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Artigo IPEN-doc 19540 Spectroscopic properties and quantum cutting in Tb3+-Yb3+ co-doped ZrO2 nanocrystals2013 - TERRA, I.A.A.; BORRERO GONZALEZ, L.J.; CARVALHO, J.M.; TERRILE, M.C.; FELINTO, M.C.F.C.; BRITO, H.F.; NUNES, L.A.O.Ultraviolet-visible to near-infrared quantum cutting (QC) materials are a promising tool to enhance the efficiency of conventional crystalline silicon solar cells. The spectroscopic properties of Tb3þ–Yb3þ co-doped ZrO2 nanocrystals are presented, and the QC mechanisms in these nanocrystals are investigated. The materials were fabricated using the sol gel method and characterized using X-ray powder diffraction, X-ray absorption near edge structure, and luminescence spectroscopy. The incorporation of Yb3þ ions into the host induced a crystalline phase change of ZrO2 from monoclinic to tetragonal to cubic symmetry and influenced the Tb valence state. The Tb3þ visible emission, excitation intensity (monitored by the Tb3þ: 5 D4 emission), decay time of the Tb3þ: 5 D4 emitter level, and down-conversion (DC) emission intensity increased with Yb3þ concentration. Furthermore, a sublinear dependence of the DC intensity on the excitation power at the Tb3þ: 5 D4 level indicated the coexistence of two different QC mechanisms from Tb3þ ! Yb3þ. The first one is a linear process in which one Tb3þ ion transfers its energy simultaneously to two Yb3þ ions, known as cooperative energy transfer, and the second one is a non-linear process involving an intermediated virtual level in the Tb3þ ion.