Análise do comportamento eletroquímico de 2-Mercaptobenzotiazol em Célula Solar Sensibilizada por corante

Abstract

Dye-sensitized solar cells (DSSCs) are third-generation devices that have shown a steady increase in energy conversion efficiency. However, one of the problems encountered for these devices is electronic recombination reactions, which can be understood as processes between the electron from the conduction band of TiO2 and the electrolyte, hindering electron transport in the electrical circuit, consequently reducing the cell's efficiency. Materials capable of anchoring to the surface of the semiconductor oxide, known as coadsorbents, have been employed in DSSCs with the aim of promoting blocking between oxide and electrolyte. 2-Mercaptobenzothiazole (2-MBT), used as a corrosion inhibitor, has sulfur atoms in its structure capable of coordinating to form hydrophobic complexes, thus enabling the formation of a protective film in the cell. The main objective of this work was to employ 2-MBT and evaluate its performance as a coadsorbent in DSSCs. Variations such as the concentration of 2-MBT, type of insertion, and impregnation time were carried out to determine the best cell operating parameters. Cells composed of working electrode (FTO/TiO2/2-MBT) were analyzed by j-E curves, photocurrent chronopotentiometry, chronoamperometry, electrochemical impedance spectroscopy (EIS), photocurrent spectroscopy (IMPS), and modulated intensity photo-voltage (IMVS). Charge extraction and the dye and coadsorbent solution were evaluated by UV/Visible spectroscopy. The results showed that the addition of 2-MBT at a concentration of 2 mg mL-1 increased the cell current density from 9.7 mA cm-2 to 11.4 mA cm-2, promoting a 20.5% increase in cell efficiency compared to the conventional cell. Electrochemical tests showed that the addition of 2-MBT in small amounts caused a decrease in the electrical resistance of the cell, indicating adsorption in TiO2 regions not filled by the dye, promoting disorganization of the electrical double layer that aids in electron injection from the cell, resulting in higher current densities, and indicating that the injection and transport of electrons in the device were facilitated.