Yet another promising photovoltaics fabrication method:
Imagine a future in which the rooftops of residential homes and commercial buildings can be laminated with inexpensive, ultra-thin films of nano-sized semiconductors that will efficiently convert sunlight into electrical power and provide virtually all of our electricity needs. This future is a step closer to being realized, thanks to a scientific milestone achieved at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab).
Researchers with Berkeley Lab and the University of California, Berkeley, have developed the first ultra-thin solar cells comprised entirely of inorganic nanocrystals and spin-cast from solution. These dual nanocrystal solar cells are as cheap and easy to make as solar cells made from organic polymers and offer the added advantage of being stable in air because they contain no organic materials.
Their point about stability is important. Think about how plastic and rubber (made from hydrocarbons) degrade under exposure to sunlght. The longer photovoltaics last the better the economics become. Also, rather than bolting the photovoltaics onto structure surfaces in separate apparatuses if the photovoltaics could get built right into structure surfaces even larger cost reductions become possible.
"Our colloidal inorganic nanocrystals share all of the primary advantages of organics -- scalable and controlled synthesis, an ability to be processed in solution, and a decreased sensitivity to substitutional doping - while retaining the broadband absorption and superior transport properties of traditional photovoltaic semiconductors," said Ilan Gur, a researcher in Berkeley Lab's Materials Sciences Division and fourth-year graduate student in UC Berkeley's Department of Materials Science and Engineering.
Gur is the principal author of a paper appearing in the October 21 issue of the journal Science that announces this new development. He is a doctoral candidate in the research group of Paul Alivisatos, director of Berkeley Lab's Materials Sciences Division, and the Chancellor's Professor of Chemistry and Materials Science at UC Berkeley. Alivisatos is a leading authority on nanocrystals and a co-author of the Science paper. Other co-authors are Berkeley Lab's Neil A. Fromer and UC Berkeley's Michael Geier.
While the initial conversion efficiency is still low the process lends itself to scaling up at low cost should they find ways to boost conversion efficiency.
In this paper, the researchers describe a technique whereby rod-shaped nanometer-sized crystals of two semiconductors, cadmium-selenide (CdSe) and cadmium-telluride (CdTe), were synthesized separately and then dissolved in solution and spin-cast onto a conductive glass substrate. The resulting films, which were about 1,000 times thinner than a human hair, displayed efficiencies for converting sunlight to electricity of about 3 percent. This is comparable to the conversion efficiencies of the best organic solar cells, but still substantially lower than conventional silicon solar cell thin films.
"We obviously still have a long way to go in terms of energy conversion efficiency," said Gur, "but our dual nanocrystal solar cells are ultra-thin and solution-processed, which means they retain the cost-reduction potential that has made organic cells so attractive vis-a-vis their conventional semiconductor counterparts."
Silicon crystals that are used in manufacturing current silicon photovoltaic cells represent a large fraction of total photovoltaics costs. Approaches that avoid the need to make lots of relatively thick crystals are probably essential for driving down the cost of photovoltaics far enough to make photovoltaic installations ubiquitous. So any new photovoltaic fabrication method that avoids the use of silicon crystals warrants notice.
Another advantage of this approach is low weight. Thin film solar cells with high durability and low weight could potentially get coated onto electric and hybrid car surfaces to recharge batteries.
Compare this report to my previous post UCLA Team Cuts Photovoltaics Cost With Plastics. Note the 15 to 20 year life expectancy for the UCLA approach. The Lawrence Berkeley material would probably last longer. But which group can boost conversion efficiency the most and the soonest?
By Randall Parker at 2005 October 25 09:31 AM Energy Tech | TrackBackThe conversion effeciency is currently about 4% ? If they can raise this to around 7% it starts looking viable from a cost standpoint. It should be interesting to watch over time.
Aren't most thin films translucent? What about layering to increase conversion efficiency?
Below is the 2002 article on the Berkeley team to which I previously linked in response to the prior UCLA polymer solar cell article. Aside from avoiding the organics they seem to have increased the efficiency from 1.7% to 3%. I didn't, however, see anything in the present article to indicate they had made much headway in their stated goals of "improving the conductivity of the nanocrystal polymer interface, removing nanorod surface traps, aligning the nanorods perpendicular to the substrate and increasing their length beyond 60nm":
http://www.eetuk.com/tech/news/rn/showArticle.jhtml?articleID=19203308
Polymer solar cells take step forward
By Nolan Fell
EETUK.com
5 April 2002 (9:13 a.m. GMT)
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A team from the University of California at Berkeley has produced a hybrid solar cell made from a polymer material containing conducting nanorods.
There is increasing interest in polymer solar cells as they have the potential to be produced more cheaply than silicon cells. As the technology is less mature, it is also developing rapidly, whereas advancements in silicon cells are only occurring incrementally.
Dr Paul Alivastos, of Berkeley's chemistry department, said that with the introduction of nanorods made from cadmium selenide (CdSe) with lengths varying from 7 to 60nm, a polymer cell achieved a solar conversion efficiency of 6.9% in a low light environment and 1.7% in normal solar conditions. Conventional silicon cells achieve efficiencies of more than 10%, with the most advanced multi-band-gap complex structure reaching 25-30%.
"The figure in normal light conditions is similar to the best polymers' performance," said Alivastos. "But polymer cells have a much more complex layer structure and we are working on applying this structure."
The higher efficiency of silicon cells is due to the higher carrier mobilities in semiconducting materials which allows charge to be transported to the electrodes more quickly and efficiently. Polymer materials inhibit charge movement through the presence of electron traps such as oxygen.
The introduction of an inorganic semiconducting material such as CdSe increases the charge transfer.
"There have been tremendous advances in the last 10 years in making nanoscale devices in solution," said Alivisatos. "And they offer a new set of design tools."
Alivastos and his team used poly (3-hexylthiophene) (P3HT) as the polymer material. Its properties make it possible to produce flexible thin films in a room temperature process. They introduced CdSe nanorods into solution.
CdSe and P3HT have similar absorbtion spectra in the visible light range, from about 300nm to 720nm. Nanorods of different diameters absorb at different wavelengths, giving Alivastos and his team the ability to tune the absorbtion wavelength by controlling the nanorods' diameters.
The team now aims to boost the cells' performance further by improving the conductivity of the nanocrystal polymer interface, removing nanorod surface traps, aligning the nanorods perpendicular to the substrate and increasing their length beyond 60nm.
"We are hoping that polymer cells will overtake silicon in terms of efficiencies within 10 years," said Alivastos.
Princeton University Researchers Achieve New Record with Near Infrared Absorbing Organic Photovoltaic Cell-- Latest breakthrough sets stage for doubling utilization of sunlight for organic solar cells.
Global Photonic Energy Corporation (GPEC), the leading developer of Organic Photovoltaic (OPV™) technology for ultra-low cost high power solar cells, today announced that the Company’s research partners at Princeton University (Princeton) and the University of Southern California (USC) have achieved a new record in an organic solar cell that is responsive to light in the near infrared (NIR) range of the solar spectrum. NIR radiation is invisible to the human eye. Many so-called “night vision” devices operate by sensing infrared light which is emitted by warm objects and makes up a substantial portion of all energy reaching the earth from the sun. Under only NIR radiation, the Princeton solar cell would appear to be generating power in the dark – as the human eye is only sensitive to visible light.
This latest achievement is the highest level of conversion performance yet achieved for an organic solar cell in the IR portion of the solar spectrum. The Company’s researchers detail this latest achievement in the December 2, 2005 issue of Applied Physics Letters.
The Global thirst for energy is continually expanding. Renewable energy sources have experienced rapid growth in recent years as costs have improved. Global solar cell production has grown over 20% annually for the last 20 year reaching sales of $6 billion in 2004. This strong growth has resulted in a world-wide shortage of semiconductor silicon driving 2005 solar cell prices higher. Cost is a critical factor in the continued expansion of the solar cell industry. Currently, solar generated power is four to six times more expensive to consumers than coal generated power.
Traditionally, photovoltaic or “solar” cells have been constructed of an inorganic semiconductor like silicon. Efficient silicon based devices, especially of large surface area, are difficult and expensive to produce. They are fragile, heavy and opaque – limiting applications and potential uses. Thus, while the cost of silicon solar cells has dropped dramatically since the 1950’s – further reductions and new capabilities are needed for additional market penetration and broader adoption.
Recent efforts have focused on the use of “organic” materials. Organic semiconductors contain the ubiquitous element Carbon and are capable of achieving ultra-low cost solar power generation that is competitive with traditional fossil-fuel sources. Organic materials have the potential to achieve ultra-low cost production costs and high power output. The materials are ultra-thin and flexible and can be applied to large, curved or spherical surfaces. Because the layers are so thin, transparent solar cells can be applied to windows creating power-generating glass that retains its basic functionality.
One challenge for organic solar cells has been the efficient capture and conversion of sunlight. Sunlight consists of photons (particles of light) that are delivered across a spectrum that includes invisible ultraviolet (UV) light, the visible spectrum of colors – violet, indigo, blue, green, yellow, orange and red -- and the invisible infrared or IR spectrum. The amount of incoming photons across the UV, visible and IR spectrums is about 4%, 51% and 45%, respectively. The photons absorbed by a solar cell directly impacts the power output. To achieve high power output, solar devices must take advantage of as much of the solar spectrum as possible. Typical organic solar cells absorb only a fraction of the visible portion of the solar spectrum. In fact, the best organic solar cells absorb and convert only about 1/3 of the total available light utilizing primarily the visible portion of the spectrum.
“This latest device demonstrates that significant power can be harvested from the IR and near-IR portion of the solar spectrum.“, said Dr. Stephen R. Forrest. “In fact, this novel approach has the potential to double the power output of organic solar devices with power harvested from the near-IR and IR portion of the solar spectrum. With this approach we are well on our way to power levels exceeding 100 watts per meter”, Forrest concluded.
Organic materials can be applied to virtually any surface using a method akin to spray painting. Production methods of this sort are easily adaptable to continuous and so called “roll-to-roll” manufacturing processes and hold the promise of dramatically reduced production costs.
Organic materials also can be used in flexible applications. GPEC’s proprietary OPV ™ technologies can be used to create photovoltaic cells of different colors or cells that act as window tinting in building integrated applications.
About Global Photonic Energy Corporation
Global Photonic Energy Corporation (GPEC) is the world leader in developing Organic Photovoltaic (OPV™) and Photo Fuel™ (Hydrogen) production technologies. GPEC is collaborating with world-class organizations to transform energy markets. GPEC has a long-standing research partnership with Princeton University and the University of Southern California.
GPEC was founded in 1994 by entrepreneur Sherwin I. Seligsohn. Mr. Seligsohn has been the Chairman of the Board and Chief Executive Officer of the Company since its inception. Mr. Seligsohn is also the founder, Chairman and Chief Executive Officer of Universal Display Corporation, a public company (NASDAQ: PANL), and American Biomimetics Corporation, a new materials sciences and technology venture group. Previously, Mr. Seligsohn founded and served as the Chairman of the Board and then Chairman Emeritus of InterDigital Communications Corporation (Formerly International Mobile Machines Corporation), a public company (NASDAQ: IDCC).
Global Photonic Energy Corporation is located at the Princeton Crossroads Corporate Center in Ewing, New Jersey, minutes away from its research partner at Princeton University.
Princeton University Researchers Achieve New Record with Near Infrared Absorbing Organic Photovoltaic Cell-- Latest breakthrough sets stage for doubling utilization of sunlight for organic solar cells.
Global Photonic Energy Corporation (GPEC), the leading developer of Organic Photovoltaic (OPV™) technology for ultra-low cost high power solar cells, today announced that the Company’s research partners at Princeton University (Princeton) and the University of Southern California (USC) have achieved a new record in an organic solar cell that is responsive to light in the near infrared (NIR) range of the solar spectrum. NIR radiation is invisible to the human eye. Many so-called “night vision” devices operate by sensing infrared light which is emitted by warm objects and makes up a substantial portion of all energy reaching the earth from the sun. Under only NIR radiation, the Princeton solar cell would appear to be generating power in the dark – as the human eye is only sensitive to visible light.
This latest achievement is the highest level of conversion performance yet achieved for an organic solar cell in the IR portion of the solar spectrum. The Company’s researchers detail this latest achievement in the December 2, 2005 issue of Applied Physics Letters.
The Global thirst for energy is continually expanding. Renewable energy sources have experienced rapid growth in recent years as costs have improved. Global solar cell production has grown over 20% annually for the last 20 year reaching sales of $6 billion in 2004. This strong growth has resulted in a world-wide shortage of semiconductor silicon driving 2005 solar cell prices higher. Cost is a critical factor in the continued expansion of the solar cell industry. Currently, solar generated power is four to six times more expensive to consumers than coal generated power.
Traditionally, photovoltaic or “solar” cells have been constructed of an inorganic semiconductor like silicon. Efficient silicon based devices, especially of large surface area, are difficult and expensive to produce. They are fragile, heavy and opaque – limiting applications and potential uses. Thus, while the cost of silicon solar cells has dropped dramatically since the 1950’s – further reductions and new capabilities are needed for additional market penetration and broader adoption.
Recent efforts have focused on the use of “organic” materials. Organic semiconductors contain the ubiquitous element Carbon and are capable of achieving ultra-low cost solar power generation that is competitive with traditional fossil-fuel sources. Organic materials have the potential to achieve ultra-low cost production costs and high power output. The materials are ultra-thin and flexible and can be applied to large, curved or spherical surfaces. Because the layers are so thin, transparent solar cells can be applied to windows creating power-generating glass that retains its basic functionality.
One challenge for organic solar cells has been the efficient capture and conversion of sunlight. Sunlight consists of photons (particles of light) that are delivered across a spectrum that includes invisible ultraviolet (UV) light, the visible spectrum of colors – violet, indigo, blue, green, yellow, orange and red -- and the invisible infrared or IR spectrum. The amount of incoming photons across the UV, visible and IR spectrums is about 4%, 51% and 45%, respectively. The photons absorbed by a solar cell directly impacts the power output. To achieve high power output, solar devices must take advantage of as much of the solar spectrum as possible. Typical organic solar cells absorb only a fraction of the visible portion of the solar spectrum. In fact, the best organic solar cells absorb and convert only about 1/3 of the total available light utilizing primarily the visible portion of the spectrum.
“This latest device demonstrates that significant power can be harvested from the IR and near-IR portion of the solar spectrum.“, said Dr. Stephen R. Forrest. “In fact, this novel approach has the potential to double the power output of organic solar devices with power harvested from the near-IR and IR portion of the solar spectrum. With this approach we are well on our way to power levels exceeding 100 watts per meter”, Forrest concluded.
Organic materials can be applied to virtually any surface using a method akin to spray painting. Production methods of this sort are easily adaptable to continuous and so called “roll-to-roll” manufacturing processes and hold the promise of dramatically reduced production costs.
Organic materials also can be used in flexible applications. GPEC’s proprietary OPV ™ technologies can be used to create photovoltaic cells of different colors or cells that act as window tinting in building integrated applications.
About Global Photonic Energy Corporation
Global Photonic Energy Corporation (GPEC) is the world leader in developing Organic Photovoltaic (OPV™) and Photo Fuel™ (Hydrogen) production technologies. GPEC is collaborating with world-class organizations to transform energy markets. GPEC has a long-standing research partnership with Princeton University and the University of Southern California.
GPEC was founded in 1994 by entrepreneur Sherwin I. Seligsohn. Mr. Seligsohn has been the Chairman of the Board and Chief Executive Officer of the Company since its inception. Mr. Seligsohn is also the founder, Chairman and Chief Executive Officer of Universal Display Corporation, a public company (NASDAQ: PANL), and American Biomimetics Corporation, a new materials sciences and technology venture group. Previously, Mr. Seligsohn founded and served as the Chairman of the Board and then Chairman Emeritus of InterDigital Communications Corporation (Formerly International Mobile Machines Corporation), a public company (NASDAQ: IDCC).
Global Photonic Energy Corporation is located at the Princeton Crossroads Corporate Center in Ewing, New Jersey, minutes away from its research partner at Princeton University.