Tunable emission of Ce³⁺ in (K, Rb)₃GdSi₂O₇ phosphors toward broadband cyan luminescence

In an effort to obtain a novel cyan-emitting phosphor, the [K1-xRbx](3)GdSi2O7: yCe(3+) materials (x = 0, 0.1, 0.2, 0.3, 0.4, y = 0, 0.005, 0.01, 0.02, 0.03, 0.04) are synthesized via a solid-state reaction pathway, and their crystal structure and luminescence behaviors are studied systematically. The chemical substitution of Rb+ in the K+ sites can enlarge the K3GdSi2O7 host lattice and help to the blue-shifting of emission band of Ce3+ ions due to the decreased crystal field splitting effect. It is also confirmed that the Ce3+ ions tend to enter [Gd1O(6)] and [Gd2O6] polyhedrons simultaneously. Consequently, the [K0.7Rb0.3](3)GdSi2O7: Ce3+ phosphor yields a broadband cyan emission centered at 492 nm with the full width at half maximum (FWHM) of similar to 115 nm upon 365 nm excitation. The optimal concentration of Ce3+ dopant is determined to be 0.01, and the concentration quenching effect can be attributed to the dipole-dipole interactions. The white light emitting diode (WLED) device fabricated by employing the discovered [K0.7Rb0.3](3)GdSi2O7: 0.01Ce(3+) phosphor displays a high color rendering index (R-a = 91.7) and a low correlated color temperature (CCT = 3749 K). This work may promote the development of cyan phosphors for near ultraviolet-converted WLEDs with high performance.