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

Abstract

AbstractSuper 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.