Life of LED-Based White Light Sources

TLDR

LEDs can have very long lifespans, but poorly designed systems often fail early, largely due to heat at the p‑n junction. The study aims to elucidate the relationship between LED life and junction heat so manufacturers can design longer‑lasting systems. Researchers performed accelerated life tests on white LEDs from one manufacturer at various ambient temperatures, using exponential decay of light output to extrapolate lifespan, and repeated the procedure on high‑power LEDs from multiple manufacturers under similar conditions. LED life decreases exponentially as temperature rises, and different products exhibit markedly different lifespans.

Abstract

Even though light-emitting diodes (LEDs) may have a very long life, poorly designed LED lighting systems can experience a short life. Because heat at the p-n-junction is one of the main factors that affect the life of the LED, by knowing the relationship between life and heat, LED system manufacturers can design and build long-lasting systems. In this study, several white LEDs from the same manufacturer were subjected to life tests at different ambient temperatures. The exponential decay of light output as a function of time provided a convenient method to rapidly estimate life by data extrapolation. The life of these LEDs decreases in an exponential manner with increasing temperature. In a second experiment, several high-power white LEDs from different manufacturers were life-tested under similar conditions. Results show that the different products have significantly different life values.