Post-synthesis Annealing Effects on SrGa2Se4:Eu Phosphors with Peak Emission Wavelength in the Green Gap

A high-quality white light source requires high luminous efficacy (lumens per input watt). Theoretically, in the “greenyellow” spectral region (with a peak wavelength at around 555 nm), the luminous efficiency (lumens per radiant watt) reaches a maximum based on the luminous efficiency function, V(λ), and can potentially generate high luminous efficacy. Unfortunately, the light-emitting diode (LED) suffers from low external quantum efficiency in the “greenyellow” region, thereby lowering the luminous efficacy value. Researchers have sought solutions such as nonpolar or semipolar InGaN/GaN LEDs. An alternative to generating green light is to use phosphor down-conversion by exciting a green emission phosphor with a near-UV or blue LED of higher external quantum efficiency. In this study, a SrGa2Se4:Eu phosphor with peak emission wavelength at 555 nm was initially synthesized and followed by a systematic study of the post-synthesis annealing. The purpose of this study was to investigate how post-synthesis annealing conditions, including annealing temperature, annealing duration, and annealing ambient atmosphere, can affect phosphor performance. The phosphor performance was characterized in terms of external quantum efficiency and emission properties. How the external quantum efficiency of the phosphor can be further improved is also discussed.