World's most efficient flexible organic light-emitting diodes created on plastic

ScienceDaily (Oct. 31, 2011) — Researchers in the University of Toronto's Department of Materials Science & Engineering have developed the world's most efficient organic light-emitting diodes (OLEDs) on plastic. This result enables a flexible form factor, not to mention a less costly, alternative to traditional OLED manufacturing, which currently relies on rigid glass.

The results are reported online in the latest issue of Nature Photonics.

OLEDs provide high-contrast and low-energy displays that are rapidly becoming the dominant technology for advanced electronic screens. They are already used in some cell phone and other smaller-scale applications.

Current state-of-the-art OLEDs are produced using heavy-metal doped glass in order to achieve high efficiency and brightness, which makes them expensive to manufacture, heavy, rigid and fragile.

"For years, the biggest excitement behind OLED technologies has been the potential to effectively produce them on flexible plastic," says Materials Science & Engineering Professor Zheng-Hong Lu, the Canada Research Chair (Tier I) in Organic Optoelectronics.

Using plastic can substantially reduce the cost of production, while providing designers with a more durable and flexible material to use in their products.

The research, which was supervised by Professor Lu and led by PhD Candidates Zhibin Wang and Michael G. Helander, demonstrated the first high-efficiency OLED on plastic. The performance of their device is comparable with the best glass-based OLEDs, while providing the benefits offered by using plastic.

"This discovery, unlocks the full potential of OLEDs, leading the way to energy-efficient, flexible and impact-resistant displays," says Professor Lu.

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The above story is reprinted from materials provided by University of Toronto Faculty of Applied Science & Engineering.

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Journal Reference:

Z. B. Wang, M. G. Helander, J. Qiu, D. P. Puzzo, M. T. Greiner, Z. M. Hudson, S. Wang, Z. W. Liu, Z. H. Lu. Unlocking the full potential of organic light-emitting diodes on flexible plastic. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.259

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Researchers use carbon nanotubes to make solar cells affordable, flexible

ScienceDaily (Sep. 27, 2011) — Researchers from Northwestern University have developed a carbon-based material that could revolutionize the way solar power is harvested. The new solar cell material -- a transparent conductor made of carbon nanotubes -- provides an alternative to current technology, which is mechanically brittle and reliant on a relatively rare mineral.

Due to Earth's abundance of carbon, carbon nanotubes have the potential to boost the long-term viability of solar power by providing a cost-efficient option as demand for the technology increases. In addition, the material's mechanical flexibility could allow solar cells to be integrated into fabrics and clothing, enabling portable energy supplies that could impact everything from personal electronics to military operations.

The research, headed by Mark C. Hersam, professor of materials science and engineering and professor of chemistry, and Tobin J. Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and professor of materials science and engineering, is featured on the cover of the October 2011 issue of Advanced Energy Materials, a new journal that specializes in science about materials used in energy applications.

Solar cells are composed of several layers, including a transparent conductor layer that allows light to pass into the cell and electricity to pass out; for both these actions to occur, the conductor must be both electrically conductive and also optically transparent. Few materials concurrently possess both of these properties.

Currently, indium tin oxide is the dominant material used in transparent conductor applications, but the material has two potential limitations. Indium tin oxide is mechanically brittle, which precludes its use in applications that require mechanical flexibility. In addition, Indium tin oxide relies on the relatively rare element indium, so the projected increased demand for solar cells could push the price of indium to problematically high levels.

"If solar technology really becomes widespread, as everyone hopes it will, we will likely have a crisis in the supply of indium," Hersam said. "There's a great desire to identify materials -- especially earth-abundant elements like carbon -- that can take indium's place in solar technology."

Hersam and Marks' team has created an alternative to indium tin oxide using single-walled carbon nanotubes, tiny, hollow cylinders of carbon just one nanometer in diameter.

The researchers have gone further to determine the type of nanotube that is most effective in transparent conductors. Nanotubes' properties vary depending on their diameter and their chiral angle, the angle that describes the arrangement of carbon atoms along the length of the nanotube. These properties determine two types of nanotubes: metallic and semiconducting.

Metallic nanotubes, the researchers found, are 50 times more effective than semiconducting ones when used as transparent conductors in organic solar cells.

"We have now identified precisely the type of carbon nanotube that should be used in this application," Hersam said.

Because carbon nanotubes are flexible, as opposed to the brittle indium tin oxide, the researchers' findings could pave the way for many new applications in solar cells. For example, the military could incorporate the flexible solar cells into tent material to provide solar power directly to soldiers in the field, or the cells could be integrated into clothing, backpacks, or purses for wearable electronics.

"With this mechanically flexible technology, it's much easier to imagine integrating solar technology into everyday life, rather than carrying around a large, inflexible solar cell," Hersam said.

Researchers are now examining other layers of the solar cell to explore also replacing these with carbon-based nanomaterials.

Besides Hersam and Marks, other authors include Timothy P. Tyler, Ryan E. Brock, and Hunter J. Karmel. This work was supported by the Argonne Northwestern-Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Timothy P. Tyler, Ryan E. Brock, Hunter J. Karmel, Tobin J. Marks, Mark C. Hersam. Organic Solar Cell Characterization: Electronically Monodisperse Single-Walled Carbon Nanotube Thin Films as Transparent Conducting Anodes in Organic Photovoltaic Devices (Adv. Energy Mater. 5/2011). Advanced Energy Materials, 2011; 1 (5): 701 DOI: 10.1002/aenm.201190021

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Researchers use carbon nanotubes to make solar cells affordable, flexible

ScienceDaily (Sep. 27, 2011) — Researchers from Northwestern University have developed a carbon-based material that could revolutionize the way solar power is harvested. The new solar cell material -- a transparent conductor made of carbon nanotubes -- provides an alternative to current technology, which is mechanically brittle and reliant on a relatively rare mineral.

Due to Earth's abundance of carbon, carbon nanotubes have the potential to boost the long-term viability of solar power by providing a cost-efficient option as demand for the technology increases. In addition, the material's mechanical flexibility could allow solar cells to be integrated into fabrics and clothing, enabling portable energy supplies that could impact everything from personal electronics to military operations.

The research, headed by Mark C. Hersam, professor of materials science and engineering and professor of chemistry, and Tobin J. Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and professor of materials science and engineering, is featured on the cover of the October 2011 issue of Advanced Energy Materials, a new journal that specializes in science about materials used in energy applications.

Solar cells are composed of several layers, including a transparent conductor layer that allows light to pass into the cell and electricity to pass out; for both these actions to occur, the conductor must be both electrically conductive and also optically transparent. Few materials concurrently possess both of these properties.

Currently, indium tin oxide is the dominant material used in transparent conductor applications, but the material has two potential limitations. Indium tin oxide is mechanically brittle, which precludes its use in applications that require mechanical flexibility. In addition, Indium tin oxide relies on the relatively rare element indium, so the projected increased demand for solar cells could push the price of indium to problematically high levels.

"If solar technology really becomes widespread, as everyone hopes it will, we will likely have a crisis in the supply of indium," Hersam said. "There's a great desire to identify materials -- especially earth-abundant elements like carbon -- that can take indium's place in solar technology."

Hersam and Marks' team has created an alternative to indium tin oxide using single-walled carbon nanotubes, tiny, hollow cylinders of carbon just one nanometer in diameter.

The researchers have gone further to determine the type of nanotube that is most effective in transparent conductors. Nanotubes' properties vary depending on their diameter and their chiral angle, the angle that describes the arrangement of carbon atoms along the length of the nanotube. These properties determine two types of nanotubes: metallic and semiconducting.

Metallic nanotubes, the researchers found, are 50 times more effective than semiconducting ones when used as transparent conductors in organic solar cells.

"We have now identified precisely the type of carbon nanotube that should be used in this application," Hersam said.

Because carbon nanotubes are flexible, as opposed to the brittle indium tin oxide, the researchers' findings could pave the way for many new applications in solar cells. For example, the military could incorporate the flexible solar cells into tent material to provide solar power directly to soldiers in the field, or the cells could be integrated into clothing, backpacks, or purses for wearable electronics.

"With this mechanically flexible technology, it's much easier to imagine integrating solar technology into everyday life, rather than carrying around a large, inflexible solar cell," Hersam said.

Researchers are now examining other layers of the solar cell to explore also replacing these with carbon-based nanomaterials.

Besides Hersam and Marks, other authors include Timothy P. Tyler, Ryan E. Brock, and Hunter J. Karmel. This work was supported by the Argonne Northwestern-Northwestern Solar Energy Research Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

Recommend this story on Facebook, Twitter,
and Google +1:

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

Timothy P. Tyler, Ryan E. Brock, Hunter J. Karmel, Tobin J. Marks, Mark C. Hersam. Organic Solar Cell Characterization: Electronically Monodisperse Single-Walled Carbon Nanotube Thin Films as Transparent Conducting Anodes in Organic Photovoltaic Devices (Adv. Energy Mater. 5/2011). Advanced Energy Materials, 2011; 1 (5): 701 DOI: 10.1002/aenm.201190021

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Revolutionary new paper computer shows flexible future for smartphones and tablets

ScienceDaily (May 4, 2011) — The world's first interactive paper computer is set to revolutionize the world of interactive computing.

"This is the future. Everything is going to look and feel like this within five years," says creator Roel Vertegaal, the director of Queen's University Human Media Lab. "This computer looks, feels and operates like a small sheet of interactive paper. You interact with it by bending it into a cell phone, flipping the corner to turn pages, or writing on it with a pen."

The smartphone prototype, called PaperPhone is best described as a flexible iPhone -- it does everything a smartphone does, like store books, play music or make phone calls. But its display consists of a 9.5 cm diagonal thin film flexible E Ink display. The flexible form of the display makes it much more portable that any current mobile computer: it will shape with your pocket.

Dr. Vertegaal will unveil his paper computer on May 10 at 2 pm at the Association of Computing Machinery's CHI 2011 (Computer Human Interaction) conference in Vancouver -- the premier international conference of Human-Computer Interaction.

Being able to store and interact with documents on larger versions of these light, flexible computers means offices will no longer require paper or printers.

"The paperless office is here. Everything can be stored digitally and you can place these computers on top of each other just like a stack of paper, or throw them around the desk" says Dr. Vertegaal.

The invention heralds a new generation of computers that are super lightweight, thin-film and flexible. They use no power when nobody is interacting with them. When users are reading, they don't feel like they're holding a sheet of glass or metal.

An article on a study of interactive use of bending with flexible thinfilm computers is to be published at the conference in Vancouver, where the group is also demonstrating a thinfilm wristband computer called Snaplet.

The development team included researchers Byron Lahey and Win Burleson of the Motivational Environments Research Group at Arizona State University (ASU), Audrey Girouard and Aneesh Tarun from the Human Media Lab at Queen's University, Jann Kaminski and Nick Colaneri, director of ASU's Flexible Display Center, and Seth Bishop and Michael McCreary, the VP R&D of E Ink Corporation.

For more information, articles, videos, and high resolution photos, visit http://www.humanmedialab.org/paperphone/ and http://www.youtube.com/watch?v=Rl-qygUEE2c

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Queen's University.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Revolutionary new paper computer shows flexible future for smartphones and tablets

ScienceDaily (May 4, 2011) — The world's first interactive paper computer is set to revolutionize the world of interactive computing.

"This is the future. Everything is going to look and feel like this within five years," says creator Roel Vertegaal, the director of Queen's University Human Media Lab. "This computer looks, feels and operates like a small sheet of interactive paper. You interact with it by bending it into a cell phone, flipping the corner to turn pages, or writing on it with a pen."

The smartphone prototype, called PaperPhone is best described as a flexible iPhone -- it does everything a smartphone does, like store books, play music or make phone calls. But its display consists of a 9.5 cm diagonal thin film flexible E Ink display. The flexible form of the display makes it much more portable that any current mobile computer: it will shape with your pocket.

Dr. Vertegaal will unveil his paper computer on May 10 at 2 pm at the Association of Computing Machinery's CHI 2011 (Computer Human Interaction) conference in Vancouver -- the premier international conference of Human-Computer Interaction.

Being able to store and interact with documents on larger versions of these light, flexible computers means offices will no longer require paper or printers.

"The paperless office is here. Everything can be stored digitally and you can place these computers on top of each other just like a stack of paper, or throw them around the desk" says Dr. Vertegaal.

The invention heralds a new generation of computers that are super lightweight, thin-film and flexible. They use no power when nobody is interacting with them. When users are reading, they don't feel like they're holding a sheet of glass or metal.

An article on a study of interactive use of bending with flexible thinfilm computers is to be published at the conference in Vancouver, where the group is also demonstrating a thinfilm wristband computer called Snaplet.

The development team included researchers Byron Lahey and Win Burleson of the Motivational Environments Research Group at Arizona State University (ASU), Audrey Girouard and Aneesh Tarun from the Human Media Lab at Queen's University, Jann Kaminski and Nick Colaneri, director of ASU's Flexible Display Center, and Seth Bishop and Michael McCreary, the VP R&D of E Ink Corporation.

For more information, articles, videos, and high resolution photos, visit http://www.humanmedialab.org/paperphone/ and http://www.youtube.com/watch?v=Rl-qygUEE2c

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Queen's University.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here