Video: MIT engineers develop paper-thin solar cells that can power any surface
The ultralight solar cells are made of semiconducting inks using printing processes that can be scaled in the future to large-area manufacturing.
MIT researchers have developed a scalable fabrication technique to produce ultrathin, lightweight solar cells that can be stuck onto any surface.
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A group of engineers at MIT have developed a rather interesting solution to be deployed in remote locations or for assistance in emergencies: solar cells made of ultralight fabric that can turn any surface into a power source.
Thinner than human hair, the durable, flexible solar cells are stuck on a strong, lightweight fabric that makes them very easy to affix to a surface, just like a sticker.
The solar cells can be laminated onto many surfaces
The metrics used to evaluate a new solar cell technology are typically limited to their power conversion efficiency and their cost in dollars-per-watt. Just as important is integrability — the ease with which the new technology can be adapted, Vladimir Bulović, the Fariborz Maseeh Chair in Emerging Technology, leader of the Organic and Nanostructured Electronics Laboratory (ONE Lab), director of MIT.nano, and senior author, said in a statement.
The lightweight solar fabrics enable integrability, providing impetus for the current work. We strive to accelerate solar adoption, given the present urgent need to deploy new carbon-free sources of energy, he continued.
Applications are aplenty; these ultralight solar cells can be easily integrated onto the sails of a boat to provide power while at sea, adhered onto tents and tarps that are deployed in disaster recovery operations, or applied onto the wings of drones to extend their flying range, as per the release.
The ultralight solar cells is one hundredth the weight of regular ones
The paper-thin solar cells are made of semiconducting inks using printing processes that can be scaled in the future to large-area manufacturing. One-hundredth the weight of conventional solar cells, the former generates 18 times more power per kilogram, which is quite impressive.
The solar cells were glued on a composite fabric that weighs only 13 grams per square meter, known as Dyneema. This fabric is known to be sturdy; adhering the solar modules to sheets of this fabric only resulted in a mechanically robust solar structure.
While it might appear simpler to just print the solar cells directly on the fabric, this would limit the selection of possible fabrics or other receiving surfaces to the ones that are chemically and thermally compatible with all the processing steps needed to make the devices. Our approach decouples the solar cell manufacturing from its final integration,” Mayuran Saravanapavanantham, electrical engineering and computer science graduate student at MIT, explained.
The device can generate 730 watts of power per kilogram
The MIT researchers found that the device could generate 730 watts of power per kilogram when freestanding and about 370 watts-per-kilogram if deployed on the high-strength Dyneema fabric, which is about 18 times more power-per-kilogram than conventional solar cells.
A typical rooftop solar installation in Massachusetts is about 8,000 watts. To generate that same amount of power, our fabric photovoltaics would only add about 20 kilograms (44 pounds) to the roof of a house, he said.
These solar cells, however, need to be encased in a material that can protect them from the environment.
Encasing these solar cells in heavy glass, as is standard with the traditional silicon solar cells, would minimize the value of the present advancement, so the team is currently developing ultrathin packaging solutions that would only fractionally increase the weight of the present ultralight devices, said Jeremiah Mwaura, a research scientist in the MIT Research Laboratory of Electronics.
Thin-film photovoltaics with functional components on the order of a few microns, present an avenue toward realizing additive power onto any surface of interest without excessive addition in weight and topography. To date, demonstrations of such ultra-thin photovoltaics have been limited to small-scale devices, often prepared on glass carrier substrates with only a few layers solution-processed. We demonstrate large-area, ultra-thin organic photovoltaic (PV) modules produced with scalable solution-based printing processes for all layers. We further demonstrate their transfer onto lightweight and high-strength composite fabrics, resulting in durable fabric-PV systems ∼50 microns thin, weighing under 1 gram over the module area (corresponding to an area density of 105 g m−2), and having a specific power of 370 W kg−1. Integration of the ultra-thin modules onto composite fabrics lends mechanical resilience to allow these fabric-PV systems to maintain their performance even after 500 roll-up cycles. This approach to decoupling the manufacturing and integration of photovoltaics enables new opportunities in ubiquitous energy generation.
Unexpected Crystalline Structure Explains Mechanism of Long-Used Solar Cell Treatment and Hints That Further Materials Discoveries Await
For more than three decades, photovoltaic researchers have known that the addition of a single chemical—cadmium chloride—creates better-performing cadmium telluride (CdTe) solar cells. But they have not understood exactly why—until now. The answer has implications for materials science that stretch well beyond solar cells.
The light-absorbing layers in CdTe solar cells are composed of a thin film of material, about 10–100 times thinner than a human hair. Lots of modern devices, from solar cells to catalytic materials to organic light-emitting diode TVs, rely on thin-film materials. The surfaces at which these thin layers meet, or interfaces, are even thinner—100,000 times thinner than a human hair—and play a crucial role in the devices’ functions. A better understanding of thin-film interfaces could improve how we fabricate many different materials, but the precise structure of interfaces at the atomic scale is often difficult to study.
A Proven, But Unexplained, Boost for Solar Cells
In CdTe solar cells, the electrical charges created by an absorbed photon can be trapped and lost at the interfaces between the light-absorbing layer and the layers that carry those charges away into electrical circuits. As early as the 1980s, CdTe researchers realized that treating the interfaces in the solar cell with a small amount of cadmium chloride (CdCl2) could reduce the loss of charges at the interfaces and improve the solar cell’s power conversion efficiency.
Clearly, the addition of CdCl2 changed the interface in a crucial way. But further experiments could not resolve the interface’s structure down to the atomic level to explain why the CdCl2 treatment was so effective. This challenge is not unique to CdTe solar cells. Interfaces are notoriously difficult to study and understand at the atomic level, especially in cases of nonideal interfaces between materials that have different crystal structures.
Modeling Offers New Insights Into Interfaces
A new approach from a team of National Renewable Energy Laboratory (NREL) researchers and colleagues at Khalifa University, Bowling Green State University, and First Solar—an American CdTe solar manufacturer—has unmasked the details of the CdCl2 interface treatment. By modeling the behavior of individual atoms and electrons, the team simulated possible arrangements for CdCl2-treated interfaces.
To calculate the electronic structure of a CdTe solar cell—and thereby determine its charge collection—the researchers first needed to determine the atomic arrangement CdCl2 interface, which had never before been done for CdTe solar cells. To achieve this, the team implemented a structure prediction algorithm for interfaces. The algorithm began with a random arrangement of atoms and then allowed them to settle, using a method called density functional theory to calculate the atomic forces. The algorithm repeatedly made small but realistic changes to the positions of the atoms at the interface, which allowed the team to identify the lowest-energy (most stable) structures.
What surprised us was that the CdCl2 that formed at the interface took a different structure than it would as a bulk material, said Stephan Lany, an NREL computational materials scientist and author on the paper. It forms a 2D structure that matches both sides of the interface, with boundary conditions different from those when it forms on its own. This means that materials and structures that we don’t know or expect might exist for other interfaces as well.
The findings, published in Applied Physics Reviews, explain how the CdCl2 treatment yields higher-performing CdTe solar cells. By smoothly connecting to the crystal structure on either side of the interface, CdCl2 reduces the defects in the crystal structure that trap charges and reduce solar cell output. Such understanding should aid further improvements to CdTe solar cells.
New Insights Suggest Further Discoveries Await
But Lany and his fellow researchers are most excited by the broader implications of their findings. The CdCl2 structure modeled at the interface does not exist in larger, bulk crystals of the material. The ultrathin interface layer allows a previously unknown form of the material to exist with unique properties. Could this be true for other materials?
I’m most excited by the realization that materials do something different when they exist as atomically thin layers on or between other materials than when they are in the bulk, Lany said. For example, thin functional layers on top of a substrate might assume unique two-dimensional crystal structures with properties different from the bulk material. This might give them new functionalities, for example, in catalysis.
NREL researchers plan to continue to study how materials behave at interfaces. The potential applications stretch beyond photovoltaics, to catalytic materials, microelectronics, electrochemistry (like the water splitting often used to make hydrogen), and detector materials.
As semiconductor devices increasingly rely on the integration of different materials across interfaces, this enhanced ability to model and tune their structures will allow us to more intentionally design them for better performance, said Kirstin Alberi, director of the Materials Science Center at NREL. Such insights could open doors for utilizing a wider range of materials than previously thought practical.
The research was funded by the U.S. Department of Energy Solar Energy Technologies Office.
Thin-Film Solar Technology (Guide)
In an industry that is constantly evolving, thin-film solar panels are an exciting and innovative product that can be used to efficiently convert sunlight into electricity.
Unlike the traditional, rigid monocrystalline or polycrystalline photovoltaic (PV) solar panels you may be used to seeing, thin-film solar cells are, well, thin and flexible.
Suitable for many unique applications, thin-film panels can be used to generate electricity in a variety of instances in which a traditional type of solar panel may be less effective.
To help you understand the pros, cons, strengths, and weaknesses of thin-film solar panels, let’s explore how they work and dive into some of the most exciting aspects of this emerging technology.
Definition of Thin-Film Solar
Thin-film solar panels harness energy from direct sunlight using one or more thin layers, or a thin film of semiconducting materials placed on a suitable base such as glass, plastic, or metal.
For an example that you are probably familiar with, solar-powered calculators are one of the most widely established applications for thin-film cells.
Thin-film solar cells can be made of a variety of materials, including popular compounds such as:
- Cadmium Telluride (CdTe)
- Copper Indium Gallium Diselenide (CuInSe2)
- Amorphous Silicon (a-Si)
- Gallium Arsenide
While thin-film solar products have been around for decades, the technology is advancing rapidly, with new ideas constantly being tested and improved. In early 2022, researchers at the University of Surrey successfully increased the energy absorption levels in a thin-film solar panel by 25%, achieving a new record of 21% efficiency.
Differences Between Thin-Film Solar Panels and Standard Silicon Solar Panels
The key differences between thin-film solar panels and standard silicon solar panels are their size, strength, and cost. Unlike bulky, rigid silicon solar panels, thin-film panels are as slim as a piece of paper, cheaper to produce, ship, and install, and can be flexible enough to mount on curved surfaces.
Today, traditional monocrystalline and polycrystalline photovoltaic (PV) solar panels are typically more efficient and durable than their thin-film counterparts. With less efficiency, a larger surface area may be required for thin-film cells to convert the same amount of sunlight into electricity as with standard silicon solar panels.
Still, as a lighter and cheaper option to produce and transport, continuous advancements in thin-film solar cells have allowed the technology to witness widespread adoption and a bright future ahead.
The Primary Thin-Film Solar Cell Materials
Ready to get technical? Here is a detailed look at the four main materials used in thin-film solar panels today:
Amorphous Silicon (a-Si) Solar Panels
As the first commercially available thin-film solar cell, Amorphous Silicon (a-Si) strips have been used since the late 1970s. Unlike the crystalline silicon wafers used in rigid panels, Amorphous Silicon cells generally have low efficiency levels but still perform well in a variety of light intensities.
Amorphous Silicon solar panels are made by depositing a layer of amorphous silicon onto a glass surface using chemical vapor deposition (CVD). The resulting material has a low thermal conductivity, which means it can absorb more heat than traditional crystalline silicon photovoltaic cells without overheating.
While cheap to manufacture and produce, a-Si panels tend to degrade more quickly than other types of thin-film solar panels, and have difficulty operating at temperatures below freezing.
Copper Indium Gallium Selenide (CIGS) Solar Panels
As one of the most popular thin-film technologies, CIGS solar cells use a series of copper, indium, gallium, and selenide layers to capture sunlight and generate electricity. CIGS panels utilize a multi-step process to collect and separate electrical charges, resulting in high-efficiency power production.
Suitable for building integration and several different flexible applications, CIGS research has created modules with thin-film solar panel efficiency levels up to 23% and rising, comparable to traditional solar panels. However, integrating copper, gallium, indium, and diselenide into one simple manufacturing process has made commercial production of the technology more difficult and expensive than other thin-film cells.
Cadmium Telluride (CdTe) Solar Panels
Second only to CIGS in popularity, cadmium telluride (CdTe) solar panels are another thin-film technology that has gained momentum in the last decade. Known for its quick and inexpensive development process, cadmium telluride solar panels have achieved similar efficiencies as traditional silicon solar panels, with reduced costs of production.
Flexible and ultra-thin, CdTe panels are among the most researched and tested technologies in new solar generation. However, the toxicity of the materials in CdTe solar panels has raised some environmental concerns.
Gallium Arsenide (GaAs) Solar Panels
With up to 40% efficiency in testing environments, Gallium Arsenide (GaAs) solar cells are another longstanding technology that is used in thin-film panels. Utilizing strong electric and heat resistant properties, GaAs solar panels have higher electron mobility than conventional silicon modules.
Tested and used in solar cars both on earth and in space (like the Mars Rover), GaAs solar cells are most applicable for high-power instances. While more expensive to produce than other thin-film technologies, GaAs solar cells continue to innovate and push the boundaries of renewable energy potential.
Advantages and Disadvantages of Thin-Film Solar Panels
Compared to traditional silicon solar collectors, thin-film solar panels come with a few distinct advantages and disadvantages.
Advantages of Thin-Film Solar Panels
- Lower Cost: Thin-film solar panels are generally cheaper to manufacture than traditional modules.
- Lighter Weight: Without any bulky or rigid parts, thin-film solar panels are easier to transport and install on a variety of surfaces.
- Flexible: With flexible arrays, thin-film solar panels can be installed on curved buildings, boats, walls, and more.
- Less Invasive: Unlike bulky silicon panels, some people consider thin-film panels less invasive and more visually appealing than large photovoltaic arrays.
Disadvantages of Thin-Film Solar Panels
- Less Efficiency: Generally less efficient than traditional panels, thin-film installations require more space to produce the same amount of electricity.
- Reduced Durability: Built for flexibility, thin-film solar panels may be more prone to cracks, breaks, and malfunctions from weather conditions like rain or snow.
- Newer Technology: The testing, manufacturing, and real-world applications of thin-film solar cells are still very limited compared to rigid PV panels.
Best Thin-Film Solar Manufacturers
As one of the fastest-growing sectors of the renewable energy industry, there are many leading manufacturers currently pursuing thin-film solar products. While formerly leading companies like Solar Frontier have moved away from the space, there are still many thin-film solar companies to watch in the coming years:
- Hanergy:Hanergy is one of the largest solar manufacturers in the world, and specializes in thin-film solar panels. With six RD centers in Beijing, Sichuan, Silicon Valley, and Uppsala, Sweden, Hanergy has made significant investments in thin-film solar cell research, resulting in almost 1,000 patents in new energy, including copper indium gallium selenide (CIGS) technology that has reached 21% efficiency.
- Renogy: With a wide range of flexible solar products, Renongy is a consumer-facing company for small-scale electricity production. Today, their thin-film solar panels can be purchased one by one, or at wholesale rates for large installations.
- SunPower: As one of the largest solar panel manufacturers in the world, SunPower’s flexible solar panels are portable, flexible, and backed by a thick, weather-resistant copper foundation. The California-based company currently sells thin-film solar panels primarily for use on the go in RVs and other small applications.
Exciting Developments in Thin-Film Solar Panels
With a strong foundation powered by decades of research and development, thin-film solar cells are among the most exciting and innovative technologies driving the future of solar power. While we may still be simply scratching the surface of their full potential, here are a few interesting advancements to look out for in the near future:
- Researchers at Stanford Oxford University have developed a new type of solar cell that uses organic molecules called perovskite solar cells, which may be cheaper and easier to produce than traditional silicon-based cells.
- Similarly, researchers are developing a working perovskite “solar paint” which can be sprayed, printed, or dyed onto a surface to conduct electricity.
- The future is also bright for thin-film building-integrated photovoltaics, such as transparent solar panels and solar shingles. In both residential and commercial applications, these technologies can bring the electricity generation of thin-film solar into the functional elements of a building.
- Looking out even further, the success of thin-film solar panels in space makes the lightweight and highly efficient technology a key element in further Galaxy exploration.
Should you get thin-film solar panels for your home’s roof?
Thin-film solar panels are currently most often utilized on commercial buildings where ample space is available since many residential roofs are limited in total surface area. With that said, technological advancements are continuing to push the efficiency of thin-film panels forward, and residential applications are slowly becoming more cost-effective.
There are many pros and cons of buying flexible solar panels and the choice to use thin-film cells should be weighed on a case-by-case basis.
The Future of Thin-Film Solar Panels
With versatility and ease of use, thin-film solar panels are among the most exciting developments in the solar industry. As the technology continues to advance, thin-film solar cells are being used in many practical applications, beyond just rooftop power generation.
If you’re considering a solar panel installation of any kind, you can talk to Palmetto to learn more about your options. With our Free Solar Design and Savings Estimate tool, you can instantly see how much you can save with solar energy.
Thin, Lightweight, Flexible Solar from a New Renewable Technology.
The game-changing solution we have all been looking for. It’s light, flexible, thin, durable, and created to exacting specifications.
Sunflare Flexible Solar Modules
Our process makes Sunflare modules better. No roll-to-roll process can create panels as uniform and reliable as Sunflare. Precise cell-by-cell manufacturing produces superior quality.
Light, thin, and flexible panels. The first CIGS panel precision-engineered to meet exacting specifications for outstanding performance and reliability.
Sunflare uses Copper, Indium, Gallium and Selenide – semiconductor materials that require minimal heat. As a result, Sunflare produces 5x less CO 2 than silicon cells found in typical solar panels. No other solar company can make the same claim.
Creation of Sunflare modules REQUIRE NONE OF THESE HIGH-ENERGY CREATION AND CONSUMPTION PROCESSES.
No purification of silicon
Every Sunflare panel is made of our SUN 2 cell starting with high-quality stainless steel, then layered with semiconductor materials only a few micrometers thick. The result is thin, lightweight and flexible solar. How thin is thin solar? Sunflare solar panels are 1.7 mm thick vs 100.0 mm for a traditional silicon solar panel.
QR code tracks exact conditions of each manufacturing step to ensure uniform quality.
1/10 of the Global Warming Potential of Silicon Modules
The production process for Sunflare solar modules results in a global warming potential (GWP) of just 1/10 of silicon modules.The Sunflare manufacturing process is very energy efficient versus silicon production which requires temperatures of 1800 degrees Celsius. Sunflare uses an extremely thin light-absorbing CIGS layer with less than 1mm of elemental materials in its production process. In addition, there’s no glass. And the Flex60 has no aluminum frame.
Note: Global Warming Process is measured as kilogram C02-equivalents. The increase of earth’s temperature is related to the increase of the emission of gases, such as CO2, methane, water vapor, nitrous oxide and CFCs, among others, from man-made sources, mainly from the burn of fossil fuels. Source: Life cycle assessment of CIGS solar modules and future integration in Zbee 12/18/2017, Sandra Roos, Magdalena Juntikka. Study reviewed and approved by Swedish independent third-party institute Miljögiraff AB.
Sunflare lightweight CIGS Modules have the lowest carbon footprint among all electricity sources.
- Sunflare lightweight modules has a CO2 foot print only 1/5 of silicon.
- Lower climate contribution than both on-shore and off-shore wind.
- Above is valid for installations both in Sweden and Arizona(USA).
Does not rely on toxic chemicals. No lead, cadmium, hydrofluoric acid, or hydrochloric acid.
Requires less water to manufacture and recycles the little water used
Materials are recycled when spent.
Unlike fossil fuels, Sunflare solar panels do not produce pollutants or release CO 2 into the atmosphere as they generate energy.
80% less energy to produce than Silicon.