Publication date: 7th July 2025
Energy Transfer-Driven Colour Tunability in Tb³⁺/Eu3+ -Doped KLa(WO₄)₂ phosphor for smart LEDs.
Simran, A Tyagi, C.Shivakumara
Abstract— The development of phosphor materials with enhanced photoluminescence and tunable emission is crucial for advancing smart lighting technologies, particularly in applications requiring customizable color output. In this study, Tb³⁺-activated KLa(WO₄)₂ phosphors were successfully synthesized via a conventional solid-state reaction method at 750 °C for 4 hours. Structural analysis using Rietveld refinement confirmed the formation of a tetragonal phase with space group I4₁/a. To further collect evidences for the structure and formation of phase FT-IR, UV-DRS, and XPS were also performed. To enhance the photoluminescence (PL) properties, co-doping with Li⁺, Ca²⁺, and Bi³⁺ ions was employed, resulting in a significant increase in PL intensity compared to the Tb³⁺-only doped samples. Among the co-dopants, Li⁺ was found to provide the maximum enhancement, which is attributed to local structural distortions and symmetry reduction around the Tb³⁺ ions, facilitating more efficient energy transfer processes. This is further confirmed by Decay measurement studies.
The phosphors exhibited notable color tunability, primarily driven by cross-relaxation among Tb³⁺ ions. This mechanism enabled emission color shifts from blue to greenish-blue and further to a prominent green. Additionally, the introduction of Eu³⁺ as a co-dopant further extended the color range, allowing the emission to shift from green to orange and red under 378 nm excitation, and from blue to purple-pink to red under 400 nm excitation. This dual tunability—achieved by varying both the excitation wavelength and dopant composition—offers precise control over the emitted color, enabling a wide color palette from cool to warm tones. The combined improvements in luminescence intensity and color versatility make these co-doped KLa(WO₄)₂³⁺ phosphors promising candidates for smart LED applications, where fine-tuned color control is highly desirable. These findings provide valuable insights into the design of phosphor materials with enhanced PL performance and customizable color outputs for next-generation lighting technologies.
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