Spectroscopic and impedance studies of reverse biased degraded dye solar cells

Abstract

The work that is presented here is focused on the results that were obtained during studies of the performance of Dye Solar Cells under certain reverse bias conditions. This reverse voltage could permanently modify or damage a cell if it is not properly protected. Various techniques were employed to determine the physical changes in the cell. It was found that a cell that was subjected to a reverse bias of 2 V for 500 minutes showed a 58% recovery. The UV-Vis spectra showed a blue shift (higher energy), the Raman showed no peak at 1713 cm-1 and the FT-IR showed the disappearance of the S-C-N absorption band at 2100 cm-1. The combined conclusion is that the –NCS ligand has been depleted and replaced with I3- ions. Nyquist and Bode plots showed an increase in the charge transfer resistance at the counter electrode. This indicates a partial oxidation of the Pt catalyst on the counter electrode. The changes in the cell after being subjected to a reverse bias potential of 2 V for 500 minutes are changes on the -NCS bonds on the Ru containing dye as well as the Pt on the counter electrode.