Shown in figure 1, a lamp of this kind relies on the same principle that powered the old TVs using cathode-ray 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.

Novel ultraviolet light bulbs would be a particularly timely development, considering the recent ban on household appliances using mercury under the Minamata Convention, a United Nations treaty signed by 128 countries that came into effect in August 2017.

Among other products, the ban targets ultraviolet fluorescent tubes, widely used for greenhouse lighting and other applications.

The text above is a summary, you can read full article here.