Highly efficient and thermally stable broadband near-infrared emitting garnet Ca3Sc2Ge3O12:Cr3+,Ce3+ phosphors for multiple pc-LED applications

With the increasing demand for the application of near-infrared (NIR) spectroscopy in security, agriculture, medical and other fields, people have been seeking efficient and intelligent NIR light sources. Herein, Cr3+ doped Ca3Sc2Ge3O12 (CSGG) broadband NIR phosphors are successfully synthesized. Under excitation of 480 nm, the emission peak of CSGG:Cr3+ is located at 785 nm, and the full width at half maximum (FWHM) is 106 nm. Low photoluminescence spectra (7 K and 77 K) support the broadband NIR emission coming from two Cr3+ luminescence centers occupying ScO6 and CaO8 sites, respectively. CSGG:Cr3+ exhibits excellent thermal stability (97% at 100 & DEG;C) and low internal quantum efficiency (IQE = 22%). The introduction of Ce3+ leads to the enhancement of IQE from 22% to 61% due to the following two reasons: the energy transfer from Ce3+ to Cr3+ and the lattice distortion which improves the parity forbidden transition of Cr3+. The mechanism of excellent luminescence thermal stability is revealed from the following perspectives: thermal activation energy, the Huang-Rhys factor and the thermal ionization effect. Benefiting from the excellent performance of CSGG:Cr3+,Ce3+ NIR phosphors, the combination with blue light chips demonstrates their potential applications in night vision security, biological imaging, and nondestructive testing.

Automated summary

By synthesizing Cr3+ doped Ca3Sc2Ge3O12 (CSGG) broadband NIR phosphors, efficient and intelligent NIR light sources are obtained. CSGG:Cr3+ has an emission peak at 785 nm with a FWHM of 106 nm under excitation of 480 nm. Low temperature photoluminescence spectra confirm the broadband NIR emission from two Cr3+ luminescence centers. CSGG:Cr3+ exhibits excellent thermal stability (97% at 100 °C) and low internal quantum efficiency (IQE = 22%). The introduction of Ce3+ enhances IQE from 22% to 61% due to energy transfer and lattice distortion. The mechanism of excellent luminescence thermal stability is explained based on thermal activation energy, Huang-Rhys factor, and thermal ionization effect. The excellent performance of CSGG:Cr3+,Ce3+ NIR phosphors enables their potential applications in night vision security, biological imaging, and nondestructive testing.