Tweet
                                               

New energy-efficient carbon nanotube light could challenge LEDs

Overview of a stand-alone flat plane-emission diode panel.
Overview of a stand-alone flat plane-emission diode panel.

UPDATED: Scientists have created a flat-panel light based on carbon nanotubes that could in future challenge LEDs in terms of energy efficiency.

The new type of energy-efficient light source has been developed by researchers at Japan’s Tohuku University, and has a power consumption of just 0.1 watts for every hour’s operation, about a hundred times less than that of an LED, according to the American Institute of Physics.

The discovery has been detailed in the journal Review of Scientific Instruments, where the researchers describe the fabrication and optimisation of the device, which is based on a phosphor screen and single-walled carbon nanotubes as electrodes in a diode structure.

“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,” lead researcher and associate professor of environmental studies at Tohoku University Norihiro Shimoi said.

“We were able to achieve a high brightness efficiency of around 60 lm/W with a green phosphor employed in a flat-plane emission panel at under 0.1 W.”

Brightness efficiency, Mr Shimoi said, was an important index in comparing the energy efficiency of different light sources, and the innovation was still behind LEDs in this regard, which can produce over 100 lm/W. The novel device shows promise, however.

Although the device has a diode-like structure, its light-emitting system is not based on a diode system. The new device has a luminescence system 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 high-speed beams of electrons through its sharp nanotube tips – a phenomenon called field emission. The electrons fly through the vacuum in the cavity and hit the phosphor screen, causing it to glow.

“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,” Mr Shimoi said.

He said the resistance of cathode electrodes with highly crystalline single-walled carbon nanotubes was very low.

“Thus, the new flat-panel device has smaller energy loss compared with other current lighting devices.”

The process of manufacture was low cost and stable, Mr Shimoi said, creating the potential for a new approach to lighting and the reduction of carbon emissions.

Comments

5 Responses to “New energy-efficient carbon nanotube light could challenge LEDs”

  • Phil says:

    The title of this article is misleading. These panels are currently about half as efficient as a
    LED. This is a promising start for a new technology but they currently have 100 times lower power consumption only because they produce 200 times less light!

  • Graeme Ambrose says:

    60 lumens per watt is not that efficient. LEDs are achieving in excess of 120 lumens per watt as do metal halide.

  • Steve Ford says:

    As Scotty said, “I cannot break the laws of physics Captain”, nor can Japanese researchers. Your article’s headline and opening paragraph are misleading and suggests that lights have 2000% efficiency…in other words the output energy is greater than the input. The article continues after this initial doozy to present some interesting developments that, thankfully, don’t break the laws of physics.

    • Tina Perinotto says:

      We’ve amended the article. Please also see what the American Institute of Physics says, http://www.newswise.com/articles/beyond-leds-brighter-new-energy-saving-flat-panel-lights-based-on-carbon-nanotubes

      • Lance Turner says:

        Except that the tech info in this article is still all kinds of wrong, especially: “has a power consumption of just 0.1 watts for every hour’s operation, about a hundred times lower than that of an LED”.

        Watts is an instantaneous measure of power. Taken over time you must use watt-hours, which is a measure of the energy used.

        Further, LEDs vary in rated power from a few milliwatts to hundreds of watts, so the second part of that sentence is just rubbish and completely meaningless.

        And, of course, there’s “a hundred times lower than that of an LED” which is nonsensical. Nothing can be 100 times lower or 100 times smaller, it is 1/100th of the size/power/whatever, or 1% or some other sensible term, but not 100 times lower. I realise that this is a common error with many journalists, many of whom have seemingly had little or no science education, but it is nonsensical rubbish.

        Then “Thus, the new flat-panel device has smaller energy loss compared with other current lighting devices”. Err, no. If the efficiency is lower then the losses are higher, it’s not rocket science.

        And “The process of manufacture was low cost and stable, Mr Shimoi said, creating the potential for a new approach to lighting and the reduction of carbon emissions.” That device is a lot more complicated than a LED, which is simply a chip mounted on a metal or ceramic substrate and enclosed in a protective case. LEDs are very cheap and extremely efficient, this device doesn’t even come close on any front. The best laboratory LEDs are over 300 lumens per watt (http://www.cree.com/News-and-Events/Cree-News/Press-Releases/2014/March/300LPW-LED-barrier) and commercially available devices at 200 L/W (Cree XP-L series).

        Of course, this is early days for the device in this article, but they seem to be reinventing the wheel. Which is the biggest problem with many researchers – they come up with new ways to do things that are already done very well simply to keep themselves in research grants. I know that sounds cynical, but it is very common practice, it’s a pity journos can’t filter out this stuff…

Comments are closed.

More Articles on this Topic