Thin-Film Photoluminescent Properties and the Atomistic Model of Mg₂TiO₄ as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu²⁺ and Ce²⁺, are commonly used for red-emitting phosphors. Mg₂TiO₄ inverse spinel has been reported as a promising matrix material for “RE-free” red light luminescent material. In this paper, Mg₂TiO₄ inverse spinel is investigated using both experimental and theoretical approaches. The Mg₂TiO₄ thin films were deposited on Si (100) substrates using either spin-coating with the sol–gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg₂TiO₄ thin films were characterized. In addition, the atomistic model of the Mg₂TiO₄ inverse spinel was constructed, and the electronic band structure of Mg₂TiO₄ was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg₂TiO₄ luminance material as well as its optimal thin-film processing conditions were comprehensively reported.