Enhanced Luminescence of Long-Wavelength Broadband Near-Infrared Germanate Phosphors

Long-wavelength broadband near-infrared (NIR) phosphors have attracted considerable interest in the fields of medical cosmetology and organic detection because of their special emission band. Herein, Ca₂GeO₄(CGO): Cr⁴⁺ NIR phosphor, presenting a broadband emission with longer wavelength ranging from 1100 to 1600 nm, has been synthesized. Further, the luminescence intensity and quantum efficiency of Cr⁴⁺ could be obviously improved via the energy transfer from Eu³⁺ to Cr⁴⁺. The energy transfer is dominated by the dipole-dipole mechanism, which can be inferred from the spectra and the decay curves. Furthermore, in order to evaluate the potential application, an NIR phosphor-converted light-emitting diode (pc-LED) based on blue chip has been prepared. Consequently, CGO: Eu³⁺, Cr⁴⁺ exhibits proper output power and wider half-width than the NIR LED chip, indicating its great prospect for long-wavelength NIR pc-LED applications.