Unraveling the origin of broadband yellow emission in Bi3+-doped LuXnGaO4 (Xn = Mg, Zn) phosphors

Abstract

Despite extensive research on the photoluminescence properties of Bi³⁺ ions, the origins of their emission and excitation bands remain elusive. Herein, we present a comprehensive analysis of the photoluminescence properties of Bi³⁺-activated LuXnGaO₄ (Xn = Mg, Zn), elucidating the underlying factors governing the intra-ionic and extra-ionic electronic transitions. By integrating crystal structure data and spectroscopic data analyses with semi-empirical formula calculations, the origins of excitation and emission states were elucidated. Moreover, the impact of alterations in chemical surroundings on the luminescence of Bi³⁺ was investigated. Both LuXnGaO₄:Bi³⁺ phosphors exhibit three excitation peaks in the near ultraviolet region and display a broadband yellow emission. However, the luminous behavior of LuMgGaO₄:Bi³⁺ and LuZnGaO₄:Bi³⁺ differs due to variations in the band gap, bond length and neighboring atoms. It is anticipated that the investigation of Bi³⁺-activated gallates presents a promising avenue for advancing wide-band and long-wavelength emitting phosphors.