Using EIS for diagnosis of dye-sensitized solar cells performance

Abstract

During the last decade interest in dye-sensitized solar cells (DSC) has grown enormously. Electrical impedance spectroscopy (EIS) is an electrochemical technique commonly used for investigation of charge carrier dynamics in these photovoltaic devices. We used EIS for characterization of our DSC; moreover, symmetric cells with counter-counter or photo-photo electrodes were realized and measured in order to simplify impedance cell analysis by separating the contribution of counter and photoelectrode, respectively. In particular, we provided very accurate illumination of the photoelectrode symmetric cell, aiming to approach the experimental conditions of a complete cell. By fitting of experimental data, we obtained values for the charge transfer resistance at the counter-electrode and the electron percolation time at the photoelectrode. Moreover, the simulation of a whole cell, combining the data from the fitting procedures above, was in good agreement with experimental data

Photocurrent response from vertically aligned single-walled carbon nanotube arrays

“…This allows us to exclude the effect of one electrode and simplifies the spectra for fitting. In a platinum counter-counter symmetrical cell we expect to see two peaks, the first is attributed to charge transfer at the Pt/FTO interface whilst the second is ionic diffusion in the electrolyte [15]. This is observed in the measured data of fig.…”

“…Also of interest to researchers is the behavior inside the DSSCs and at interfaces between each element. This can be elucidated by electrochemical impedance spectroscopy (EIS) [13][14][15]. The cell design shown in Figure 1 replaces the dye-sensitized TiO 2 with an array of vertically aligned SWCNT that is chemically attached to FTO coated glass by a technique previously performed extensively in our research group [16][17][18][19][20].…”

The optimisation of dye sensitised solar cell working electrodes for graphene and SWCNTs containing quasi-solid state electrolytes

“…Symmetric cells composed of our electrolyte sandwiched between two Pt based counter electrodes were fabricated and EIS measurements were performed. Symmetric cells such as this allow evaluation of the processes occurring at the Pt/electrolyte interface (Liberatore et al, 2009;Meng et al, 2014). The EIS Nyquist and Bode plots of the cells fabricated with the SWCNT and hybrid (SWCNT-graphene) electrolytes are shown in Fig.…”

“…The counter-counter symmetric cells are represented by the equivalent circuit shown in Fig. 4 of (Liberatore et al, 2009). The series resistance (Rs) represents the sheet resistance of the FTO glass, and is intrinsic to the transparent conducting oxide (TCO) glass itself.…”

“…which represents an imperfect capacitor is introduced instead of capacitance because of the elevated porosity of the interface (Liberatore et al, 2009). A n value = 1 describes an ideal capacitor while the case n = 0 describes a pure resistor.…”