Material Degradation in Solid State Lightening Applications (MatDegSSL)
During service LEDs could fail due to the degradation of each of the components including lens, encapsulant, chip, phosphor layer and interconnects. One of the most important degradation mechanisms is the yellowing of the LED plastic lens and encapsulants, which could result in a significant lumen depreciation and change in chromatic properties of the LED. The yellowing of encapsulant/lens could be ascribed to prolonged exposure to short wavelength emission (blue/UV radiation), temperature, and the presence of phosphors, with temperature having a very crucial influence. Temperature increase during service could be due to a combination of junction temperature, ambient temperature and LED self-heating. The main aim of this project is finding out the main chemical optical and reason of lumen depreciation and yellowing.