Plastic Identification by Using Energy Transfer Enhanced Broadband Short-Wave Infrared Phosphor Mg3Ga2GeO8:Cr3+, Ni2+

Recently, short-wave infrared (SWIR) luminescent materials have attracted much attention because of their excellent characteristics in optical device applications. Some research has focused on discussing the luminescence enhancement of these materials through metal ion doping. In this study, a series of Cr3+/Ni2+ codoped SWIR phosphors Mg3Ga2GeO8 (MGGO) were synthesized using a solid-state reaction. The phosphors show broad emissions in the spectral range 1,100–1,700 nm in the SWIR field. The emission intensity of Ni2+ could be greatly enhanced by Cr3+ because of the energy transfer from Cr3+ to Ni2+. This energy transfer phenomenon has been successfully proved by the excitation and emission spectra overlap and the decay lifetime curve. By taking the X-ray absorption near edge structure, we confirmed that there is no oxidation-state transition occurring on both Cr3+ and Ni2+. Using Gaussian peak fitting, we successfully have a detailed explanation of the phenomenon of the emission peak shift. Finally, the Cr3+/Ni2+ codoped MGGO phosphors were combined with blue light emitting diode (LED) chips to fabricate a SWIR-LED light source device. This device showed high stability and the ability of plastic-type identification to help plastic waste classification more efficiently.