Optical Power Degradation Related to Turn-On in Commercial 265 nm UV-C LEDs

In this work, we investigated the optical power drops present after the turn-on of high-power commercial UV-C LEDs. We demonstrated that degradation occurs in correspondence with the turn-on of the device. By slowing the turn-on transient, 5.8 mA/s rate, we demonstrated that even a gradual increase in the current could not prevent the phenomenon, indicating that it is not correlated to the sudden change in temperature and electric field. From thermal characterization and voltage transients, we extrapolated a high thermal coefficient for this UV LED with respect to the visible counterpart. Moreover, from a visual inspection, we observed a degradation of the encapsulation, which could be caused by both the high temperatures reached and by the energy of the emitted photons.