Materials challenges for solid-state lighting

The use of highly efficient semiconductor light-emitting diodes (LEDs) suitable for illumination applications will enable huge energy savings and have a very positive effect on the environment. This talk will discuss materials challenges in solid-state lighting, including a new class of materials, low-refractive-index materials, with refractive indices much lower than conventional materials. Arrays of SiO$_{2}$ nanorods are shown to have unprecedented low refractive indices ($<$~1.10) yet viable thin-film properties. Their use for omni-directional reflectors and the resulting improvement in LED light-extraction efficiency will be discussed. We will show that optimized phosphor distributions in white LED lamps, particularly remote-phosphor distributions, combined with diffuse reflectors, strongly enhance luminous efficiency. Finally, we will discuss materials issues that limit the efficiency of ultraviolet (UV) light emitters.