Investigation on Dye Regeneration Kinetics at P-Type Sensitized Nanoparticle Nickel Oxide Film by Scanning Electrochemical Microscopy

Abstract

The efficiency of a NiO-sensitized solar cell is determined by the kinetics of hole injection and dye regeneration reactions at the NiO/dye/electrolyte interface. In this research, the photochemical regeneration kinetics of dye adsorbed on the NiO film was investigated by scanning electrochemical microscopy (SECM). Besides, organic C343 and P1 sensitizers in combination with iodide-based, cobalt-based, and thiolate-based electrolytes were selected to understand the effect of sensitizers and redox shuttles on the dye regeneration process. As a result, a fast regeneration kinetic rate constant was conformed in the thiolate-based sample compared with cobalt-based and iodide-based, demonstrating that the organic redox shuttle was an efficient mediator to optimize the performance of p-type DSSC. Furthermore, the regeneration rate constants ( $k_{\text{eff}}$ ), reduction rate constants ( $k_{\text{red}}$ ), and absorption cross section ( ${Ф}_{\text{hv}}$ ) were investigated for organic dyes and electrolytes. That is, an effective dye regeneration rate constant $k_{\text{red}}$ of $6.95\times {10}^5$  mol-1cm3s-1 for NiO/P1 and $k_{\text{red}}$ of $3.75\times {10}^5$  mol-1cm3s-1 for NiO/C343 was found at various wavelengths. Therefore, the experimental results demonstrate that regeneration kinetics are dependent on the type of electrolyte and dye used. Moreover, the results suggest that scanning electrochemical microscopy is a powerful method for screening efficient dyes and electrolytes for charge transfer reactions in P-type dye-sensitized solar cells.