Influence of impregnation time on TiO2 films sensitized with N719 and 2-Mercaptobenzothiazole: An electrochemical analysis

Dye sensitized solar cells (DSSC) are low-cost photovoltaic devices with easy production. They operate with a photoanode, a photocathode, and an electrolyte responsible for charge permeation within the cell. Recent research focus in DSSCs has aimed at enhancing their energy conversion properties, such as the insertion of new materials to reduce electronic recombination, utilization of gel electrolytes, dye synthesis, and studying cell assembly parameters. This study examined the effects of various immersion durations (6, 12, and 24 h) on TiO2 semiconductor films immersed in solutions containing charge carriers (N719 and 2-Mercaptobenzothiazole). To characterize the electrochemical properties, analyses such as current density versus potential curves (j-V), Electrochemical Impedance Spectroscopy (EIS), charge extraction, Intensity-Modulated Photovoltage (IMVS), and Photocurrent Spectroscopy (IMPS) were performed. It was found that the cell with 24 h of impregnation, presented a higher current density, consequently increasing efficiency (η = 5.76%). Impedance analyses showed that the 24-h samples facilitated charge transport, reducing cell resistance, consistent with charge extraction measurements. Lastly, IMPS and IMVS tests revealed that 24 h of immersion generated shorter collection times (τc = 0.016 ± 0.01) and longer electronic recombination times (τr = 0.07 ± 0.007), aiding the charge transport process.