Investigation on the Luminescent Property and Application of In2BP3O12:Cr3+ Broadband Near-Infrared Phosphor

Near-infrared (NIR) spectroscopy technique plays an important role in night-vision surveillance, food analysis, bioimaging and agriculture fields, and the development of compact and efficient NIR light source is a precondition for their massive commercial applications. Phosphor-converted light emitting diodes (pc-LED) have the advantages of compactness, low-cost, and long operating lifetime, thus have attracted considerable attentions in recent years. The key point is to exploit high performance NIR phosphors which can be excited efficiently by blue diode chips. A number of Cr3+-activated phosphors have been investigated aiming at NIR pc-LED applications. Nevertheless, most of the NIR phosphors show relatively short peak wavelength and narrow full width at half maximum (FWHM), resulting in spectral deficiency in the range 900 similar to 1100 nm. The phosphors with ultrabroad bandwidth are more desirable for spectroscopic applications. In this work, a novel broad-band NIR light emitting phosphor In2BP3O12:Cr3+ is synthesized by solid state reaction method. The structure, concentration and temperature dependent luminescence properties, electron-phonon coupling as well as the NIR LED performances and applications of the In2BP3O12:Cr3+ have been investigated. Upon 480 nm excitation, the In2BP3O12:Cr3+ phosphor shows a broad emission band peaked at 950 nm and covering 750 similar to 1350 nm (bandwidth of similar to 210 nm), which is owing to the T-4(2)->(4)A(2) transition of Cr3+ ions. It is found that the emission intensity of the phosphor at 373 K keep 40% of that at room temperature. A NIR pc-LED is packaged by combining the In2BP3O12:Cr3+ phosphor and a commercial blue InGaN chip, which generates broad NIR light emissions with an output power of similar to 5 mW at 60 mA drive current. When this NIR pc-LED is used to illuminate the human palm, the blood vessels in the palm are clearly imaged by a NIR charge coupled device (CCD) camera. These results suggest that the In2BP3O12:Cr3+ is a promising phosphor for fabricating NIR pc-LEDs, which are potential for non-destructive analysis in the fields of biology and medicine.