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A Bill Gates-based photovoltaic technology that may be solar energy s future…

A Bill Gates-based photovoltaic technology that may be solar energy s future…

    Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

    A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite (CH3NH3PbX3) materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in 2013. The perovskite materials can be used not only as light-Absorbing layer, but also as an electron/hole transport layer due to the advantages of its high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3.8% in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate for the new generation of solar cells to replace traditional silicon solar cells in the future. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and FOCUS on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-Absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.

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    Zhou, D., Zhou, T., Tian, Y., Zhu, X., Tu, Y. (2018). Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives. Journal of Nanomaterials. Hindawi Limited. https://doi.org/10.1155/2018/8148072

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    A Bill Gates-based photovoltaic technology that may be solar energy’s future

    In 1839, German scientist Gustav Rose went prospecting in the Ural Mountains and discovered a dark, shiny mineral. He named the calcium titanate perovskite after Russian mineralogist Lev Perovski. The mineral was one of many that Rose identified for science, but nearly two centuries later, materials sharing perovskite’s crystal structure could transform sustainable energy and the race against climate change by significantly boosting the efficiency of commercial solar panels.

    Solar panels accounted for nearly 5% of U.S. energy production last year, up almost 11-fold from 10 years ago and enough to power about 25 million households. It’s the fastest-growing source of new power, too, accounting for 50% of all new electricity generation added in 2022. But nearly all of the solar modules that are used in power generation today consist of conventional silicon-based panels made in China, a technology that has changed little since silicon cells were discovered in the 1950s.

    Other materials used, like gallium arsenide, copper indium gallium selenide and cadmium telluride — the latter a key to the largest U.S. solar company First Solar’s growth — can be very expensive or toxic. Backers of perovskite-based solar cells say they can outperform silicon in at least two ways and accelerate efforts in the race to fight climate change. Just this week, First Solar announced the acquisition of European perovskite technology player Evolar.

    The silicon limits of solar cells

    Photovoltaic cells convert photons in sunlight into electricity. But not all photons are the same. They have different amounts of energy and correspond to different wavelengths in the solar spectrum. Cells made of perovskites, which refer to various materials with crystal structures resembling that of the mineral, have a higher absorption coefficient, meaning they can grab a wider range of photon energies over the sunlight spectrum to deliver more energy. While standard commercial silicon cells have efficiencies of about 21%, laboratory perovskite cells have efficiencies of up to 25.7% for those based on perovskite alone, and as much as 31.25% for those that are combined with silicon in a so-called tandem cell. Meanwhile, even as silicon efficiencies have increased, single-junction cells face a theoretical maximum efficiency barrier of 29%, known as the Shockley-Queisser limit; their practical limit is as low as 24%.

    Furthermore, perovskite cells can be more sustainable to produce than silicon. Intense heat and large amounts of energy are needed to remove impurities from silicon, and that produces a lot of carbon emissions. It also has to be relatively thick to work. Perovskite cells are very thin — less than 1 micrometer — and can be painted or sprayed on surfaces, making them relatively cheap to produce. A 2020 Stanford University analysis of an experimental production method estimated that perovskite modules could be made for only 25 cents per square foot, compared to about 2.50 for the silicon equivalent.

    Industries will set up production lines in factories for commercialization of their solar cells before 2025, says Toin University of Yokohama engineering professor Tsutomu Miyasaka, who reported the creation of the first perovskite solar cell in 2009. Not only for use in outdoor solar panels but also indoor IoT power devices, which will be a big market for perovskite photovoltaic devices because they can work even under weak illumination.

    Backing next-generation climate technology

    Companies around the world are starting to commercialize perovskite panels. CubicPV, based in Massachusetts and Texas, has been developing tandem modules since 2019, and its backers include Bill Gates’ Breakthrough Energy Ventures. The company says its modules are formed of a bottom silicon layer and a top perovskite layer and their efficiency will reach 30%. Their advantage, according to CEO Frank van Mierlo, is the company’s perovskite chemistry and its low-cost manufacturing method for the silicon layer that makes the tandem approach economical.

    Last month, the Department of Energy announced that CubicPV will be the lead industry participant in a new Massachusetts Institute of Technology research center that will harness automation and AI to optimize the production of tandem panels. Meanwhile, CubicPV is set to decide on the location of a new 10GW silicon wafer plant in the U.S., a move it says will speed tandem development.

    Tandem extracts more power from the sun, making every solar installation more powerful and accelerating the world’s ability to curb the worst impacts of climate change, said Van Mierlo. We believe that in the next decade, the entire industry will switch to tandem.

    In Europe, Oxford PV is also planning to start making tandem modules. A spinoff from Oxford University, it claims a 28% efficiency for tandems and says it’s developing a multi-layered cell with 37% efficiency. The company is building a solar cell factory in Brandenburg, Germany, but it has been delayed by the coronavirus pandemic and supply-chain snags. Still, the startup, founded in 2010 and backed by Norwegian energy company Equinor, Chinese wind turbine maker Goldwind and the European Investment Bank, is hopeful it can start shipments this year pending regulatory certification. The technology would initially be priced higher than conventional silicon cells because tandem offers higher energy density but the company says the economics are favorable over the full lifetime of usage.

    Many solar upstarts over the years have attempted to break the market share of China and conventional silicon panels, such as the notoriously now bankrupt Solyndra, which used copper indium gallium selenide. First Solar‘s cadmium telluride thin film approach survived a decade-long solar shakeout because of its balance between low-cost relative to crystalline silicon and efficiency. But it now sees tandem cells as a key to the solar industry’s future, too.

    Perovskite is a disruptive material without disrupting the business model — the entrenched capacity to manufacture based on silicon, says Oxford PV CTO Chris Case. Our product will be better at producing lower-cost energy than any competing solar technology.

    The Brandenburg, Germany manufacturing plant of Oxford PV, a spinoff of Oxford University, that claims a 28% efficiency for its tandem solar cells and says it’s developing a multi-layered cell with 37% efficiency.

    Caelux, a California Institute of Technology spinoff, is also focused on commercializing tandem cells. Backed by VC Vinod Khosla and Indian energy, telecom and retail conglomerate Reliance Industries, Caelux wants to work with existing silicon module companies by adding a layer of perovskite glass to conventional modules to increase efficiency by 30% or more.

    Questions about performance outside the lab

    Perovskites face challenges in terms of cost, durability and environmental impact before it can put a dent in the market. One of the best-performing versions is lead halide perovskites, but researchers are trying to formulate other compositions to avoid lead toxicity.

    Martin Green, a solar cell researcher at the University of New South Wales in Australia, believes silicon-based tandem cells will be the next big step forward in solar technology. But he cautions that they are not known to work well enough outside the lab. Perovskite materials can degrade when exposed to moisture, a problem with which researchers have claimed some success.

    The big question is whether perovskite/silicon tandem cells will ever have the stability required to be commercially viable, said Green, who heads the Australian Centre for Advanced Photovoltaics. Although progress has been made since the first perovskite cells were reported, the only published field data for such tandem cells with competitive efficiency suggest they would only survive a few months outdoors even when carefully encapsulated.

    In a recent field trial, tandem cells were tested for over a year in Saudi Arabia and were found to retain more than 80% of an initial 21.6% conversion efficiency. For its part, Oxford PV says its solar cells are designed to meet the standard 25- to 30-year lifetime expectancy when assembled into standard photovoltaic modules. It says its demonstration tandem modules passed key industry accelerated stress tests to predict solar module lifetimes.

    Japan’s on-building perovskite experiments

    ​In Japan, large, flat expanses of land that can host mega-solar projects are hard to come by due to the archipelago’s mountainous terrain. That’s one reason companies are developing thin, versatile perovskite panels for use on walls and other parts of buildings. Earlier this year, Sekisui Chemical and NTT Data installed perovskite cells on the exterior of buildings in Tokyo and Osaka to test their performance over a year. Electronics maker Panasonic, meanwhile, created an inkjet printer that can turn out thin-film perovskite cells in various sizes, shapes and opacities, meaning they can be used in regular glass installed on Windows, walls, balconies and other surfaces.

    Onsite power generation and consumption will be very beneficial for society, says Yukihiro Kaneko, general manager at Panasonic’s Applied Materials Technology Center. For Japan to achieve its decarbonization goal, you would need to build 1,300 ballpark-sized mega-solar projects every year. That’s why we think building solar into Windows and walls is best.

    Exhibited at CES 2023, Panasonic’s 30cm-square perovskite-only cell has an efficiency of 17.9%, the highest in the world, according to a ranking from the U.S. National Renewable Energy Laboratory. The manufacturer stands to get a boost from regulations such as a recently announced requirement that all new housing projects in Tokyo have solar panels starting in 2025. Panasonic says it aims to commercialize its perovskite cells in the next five years.

    Perovskite cell inventor Miyasaka believes perovskite-based power generation will account for more than half of the solar cell market in 2030, not by replacing silicon but through new applications such as building walls and Windows.

    The Rapid progress in power conversion efficiency was a surprising and truly unexpected result for me, said Miyasaka. In short, this will be a big contribution to realizing a self-sufficient sustainable society.

    Perovskite solar cells: why they’re the future of solar power

    At the leading edge of scientific discovery and renewable energy research, a class of materials called perovskites has excited the imaginations of some of the world’s top scientists and engineers.

    These incredible materials have the ability to generate more electricity from the sun than almost anything else, potentially at a much lower cost than traditional silicon solar cells. But perovskites have so far required a lot of testing and trial-and-error, and no single application has reached the point of commercialization. The study of perovskite solar cells has come a long way in a very short time, but there are some big hurdles to overcome.

    Because of the work of many dedicated researchers, some perovskite products may be coming to the market within the next year or two, so it’s important to learn about them now. Unfortunately, most of the information about perovskites on the web is directed at the researchers and scientists who study and work with these materials, and that stuff is necessarily pretty dense and technical.

    What follows below is our attempt to cover perovskite materials in detail, but without a lot of the technical jargon and hard-to-understand concepts of a scholarly journal article. Someday soon, you may be able to have perovskite solar panels installed on your roof, so it’s time to learn about these exciting materials and what they might mean for rooftop solar in the very near future.

    What is a perovskite?

    Perovskites are a class of materials with a distinctive crystal structure similar to a mineral of the same name first discovered in Russia in 1839. Many varieties of perovskites exist, but the most interesting of these for the solar industry are crystals built out of organic and inorganic molecules connected to atoms of lead or tin.

    The structure of one perovskite material used in solar cells. Image source: Science Advances

    bill, gates-based, photovoltaic, technology

    The image above is a representation of the structure of one kind of lead halide perovskite crystal. It has a grid of 8-sided molecules called lead halides (an atom of lead connected to 6 halogen atoms of either iodine, chlorine, or bromine), surrounding a smaller molecule called a methylammonium cation (we promise this is as science-y as this article gets).

    Why perovskites are important

    Perovskites are exciting for several reasons, but the reason we’re going to talk about relates to the photovoltaic effect, which means “energy from light.”

    The tin or lead present in these materials are good for making solar cells in the same way silicon is used for making solar cells. Atoms of these elements are ideal for forming molecules with other atoms that are semiconductor materials, whose electrons can be excited by light energy and directed along a wire to produce electricity.

    Unlike silicon crystals, perovskite crystals are pretty easy to make under fairly ordinary conditions. Silicon must first be heated to extremely high temperatures to produce material with the right purity and crystal structure to make electricity; perovskites can be created by mixing chemicals in solution and coating a surface with that solution. The process is a bit more complicated than we’re letting on, but for the most part, producing the perovskite solar cells of the future will likely be significantly cheaper and easier than making silicon cells.

    Perovskites are also important because their ability to make electricity can be “tuned” by controlling the kinds of molecules that are produced in the manufacturing process. This tuning results in materials with the ideal “bandgap,” which is the amount of energy needed to push an electron to a higher energy level so it can carry an electrical charge across a circuit.

    Perovskites, efficiency, and the bandgap

    Every atom in the universe has one or more electrons floating around its nucleus, and the negatively-charged electrons are attracted to the positively-charged nucleus. Molecules made up of many atoms form based on the number of electrons each atom has, and the shared electrons float around the molecule. The outermost electrons are said to be in the “valence Band” of the atoms they orbit.

    Solar electricity is generated when photons of light “bump” the outermost electrons of a semiconductor material to a higher energy state, thereby pushing them out of the valence Band and into the “conduction Band” of the molecule. The minimum amount of energy needed to push an electron from the valence Band to the conduction Band is called the bandgap.

    When an electron is pushed into the conduction Band, it is no longer stuck in the orbit of the molecule; instead, it becomes a charge carrier that can move through the material it’s part of, carrying electrical energy that we can use.

    How sunlight causes electrons to become charge carriers in a solar cell.

    Photons of different colors of light carry different amounts of energy, measured by units called “electronvolts” (eV). Photons of visible light have energies of between 1.75 eV (deep red) and 3.1 eV (violet). An ideal photovoltaic material has a bandgap of 1.34 eV, because that’s the point at which the maximum amount of visible light will convert electrons to charge carriers.

    There’s a concept in solar related to the bandgap called Power Conversion Efficiency, or PCE, which is the amount of solar energy that can be converted to electricity by a solar cell. A solar cell that uses a single connection (more commonly called a junction) between layers of positive and negatively-charged materials with the ideal bandgap can convert 33.7% of all incoming light to electricity. This ideal efficiency is called the Shockley–Queisser limit, named after the physicists who discovered it.

    Perovskites can be tuned to various bandgaps within a wide range, while other materials only have one.

    The trouble with the Shockley–Queisser limit is that no single material we know of has the perfect bandgap to reach it.

    Silicon solar cells have a theoretical bandgap of about 1.2 eV, meaning they have a maximum PCE of around 32%. The best perovskite materials can reach about 31%, but there are reasons why it might be better to use a perovskite material with a higher or lower bandgap, even though it wouldn’t be ideal for use by itself. That brings us back to the concept of “tuning the bandgap,” as we discussed above.

    By controlling the chemical makeup of a perovskite crystal, materials scientists can manufacture perovskite materials to have a bandgap very close to ideal for converting light to electricity, but they can also create multi-layered perovskite solar cells in which each layer has a different bandgap. Having multiple layers means high-energy photons excite electrons in layers with a wider bandgap, and low-energy photons excite electrons in layers with a narrower bandgap. In this way, more of the total solar energy gets converted into electricity.

    This technology has shown great progress in recent years, and multi-junction cells made up of perovskite layers of varying bandgaps have already reached a conversion efficiency of 26%, despite having been researched since just 2013. over, a tuned layer of perovskite can be added in a “tandem cell” arrangement with a traditional silicon cell to capture photons the silicon can’t convert, thereby increasing power conversion efficiency.

    The structure of perovskite-silicon tandem solar cell (on the left) and perovskite-perovskite tandem solar cell (on the right). Image source: Science Advances

    Some day, combining perovskite solar technology with the best of silicon-based tech might be the key to unlocking solar cells that can turn 50% of sunlight into electricity. That would be huge, considering that Maxeon currently has the highest efficiency rating on the market with their solar panels converting 22.8% of electricity into usable power.

    The key takeaway of the above is this: perovskite cell efficiency might never be as good as the best silicon solar cells, but it will be good enough at a low-enough cost that the amount of electricity they produce per dollar spent on them will be much, much lower than silicon-based photovoltaic products.

    The promise of perovskite solar cells can’t be understated. The reductions in cost they might provide is so exciting that the U.S. federal government has invested millions of dollars in perovskite research through the Office of Energy Efficiency and Renewable Energy. In 2020, 20 million in funding was available for perovskite research, spread among initiatives to develop cell technology, manufacturing best practices, and cell testing procedures.

    bill, gates-based, photovoltaic, technology

    How are perovskite solar cells made?

    We’re going to keep this simple, because it isn’t necessary to know all the chemistry that goes into creating these things to understand how they work. Basically, perovskites can be created using “wet chemistry” in which materials like methylammonium lead iodide, methylammonium halide, and other additives are mixed together in a solution. The mixture is then deposited on a substrate like glass, metal oxide, flexible polymers, a silicon solar cell, or even transparent wood (wow!).

    The deposition of the perovskite solution is usually done via spin-coating, which is kind of the same concept as the Spin-Art machines children use to make splotchy paintings on thick paper. The solution is dripped or sprayed onto the substrate, which is then spun at a high enough speed to spread a thin layer of the solution across its surface. When the solvents in the mixture evaporate, they leave behind perovskite films; thin layers of perovskite crystals ready to be wired into a solar cell.

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    Different types of perovskite solar cells

    All solar cells, no matter what they’re made of, have certain things in common.

    bill, gates-based, photovoltaic, technology

    They must all have at least one negative layer and one positive layer of photovoltaic material; and they must have conductive front and back electrodes to carry the sun-charged electrons from the negative layer along a wire to produce electricity before returning them to the positive layer. Once mounted in a solar module, the cells are sealed in an encapsulation layer to protect them against damage from weather.

    There are essentially two different types of perovskite solar cells: thin-film cells with perovskite as the only photovoltaic material, and tandem cells, which have either multiple layers of perovskite or a thin perovskite layer on top of traditional crystalline silicon.

    To complicate matters a little, there are also thin-film tandem cells with a perovskite layer on top of copper indium gallium selenide (CIGS), which is an already-perfected thin-film solar technology.

    Thin-film vs tandem solar cell structure. Image source: U.S. DOE

    Pros and cons of perovskites

    As we discussed above, perovskites are exciting because they convert solar energy into electricity nearly as well as silicon, but can potentially be manufactured much more cheaply. Unfortunately, there are downsides to perovskites, as well.

    Advantages

    • Relatively easy to manufacture and deposit onto a surface using low-cost processes
    • Potential for high power conversion efficiency
    • Tunable bandgap, meaning it can be manufactured to be almost ideal for solar energy generation
    • Production requires 20 times less material than silicon cells, and doesn’t use rare earth metals
    • Manufacturing process is much less energy intensive than that of traditional solar cells

    Disadvantages

    • Perovskites break down over time when exposed to moisture, light, heat and oxygen, meaning there needs to be additional technologies developed to stabilize the cells for widespread use
    • The very best perovskites at generating energy contain lead, which is a neurotoxin; however, the industry is working on ways to reduce potential perovskite toxicity
    • Perovskite cells are not yet ready for commercial sales

    The advantages of perovskite materials for photovoltaic applications are hard to overstate, and researchers have made some progress in solving the drawbacks of lead content and material stability.

    Some possible solutions include replacing lead perovskites with tin-based ones (although experimental tin perovskites have much lower power conversion efficiency), and special polymer encapsulants that bind to the lead and stop it from leaching out in case the cells become damaged.

    Who makes perovskite solar cells and when can people buy them?

    Perovskite solar cells in a lab. Image source: EE Power

    Nearly all perovskite solar cells are currently made by researchers in places like the National Renewable Energy Laboratory (NREL), to be poked and prodded and tested for their ability to make solar power and long-term stability and durability under common environmental conditions. These are mostly postage-stamp sized test cells, not ready for sale to the public. There are some companies, though, who say that large-scale commercialization of perovskites is not far away.

    OxfordPV

    One such company, Oxford PV, touts its high-efficiency perovskite/silicon tandem cells as being nearly ready. Oxford’s big breakthrough in perovskite photovoltaics was the announcement of a 29.52% efficient tandem cell in December, 2020—the highest efficiency ever verified in a solar cell at the time.

    In 2021, Oxford released news that work on its manufacturing facility in Brandenburg, Germany was complete, and that production would begin sometime “in 2022.” But in announcing the completion of the facility, Oxford simultaneously broke ties with Meyer Burger, the partner that helped them build it. That parting-of-the-ways led to a rather messy separation, and as of this writing, the Brandenburg facility is not making tandem perovskite-silicon cells as expected.

    Qcells

    Perhaps the second likeliest candidate to market perovskite products is Qcells, which has said it is building a perovskite manufacturing line into a new South Korean facility. Qcells is one of the largest solar module manufacturers in the world, and it has plans to expand its facilities across the globe, including doubling the size of its facility in Dalton, Georgia, which is already the largest solar manufacturing plant in the western hemisphere.

    Saule

    Another company, Saule Technologies, is currently looking for licensing partners for its “kinetic solar blinds,” which feature inkjet-printed perovskites added to wide-bladed venetian-style blinds, as seen in the image below.

    Saule Technologies is exciting because it was founded by Olga Malinkiewicz, who made breakthrough discoveries in perovskite technology while working as a PhD student at the University of Valencia. Her work was one of the catalysts for the explosive growth in perovskite research. Despite the promise of these products, it should be noted that Saule has been looking for a partner for this technology for nearly 2 years, without a taker.

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    Key takeaways

    • Perovskites are materials with specific crystal structures that exhibit a photovoltaic (electricity from light) effect.
    • These materials have the potential to revolutionize the solar industry by greatly increasing efficiency and reducing the cost to manufacture solar panels.
    • Scientists have been working hard on perfecting these materials since 2009, and commercially-available solar cells may be coming out in the next year.
    • The advantages of perovskites for making solar cells are hard to overstate, but there are drawbacks—such as the presence of lead in these materials—that must be overcome before they can become truly widespread.

    Ben Zientara

    Solar Policy Analyst and Researcher

    Ben is a writer, researcher, and data analysis expert who has worked for clients in the sustainability, public administration, and clean energy sectors.

    efficient perovskite-based solar cells thanks to supramolecular chemistry

    © Politectico Milano

    Supramolecular chemistry and the intermolecular interaction involving halogen atoms in organic molecules can help improve the performance of perovskite-based solar cells. Thus enabling them to achieve high levels of efficiency and increased stability. This is the conclusion of researchers at the Politecnico di Milano who has published in the prestigious Angewandte Chemie International Edition.

    Organic-inorganic hybrid perovskites – ionic compounds consisting of small organic cations and metal halides – have been known since the 19th century, but they have only recently been used in optoelectronics to construct lasers diodes, photodetectors, and solar cells. In particular, the first perovskite-based photovoltaic cell was produced in 2009. Since then, there has been intensive research into achieving an efficiency of more than 25 percent, which would surpass even the silicon that currently dominates the photovoltaic market.

    Energy losses

    The low cost and excellent perovskites’ performance make them very attractive for photovoltaic applications. However, there are still several problems that prevent these materials from entering the market. First of all, there is their low stability in air and humidity. In addition, the presence of defects, i.e., imperfections in the crystal lattice, can generate ‘trap states’ that interfere with the movement of charge carriers (electrons and holes) generated by the light within the material, trapping them and causing electrical energy losses. Generally, these trap states are unbound halide ions that can move under the effect of an electric field and recombine with holes.

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    Perovskite solar cells have a number of advantages over silicon solar cells. It is a cheaper raw material, less of it is needed, and the […]

    The study conducted at the Politecnico showed that using additives capable of forming halogen bonds with the halide ions present in perovskites provides significant advantages for developing solar cells with better crystallinity and more excellent stability. Halogen bonding enables fluorinated molecules to be introduced, which passivate the surface halides to produce hydrophobic and water-repellent perovskites. In this way, trap states are blocked, and efficiency is increased.

    Halogen bonding

    In addition, the surface modification of perovskite with bifunctional molecules capable of forming halogen bonds enables better integration of the perovskite within the solar cell, facilitating the generation of electrical current.

    From the data reported, it appears that halogen bonding has considerable potential for the development of a new generation of solar cells based on perovskites. However, a better atomic/molecular understanding of these materials is needed to exploit halogen bonding advantages fully.

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    Innovation Origins is the European platform for innovation news. In addition to the many reports from our own editors in 15 European countries, we select the most important press releases from reliable sources. This way you can stay up to date on what is happening in the world of innovation. Are you or do you know an organization that should not be missing from our list of selected sources? Then report to our editorial team.

    Perovskite solar cells

    The mineral perovskite, named after the Russian mineralogist Count Lev Perovski, was used in solar cells for the first time in 2009. Since then, scientists have demonstrated increasing energy yields from these perovskite solar cells in the laboratory. We’re currently working to scale up this new and promising technology.

    A few years ago, perovskite solar cells were shown to be just as efficient as traditional crystalline silicon (c-Si) cells. There are therefore high expectations for this thin-film PV technology. And all indications are that these perovskite solar cells form a good tandem with c-Si solar panels. This tandem combination is expected to deliver cost-effective solar panels with yields of above 30%. In theory, tandems could achieve a maximum energy yield in excess of 40%.

    Benefits of perovskite

    There are important benefits in using perovskite as a semiconductor in PV modules:

    • The raw materials used to produce perovskite are very cheap.
    • Only a very thin layer of perovskite is needed in a solar cell. This reduces material costs even further.
    • You can apply perovskite using a relatively simple deposition process (applying layers to a specific base – the substrate) that doesn’t require any costly machinery.
    • You can deposit the layers of perovskite at low temperatures. This also keeps down production costs.
    • It takes relatively little energy to make a perovskite cell. This means that the solar cell quickly recoups the costs of the energy that was needed to make it.

    Perovskite solar cells on glass and foil

    With the current state of perovskite solar cell technology, we can in principle achieve the same module efficiency on glass or foil as with another technology. In the Solliance partnership, we’ve already demonstrated a module efficiency of 16% with scalable production processes. The aim is to demonstrate 18 to 20% module efficiency by 2023. This and the low cost of the manufacturing process could make the perovskite solar cell a paradigm in the world of solar cells.

    As with Copper Indium Gallium Selenide (CIGS), you can apply perovskite to glass, but also to flexible foils. In turn, you can integrate these into products, such as car roofs or siding. In the case of a transparent substrate such as glass or plastic, it’s also possible to make perovskite-based solar cells semi-transparent, for use in Windows, for examples.

    Transparency is also needed for the promising application of perovskite solar cells in tandem technology. When they’re combined with silicon solar cells, the efficiency could exceed 30%.

    Our perovskite research

    In the Solliance partnership, led by TNO, Eindhoven University of Technology (TU/e) and imec, we have the technology and equipment in-house to develop and demonstrate the upscaling processes for perovskite PV modules. Both sheet-to-sheet and roll-to-roll. Considerable research and development are still needed for this project.

    Efficiency

    An important element of the research is improved efficiency. We’re working to create PV modules with the highest possible energy yield. To achieve this, we need to understand which factors affect the yield and how these can be influenced.

    Stability

    Stability is also important, as solar cells and the modules in use must be stable. This means that after 20 years, the output of the module when in use must not drop by more than 20% in relative terms. The factors that can have a negative impact on stability are water, air, temperature, electrical influence of the PV system, sometimes even light, and nearly always a complicated combination of these factors. For this reason, we’re constantly searching for the causes of possible instability. We try to remove these causes by using other materials and other processes.

    Special protective layer

    A disadvantage of perovskite is that it is not very water resistant. This places high demands on the barrier layer – the protective layer of PV modules. We’ve had good results with Atomic Layer Deposition (ALD). If we apply this technology for the inner layers, we don’t need such a strong barrier layer to make the modules moisture-resistant. In 2020, we showed that perovskite passes stress tests that we also use to test commercial modules.

    Reduction of toxicity

    The current generation of perovskite PV modules contain a very small amount of lead: approximately half a gram per square metre. Because lead may enter the environment if a solar panel is damaged, we’re investigating how great this harmful influence is and how we can limit it. Together with other Solliance partners, we’re identifying the potential risks and researching alternatives, with the aim of avoiding the use of lead.

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