Electrochemical Investigation of PEDOT Counter Electrode for Dye-Sensitized Solar Cells

Abstract

Conversion efficiency of a dye-sensitized solar cell (DSC) using poly(3,4-ethylenedioxythiophene) (PEDOT)-coated transparent conducting substrate as counter electrode was shown to be 7.88 %, which is slightly higher compared to a DSC using classical platinum sputtered counter electrode (7.65 %). From electrochemical impedance analysis, the PEDOT based cell was found to show lower charge-transfer resistance assigned to the I⁻/I₃⁻ redox reaction as a mediator on the counter electrode compared to the platinum based cell. More quantitatively, electron transfer rate constant (k⁰) for the I⁻/I₃⁻ redox reaction on the counter electrode was remarkably estimated by voltammetric kinetic analysis. The k⁰ obtained for the PEDOT electrode (3.47 × 10⁻³ cm s⁻¹) was larger than that for the platinum electrode (2.76 × 10⁻³ cm s⁻¹) by comparing the approximately same electrode thickness and surface roughness. This research revealed the higher conversion efficiency of the PEDOT based cell is attributed to essentially faster the mediator reaction (reduction of I₃⁻) on the counter electrode in its cell.