Insect eyes inspire new solar cell design from Stanford
Packing tiny solar cells together, like micro-lenses in the compound eye of an insect, could pave the way to a new generation of advanced photovoltaics, say Stanford University scientists.
In a new study, the Stanford team used the insect-inspired design to protect a fragile photovoltaic material called perovskite from deteriorating when exposed to heat, moisture or mechanical stress. The resultsare published in the journal Energy & Environmental Science (E&ES).
“Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon,” said Reinhold Dauskardt, a professor of materials science and engineering and senior author of the study. “The problem is that perovskites are extremely unstable and mechanically fragile. They would barely survive the manufacturing process, let alone be durable long-term in the environment.”
Most solar devices, like rooftop panels, use a flat, or planar, design. But that approach doesn’t work well with perovskite solar cells.
“Perovskites are the most fragile materials ever tested in the history of our lab,” said graduate student Nicholas Rolston, a co-lead author of the E&ES study. “This fragility is related to the brittle, salt-like crystal structure of perovskite, which has mechanical properties similar to table salt.”
Eye of the fly
To address the durability challenge, the Stanford team turned to nature.
“We were inspired by the compound eye of the fly, which consists of hundreds of tiny segmented eyes,” Dauskardt explained. “It has a beautiful honeycomb shape with built-in redundancy: If you lose one segment, hundreds of others will operate. Each segment is very fragile, but it’s shielded by a scaffold wall around it.”
Using the compound eye as a model, the researchers created a compound solar cell consisting of a vast honeycomb of perovskite microcells, each encapsulated in a hexagon-shaped scaffold just 0.02 inches (500 microns) wide.
“The scaffold is made of an inexpensive epoxy resin widely used in the microelectronics industry,” Rolston said. “It’s resilient to mechanical stresses and thus far more resistant to fracture.”
Tests conducted during the study revealed that the scaffolding had little effect on the perovskite’s ability to convert light into electricity.
“We got nearly the same power-conversion efficiencies out of each little perovskite cell that we would get from a planar solar cell,” Dauskardt said. “So we achieved a huge increase in fracture resistance with no penalty for efficiency.”
Durability
But could the new device withstand the kind of heat and humidity that conventional rooftop solar panels endure?
To find out, the researchers exposed encapsulated perovskite cells to temperatures of 185 degrees Fahrenheit (85 degrees Celsius) and 85 percent relative humidity for six weeks. Despite these extreme conditions, the cells continued to generate electricity at relatively high rates of efficiency.
Dauskardt and his colleagues have filed a provisional patent for the new technology. To improve efficiency, they are studying new ways to scatter light from the scaffold into the perovskite core of each cell.
“We are very excited about these results,” he said. “It’s a new way of thinking about designing solar cells. These scaffold cells also look really cool, so there are some interesting aesthetic possibilities for real-world applications.”
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Pie! In the SKY! Look! Bye and bye.
Human ingenuity is infinite. Innovation may be able to improve efficiency.
This is real chemical engineering. This is an example that disproves the Malthusian pessimism.
Even if this doesn’t pay out, something will.
‘Something will pay out.’ No it won’t – because even 100% efficiency isn’t enough. You can’t cheat the fundamental facts of day and night, low watts/m2 available even in summer, permanent dusk or at best low angle and weak sun and short days in the winter. It’s the same reason battery technology will never make a sudden leap onto a new level – you can’t cheat the laws of physics/nature/energy density blah blah.
Actually, that’s exactly how fundamental changes take place—through disruptive technologies. I suspect something along those lines will be precisely what happens in the battery tech sector. And when it does, there’s any number of possibilities that can go along with it—from converting to renewable energy or utilizing more of the latent energy through waste heat recovery. Or … something.
Its an interesting engineering application of a less than ideal material, but since its efficiency is the same as existing technology which isn’t that impressive anyway, I don’t see any major breakthough.
i love it when people predict ‘breakthrough’ when technology is already pushing physical limits.
100% eff. solar still not good enough.
Batteries much better than existing would break physical laws that govern batteries.
The only limitless area for exploitation would seem to be human gullibility.
There is no way round the problem of intermittency. Nature does solar in the best and greenest way – it’s called plants.
“Actually, that’s exactly how fundamental changes take place—through disruptive technologies. I suspect something along those lines will be precisely what happens in the battery tech sector.”
No. Batteries work by low-temperature redox chemistry. There is no way you can get large amounts of energy out of that without rewriting basic conservation laws. There may be high-density electrical storage sometime in the future, but you can be very sure it won’t be from chemical batteries.
> [AZ1971] fundamental changes take place—through disruptive technologies.
I get your point, but it’s getting difficult to sort out disruption to existing technology, which is one way of pursuing an extra shot of venture capital by making it an us-vs-them game… with the other disruptions, disruption to daily lives by handicapping existing workable technology (subsidies), disruption to human civilization’s likelihood of survival as resources are committed to things that won’t ultimately solve and scale. In this case hexagonal structure is being used as a work-around to make something exceedingly impossibly fragile into something very fragile, so that it stands a chance of enduring some short warranty period. Haven’t we endured enough of this concept from all directions in this post-modern world? I refer to ‘new’ ideas that leverage the functionality of older methods and designs by shaving corners, attaining ‘more’ at the expense of durability and easy manufacture. And the hidden cost of replacing things that replaced other things that more seldom needed replacement. No one is keeping score anymore!
I live in a simple world of infrastructure and toys. Infrastructure brings me continuous electricity, clean water, heat in Winter, driveable roads at a reasonable cost of living. Toys are anything beyond this, including the moldy carpet in Houston is soon to be torn out and replaced by new plush carpet by insurance companies because this country is suffering a mass delusion that carpet is anything but a stupid indulgence that forces insurers to raise premiums and unfairly collect from people with practical water-resistant floors, because bare-footed utopian hippies repeatedly imagine (on the first day) that every carpeted room ‘might’ becomes a place of throw-pillows and casual Roman orgies. It doesn’t. We trudge on it instead so it can wear out to be replaced. It gets fleas skin flakes and mites and worse whether or not you own a pet.
That sounds like some strange rant I know, but I’m willing to bet that the money about to be spent on carpet restoration alone in Houston would be enough to take molten salt LFTR technology closer enough to working prototype, that we all (planet-wide) might see it power the grid within our lifetimes. But carpeting, and solar cells, seem to be more interesting toys right now. That is one of those “we could save the world if we don’t order pizza” fallacies but it works for me because I am moving soon to a place with carpeting for lack of choices and will pay a premium for it.
If it’s all about orgies, then I promise that with reliable base load energy coming from within a few weather-proof buildings powering the grid completely, perpetually, I promise we will have more and better ones.
If people could easily lift their carpets and see what is growing underneath they’d tear it out after a month. Glue is put down deliberately to keep them ignorant while they blame respiratory ailments and allergies on other things.
While I do not think solar cells are a replacement for fossil fuels this approach has definite possibilities for at least making them cheap enough to be viable for air conditioning where the power generated is most when needed unlike using it for general purposes where most is needed at night and in cold and the dark.
We do need battery technology to make the same leap so that inexpensive readily available materials can be used for a battery of significant performance before any renewable source is more than just a pie in the sky eco freak solution that is not of this world..
Intriguing!
One can hope it is scalable and the costs of the hexagonal wall ‘support structure’ does not negate the low cost benefits of the perovskite solar cell material. Carbon forms hexagonal cell structures…. Hmmmm.
“To find out, the researchers exposed encapsulated perovskite cells to temperatures of 185 degrees Fahrenheit (85 degrees Celsius) and 85 percent relative humidity for six weeks.”
But the issue isn’t durability at 185F, its durability when exposed to a daily cycle of 185F – 70F and so on day after day. How does it do then?
Bingo.
Or extreme arid conditions and low temperatures. One has to wonder why the researchers chose high humidity to test in when the best solar regions in the US are in the Southwest where relative humidity can be as low as 3%. What of higher latitudes where the temperatures can get down to -40°C? More testing absolutely needs to be done before it can be labeled as being reliable.
And don’t forget physical shaking from, say, lightening/thunder that shakes the structure or high, gusting winds or a tree branch falling on it.
wouldn’t it be even higher range? for some reason thought direct sunlight caused areas to come close to boiling (212f) even in below 30 deg F ambient.
or am I thinking older type solar used for water heating?
How do they hold up to rain? Hail? Snow?
Now if only they could make solar cells from blatherskite…
No shortage of that!
Just letting you know this is not the church.
What does it cost, and how does it perform in the real world?
‘strength’ is in the eye of beholder
insects not only have hexagon compound eye, but many of them build hexagon structures: bees, wasps, hornets, etc. Hexagon is one of the strongest shapes which can equally well create flat or spherical objects (e.g. buckyball molecules)
Bees particularly have cooling and humidifying functions.
The workers sit at the entrance of the hive fanning a breeze to keep the brood at an optimum temperature,’the murmur of innumerable bees’.
They only fly under stringent conditions and return to the hive when conditions deteriorate.
Not so for solar cells on a hostile roof top.
Some of the energy collected would have to be used to maintain the collector at an optimum temperature and humidity.
From the article: “Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon,” said Reinhold Dauskardt”
What advantages do perovskites have over silicon in this application?
Indeed. A lot of breathless implications of some kind of breakthrough, yet, in the end, it reads like a lot of noise about something that, at best, might be a “good” as conventional Si solar cells.
So, who’s money is funding this self-stimulation?
So far, it does not look like perovskite production emits nearly as much CO2 as does the production of silicon, so it that regard it is a large improvement.
No. CO₂ is good. If you had said that it needs less energy to make…
Theoretically materials cost. But there are several tough inherent problems in the perovskite materials systems.
Ability to use wet chemistry to produce. https://en.wikipedia.org/wiki/Perovskite_solar_cell is reasonably evenhanded.
The remarkable thing about the insect compound eye is that it has infinite depth of focus.
Even though resolution and pixel size decline with distance.
This is why flies are so darned hard to kill – they see you clearly wherever you are in the room.
How does that work? A semi-infinite number of pinhole cameras?
Flies take off backwards before they fly forward. Aim behind them.
If it’s a genuine advance in solar power, it’s an advance.
Let someone besides the taxpayer fund it.
They might get rich.
Neither is it not the church – all persuasions welcome here
IMO supernatural fantasies shouldn’t be welcomed on a science blog.
Perovskites are the most fragile materials ever tested in the history of our lab,” said graduate student Nicholas Rolston
Obviously they haven’t experimented yet with Michael Mann’s skin.
Good to see that research is going into improving PV cost and durability but fact is PV is limited. I want research into providing base electricity load that will benefit people at any location, time of day, and season of the year. Like nuclear 🙂
A nuclear dragonfly?
Sounds like the premise next for the next Godzilla movie!
(Sorry. I just watched a Godzilla movie yesterday.8-)
PS I remember seeing King Kong vs Godzilla in the theaters when it was first released.
The great green contradiction continues unabated.
We are told that renewable energy is already so cheap and reliable and competitive that fossil and nuclear are already priced out of an un-subsidised competition (yeah-right!).
And yet…
The search goes on for technological improvements to the performance of renewables, a search that possesses the unmistakable flavour of desperation.
The perovskites are various organometallic halides. A number of stability problems in addition to mechanical. Moisture barrier is going to be a huge practical and cost problem. Record lab efficiency is 22.1 in a 1 cm device. But panel scale thin films run ~15% due to hard to control defects. So whether this will ever be competitive compared to CdTe or the various silicon approaches is still very much an open question.
Actually original perovskite is CaTiO3 a natural mineral that occurs with rare earth carbonate minerals in an intrusive carbonate rock known rather obviously as carbonatite. I think became an adjective in describing a family of compounds exhibiting perovskite structure.
GP, correct. Perovskite in materials science means any crystal structure equivalent to CaTiO3. For example, all of the high temperature superconductor ceramics are perovskites. All the solid oxide fuel cell ceramics (Bloom Energy) that don’t use platinum are perovskites. As are these organometallic halides.
This is a fantasy. What a waste of money
Perovskite photovoltaics are being studied around the world because of their ease of manufacture (therefore lower cost) and possibility of efficiencies in the high 20 percent range. Lots of manufacturing and engineering problems to overcome. See
https://en.wikipedia.org/wiki/Perovskite_solar_cell
This post presents a possible solution to some durability problems. If it were not for push for solar photovoltaics to combat a non-existent atmospheric CO2 problem, perovskite PV would be of only academic interest and receive no funding.
Give it up, regardless of any incremental increases in efficiency, the power is still uncontrollable and of low quality and value.
It won’t make a #$%@ur momisugly bit of difference. The sun still sets every day. Clouds still cover the sun. The annual progression of the seasons will still diminish the amount of sun shine during the winter. Solar power can never be economic as long as those facts continue to be true.
How much electricity does the “scaffold” generate?
If the design is viable, it will reduce the blight factor of grey energy. Positive progress.
This was done a few years ago by a research team at Clarendon Laboratory, University of Oxford.
https://www.nature.com/articles/ncomms3761
The power in Houston pretty much stayed on the whole time. It would be fun to find out what the sources of the energy were. Did they shut the windmills down? Just asking.
nuclear power station IIRC.
Do they work in the dark?
No mention of working in the dark. These innovators never seem to tackle the real problem.
There is really no point in improving a device that is not fit for purpose.
Np problemo. You just shone lights on them – like they do in Spain.
“….like they do in Spain.” I remember that article. The solar power company was scamming the government for more subsides money by using generators at night to power lights aimed at solar panels. Didn’t Spain’s largest solar producing company go out of business?