Japanese make planar light source that is one hundred times more energy efficient than an LED

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.

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.

[EETimes] The lighting panel powered by carbon nanotube field emitters stimulating a phosphor to glow will be less expensive than light-emitting diode (LED) lighting and brighter than organic light emitting diode (OLED) panels, according to Prof. Norihiro Shimoi, lead researcher at Tohoku University in Japan.

So far, Shimoi’s lab has demonstrated a prototype — similar in design to a flat version of the cathode ray tubes (CRTs) of old — that achieves the goal of low power but has yet to be optimized to reach 60 lumens per watt.

“This prototype is designed as a lighting (illumination) lamp with very low power consumption of 1/100 against LED devices, and it will not be released until 2019,” Shimoi told us.

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.

The Review of Scientific Instruments 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.

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