Structure, luminescence properties, and valence-induced spectral behavior of a bismuth-activated garnet phosphor

Abstract

The increasing demand for full-visible-spectrum lighting has prompted the development of novel phosphors with multicolor emission. Trivalent Bi³⁺-activated phosphors, known for their tunable emission without spectral reabsorption phenomena, hold great potential for n-UV LED applications. A better understanding of the Bi³⁺ luminescence and valence transformation is significant. In this study, a bismuth-activated blue emitting phosphor Lu₂SrAl₄SiO₁₂:Bi³⁺ (LSAS:Bi³⁺) with a garnet structure was successfully designed and synthesized via the high-temperature solid-state method. The crystal structure, electronic structure, and luminescence properties together with their relation are fully illustrated. The energy diagram of LSAS:Bi³⁺ was assigned through theoretical calculations and spectral analysis. Furthermore, we analyzed the luminescence of Bi²⁺ induced by electron beam excitation, demonstrating the transformation of Bi³⁺ in the LSAS matrix. This finding enhances the understanding of the luminescence properties of bismuth-activated phosphors. The WLED device with full-visible-spectrum was obtained based on LSAS:Bi³⁺ with an n-UV chip and green and red phosphors. This study not only provides insights into the structure–performance relationship of bismuth-activated phosphors but also expands their potential applications in optoelectronic devices.