New solar cell design is modeled after bugs eyes

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.

Schematic of a compound solar cell, where a hexagonal scaffold (gray) is used to partition perovskite (black) into microcells to provide mechanical and chemical stability. CREDIT Courtesy: Dauskardt Lab/Stanford University

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.

A compound solar cell illuminated from a light source below. Hexagonal scaffolds are visible in the regions coated by a silver electrode. The new solar cell design could help scientists overcome a major roadblock to the development of perovskite photovoltaics. CREDIT Dauskardt Lab/Stanford University

“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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97 thoughts on “New solar cell design is modeled after bugs eyes

    • 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.

      • It’s the same reason battery technology will never make a sudden leap onto a new level

        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.

      • “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..

  1. 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.

  2. “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?

    • 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?

  3. ‘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.

  4. 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?

  5. 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.

  6. If it’s a genuine advance in solar power, it’s an advance.
    Let someone besides the taxpayer fund it.
    They might get rich.

  7. 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.

  8. 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 :-)

  9. 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.

  10. 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.

  11. 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.

  12. It won’t make a #$%@ 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.

  13. 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.

    • 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.

      • “….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?

  14. It seems from the above construction model, the scaffolding reduces the area that can generate electricity, by around 30%, bringing down the planar efficiency to 14%. The image of the actual deposed surface indicates 30% scaffolding may not be met.

  15. “Actually, that’s exactly how fundamental changes take place—through disruptive technologies. ”

    Do you mean something like making electricity with steam turbines burning coal? Or were you thinking of converting mass to energy by fission uranium?

    Change has already happened. Now some of those freed from the slavery of muscle power worry that the sky is falling because they have no experience providing for there own needs.

    The sky is not falling. The power industry is not having a problem producing the finite amount of power that society needs.

  16. Millions of years of “experiments” confirm they work.
    Which is not to say they can somehow power civilization, but we are all dreamers.

  17. Here is another problem with this study. Solar cost divides into two parts. The panels (as here) and Balance of System (BOS, mounting brackets, Dc/Ac, cleaning, and such). For utility PV solar, BOS is already more than half. BOS does not scale with panel cost/volume. Is immune to lower cost PV such as speculated here.

  18. Hey, solar haters, get a grip. Technological improvements are awesome. Period. Just because grid-scale photovoltaics doesn’t make much economic sense yet without reliable backup doesn’t mean that will always be the case or that PV power is bad. PV panels are becoming increasingly popular on homes to offset daytime electricity costs, especially when running power-hungry air conditioners. And regardless of how you feel about CO2 emissions, fossil fuels still produce real pollution that can be mitigated by using solar PV. Technology is awesome. Stop being sourpusses.

    • Residential installations are becoming popular because tax credits and other subsidies make them attractive. No solar installation at any scale can stand on its own economically, though. At best, they just barely break even by the time the panels are in need of replacement (about 20 years).

      There are a lot of deceptive claims being made out there because the true cost is obscured. The reality is that we all are paying for very expensive solar electricity generation, just so that those on the receiving end can ignorantly crow about the “cheap” energy they are receiving. It’s all an illusion.

      • Mike, stop hating solar. Technological improvements are awesome. PV panels are used all over the place from solar-powered watches and calculators to satellites, the International Space Station, Mars rovers, and lots of other applications. Most of those applications aren’t subsidized and solar is highly practical for their power-generation needs. They stand on their own economically. Sure subsidies have accelerated the adoption of household PV panels, but it will happen anyway because the costs continue to drop as—guess what?—technology improves. I’m planning eventually to install PV panels with battery backup to reduce reliance on the grid and not need to store gallons and gallons of fuel for a backup generator. I live where the sun shines most days and batteries can handle the rest at night and then some. Stop grousing about solar and be happy. It’s a great technology for a lot of applications.

      • Stinker, you are the first one who ever suggested – albeit indirectly – that Mars rovers might have been connected to the grid. Solar has its place, but I hate paying a premium to PG&E because of “cheap” solar. How come you don’t have solar yet? Our host Anthony does, and you can read his report – including how subsidies influenced his decision.

    • Hey, pointing out that solar only exists because of massive subsidies, don’t work, and do nothing to “help” the climate is no reason to hate skeptics.

    • Solar still produces real pollution.
      I have absolutely ZERO objection to those who purchase solar if it competes on an equally footing, unsubsidized.

    • Solar conversion efficiency of a leaf is about 10%, modern panels are over 20%. But they have to be manufactured and maintained, they don’t grow by themselves.

  19. “Delicate”, “fragile”, “expensive”‘, and “relatively high output “.
    Run, don’t walk from this.

  20. Guys, you should learn to read scientific reports:

    > 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.

    Have you ever heard that it is the temperature and humidity that degrade the efficiency of PV? Or is it actually UV on the issue of which the report is curiously silent?

    miso

  21. ‘ I live where the sun shines most days and batteries can handle the rest at night and then some. Stop grousing about solar and be happy. It’s a great technology for a lot of applications.’

    Well, who’s a lucky boy then ! For those of us who live in less advantageous situations (the UK for example ) when the green blob has driven conventional energy sources into the ground we face long dark cold winters where PV or wind will never provide the levels of energy required to survive, especially when our idiot politicians fulfil their desire of removing gas as an alternative supply of domestic energy. Still, never mind, you can watch from your nice sunny position and watch us descend into pre-medieval existence.

  22. I kind of hate to be so cynical, but this is a solution in search of a problem, it seems.

    Contrast…

    Silicon solar cells: Less than $0.35 a watt “naked”, from China. 18% to 22% efficiency
    Perovskite solar cells: killed by humidity, vibration, still in the labs. 12% to 28% efficiency

    LAST I heard, it was (and is) not the efficiency of solar cells that is making their case less-than-economical. Its cost. And anything that’s still “in the labs” and requires nano-patterned crazy-sensitive (but ‘otherwise attractive’) materials, compared to bog-standard, bulk-manufactured, 35¢ a watt silicon, is just kind of crazy.

    But remember, all those Solar Research Institutes at every last progressive leaning College or University need to keep applying for grant-money to do underwater basket weaving research, even tho the NAPKIN MATH doesn’t actually work out. Because pure research is a noble endeavor for scientists, even if the results are basically predictable, and the possibilities of a “revolution” rather blindingly slight.

    As it is said, “you never know” what might come forth.
    And that is true.

    The Grad Student(s) researchers will undoubtedly get their PhDs, with plenty of curriculum vitae declaring that the goatskin holder is capable of magnificent achievement in nano-fabrication, solar materials and underwater basket weaving. And he or she will end up working first for a few start-ups that’ll flop, but which will benefit from their PhD laurels in finding gullible venture capital monies. Then around 33 or so, they’ll land a cushioned job at Chevron or ADM or Ford … get paid $150,000+ a year, marry, have kids, live in the Hamptons and speak at Old Man Investor events.

    Life.
    GoatGuy

  23. Basically, it is just development of potentially new types of solar cells. I’m fine with that.

    Solar cells need to be developed further. Developed to the point where they are as cheap as wallpaper, both to manufacture, and to install and replace. There is a long way to go. This particular line of research is not yet even up to the standard of existing solar cells, but that is to be expected from any genuinely novel technology.

    OK, most attempts at improvement will run into the sand, but I can’t object to people trying to actually make something better as long as they don’t lie about what they have achieved or might achieve. By contrast, most global-warming-scientists have never been involved with the difficulties of actually making something useful, or even potentially useful. It is an ‘industry’ that lives off those complaining about the inadequacies of real life industries that actually make the things that keep us alive. Policy makers need to start carefully distinguishing between them when it comes to funding.

    • I was on the Board of a novel solar cell startup (out of Argonne National lab, failed after 2 years as the 3d nanomaterials science did not work out in the lab the way it did on paper. i was also peripherally involved with Konarko (theynlooked at buying my NanoCarbons invention to save themselves from complete failure). Here are the basic conundrums. 1. The single bandgap Shockley-Queisser quantum efficiency limit is 31%. The best monocrystalline cells are already at 26, and panels made therefrom about 22%. But expensive. All the ‘cheap’ approaches (die sensitized, organic, perovskites) are much lower efficiency and suffer severe lifetime issues. 2. For polysi and CdTe, the BoS costs are more than half and neither scale nor come down learning curves. Lower panel cost does NOT alter that installed cost reality. First Solar CdTe is about $0.47/w for panels, but still ~$1.50/w for utility scale installations. 3. Sun does not shine at night and we have no feasible, economic storage mechanism despite Tesla’s fantasies.

      • ristvan

        All the ‘cheap’ approaches (die sensitized, organic, perovskites) are much lower efficiency and suffer severe lifetime issues.

        What about amorphous Silicon higher voltage cells? (42-48 volts DC) – I understand that amorphous silicon does better (is much more efficient) in diffuse light conditions, and degrades less than single-crystal silicon, but is less efficient that single crystal silicon in pure, clean direct light conditions that are the “standard” against which all cells are judged.

  24. Like climate science in which linear researchers accept a presumed given at the outset that anthropogenic CO2 will kill the planet, solar researchers are stuck by their linear thinking of literally ‘framing’ the problem in squares that sterilize vast tracts of land for low output, when the real problem is arguably this very large land requirement.

    Back up a frame. How about researching the bimetal Seebeck effect.

    https://en.m.wikipedia.org/wiki/Thermoelectric_effect

    I read a technical note in “Chemical Engineering” a couple of years ago about a bimetal product that was manufactured in a ‘fur-like’ format, comprising thousands of bimetal circuits

    • Oops didn’t finish. This product could be used to recover low grade waste heat from a large variety of sources – stacks, processes, exhausts, possibly waste heat from solar panels or entire bimetal fur solar heat converters, or roof top heat collector converters – the process even refrigerates and could be used on homes for power gen and relieving A/C usage.

      It seems real innovation needs to start in the changed thinking of researchers.

  25. I suspect there would be a lot to explore in the ‘nano’ field if applied to thermocouples.

    Space probes have used expensive nuclear batteries using thermocouple, but of a more traditional construction.

    Nano couples may get us to serious power densities?

    • Steve see my two posts above yours to add to your thoughts for alternative solar/waste heat electricity.

    • Space probes generating electricity from radioactive decay heat (usually a slug of plutonium) use solid state thermoelectric generators made from expensive 3-5 semiconductor materials such as (typically) gallium arsenide. No way to get here (commercial, practical) from there (multibillion dollar deep space probes like Cassini). Since I have some nanomaterials inventions/patents and former competitors, as well as Board experience on a nanomaterials solar venture, have a sense as to where nanomaterials are technically interesting and where they might also be practically interesting. The only present possibility I know of in energy is the Fiskers Nanotech Lithium Ion Capacitor (LiC). Wrote that up in a guest post over at Judith Curry’s a few months ago. Fisker has since backed out (at least partly) because the development timeframe exceeds his promised EV launch schedule. First car will have LG Chem LiB, same as Chevy Bolt.

      • ristvan

        Space probes generating electricity from radioactive decay heat (usually a slug of plutonium) use solid state thermoelectric generators made from expensive 3-5 semiconductor materials such as (typically) gallium arsenide. No way to get here (commercial, practical) from there (multibillion dollar deep space probes like Cassini).

        Deep space, expensive, hard to build, relatively low power for the high weight (even higher if the radioactive ion generator has to be shielded to allow close approach by humans!) but long-lived. Rule of thumb: Anything closer than Mars-Earth-moon orbits is better served with solar cells, IF they can be rigged on the probe or satellite. (Apollo-Gemini used fuel cells because they could use the water generated, and could not rig that era’s solar cells aerodynamically during launch. The Agena and similar probes could deploy solar cell arrays for earth-moon orbits. )

  26. Ah, the wonders of fossil carbon. Never a subsidy, billions in profit, ideal working conditions for coal miners, infinite untapped resources, continuous supply of black aerosol to cool the earth, CO2 and sulfate in rain to nourish crops! What’s not to love?

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