Light-emitting materials have been extensively investigated because of their widespread applications in solid-state lighting, displays, sensors, and bioimaging. In these applications, it is highly desirable to achieve tunable luminescence in terms of luminescent intensity and wavelength. Here, a convenient physical approach of temporal and remote tuning of light-emitting wavelength and color is demonstrated, which is greatly different from conventional methods. It is shown that by modulating the frequency of magnetic-field excitation at room temperature, luminescence from the flexible composites of ZnS:Al, Cu phosphors induced by the piezophotonic effect can be tuned in real time and in situ. The mechanistic investigation suggests that the observed tunable piezophotonic emission is ascribed to the tilting band structure of the ZnS phosphor induced by magnetostrictive strain under a high frequency of magnetic-field excitation. Furthermore, some proof-of concept devices, including red-green-blue full-color displays and tunable white-light sources are demonstrated simply by frequency modulation. A new understanding of the fundamentals of both luminescence and magnetic-optics coupling is thus provided, while offering opportunities in magnetic-optical sensing, piezophotonics, energy harvesting, novel light sources, and displays.
Keywords: RGB color; magnetic sensors; mechanoluminescence; metal-ion doped phosphors; piezophotonic effect.
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