Overview of degradation mechanims in LED-based products

PROJECT TITLE: Overview of degradation mechanims in LED-based products

In this project degradation mechanisms of optical materials, used in light emitting diodes (LEDs)-based products, are reviewed. LEDs provide brighter displays on electronic devices and consume less power, compared to conventional light sources. The LED technology is expected to replace traditional lighting sources such as fluorescent, halogen and conventional incandescent bulbs in many applications, owing to the fact that it is comparatively much more reliable in most indoor and outdoor applications. This paper is aiming at describing the influences of structure and application conditions on the degradation mechanisms of optical organic materials in LEDs which lead to the lumen depreciation, discolouration and colour shift. The contributions of different degradation mechanisms of optical and package materials in LED-based products to the lumen depreciation and colour shift are methodically reviewed. The kinetics of degradation in real life applications is obviously relatively slow and in most cases it takes several years to observe an obvious deterioration of the optical outputs of the package. The concept of accelerated degradation tests, based on available standards, is also discussed and the way how results of an accelerated test can be used in real time applications is explained.