Beyond LEDs: Brighter & More Efficient

Japanese scientists have used carbon nanotubes to develop a new light source that is hundred times more energy-efficient than LEDs.

AsianScientist (Oct. 21, 2014) – Scientists from Tohoku University in Japan have developed a new type of energy-efficient flat light source based on carbon nanotubes with a power consumption that is about hundred times lower than that of an LED. The findings have been published in Review of Scientific Instruments.

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.

Electronics based on carbon, especially carbon nanotubes, are emerging as successors to silicon for making semiconductor materials; owing to their nano-scale needle shape and extraordinary properties of chemical stability, thermal conductivity and mechanical strength. They may expected to enable a new generation of brighter, low-power and low-cost lighting devices that could challenge the dominance of light-emitting diodes in the future while also helping to meet ever-escalating demand for ‘greener’ bulbs.

The device here is based on a phosphor screen and single-walled carbon nanotubes as electrodes in a diode structure, akin to a field of tungsten filaments shrunk to microscopic proportions.

The research team assembled the device from a mixture containing highly crystalline single-walled carbon nanotubes dispersed in an organic solvent, which were then combined 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 Professor Shimoi Norihiro, the lead researcher and an associate professor of environmental studies at the Tohoku University.

Brightness efficiency indicates 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, Prof. Shimoi said. For instance, LEDs can produce 100s Lumen per Watt and OLEDs (organic LEDs) around 40.

Manufacturing the device is a low-cost but stable process to fabricate large-area and uniformly thin films. As such, the researchers hope that their flat-plane emission device has the potential to provide a new approach to lighting in people’s life style, as well as reduce carbon dioxide emissions on the earth.

The full article can be found at: Bahena-Garrido et al. (2014) Planar Light Source Using a Phosphor Screen with Single-walled Carbon Nanotubes as Field Emitters.

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Source: American Institute of Physics; Photo: photonic.syntrophy/Flickr/CC.
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