Does deep ultraviolet UVC-LED produce ozone when working?
Does not produce.
1. How does ultraviolet light produce ozone?
Theoretically, the photon energy is higher than the bond energy to break the chemical bond. Therefore, ultraviolet rays with a wavelength shorter than 243 nm can excite oxygen in the air or water to produce ozone. UVC-LEDs with wavelengths higher than 243 nm do not produce ozone.
Low-pressure mercury lamps produce ozone, because the vapor pressure of 1.3～13P low-pressure mercury lamps naturally has 185nm vacuum ultraviolet rays in the light emission spectrum. This ultraviolet light will stimulate the oxygen in the air to produce a chemical reaction and turn it into ozone. This essentially means that ultraviolet rays break the oxygen-oxygen covalent bond in the oxygen molecule, and then combine with the oxygen molecule to form O3. UVC-LED will not produce ozone, because the covalent bond energy of oxygen and oxygen is as high as 5.1eV, which requires ultraviolet rays with a wavelength of at least shorter than 243nm to be interrupted, and eventually ozone is generated.
2. Why doesn't LED produce ozone?
The low-pressure mercury lamp increases the energy level transition probability of short-wave ultraviolet by controlling the vapor pressure, but it will also be accompanied by other transitions, mainly emitting light at 254 and 185nm. UVC-LED first energy level transition probability is dominant, so it emits pure light, and the common UVC-LED wavelength is higher than 255 nm.
The low-pressure mercury lamp is a gas light source, and its excited state energy level position has been determined by the substance of mercury. So although there are high-pressure, medium-pressure, and low-pressure mercury lamps, the difference in vapor pressure is mainly to adjust the probability of transition between different excited states, that is, the relative intensity of different characteristic peaks. Therefore, low-pressure mercury lamps mainly emit light at 254 and 185nm. UVC-LED is an AlGaN semiconductor light-emitting diode with a quantum well structure. The E0 transition is dominant, and there is only one peak wavelength, such as 275nm. It can be found that the FWHM of the main peak of the deep ultraviolet LED spectrum is significantly lower than that of blue light, which is also due to the quantum well luminescence Compared with multi-size quantum dot light-emitting devices, the electronic transition is more unitary. Because the current UVC-LEDs that can be mass-produced have luminous wavelengths that are not lower than 243nm, the deep-ultraviolet UVC-LEDs used for sterilization and disinfection do not produce ozone.
