Infrared-to-visible upconversion processes in Pr3+/Yb3+-codoped KPb2Cl5 -: art. no. 165101

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 D-1(2) level, and less intense blue, green, and red emissions from the P-3(0,1) levels of Pr3+ have been observed under resonant excitation in the (1)G(4) level of Pr3+. As regards to Yb3+, when the F-2(5/2) level is resonantly excited, the visible emissions are also present but the blue, green, and red emissions from P-3(0,1) levels are enhanced if compared with the orange luminescence from level D-1(2). On the other hand, excitation at the high-energy wing of the F-2(5/2) level originates emission only from P-3(0,1) levels. The upconverted fluorescence from the D-1(2) and P-3(0,1) 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.