Defect Dynamics and Internal Quantum Efficiency Decay Resultant Ultraviolet C‐Band Light‐Emitting Diode Lifetime Performance

The internal quantum efficiency (IQE) decay resultant lifetime performance of ultraviolet C‐band (UVC) light‐emitting diodes (LEDs) is investigated, and an LED lifetime model is deduced assuming that defect generation is the sole cause for IQE decay and the defect generation process is to maximize the entropy of the defects. The proposed model reveals that the lifetime of an LED is proportional to its radiative recombination coefficient and inversely proportional to the product of its initial nonradiative recombination coefficient and defect growth interest rate, thus providing explicit dependence of the lifetime on the LED junction temperature and current density. The model fits excellently well to full sets of lifetime measurement data, which were collected from UVC LEDs stressed at different currents and different ambient temperatures for 2500 up to ≈10 000 h. The sensitivity of the lifetime to the junction temperature and current density is revealed for some UVC LEDs. Using the model, a lifetime of ≈96 000 h is projected to maintain 70% of the initial optical output power for a UVC LED based on a stress test for ≈10 000 h.