PROJECT TITLE :

Short- and Long-Term Reliability Studies of Broadband Phosphor-Converted Red, Green, and White Light-Emitting Diodes

ABSTRACT:

Phosphor-converted lightweight-emitting diodes (LEDs) are now widely employed in all kinds of illumination applications. Their structures are a lot of involved compared with that of chip-solely band-gap LEDs. We describe the extra producing steps concerned in phosphor-converted LED manufacturing and how these additional features impact the reliability of such devices. Our studies checked out each the short-term and long-term behavior of phosphor-based LEDs. Devices were tested for times starting from a few hours to forty 000 hours. Some tests were performed at elevated temperatures of up to 70 °C. The light outputs of LEDs were studied as functions of your time, temperature, and drive currents of up to a pair of.5 A. Shifts in chromaticity point of these LEDs were also investigated as functions of drive current and, therefore, LED die temperature. These studies lead to several conclusions regarding the reliability and degradation behavior of phosphor-based mostly LEDs that are elaborated during this paper.