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The various synthesis conditions to obtain a material based on SiO 2-TiO 2 co-doped with Er 3+ /Yb 3+ /Eu 3+ were investigated, searching for those that present the greatest potential to improve the efficiency of solar cells. Conditions adjusted included heat-treatment temperatures, concentrations of matrix, and concentrations of dopants. Raman spectroscopy results demonstrated the effect of the annealing temperatures on the TiO 2 phase transition and the crystalline phase of the materials, which interfere with the photoluminescence of the materials. The band gap of the materials was evaluated by diffuse reflectance and it decreased due to the doping. The materials were able to absorb UV and IR energy and emit in the visible region, verified by the down conversion, up conversion and the double excitation of the materials. The results showed that the materials may be used as a strategy to use a greater portion of the solar spectrum, improving solar cell efficiency.

Materials containing rare earth ions with photoluminescent properties have been investigated as efficient phosphors for applications in photonics. In this work We reports on preparation of Eu 3 þ -doped Al 2 O 3 with different concentrations of Eu 3 þ , in relation to the amount of moles of Al 3 þ , has been prepared using a simple and inexpensive synthesis. XRD showed that the alumina-based materials calcined at 400 and 600 1C were predominated by the γ-Al 2 O 3 phase. However the materials heat-treated above 800 1C showed mixture of γ and α-Al 2 O 3 phases. SEM presented results demonstrating that the heat-treatment at increased temperature favors a larger particle size with inhomogeneous morphology. It was observed with photoluminescence spectroscopy that theEu 3 þ -doped Al 2 O 3 materials showed intense photoluminescence emission around 612 nm under excitation at 394 nm. This emission in the visible region was assigned to a down-shifting phenomenon attributed to the intraconfigurational f-f transitions of Eu 3 þ . Intense emission around 693 nm assigned to Cr 3 þ were observed, and the intensity is controlled by the heat-treatment temperature of synthesis. The lifetime found for these materials are of the order of milliseconds at 612 nm. In summary the materials obtained in this work show properties than can be used for photonics applications.

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