| Resumo: | In this work we report infrared-to-visible upconversion luminescence in the low-phonon-energy host material KPb2Cl5 codoped with Pr3+ and Yb3+ ions. An orange luminescence from the 1D2 level, and less intense blue, green, and red emissions from the 3P0,1 levels of Pr3+ have been observed under resonant excitation in the 1G4 level of Pr3+. As regards to Yb3+, when the 2F5/2 level is resonantly excited, the visible emissions are also present but the blue, green, and red emissions from 3P0,1 levels are enhanced if compared with the orange luminescence from level 1D2. On the other hand, excitation at the high-energy wing of the 2F5/2 level originates emission only from 3P0,1 levels. The upconverted fluorescence from the 1D2 and 3P0,1 levels occurs by energy transfer upconversion and/or excited-state absorption processes depending on the excitation wavelength. The possible mechanisms which lead these processes are discussed.
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