly fitted enclosure (transparent to UV or other useful wavelengths), and using the dye in suitable liquid solvent, so that only a thin film is present over the solar cells to minimize volume and unwanted absorption? Adding a simple recirculation pump setup to refresh the dye over the solar cells from a reservoir. no mess, no contact or toxic hazards.
1 / 5 (1) Jun 11, 2012
... allows energy, normally lost in solar cells, to be turned into electricity....

Seems like it's an organic compound,. so before we go 'Eureka' we should see how well it holds up to prolonged exposure to UV. ... Clever.

And if similar to the Graphene "thermal electric" fuzzy sheets (reported several months ago), credit where that credit is due.

The application of thermal-voltaics to the "dark side" of a photo cell is certainly viable ... as the cells heat up from Solar exposure, the thermal differential is converted / added to electron excitation (increased power). ... A laminated, multi-layered cell is quite viable.

The Aussie and German methodology roughly described, the (organic) Carbon added (directly) to the Silicon brew, is quite possibly a small "e" eureka moment.

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