Site occupancy and enhanced luminescence of broadband NIR gallogermanate phosphors by energy transfer

Abstract

Super broadband near-infrared (NIR) La3Ga5GeO14(LGGO): Cr3+ phosphor is in urgent needs for food testing. Unfortunately, it suffers from poor luminescence intensity in applications. Herein, the enhanced NIR luminescence performance can be realized in LGGO: Pr3+, Cr3+. The preferential crystallographic site of Cr3+ is validated on the basis of EPR spectrum, Rietveld refinement, and the first-principles DFT calculations. It is of great importance that the as-prepared phosphors can be excited by blue light (460 nm), which is beneficial to the application of blue-pumped LEDs. The critical distance of Pr3+ in LGGO host has been calculated by concentration-quenching method. For co-doped sample, it is observed that Cr3+ luminescence intensity enhancement by a factor of 3 can be achieved by doping Pr3+ owing to the energy transfer from Pr3+ to Cr3+. In addition, the introduction of Pr3+ can also improve the Cr3+ luminescence intensity at elevated temperature. Furthermore, using the optimized phosphor, a blue-based NIR phosphor-converted LEDs (NIR pc- LEDs) is fabricated, the forward voltage and the intensity of LED hardly change after thermal aging for 500 hours under high temperature/ high humidity condition, indicating its great reliability for NIR pc-LEDs. Therefore, LGGO:Pr3+, Cr3+ has great potential to serve as an attractive candidate in the application of blue light-excited NIR pc-LEDs in view of its capability for blue to enhanced broadband NIR conversion.