Solid-state lighting—a benevolent technology

TLDR

Solid‑state light sources are transforming general lighting by offering near‑unit power efficiency and unprecedented control over spectral composition and temporal modulation, features that set them apart from conventional lamps. The review aims to evaluate how solid‑state lighting affects energy use, the environment, and emerging applications, while examining key technical advances such as phosphor distribution, reflector design, and low‑index thin‑film materials. The authors analyze solid‑state lighting by assessing its energy and environmental implications and by surveying technical innovations—including novel phosphor distributions, omni‑directional reflectors, and ultra‑low‑index thin‑film materials—that drive progress. Solid‑state lighting promises substantial reductions in global energy use, greenhouse‑gas and pollutant emissions, and offers new functionalities, with low‑index materials further accelerating progress.

Abstract

Solid-state light sources are in the process of profoundly changing the way humans generate light for general lighting applications. Solid-state light sources possess two highly desirable features, which set them apart from most other light sources: (i) they have the potential to create light with essentially unit power efficiency and (ii) the properties of light, such as spectral composition and temporal modulation, can be controlled to a degree that is not possible with conventional light sources such as incandescent and fluorescent lamps. The implications are enormous and, as a consequence, many positive developments are to be expected including a reduction in global energy consumption, reduction of global-warming-gas and pollutant emissions and a multitude of new functionalities benefiting numerous applications. This review will assess the impact of solid-state lighting technology on energy consumption, the environment and on emerging application fields that make use of the controllability afforded by solid-state sources. The review will also discuss technical areas that fuel continued progress in solid-state lighting. Specifically, we will review the use of novel phosphor distributions in white light-emitting diodes (LEDs) and show the strong influence of phosphor distribution on efficiency. We will also review the use of reflectors in LEDs with emphasis on 'perfect' reflectors, i.e. reflectors with highly reflective omni-directional characteristics. Finally, we will discuss a new class of thin-film materials with an unprecedented low refractive index. Such low-n materials may strongly contribute to the continuous progress in solid-state lighting.