Phosphors for LED Lighting

Nearly every white LED bulb works the same way. A blue or near-UV LED chip is coated with one or more inorganic phosphors, which absorb part of the LED emission and re-emit it at longer wavelengths. The phosphor sets almost everything a person notices about the light: its color, how faithfully it renders the objects around us, and whether it holds up as the lamp heats during operation. Most commercial phosphors were found by trial and error, and only a handful of host crystal structures meet the demands for efficiency and thermal stability.

The Brgoch group uses machine learning to decide which compounds are worth making. The group showed that the Debye temperature, a measure of structural rigidity that can be predicted for thousands of compounds at once, is a reliable guide to photoluminescent quantum yield, a screen that led to the efficient and thermally robust NaBaB₉O₁₅:Eu²⁺. The group’s models predict thermal quenching, emission energies, and excitation energies before any synthesis begins, so that lab time goes to the compositions most likely to succeed.

The group’s work targets the cyan gap in the visible spectrum, lighting designed around human circadian response, narrow-band emitters for wide-gamut displays, and broadband near-infrared phosphors based on Cr³⁺ for compact spectrometers, night vision, bio-imaging, and food-quality analysis. New compositions are prepared by high-temperature solid-state and ammonothermal routes and characterized by powder X-ray and neutron diffraction, optical spectroscopy, and density functional theory (DFT) calculations.