engleski

The development of geopolymer materials into thin- films for the application in vertically mounted solar cells

Geopolymers are considered as the third generation of concrete due to their sustainability in the preparation of cement with properties like other construction materials, adding up the value to the environmental issues worldwide. A contribution in the overlapping construction and energy materials could ensue from preparing geopolymers in the form of a paste that can be developed into thin-film. In that matter, materials with specific properties such as aluminosilicates, activated by alkali solutions, require investigation by a considerable amount of advanced techniques. They may be considered as an inorganic binary system that consists of: (i) a reactive solid source of SiO2 and Al2O3, and (ii) an alkaline activation solution. Geopolymer systems composed of common aluminosilicate precursors such as fly ash or metakaolin require curing temperatures up to 80 °C to achieve gel state as well as early strengths, late strengths and final setting. Keeping environmental issues in mind, gelation and curing conditions of the geopolymerisation process should be optimized and lowered in terms of energy. Precursors based on amorphous mullite material raise considerable attention due to its facile laboratory preparation. The preparation of new geopolymer formulations with characteristic properties, the investigation of relationships among compositions, structure, sample configuration and mechanical properties are important for understanding the mechanisms involved in the evolution of these materials. In this talk, the preparation of geopolymer samples will be presented, and the influence of precursors and additives will be discussed. For that purpose, amorphous sol-gel obtained mullite composition precursor was used as a source of SiO2 and Al2O3. On the other hand, for the alkaline activation solution, we investigated the influence of different ions, so we used both potassium and sodium hydroxide (8M) and potassium, or sodium silicate solution mixtures by keeping the liquid to solid ratio constant (i.e. 1.6). Every combination of investigated samples was prepared in bulk, and by a tape-casting method in a thin- film configuration. Bulk samples were characterized by XRD, DTA/TGA, FTIR and SEM. In thin-film samples, electrically conductive polymer is added in addition to gain conductive properties. In a configuration like that, geopolymers could be used as a new generation of electrodes in vertically mounted solar cells. For that purpose, electrical properties of prepared thin-film samples were investigated by the Solid- State Impedance Spectroscopy method and obtained results will also be presented in this talk.

Geopolymer, Mullite ; Thin-film system ; Solar cells ; Impedance spectroscopy

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