Célula Fotovoltaica ZnO@ZnS Core@Shell, Obtida a Partir do Método Hidrotérmico Assistido por Microondas

Abstract

Several countries have been looking for alternative forms of energy, with the aim of reducing pollution of the environment, such as wind energy, biomass, photovoltaic energy, among others. The photovoltaic effect is the principle of the conversion of solar energy into electricity, which bases the various types of existing photovoltaic cells. In this sense, this research aims to describe the development - synthesis and assembly - of photovoltaic cells of the core@shell ZnO@ZnS type, as well as performing the conversion efficiency test of the proposed systems. The synthesis was carried out using the microwave-assisted hydrothermal method, using the zinc acetate and sodium hydroxide precursors to obtain zinc oxide (ZnO) and thiourea together with zinc acetate to obtain of the ZnO coating, in order to originate the core@shell ZnO@ZnS system. The preparation of the photoelectrodes and counter electrodes of the cells were done on fluorine-doped tin oxide (FTO) plates. The deposition of the ZnO@ZnS compound on the FTO plate, for the formation of the photoelectrode, was performed by doctor blade, undergoing subsequent heat treatment, while the counter electrodes were made with carbon and platinum. As electrolytes the redox pairs were used potassium iodide and lithium iodide. To characterize the synthesis and the film, X-ray diffraction measurements, field scanning electron microscopy and UV-visible spectroscopy were performed. As for the electrical measurements was carried out lifting the response curve voltage Vs. time (V Vs. t), current density of short-circuit Vs. voltage (j Vs. V) in the dark and current density Vs. voltage, under a standard of 1000 W/m 2 , which were important to determine the short-circuit current, open-circuit voltage and, consequently, the form factor and the solar-to-electric conversion efficiency of the photovoltaic cell. With the results obtained from the construction of the cells, it was possible to infer that the photo-electrode developed with the compound ZnO@ZnS has potential for photovoltaic applications, presenting photovoltaic response, whatever the electrolyte and/or counter electrode used. The cells presented efficiency fewer than 1%, and the lithium and platinum cell presented the best conversio n efficiency (0.00289%). However, the aim of the work was to develop a cell without sensitizing that had a better longevity and that did not degrade, a fact that was observed since the cells remained in operation even after the replacement of the electrolyte. In this way, reaching the balance between efficiency and life time can be a guideline for n ew studies that take the core@shell systems to new perspectives, as well as serve as motivation for other researchers to use such knowledge in the field of photovoltaic cells, and for other aplications.