Control of Narrow-Band Emission in Phosphor Materials for Application in Light-Emitting Diodes

Light-emitting diodes (LEDs) are widely used around the world. Scientists are attempting to develop LED devices that not only have high brightness but also have a high color rendering index (CRI). Phosphor materials play important roles in tuning and optimizing the final luminescent spectrum. Narrow-band emission phosphors must be incorporated into LED chips to achieve high CRI and efficacy. From this perspective, we introduce and discuss key points in the narrow-band emission spectrum. Three sets of phosphor examples, namely, Eu-doped (Ba,Sr)Si2O2N2, UCr4C4-type structures, and beta-SiAlON systems, are used to explain these points. First, we discuss the highly symmetrical local coordination environment of activators, which include cuboid and nine-coordinate structures. Second, we reveal the second shell effect of the substituted cation channel. Third, we discuss the interaction between the electron from the activator and the vibration from the host lattice (electron-lattice interaction). These model systems help establish and design rules for narrow-band emission phosphors and may guide future studies in discovering potential phosphor candidates for practical applications.