Performance and Degradation of Commercial Ultraviolet-C Light-Emitting Diodes for Disinfection Purposes

Herein, the reliability of commercial ultraviolet-C (UV-C) light-emitting diodes (LEDs) subjected to constant current stress is reported. Electrical, optical, and spectral analyses are carried out on UV-C LEDs with an emission peak of 275 nm and a nominal optical power of 12 mW at 100 mA. Degradation tests are carried out at the maximum rated current, the double and at three times the maximum. The LED lifetime is found to be inversely proportional to the third power of the stress current density, indicating that the degradation mechanism might be activated by high-energy electrons arising from Auger-Meitner recombination. Electrical characterization indicates an increase in defect-related leakage, whereas the spectral analysis identifies a variation in two emission peaks which can be ascribed to a defect density increase in the active region and the p-gallium nitride (GaN) layer of the LEDs. A final remark comes from the strong dependence of lifetime on operating current: increasing current to lower the number of LEDs in a system is not an optimized strategy. In fact, this has a substantial impact on system lifetime, thus lowering the total number of permitted disinfections.