Why is UVLED light source a cold light source?

As a cold light source, UVLED is UV compared with traditional mercury lamp, which means that the temperature irradiated by UV LED is obviously lower than that irradiated by traditional mercury lamp, and the analysis is as follows:

LED ultraviolet light source has a single wavelength, while traditional ultraviolet lamps have a wide band of 200-400nm. According to different applications (ultraviolet curing, ultraviolet disinfection and sterilization, ultraviolet plant lamps), LED ultraviolet rays can be made into corresponding wavelengths according to needs, while mercury lamps cover the whole band. In fact, it is useful that the useless wave band in the mercury lamp is absorbed by the product and converted into heat, especially infrared radiation, thus increasing the surface temperature of the irradiated object.