Unveiling the Aging Effect at the Interface of N719 Dye-Sensitized Solar Cells

The energy-generating charge transportation in dye sensitized solar cells (DSSCs) occurs at the photoanode interface, and degradation at the interface can severely impact the cell performance. The study investigates the degradation of DSSCs and the main factors causing the decrease in cell performance over time. The DSSCs investigated here maintain their stability in the dark but upon light exposure, the cell degraded. The surface-sensitive techniques X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and neutral impact collision ion scattering spectroscopy (NICISS) are employed to investigate the change in the elemental and chemical composition at the electrode interface. Fourier transform infrared spectroscopy (FTIR) is applied to investigate the change in functional groups throughout the dye TiO₂ interface. The XPS and NICISS results confirm the penetration of I_x⁻ (x = 1 or 3) species into the dye layer as the main reason for cell degradation. FTIR and UV–vis DRS show the interaction of electrolytes with the dye molecule resulting in changes in the dye structure under light resulting in cell degradation. The main reason for the cell degradation observed is the penetration of I_x⁻ into the dye layer which further instigates changes in the dye molecule affecting the light absorption ability of the dye and thus, decreasing the generation of photoelectrons resulting in poor performance of the cell over time.