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.