Time-Resolved Operando Spectroscopy for Dye-Sensitized Solar Cells from Multiple Perspectives

We have performed time-resolved operando measurements based on continuous wave photo-induced absorption (cw-PIA) spectroscopy to investigate the behaviors of carriers in operating dye-sensitized solar cells (DSSCs). We demonstrate that PIA signals are obtained from the electron carriers of the fluorine-doped tin oxide (FTO) electrode and these signals can be utilized to study the operation dynamics of DSSCs. The time-resolved operando experiments observe the PIA signals of electron carriers individually from the FTO electrode and a TiO₂ layer together with photocurrent measured simultaneously. We reveal that the transfer of electron carriers in DSSCs after photoexcitation is very slow and occurs in the order of TiO₂, FTO, and photocurrent. These PIA signals and photocurrents reach equilibrium at approximately the same response rate determined by the transfer rate of iodine ions, which corresponds to the rate for the entire operating cycle. These operando measurements from multiple perspectives are effective for elucidating the operational mechanism in real solar cells and are widely applicable to a variety of solar cells.