Near-infrared luminescent properties and applications of Fe3+-doped YAG phosphors

This study employed the high-temperature solid-phase method to successfully synthesize a comprehensive range of Y3Al12O5: xFe3+ novel near-infrared (NIR) phosphors based on yttrium aluminum garnet material. The samples were subjected to characterization utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy, first-principles calculations, excitation and emission spectroscopy, as well as temperature-dependent luminescence intensity analysis. Subsequently, the specimens were encapsulated within light-emitting diodes (LED) to facilitate their application in night vision and biometric sensing. The results revealed that all sintered samples were phase-pure, with particle sizes around 0.6 mu m, exhibiting uniform and fully developed morphology. The absorption spectroscopy indicated a decrease in the bandgap with increasing Fe3+ doping concentration. The first-principles results revealed that the doping of Fe3+ introduces Fe-d orbitals, and their contribution to the conduction bands is nearly comparable to that of the d orbitals of the Y3+. The spectroscopic results indicated that the samples can be excited through charge transfer of O2- -> Fe3+, leading to near-infrared emission at 784 nm with a full width at half maximum (FWHM) of 77 nm at 280 nm, and the FWHM is 73 nm under excitation at 411 nm. The thermal stability analysis revealed that as the temperature increased, there was no observed redshift or blueshift in the emission spectra. The encapsulated NIR LED allows clear visibility of blood vessels on the hand and cacti in a dark room environment. All the aforementioned results provide substantial evidence for the significant application potential of Y3Al12O5: xFe3+ NIR phosphors in biometric sensing and night vision.