Invited talk: Promises and challenges in light-emitting diodes for 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 illustrate the new world of lighting including the pervasive changes to be expected in lighting, displays, communications, and biotechnology. The presentation will also address the formidable challenges that must be addressed to further advance solid-state lighting technology. These challenges offer opportunities for research and innovation. Specific challenges include light management and carrier transport. As an example, we will discuss new optical thin-film materials with a tunable refractive index. We will also discuss the hotly debated efficiency droop, that is, the decreasing LED efficiency at high currents.