Phosphors for Solid-State White Lighting

TLDR

Phosphors are essential for solid‑state white lighting, converting III‑nitride UV/blue LEDs into visible light via down‑conversion in crystalline oxides, nitrides, or oxynitrides doped with Ce³⁺ or Eu²⁺ whose electronic configurations allow tunable emission. This review surveys the current requirements and key aspects of the phosphor conversion process, examines widely used phosphor families, and outlines empirical rules for developing improved host materials. The authors analyze how host crystal chemistry and dopant electronic states govern down‑conversion efficiency, compare existing phosphor families, and propose design guidelines for new host materials.

Abstract

Since the mid-1990s, phosphors have played a key role in emerging solid-state white-lighting technologies that are based on combining a III-nitride-based near-UV or blue solid-state light source with downconversion to longer wavelengths. Almost all widely used phosphors comprise a crystalline oxide, nitride, or oxynitride host that is appropriately doped with either Ce 3+ or Eu 2+ . These ions, with [Xe] 4f n 5d 0 configurations (n = 1 for Ce 3+ and 7 for Eu 2+ ) have proximal excited states that are [Xe] 4f n−1 5d 1 . Optical excitation into these states and concomitant reemission can be tuned into the appropriate regions of the visible spectrum by the crystal these ions are hosted in. In this article, we review the current needs and key aspects of the conversion process. We describe some currently used families of phosphors and consider why they are suitable for solid-state lighting. Finally, we describe some empirical rules for new and improved host materials.