Síntese e caracterização de compostos metálicos com ligantes nitrogenados/carboxilatos para uso como fotossensibilizadores em células solares

Abstract

In the last decades, the global demand for electric energy has grown a lot, causing more and more research to be developed and obtained as sources of energy that are renewable and sustainable. In this sense, solar cells sensitized by dye (Dye Sensitized Solar Cell, DSSC) have been extensively studied, since this type of solar cell has advantages over conventional cells, including lower manufacturing costs and greater capture of diffused light. The photosensitizers (dyes) most used to date are ruthenium (II) complexes, however, due to the high cost and toxicity of these materials, the objective is to synthesize and characterize compounds using low-cost metals, such as copper and cobalt (II) coordinated to different ligands, and test them as photosensitizers in a DSSC type solar cell, using titanium oxide as a semiconductor and glass substrate with FTO. The compounds with the carboxylate ligands were removed from the stoichiometric reaction, in aqueous medium, from the salts, CuSO4.5H2O or CoCl2, on the solution of the sodium salts of the respective ligands 5-aminoisophthalate, 5-hydroxyisophthalate, 2-aminoterephthalate, 4, 4 '-oxybis benzoate, 2,5-pyridinecarboxylate. The copper (II) complex with Schiff's base ligand, pyrazolimine (NaphHPz), was created from the reaction between copper (II) carbonate and the ligand, under reflux. The compounds obtained in the solid state were characterized by thermal analysis (TG-DSC), in order to determine stoichiometry, degree of hydration, purity and thermal stability, also characterized by infrared spectroscopy (FT-IR), in order to suggest the way coordination and the absorption spectroscopy technique of the UV-Vis region to assess which spectral region the compounds and free ligands absorb light from. The efficiency of the cells produced with the different sensitizers (complexes and ligands) varied from 0.002 to 0.108% with the use of a solar simulator. The efficiency values for the compounds were compared with cells sensitized with the dye N3 ®, used as a reference standard, produced and tested under the same experimental conditions as this work. Based on literature data, the type of anchor group for the free and complex ligand was evaluated as a function of UV-Vis absorption, as well as the efficiency values of choice.