Multisite-Occupancy-Driven Efficient Multiple Energy Transfer: A Straightforward Strategy to Achieve Single-Composition White-Light Emission in Ce3+-, Tb3+-, and Mn2+-Doped Silicate Phosphors

Abstract

It is unquestionably true that site occupation and energy transfer play important roles in the luminescent properties of optical materials from both practical applications and theoretical research. In this paper, multisite-occupancy-driven multiple energy transfers were used as a straightforward strategy to achieve single-composition white-light emission in Ce³⁺-, Tb³⁺-, and Mn²⁺-doped Ba_1.2Ca_0.8SiO₄ (BCS) phosphors. The Ce³⁺-, Tb³⁺-, and Mn²⁺-doped T-phase orthosilicate BCS samples were synthesized by traditional solid-state reactions. The phase composition was checked via X-ray diffraction (XRD), and the luminescent properties were systematically studied by photoluminescence spectroscopy and fluorescence decay curves. A detailed study on the efficient and multiple energy transfers of Ce I → Mn²⁺, Ce II → Tb³⁺, and Ce II → Tb³⁺ → Mn²⁺ was carried out. Satisfactorily, the selected phosphor exhibits a high internal quantum efficiency (QE) of 81% and good thermal stability. In addition, an evident negative thermal quenching phenomenon, i.e., the emission intensity increases with increasing temperature, is provided. Moreover, the mechanism of negative thermal quenching was proposed. On the basis of these excellent luminescence properties, a white LED with color-rendering index (R_a = 89) was fabricated by integrating the phosphor on an n-UV 365 nm chip. These results show that the materials present potential application in the field of phosphor-converted white LEDs.