Blog - Category: carbon nanotube

Carbon nanotube lighting, better than LED?

Scientists working in Japan may have developed a light source more efficient than LED.

Tohuko University in Japan describe the fabrication of a device which is based on a phosphor screen and single-walled carbon nanotubes as electrodes in a diode structure. It has been suggested that the light emitting source can be thought of as a field of tungsten filaments shrunk to microscopic proportions.

Planar light source device through a neutral density filter. Photo credit: N.Shimoi, Tohoku University

The scientists assembled the device from a mixture liquid containing highly crystalline single-walled carbon nanotubes dispersed in an organic solvent mixed with surfactant – a soap-like chemical. Then, they painted this 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 with low energy consumption.

It has been argued that the way the light source functions is more like a cathode ray tube than a diode. The carbon nanotubes are said to act like cathodes while a phosphor screen in a vacuum cavity acts as the anode.

Single-walled carbon nanotubes are said to have zero defects in the carbon network on the surface and extremely low resistance, meaning energy losses in the lighting device are extremely low.

Lead researcher and associate professor of environmental studies at Tohuko University, Norihiro Shimoi, told AIP Publishing that the ‘diode’ panel had a brightness efficiency of 60 lumens per watt meaning it held ‘excellent potential for a lighting device with low power consumption’. The light source was also found to be flicker free and to provide ‘good brightness homogeneity’ while the wet-coating process was said to be low cost.

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

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