Promises and challenges in light-emitting diodes for high-power lighting applications

Lighting technologies based on semiconductor light-emitting diodes (LEDs) offer unprecedented promises that include three major benefits: (i) Gigantic energy savings enabled by efficient conversion of electrical energy to optical energy; (ii) Substantial positive contributions to sustainability through reduced emissions of global-warming gases, acid-rain gases, and toxic substances such as mercury; and (iii) The creation of new paradigms in lighting driven by the unique controllability of solid-state lighting sources. Due to the powerful nature of these benefits, the transition from conventional lighting sources to solid-state lighting is virtually assured. This presentation will discuss one of the formidable challenges of LED technology: The efficiency droop, that is, the decreasing GaInN LED efficiency occurring at high current densities. We will discuss the origin of the efficiency droop as well as ways to reduce the droop.