Photon management in La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+ by two step cross-relaxation and energy transfer

A luminescence study from UV to NIR of La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+ is reported. Emission spectra of La2BaZnO5:Tm3+, Yb3+ reveal an unexpected high intensity of the Tm3+ 3F4 → 3H6 emission at 5000 cm−1 upon excitation in the Tm3+ 1G4 level. This unusual efficiency is explained by two successive cross-relaxation steps between Tm3+ ions, resulting in potential emission of three NIR photons for each absorbed visible photon. Emission and decay spectra of La2BaZnO5:Pr3+, Yb3+ give evidence for a Pr3+ (3P0 → 1G4) to Yb3+ (2F7/2 → 2F5/2) energy transfer. The Pr3+ (1G4 → 3H4) to Yb3+ (2F7/2 → 2F5/2) energy transfer could not be derived from our data.