Analysis of charge transport properties of dye-sensitized solar cell (DSSC) with TiO2 working electrode by employing electrochemical impedance spectroscopy (EIS)

Abstract

In this paper DSSCs of various electrode thicknesses (L = 3 ?m?12 ?m) are assembled using N719 dye, an iodide (I????)/triiodide (I???? ????) redoxliquid electrolyte and TiO2 (P-25) working electrode (WE). The theoretically modeled equations defining various bulk and interface impedances are incorporated with EIS spectrum analyzer software to fit the simulated EIS curves with experimentally measured EIS curves to evaluate the charger transfer and recombination properties of the assembled DSSCs. EIS fitting parameters investigated to study the impact of WE thickness on the charge transport properties of assembled DSSC. It is observed that the charger transfer resistance at TiO2/electrolyte interface (Rk) and series resistance (Rs) are reduced from 8 ?cm2 ? 4.05 ?cm2and 14.5 ?cm2?10.06 ?cm2 respectively which shows consistency with improvement in electron life time (?e) from 5.8 ms ?12.4 ms for increasing WE thickness, L = 3 ?m?12 ?m. The combined impact of significant reduction in Rk and Rs along with improved trend of ?e can be considered as major factors for efficient electron injection across Dye/TiO2 interface hence increases short circuit current (Isc) from 1.485 mA ? 2.365 mA and photovoltaic conversion efficiency (?) from 3.55 % ? 5.46 % for L = 3 ?m?12 ?m, respectively. Moreover, a remarkable increment in ? (~45%), ?e (~56.3%) and a noticeable reduction in Rk(~38.75 %), Rs (~23.8 %) are observed for WE variations (L = 3 ?m?6?m) and further shows insignificant change for thicker WE (L> 6?m)