LED lighting has swept the world, appearing in smart homes, streetlamps and even swimming pools and hot tubs. Lauded for their energy efficiency, flexibility, and ease of use, they appear to be the gold standard in lighting.
Or are they?
Researchers from the Moscow Institute of Physics and Technology and Lebedev Physical Institute of the Russian Academy of Sciences have designed and tested a prototype cathodoluminescent lamp for general lighting. The new lamp, which relies on the phenomenon of field emission, is more reliable, durable, and luminous than incandescent lighting. And it is set to give LEDs a run for their money, too.
Ironically, cathodoluminescent lamps may seem like a step backward in technology; they rely on the same principle that powered cathode-ray television tubes.
A negatively charged electrode, or cathode, at one end of a vacuum tube serves as an electron gun. A potential difference of up to 10 kilovolts accelerates the emitted electrons toward a flat positively charged phosphor-coated electrode — the anode — at the opposite end of the tube. This electron bombardment results in light.
Cathodoluminescent lamps have the advantage of being able to emit light almost at any wavelength, from the red to ultraviolet, depending on which fluorescent material is used.
Cathodoluminescent UV light bulbs contain no mercury, making them cleaner than traditional fluorescent and compact fluorescent (CFL) bulbs, which were banned in 128 countries as of August 2017.
While mercury lamps have been largely phased out, certain industries still rely on them for things such as water treatment, air disinfection, and certain medical procedures.
“Cathodoluminescent lamps could be used in operating room decontamination, UV irradiation of throat and tonsils, and dental filling curing,” says Mikhail Danilkin of Lebedev Physical Institute, RAS.
However, just like the CRT television sets of old, past versions of cathodoluminescent light bulbs were bulky and slow to warm up.
The Russian researchers’ new version of field emission cathodes, however, require no warm-up. Instead, a cold cathode emits electrons under an electrostatic field alone, due to tunneling.
“Our field emission cathode is made of ordinary carbon,” says Professor Evgenii Sheshin, deputy chair of vacuum electronics at MIPT, who led the research team. “But this carbon is not used merely as a chemical, but rather as a structure. We found a way to fashion a structure from carbon fibers that is resistant to ion bombardment, outputs a high emission current, is technological and affordable in production.”