Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Beyond LEDs: Brighter, New Energy -Saving Flat Panel Lights Based on Carbon Nanotubes

15.10.2014

Planar light source using a phosphor screen with highly crystalline single-walled carbon nanotubes (SWCNTs) as field emitters demonstrates its potential for energy-efficient lighting device.

Even as the 2014 Nobel Prize in Physics has enshrined light emitting diodes (LEDs) as the single most significant and disruptive energy-efficient lighting solution of today, scientists around the world continue unabated to search for the even-better-bulbs of tomorrow.


N.Shimoi/Tohoku University

Planar light source device: Front

Enter carbon electronics.

Electronics based on carbon, especially carbon nanotubes (CNTs), are emerging as successors to silicon for making semiconductor materials. And they may enable a new generation of brighter, low-power, low-cost lighting devices that could challenge the dominance of light-emitting diodes (LEDs) in the future and help meet society’s ever-escalating demand for greener bulbs.

Scientists from Tohoku University in Japan have developed a new type of energy-efficient flat light source based on carbon nanotubes with very low power consumption of around 0.1 Watt for every hour’s operation--about a hundred times lower than that of an LED.

In the journal Review of Scientific Instruments, from AIP publishing, the researchers detail the fabrication and optimization of the device, which is based on a phosphor screen and single-walled carbon nanotubes as electrodes in a diode structure. You can think of it as a field of tungsten filaments shrunk to microscopic proportions.

They assembled the device from a mixture liquid containing highly crystalline single-walled carbon nanotubes dispersed in an organic solvent mixed with a soap-like chemical known as a surfactant. Then, they “painted” the mixture onto the positive electrode or cathode, and scratched the surface with sandpaper to form a light panel capable of producing a large, stable and homogenous emission current with low energy consumption.

“Our simple ‘diode’ panel could obtain high brightness efficiency of 60 Lumen per Watt, which holds excellent potential for a lighting device with low power consumption,” said Norihiro Shimoi, the lead researcher and an associate professor of environmental studies at the Tohoku University.

Brightness efficiency tells people how much light is being produced by a lighting source when consuming a unit amount of electric power, which is an important index to compare the energy-efficiency of different lighting devices, Shimoi said. For instance, LEDs can produce 100s Lumen per Watt and OLEDs (organic LEDs) around 40.

Although the device has a diode-like structure, its light-emitting system is not based on a diode system, which are made from layers of semiconductors, materials that act like a cross between a conductor and an insulator, the electrical properties of which can be controlled with the addition of impurities called dopants.

The new devices have luminescence systems that function more like cathode ray tubes, with carbon nanotubes acting as cathodes, and a phosphor screen in a vacuum cavity acting as the anode. Under a strong electric field, the cathode emits tight, high-speed beams of electrons through its sharp nanotube tips -- a phenomenon called field emission. The electrons then fly through the vacuum in the cavity, and hit the phosphor screen into glowing.

“We have found that a cathode with highly crystalline single-walled carbon nanotubes and an anode with the improved phosphor screen in our diode structure obtained no flicker field emission current and good brightness homogeneity,” Shimoi said.

Field emission electron sources catch scientists’ attention due to its ability to provide intense electron beams that are about a thousand times denser than conventional thermionic cathode (like filaments in an incandescent light bulb). That means field emission sources require much less power to operate and produce a much more directional and easily controllable stream of electrons.

In recent years, carbon nanotubes have emerged as a promising material of electron field emitters, owing to their nano-scale needle shape and extraordinary properties of chemical stability, thermal conductivity and mechanical strength.

Highly crystalline single-walled carbon nanotubes (HCSWCNT) have nearly zero defects in the carbon network on the surface, Shimoi explained. “The resistance of cathode electrode with highly crystalline single-walled carbon nanotube is very low. Thus, the new flat-panel device has smaller energy loss compared with other current lighting devices, which can be used to make energy-efficient cathodes that with low power consumption.”

“Many researchers have attempted to construct light sources with carbon nanotubes as field emitter,” Shimoi said. “But nobody has developed an equivalent and simpler lighting device.”

Considering the major step for device manufacture--the wet coating process is a low-cost but stable process to fabricate large-area and uniformly thin films, the flat-plane emission device has the potential to provide a new approach to lighting in people’s life style and reduce carbon dioxide emissions on the earth, Shimoi said.

The article, " Planar light source using a phosphor screen with single-walled carbon nanotubes as field emitters," is authored by Sharon Bahena-Garrido, Norihiro Shimoi, Daisuke Abe, Toshimasa Hojo, Yasumitsu Tanaka, Kazuyuki Tohji. It will be published in the journal REVIEW OF SCIENTIFIC INSTRUMENTS on October 14, 2014 (DOI: 10.1063/1.4895913). After that date, it can be accessed at:
http://scitation.aip.org/content/aip/journal/rsi/85/10/10.1063/1.4895913

ABOUT THE JOURNAL

The journal Review of Scientific Instruments, which is produced by AIP Publishing, presents innovation in instrumentation and methods across disciplines. See: http://rsi.aip.org/

Zhengzheng Zhang | newswise

More articles from Power and Electrical Engineering:

nachricht Energy hybrid: Battery meets super capacitor
01.12.2016 | Technische Universität Graz

nachricht Tailor-Made Membranes for the Environment
30.11.2016 | Forschungszentrum Jülich

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>