Research challenges to ultra-efficient inorganic solid-state lighting

Solid‐state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next several years. This efficiency is significantly higher than that of traditional lighting technologies, giving solid‐state lighting the potential to enable significant reduction in the rate of world energy consumption. Further, there is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even more significant reduction in world energy usage. In this article, we discuss in some detail: (a) the several approaches to inorganic solid‐state lighting that could conceivably achieve “ultra‐high,” 70% or greater, efficiency, and (b) the significant research questions and challenges that would need to be addressed if one or more of these approaches were to be realized.