Sulphonate anchored hemicyanine dyes for dye solar cell: A study on dipole moment and polarity

Abstract

The effect of the molecular architecture of dye on the performance of a hemicyanine based dye sensitized solar cell (DSSC) has been studied using theoretical and experimental tools. These dyes were utilized as sensitizers in DSSC and then later were characterized using various techniques like I-V, impedance, electron transfer kinetics, dielectrics, and Tafel polarization in order to study the photovoltaic performance. The dye having a p-OH group (INS 1) exhibited very good photon to electricity conversion efficiency (3%) along with good fill factor while the dye having a p-OMe group (INS 2) lagged behind in performance. The substituent effect was studied theoretically as well as experimentally emphasizing the dipole moment of the dye in various directions. Theoretical investigation reveals that the presence of a p–OH group in the donor unit enhances the dipole moment of the molecule in comparison to a p-OMe group, thereby imparting longer lifetime of excited state leading to better charge transfer at the TiO2/dye interface.