Ultra-thin solar cells can bend around a pencil

June 20, 2016, American Institute of Physics
Ultra-thin solar cells are flexible enough to bend around small objects, such as the 1mm-thick edge of a glass slide, as shown here. Credit: Juho Kim, et al/ APL

Scientists in South Korea have made ultra-thin photovoltaics flexible enough to wrap around the average pencil. The bendy solar cells could power wearable electronics like fitness trackers and smart glasses. The researchers report the results in the journal Applied Physics Letters.

Thin materials flex more easily than thick ones - think a piece of paper versus a cardboard shipping box. The reason for the difference: The stress in a material while it's being bent increases farther out from the central plane. Because thick sheets have more material farther out they are harder to bend.

"Our photovoltaic is about 1 micrometer thick," said Jongho Lee, an engineer at the Gwangju Institute of Science and Technology in South Korea. One micrometer is much thinner than an average human hair. Standard photovoltaics are usually hundreds of times thicker, and even most other thin photovoltaics are 2 to 4 times thicker.

The researchers made the ultra-thin from the semiconductor gallium arsenide. They stamped the cells directly onto a flexible substrate without using an adhesive that would add to the material's thickness. The cells were then "cold welded" to the electrode on the substrate by applying pressure at 170 degrees Celcius and melting a top layer of material called photoresist that acted as a temporary adhesive. The photoresist was later peeled away, leaving the direct metal to metal bond.

The metal bottom layer also served as a reflector to direct stray photons back to the solar cells. The researchers tested the efficiency of the device at converting sunlight to electricity and found that it was comparable to similar thicker photovoltaics. They performed bending tests and found the cells could wrap around a radius as small as 1.4 millimeters.

The team also performed numerical analysis of the cells, finding that they experience one-fourth the amount of strain of similar cells that are 3.5 micrometers thick.

"The thinner cells are less fragile under bending, but perform similarly or even slightly better," Lee said.

A few other groups have reported solar cells with thicknesses of around 1 micrometer, but have produced the cells in different ways, for example by removing the whole substract by etching.

By transfer printing instead of etching, the new method developed by Lee and his colleagues may be used to make very flexible with a smaller amount of materials.

The thin can be integrated onto glasses frames or fabric and might power the next wave of , Lee said.

Explore further: Team creates functional ultrathin solar cells

More information: "Ultra-thin Flexible GaAs Photovoltaics in Vertical Forms Printed on Metal Surfaces without Interlayer Adhesives," by Juho Kim, Jeongwoo Hwang, Kwangsun Song, Namyun Kim, Jae Cheol Shin and Jongho Lee, Applied Physics Letters, June 20, 2016. DOI: 10.1063/1.4954039

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gkam
1.8 / 5 (10) Jun 21, 2016
Willie is working on some stuff we can wear using high-level nuclear waste.

https://www.publi...aste?utm

WillieWard
2.3 / 5 (6) Jun 21, 2016
"byproducts of hydraulic fracturing, or fracking, create radioactive waste"
"Fracking" to compensate the intermittency of your rooftop PV.
Buy batteries and go off the grid hypocrite.
kochevnik
2.6 / 5 (5) Jun 21, 2016
@Willietard Buy batteries and go off the grid hypocrite.
Solar corresponds with human activities, so batteries not so necessary for a small budget but for load balancing, such as starting up motors. Panels much less expensive than batteries so better to add more solar than battery. For battery I understand Edison's nickel-iron to be most suitable. Very common here in Russia military
WillieWard
2.1 / 5 (7) Jun 21, 2016
so batteries not so necessary
yes stay connected the grid, let fossil-fuel plants do their job when sun is not shinning or wind is not blowing. very very convenient win-win situation.
gkam
1.9 / 5 (9) Jun 21, 2016
Willie does not understand how the systems work. By producing my power in the daytime, I give the utility and my neighborhood clean and cheap power when it is most needed, and take mine at night when it is cheaper to generate,. It helps everybody that way.

You outsiders, you sideliners have NO IDEA of what the consequences would be for your silly and simple concepts.
WillieWard
2.7 / 5 (7) Jun 21, 2016
take mine at night when it is cheaper to generate..
from fossil-fuel plants hypocrite
gkam
1.5 / 5 (8) Jun 21, 2016
We have geothermal, wind and hydropower, plus the PV and solar thermal, plus other clean sources. We are not there yet, but closing in on 21st Century pure clean power.

Where are you, . closing in on the 20th Century?
WillieWard
3.4 / 5 (5) Jun 21, 2016
We have geothermal, wind and hydropower, plus the PV and solar thermal, plus other clean sources.
clean? are they manufactured in wind/solar-powered factories?
don't forget hydro, dams have changed entire ecosystems and displaced thousands of people; wind/solar takes a lot of land/offshore areas and ruins natural landscapes; geothermal in some way is equivalent to fracking regarding environmental impacts.
"Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4) and ammonia (NH3)."
"In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals, such as mercury, arsenic, boron, antimony, and salt."
https://en.wikipe..._effects
https://en.wikipe...l_impact
Nuclear power causes the lowest impact per gigawatt produced.
WillieWard
2.6 / 5 (5) Jun 21, 2016
There are bunches of pictures and videos showing bird and bat deaths that are related directly to wind blades and solar mirrors, while against nuclear power just biased studies that include abandoned copper mines.
https://stopthese...agle.jpg
http://www.family...ARGE.jpg
http://www.scient...mp;h=335
http://i2.wp.com/...00%2C199
http://www.windby...agle.jpg
http://www.youtub...AvD8VAbI
WillieWard
2.6 / 5 (5) Jun 21, 2016
Nuclear power is carbon-free energy, safe and eco-friendly; the more people know about it, the more they favor it; just listen to people who know!
https://www.youtu...3BtrWo2A
http://nuclear-ec...4251.jpg
stop fracking, stop bird-choppers/landscape-destroyers, mother nature will thank us.
Whydening Gyre
4.2 / 5 (5) Jun 21, 2016
@Willietard Buy batteries and go off the grid hypocrite.
Solar corresponds with human activities, so batteries not so necessary for a small budget but for load balancing, such as starting up motors. Panels much less expensive than batteries so better to add more solar than battery. For battery I understand Edison's nickel-iron to be most suitable. Very common here in Russia military

Thought you were in LA...?
betterexists
5 / 5 (1) Jun 22, 2016
Make it MANDATORY To WEAR Them!
kochevnik
3 / 5 (4) Jun 22, 2016
so batteries not so necessary
yes stay connected the grid, let fossil-fuel plants do their job when sun is not shinning or wind is not blowing. very very convenient win-win situation.
No, it runs purely off the sun. Learn to read
There are bunches of pictures and videos showing bird and bat deaths that are related directly to wind blades and solar mirrors, while against nuclear power just biased studies that include abandoned copper mines.
Nuke plants kill fish and wildlife by overheating surrounding waters. Centralizationkills many thousands of birds by electrocution while windmills can mount on a roof and provide 10 kilowatts. If you love birds you would choose solar and ban nuclear
WillieWard
3.4 / 5 (5) Jun 22, 2016
Pseudo-environmentalists' logic is tragically funny: if we slaughter fewer birds than cats, so we're eco-friendly. Oops except cats do not butcher eagles in midair. Poor birds, with this kind of Eco-friends, who needs enemies.
kill fish and wildlife
"Fish screens are typically installed to protect endangered species of fishes"
https://en.wikipe...h_screen
"Technical solutions (such as fish screens and plume eliminators) can effectively mitigate many of these impacts"
http://www.world-...nts.aspx
Nuclear power is much more ecologically friendly.

gkam
1 / 5 (5) Jun 22, 2016
Copy and paste away, Willie.

We can do it, too:

http://www3.nhk.o...0621_35/

Meanwhile, how are the nukes working? Why are so many closing? Aren't they already paid off, and still cannot compete?
WillieWard
2.6 / 5 (5) Jun 22, 2016
Why are so many closing?
Carbon-free nuclear power plants are being closed to give place to coal oil natural gas/fracking to compensate intermittency of your eco-friendly bird-choppers/landscape-destroyers. Wind/solar energy is considered a Non-Dispatchable Technology; you get it when you get it, not when you want it or need it. You should know it because you have a rooftop PV and cannot permanently go off the grid.
gkam
1 / 5 (5) Jun 22, 2016
I do not want to go off the grid, Willie. Or I would.

What is your fixation on going off the grid? I am a former utility engineer, Willie, and know how to serve both myself and my society as well. My trading of high-value peak power I produce for cheaper power at night creates a win-win situation for all of us here. Sorry about you.
TheGhostofOtto1923
2.8 / 5 (11) Jun 22, 2016
What is your fixation on going off the grid? I am a former utility engineer, Willie, and know how to serve both myself and my society as well. My trading of high-value peak power I produce for cheaper power at night creates a win-win situation for all of us here. Sorry about you
IOW george kamburoff has willingly given up his Position as Utility Engineer to single-handedly save California from ruin, using only his wife's money and the mighty power of egomaniacal delusion.
https://youtu.be/BdIev12fCPs
kochevnik
3 / 5 (4) Jun 22, 2016
Pseudo-environmentalists' logic is tragically funny: if we slaughter fewer birds than cats, so we're eco-friendly. Oops except cats do not butcher eagles in midair. Poor birds, with this kind of Eco-friends, who needs enemies.
Yes WillieTard your nuke plants electrocute thousands of eagles, because you are a centralization relic from last century. New model is distributed energy no power lines needed no eagles affected. House 10Kw wind turbine too small to seriously hurt eagle
WillieWard
2.3 / 5 (6) Jun 22, 2016
electrocute thousands of eagles...no power lines needed no eagles affected...
as if wind/solar farms were using wireless power transmission technology.
As far as I can remember, interconnecting grids among European countries was a hope to compensate intermittency, but it has served just to increase more and more reliance on fossil fuels, maybe next step would be interconnecting north-south/eastern-western hemispheres with HVDC(High Voltage Direct Current) for ecologically friendly electrocuting birds and bats in midair.
betterexists
5 / 5 (1) Jun 23, 2016
Wear them on the backs supported by cloth below
antialias_physorg
3.7 / 5 (6) Jun 23, 2016
Pseudo-environmentalists' logic is tragically funny: if we slaughter fewer birds than cats, so we're eco-friendly.

No. If we slaughter fewer birds with renewables than with nuclear/fossil fuel power plants that's a win. And, as has been pointed out to you repeatedly, renewables slaughter far fewer birds than the old energy forms do. (by a factor of two when compared to nuclear powerplants and by a factor of 30 when compared to coal powerplants)

As for your ludicrous claim that this bird mortality from windfarms is a serious threat to bird populations (even if in lala-land coal and nukes killed zero birds). Just for comparison: WINDOWS kill 30000 times more birds per year than wind farms (and cats roughly 15000 times as much as windfarms)

So even if we reduced bird mortality from windfarms to zero the benefit would be 0.002%

Now, even someone as terminally crazy as you couldn't argue that this is a contribution that 'endangers' anything.
kochevnik
3.4 / 5 (5) Jun 23, 2016
electrocute thousands of eagles...no power lines needed no eagles affected...
as if wind/solar farms were using wireless power transmission technology.
More centralization tech from Willietard. As I wrote new paradigm is distributed electric using neighborhood PV and wind. Of course apartment renters like Willietard may be forced to use centralization tech
WINDOWS kill 30000 times more birds per year than wind farms
Now watch Willietard whine about solar windows killing birdies
WillieWard
2.3 / 5 (6) Jun 23, 2016
Renewable cult lives in a particular world where all homes, car parking and factories have rooftop solar PV/windmills with decentralized energy storage, with no fossil fuels for backup, with no huge wind/solar farms i.e. "zero land", and all pictures and videos showing toxic wastes and slaughtered birds and bats are a fake; it seems that renewable cult feed back themselves collectively with their own fibs as any creed/belief.
antialias_physorg
3.9 / 5 (7) Jun 23, 2016
Oops except cats do not butcher eagles in midair

Ya know. I done gone and looked it up. The confirmed number of eagles killed by wind turbines in a 5 year timepsan (2008-2013) was 67. That's 13 per year. That's ALL eagle types.
(For reference: bald eagles/golden eagles number around 70000 in the US)

Even if this figure were off by 2 orders of magnitude(!) that wouldn't drive eagles (any kind) into extinction. I call a big 'ol "BS" on Willie's 'facts'.
WillieWard
2.6 / 5 (5) Jun 23, 2016
We support assertions with credible links..
ok biased antinuclear/pro-renewable websites are credible sources.
WillieWard
2.6 / 5 (5) Jun 23, 2016
ok so it is not true that renewable needs large land/offshore areas, disturbs wildlife's habitats, ruins natural landscapes, and depends on fossil fuels to compensate intermittency, to mine/manufacture/transport, i.e. renewable very symbiotic with fossil-fuel industry.
antialias_physorg
4 / 5 (4) Jun 24, 2016
ok so it is not true that renewable needs large land/offshore areas, disturbs wildlife's habitats, ruins natural landscapes,

False dichotomy.

The question is not "does it?"
The question is "does it do so to a greater extent than fossil fuels/nuclear per GWh energy produced?"
And all research says: "No."

and depends on fossil fuels to compensate intermittency,

Currently it does depend on this. Note the 'currently'. That is changing fast. And even if we did nothing then it ONLY depends on fossil fuels/nuclear intermittently...which means much less of those are needed. Which still would be a benefit to the environment in all respects.

The thing you're not getting (well, one of the thousands of things you're not getting): You have to build up production capacity first. THEN you build up storage capacity. The other way around makes no sense (in power generation...and in no other form of production as well)

gkam
1 / 5 (5) Jun 24, 2016
Willie, you did yourself a disservice by being adamantly for nukes to the point of silliness.
WillieWard
3.7 / 5 (3) Jun 24, 2016
you did yourself a disservice by being adamantly for renewables to the point of silliness as you are doing the fossil-fuel industry's dirty work by killing off their main competition(carbon-free nuclear power) for them.
"the fracking revolution in energy production has unleashed such a glut of cheap natural gas that nuclear power can't compete on a cost basis"
"the story seems to reinforce the fact that every time you vote against nuclear power you are voting in favor of fossil fuels, and this is true even in a country aggressively committed to renewables."
kochevnik
3.7 / 5 (3) Jun 24, 2016
"the story seems to reinforce the fact that every time you vote against nuclear power you are voting in favor of fossil fuels, and this is true even in a country aggressively committed to renewables."
False dichotomy. Second gen factories such as the Musk plant in Reno are solar powered, and have no gas line feed by design so engineers discard it as an option

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