What happened? MIT researchers are rethinking how light can be manipulated within solar cells. They have applied an antireflection coating, a novel combination of multi-layered reflective coatings and a tightly spaced array of lines to the backs of ultrathin silicon films to boost the cells' output by as much as 50 percent. [No official statement has been released on original vs improved efficiency level.]
The coatings on the back of the solar cell force the light to bounce around longer inside the thin silicon layer, giving it time to deposit its energy and produce an electric current. "Without these coatings, light would just be reflected back out into the surrounding air" said Peter Bermel, an MIT postdoctoral physics researcher.
"It's critical to ensure that any light that enters the layer travels through a long path in the silicon," Bermel said. "The issue is how far does light have to travel [in the silicon] before there's a high probability of being absorbed" and knocking loose electrons to produce an electric current.
Why is this important to the future? Depending on the range of its applications, this type of breakthrough could transform solar efficiencies for traditional crystalline (glass substrate) solar cells as well as thin film (carbon substrate) solar.
While we invest in commercializing solar energy systems, we must not turn our backs on funding basic science that can yield fundamental breakthroughs. "The simulated performance was remarkably better than any other structure, promising, for 2-micrometer-thick films, a 50 percent efficiency increase in conversion of sunlight to electricity," said Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, who directed the project.
Researchers at US Los Alamos National Laboratory (LLNL) have confirmed a unique energy phenomena known as 'carrier multiplication' via nanoscale sized semiconductor crystals that could improve the efficiency of solar cells by squeezing more energy out of inbound photons.
Traditional solar cells absorb a photon of light that releases an electron to generate an electrical current. Any excess energy from the photon reaction is wasted as heat or vibration. The notion of 'carrier multiplciation' rests on the idea that we can get multiple electrons released from a single photon by forcing electrons into a more confined space.
This idea was observed several years ago, but has been criticized as a phantom phenomena via a process known as 'photoionization. Now a research team led by Victor Klimov has confirmed that semiconductor crystals designed at the nanoscale (billionth of a meter) can channel this excess photon energy into a group of tightly packed electrons, leading to a more efficient solar cell.
The team did not release statements about commercialization or scalable efficiencies. “Researchers still have a lot of work to do,” Klimov cautioned. “One important challenge is to figure out how to design a material in which the energetic cost to create an extra electron can approach the limit defined by a semiconductor band gap. Such a material could raise the fundamental power conversion limit of a solar cell from 31 percent to above 40 percent.”
The future where buildings integrate energy generation systems like 'thin film' solar rooftops might be closer than you think.
Instead of designing expensive, bulky and ugly glass based solar panels, solar start ups are pushing down costs of plastic-substrate based 'thin film' solar cells that resemble today's roof shingles. The field also includes 'Big Chemistry' players like Dow and DuPont who hope to drop the costs of advanced solar materials.
PV Tech is reporting on the continued push by Dow Chemical to expand mainstream construction use power-generating roof shingles by 2011. Dow has already committed more than $3 billion towards polysilicon production that will help lower the global costs of solar cells.
The world of thin film (polymer-based organic) photovoltaics continues to evolve as start ups ramp up early branding efforts around product releases and higher volume production plans.
“This facility has state-of-the-art printing capabilities that are ready for full operation, with the future potential to produce over a gigawatt of flexible plastic solar modules per year,” commented Howard Berke, executive chairman and co-founder of Konarka. “Our technical leadership and innovation in flexible thin film solar, along with this facility’s capabilities of producing in excess of 10 million square meters of material per year, will allow us to produce Power Plastic for indoor, portable, outdoor and building integrated applications.”
Konarka has long been considered a leading start up in the solar field, but this Gigawatt production capacity helps to cement its position among a growing base of thin film competitors. Analysts have been fond of describing ‘spectacular growth’ ahead for thin film solar, but near term expansion is not likely to be as easy as paper forecasts as the solar industry confronts fundamental challenges including rising costs of raw materials. Rising costs aside, the solar industry is expected to grow from a market volume of 5.6 GW in 2008 to 79.5 GW in 2015. And if thin film companies like Konarka can continue to open large scale MW and GW capacity plants they should certainly expect bright days ahead.
The Solar industry is growing up and going global. Now materials giant Dow Corning is investing $3 billion into basic materials for traditional photovoltaics and thin film solar.
The Chemistry side of Solar The full potential of solar energy depends on our ability to make big advances in materials science.
How quickly solar can grow depends on our ability to design nanoscale structures that maximize the conversion of photons into electricity, photons into heat, or photons into hydrogen. And how many utilities and consumers take the leap!
So when we see 'Big Chemistry' companies get involved in the solar industry materials market, that should be a signal of growth (and growth pains) ahead!
Dow goes Greenby Being Black Dow Corning Corporation has announced several billion dollars of investment to provide critical materials to the fast-growing solar technology industry for both glass based solar and carbon based thin film.
Dow Corning and its Hemlock Semiconductor joint venture will begin manufacturing high purity monosilane, a key specialty gas used to manufacture thin-film solar cells and liquid crystal displays (LCDs). Combined with the new $1.2 billion build up at a Clarksville, Tennesee facility and the $1 billion expanded monosilane plant in Hemlock, Michigan operations may add up to 34,000 metric tons of polysilicon capacity for the fast-growing solar industry. Construction of both the Michigan expansion and the new Tennessee site will begin immediately.
Researchers at US Los Alamos National Laboratory (LLNL) have confirmed a unique energy phenomena known as 'carrier multiplication' via nanoscale sized semiconductor crystals that could improve the efficiency of solar cells by squeezing more energy out of inbound photons.
Traditional solar cells absorb a photon of light that releases an electron to generate an electrical current. Any excess energy from the photon reaction is wasted as heat or vibration. The notion of 'carrier multiplciation' rests on the idea that we can get multiple electrons released from a single photon by forcing electrons into a more confined space.
Carrier multiplication was observed several years ago, but has been criticized as a phantom phenomena via a process known as 'photoionization'. But now a research team led by Victor Klimov has confirmed that semiconductor crystals designed at the nanoscale (billionth of a meter) can channel this excess photon energy into a group of tightly packed electrons, leading to a more efficient solar cell.
The team did not release statements about commercialization or scalable efficiencies. “Researchers still have a lot of work to do,” Klimov cautioned. “One important challenge is to figure out how to design a material in which the energetic cost to create an extra electron can approach the limit defined by a semiconductor band gap. Such a material could raise the fundamental power conversion limit of a solar cell from 31 percent to above 40 percent.”
European researchers at Fraunhofer ISE have achieved another record efficiency of 41.1% in the conversion of sunlight into electricity using a ‘multi-junction’ class of solar cells.
The cells are made out of gallium-based materials suited for the solar spectrum that reaches the surface of the Earth. The team managed to increase the regions of the material that are electrically active to attain the high efficiencies.
Prof. Eicke R. Weber, Director of Fraunhofer ISE emphasizes, “This is an especially good example of how the control of crystal defects in semiconductors can lead to a breakthrough in technology.”
Fraunhofer ISE is working with Azur Space and Concentrix Solar GmbH to commercialize their technology. “The high efficiencies of our solar cells are the most effective way to reduce the electricity generation costs for concentrating PV systems,” says Dr. Andreas Bett, Department Head at Fraunhofer ISE. “We want that photovoltaics becomes competitive with conventional methods of electricity production as soon as possible. With our new efficiency results, we have moved a big step further towards achieving this goal!”
Researchers at the Georgia Institute of Technology have developed a unique super-'hydrophobic' (water repelling) surface coating that 'boosts the light absorption of silicon photovoltaic cells both by trapping light in three-dimensional structures, and by making the surfaces self-cleaning allowing rain or dew to wash away the dust and dirt that can accumulate on photovoltaic arrays'.
The 'self cleaning' design mimics the water repelling surface of a lotus leaf, 'which uses surface roughness at two different size scales to create high contact angles that encourage water from rain or (desert dew) condensation to bead up and run off. As the water runs off, it carries with it any surface dust or dirt – which also doesn't adhere because of the unique surface properties'.
"The more sunlight that goes into the photovoltaic cells and the less that reflects back, the higher the efficiency can be," said C.P. Wong, Regents' professor in Georgia Tech's School of Materials Science and Engineering. "Our simulations show that we can potentially increase the final efficiency of the cells by as much as two percent with this surface structure."
"A normal silicon surface reflects a lot of the light that comes in, but by doing this texturing, the reflection is reduced to less than five percent," said Dennis Hess, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering. "As much as 10 percent of the light that hits the cells is scattered because of dust and dirt of the surface. If you can keep the cells clean, in principle you can increase the efficiency. Even if you only improve this by a few percent, that could make a big difference."
Thin film solar is coming! And the industry is already shaping up to be very global with partnerships being formed across Germany, Japan, Korea, Italy, China and the United States.
2009-11 is likely to be a very dynamic period for the first stage of growth in thin-film solar panels 'printed' on top of plastic materials. Planned production in the US, Europe and China is growing quickly with new megawatt (MW) plants coming online in the next 18 months. The biggest problem might be supply outpacing market adoption! Now we need to find enough companies and customers ready to integrate thin film in building materials like rooftops.
What happened? US-based Air Products will supply China's Best Solar Hi Tech Co., Ltd, with on-site gases and equipment to support a new thin-film photovoltaic facility in Suzhou, Jiangsu Province. When the facility comes online at its full capacity, it will have an annual solar module manufacturing capacity of 330MW. Best Solar's subsidiary plants are expected to produce at a total capacity of 1GW.
Last week Italy's largest power company Enel SpA announced a joint venture with Sharp to develop 189 megawatts of power generation by the end of 2012.
Meanwhile the US and Germany appear to be hedging their bets by investing in plants in both countries.
Who says that 'cleantech' needs to be about 'energy independence'?
Globally interdependent seems the best (and most likely) path forward.
The thin film solar industry is going global. In the past few months we have seen manufacturing agreements that have connected companies based in the US, Italy, Japan, Korea, China and Turkey. And now we have the first major equity stake from a global energy giant Total.
Konarka partners with French oil giant Konarka has just announced on Monday that it received $45 million in equity financing from the U.S. division of French oil and gas giant Total. The arrangement also includes R&D agreements with Total’s chemical subsidiaries (Atotech, Bostik, Hutchinson, Sartomer) to further development of the startup’s thin-film, organic solar cell technology
With this stake, Total will become the leading shareholder with a 20% equity stake. This is its first major equity stake in a thin film maker, and will expand Total's current silicon-based solar portfolio with Photovoltech and Tenesol.
Materials Science solutions for Distributed Solar Power
The future where buildings integrate energy generation systems like 'thin film' solar rooftops might be closer than you think. 
European researchers at Fraunhofer ISE have 
Researchers at the 
