Camadas de bloqueio de PTFE construídas por evaporação térmica

Abstract

This work focuses on the construction of blocking layers, built by thermal evap oration, for application in dye-sensitized solar cells. For that, we carried out the assembly and instrumentation of a thermal evaporator for the deposition of these layers, validating its functionality, producing and characterizing the samples produced. Thin films of polytetrafluoroethylene (PTFE) deposited on a common glass substrate were produced. The heat treatment of the deposited films was optimized and it was found that the best method was the hot plate at a constant temperature of 240°C, showing excellent adhesion. These films were characterized by UV-Vis spectroscopy, mechanical profilometry, optical profilometry and ellipsometry. Ellipsometry showed inconclusive results due to high roughness which generated light scattering, making the theoretical adjustment impossible. The mechanical profilometry, due to the low vertical resolution, made it impossible to measure the thickness of the films, as well as the accurate measurement of the roughness. Optical profilometry allowed the resolution of the profile of the structures present on the surface of the films, as well as the quantification of thickness and roughness for different deposition rates. The transmittance of these films, obtained by UV-VIS spectroscopy measurements, show an increase in value for a wide spectrum of wavelengths for different deposition config urations. In addition to the anti-reflection effect generated by the PTFE deposition, the results suggest the presence of luminescence in the films, something already recorded in the literature. The luminescence, by hypothesis, would be generated by the hy bridization of the carbon orbitals due to temperature during the deposition and drying process. PTFE films deposited via thermal evaporation are promising for application as a blocking layer for Dye-Sensited Solar Cells (DSSCs), due to the gain in light intensity that can lead to an increase in efficiency, as well as for any other applications that need to gain light intensity.In addition to the characterizations for application as a blocking layer, we verified the use of these films as a protective coating on silicon-based solar cells, where we did not obtain a significant gain or loss of efficiency in energy conversion, indicating multifunctional applications, such as self-cleaning and anti-corrosion protection. Ceramic powders of zinc oxide and titanium dioxide were synthesized for the construction of DSSCs, which in turn were characterized by X-ray diffractometry, which corroborated the success of the synthesis. It is intended, in the future, to build DSSCs using blocking layers with different topographies. The cells will be constructed in a standard way using Fluorine-doped Tin Oxide (FTO) substrates, using the prepared ceramic powders and depositing them via casting, using ruthenium for sensitization and the iodide/triodide pair as a redox pair. The final objective would be to test these solar cells against a solar simulator, using a potentiostat, in order to verify the existence of an efficiency gain in energy conversion.