A Novel Cyan Phosphor (K,Rb)₃GdSi₂O₇:Ce³⁺ for Full‐Spectrum Lighting through Local Structure Tailoring

Abstract

Crystal‐field engineering can obtain targeted emission more effectively, compared with the laborious experimental screening of new hosts. However, there still lack of paradigms for obtaining Ce³⁺‐doped cyan phosphors by crystal‐field engineering, and the correlation between the emission and the local structure of the Ce³⁺ ions has rarely been disclosed. Herein, through substituting the K⁺ in K_3‐yRb_yGdSi₂O₇:Ce³⁺ with Rb⁺, the emission color changes from yellow‐green to cyan and finally to blue. In addition, the emission intensity and thermal stability greatly improve, as the internal quantum efficiency increases from 39.4% (y = 0) to 83.6% (y = 1.2), and the thermal activation energy increases from 0.25 eV (y = 0) to 0.36 eV (y = 1.2). The optimized luminescent properties have been interpretated from the change in energy level splitting and configuration coordinate of Ce³⁺, both of which originate from the elongated Ce³⁺─O²⁻ bonds. Finally, the cyan‐emitting phosphor K_1.8R_1.2GSO:Ce³⁺ is applied to bridge the cyan gap in a fabricated white light‐emitting diodes, and the color rendering index is improved from 90.8 to 93.4. This work not only provides an efficient cyan phosphor, but also highlights an avenue for the rational design of phosphors with optimal luminescent properties.