Effect of Dy3+ and Eu3+ 4f Band Gap States on Luminescence and Energy Transfer in Monoclinic Lutetium Tungstate

The 4f band gap states (BGSs) of Dy and Eu ions play an important role in luminescence and energy transfer in monoclinic Lu2WO6. The corresponding white and red light emissions were ascribed to electrons' transition from spin-down 4f states to BGSs and from BGSs to spin-up 4f states. The formation energy gradually increased or decreased with the increment of Dy or Eu content, indicating that Lu2WO6 easily introduced Eu with high concentration. Through fluorescence lifetime and Rietveld refinement, the exchange interaction energy migration mode from host to Dy and Eu ions was assumed to be electron transport from the conduction band (CB) to 4f states in the CB and 4f BGSs. From partial charge density and Bader charge analysis, electron transfer was supposed from Dy3+ BGS to Eu(3+ )BGS via dipole- dipole interaction in the codoping samples. The white, red, and pale red light-emitting diode (LED) lamps were fabricated using a 365 nm chip and the Dy3+/Eu3+-doped Lu2WO6. This research sheds light on the luminescence mechanism of rare-earth elements-doped Lu2WO6 and explores their potential application in lighting and displays.