Solar 4.0: Ultra Efficient Solar Panel Breakthrough

every single hour enough solar energy reaches the Earth's surface to power our planet's energy needs for an entire year we're on the verge of a solar Revolution with a new Contender perovskites that are cheaper and already rivaling silicon solar cells efficiency last month a groundbreaking 250 percent increase in light conversion efficiency was reported by researchers at the University of Rochester let's take a look at this latest breakthrough to understand if it really is the future of solar energy to truly understand the significance of this solar energy breakthrough we first need to understand what a parovsky is and why it's causing such a stir Perot Sky actually refers to a class of materials that have a specific crystal structure a cubic lattice with a positive atom at its core and at its corners and a negatively charged atom at its face of each of the cube sides as a result a large number of different elements could be combined together to form a perovskite structure this allows researchers and Engineers to tune the physical Optical or electrical characteristics of the material that they're trying to build our question is why do they offer such a huge advantage over traditional silicon solar cells the Silicon used in a conventional solar cell manufacturer requires an expensive multi-step process that's very energy intensive to grow a perfect defect-free silicon crystal these silicon crystals also only convert a very narrow band of light into electricity typically just 18 to 22 of the energy coming from sunlight this makes silicon cells both heavy and inefficient a perovskite by comparison can be deposited as a thin film on a substrate layer meaning they can be manufactured using simple techniques like screen printing for a fraction of the cost and energy of silicon solar cell manufacture now here it looks basically like their screen printing t-shirts it's not quite that simple but it is surprisingly close this also means that while traditional solar cells are thick and heavy perovskite materials can be small light and flexible even attached to a wide range of materials this thin film coating approach gives perovskites their other major advantage they increased cell efficiency different layers can be tuned to make use of different parts of the light spectrum by varying the material combination or properties where silicon-based solar cells can only draw energy from higher or redder end of the energy Spectrum perovskates can be adjusted to capture different energy bands and then they can be applied one on top of the other to capture as broad of a spectrum as possible in theory you could infinitely stack these solar cells but in practice we typically see just two layers used otherwise you get diminishing returns of less light reaching the lower layers and added complexity and added cost now we don't worry here about capturing higher or lower energy bands because not many high energy UV photons actually reach the Earth's surface due to our atmosphere and we also ignore the lower spectrum because photons in the infrared don't really carry that much energy but these ideas in perovskites are already reasonably well known the researchers in Rochester reported a further 250 percent efficiency increase on top of these effects using nothing but a simple mirror how did they do it for the mirror shows many things thank you what I want to start by doing is looking at a traditional photovoltaic Excel as they are simpler but analogous enough to a perovskite solar cell that they can teach us a lot of the underlying physics if we take two semiconductor materials one that's positively charged a p-type material and one that's negatively charged an n-type material and sandwich them together as you do so some of those free electrons from the n-type material rush over and fill the available spaces which we call holes in the positively charged material this process recombination creates a neutrally Charged region between the two materials if we then expose the materials to sunlight the light can break apart this neutral region creating electron hole pairs or exatons as they are charged they get pushed out of this electrically neutral region to either side where they can be collected by an electrode and then recombined later after doing some useful work for us and that broadly at least is the picture of how we create electricity from a photovoltaic cell at least the idealized picture in reality these electrons and holes that are generated they often recombine within the solar cell before making it to those contacts either because they recombine with themselves with each other or because they combine with the bulk material these recombination events contribute significantly to decreasing the overall Energy Efficiency of a solar cell so this is where those researchers at the University of Rochester Focus their attention in fabricating their perovskite solar cells they added a silver layer that they referred to as a mirror below the perovskite and they found that they were able to drastically reduce these electron hole recombination events this mirroring effect improved the photocurrent liberated from the device by a factor of 250 percent but how could this possibly be I'm familiar with the need to run in the other direction when I see a mirror but why would an electron's Behavior be influenced by just being close to a mirrored surface seems crazy to understand it we need to remember that the electrons in a metal unlike a semiconductor are free to move around like a liquid in fact we call them often an electron C where they always try to Flow Away from areas of like charge and towards areas of opposite charge because Opposites Attract when you put very thin layers of metal next to a dipole system that electron C couples to the dipole and applies a bit of a restoring Force encouraging them to relax into a lower energy state if this is something like a fluorescent dipole system this causes them to emit photons faster because they are collapsing more quickly into an unexcited State this phenomena is called the Purcell effect I actually use this as part of my PhD to enhance the output of fluorescent particles that I was studying I placed tiny pieces Nano size so a few tens or hundreds of atoms worth of gold next to individual fluorescent particles and it caused them to emit more photons more regularly essentially making them brighter and making them easier to detect but interestingly the research team found that as they increased the thickness of the metal next to the dipole the silver layer this effect started to reverse and the recombination rate actually started to drop they propose in their paper that the silver layer is creating a mirror image to the electron hole pair created when the photon strikes the perovskite in effect the electrons in the metal are pushed away from the porovsky electrons location creating a pseudo Hull and the hole in the perovsky attracts charge creating a pseudoelectron in the material so it essentially creates a mirror image of that charged dipole in the metal which is kind of crazy this silvery mirror image of the electron hole pair air reduces the local density of optical States available for the exoton to inhabit or Decay through which is a fancy way of saying it makes it harder for the exoton the Actron whole pair to Decay or collapse essentially extending the likelihood that the pair lives long enough to exit through the appropriate electrical contacts and become electricity and we absolutely see that in the photoresistivity data an increased silver layer thickness produces a significantly higher photocurrent kind of amazing obviously as this is a new observation we need to wait until other labs around the world confirm that it does in fact happen this way but if true this is a really powerful way of improving solar cell efficiency so our remaining question is when does this thing actually hit the shells of every good Tech supplier near you when do we get Mass adoption and there there is unfortunately some Kinks to work out [Music] while perovskite solar cells have shown great promise the stability of these materials remains kind of a concern some perovskites can degrade under prolonged exposure to heat moisture things like UV or radiation which would limit their lifespan as they are a thin film technology they can be particularly brittle Additionally the most common perovskites usually contain lead which raises some level of concern about their environmental impact but researchers are already on the case there are alternatives to lead for perovskite construction though they are in the early stages of manufacture teams around the world are developing methods for Extrusion of perovskites that would allow them to survive harsh environments intact if we can crack these problems and prove and perfect this efficiency enhancing mirroring phenomena we could be jumping straight over the third age of thin film solar cells and into the dawn of the fourth generation of solar if efficiency if you like this video you might like last week's video about another breakthrough the world's first room temperature superconductor again from the University of Rochester however this one you might need to look past allegations of data manipulation plagiarism and fraud there we go University of Rochester I've debunked one I've celebrated one no hard feelings unless this one turns out to be fraudulent and then I'm gonna be so mad leave a like thanks very much for watching I'll see you next week all right

Channel: Dr Ben Miles

Views: 578,817

Keywords: science, startup, spinout, research, how to run a business, business, innovation, future, investment, deep tech, deep science, future technology

Id: BtOSAOaAmUM

Length: 10min 12sec (612 seconds)

Published: Sun Apr 09 2023