Available online 12 September 2013
Source:Journal of Photochemistry and Photobiology A: Chemistry
Author(s): Hitoshi Kusama , Takashi Funaki , Kazuhiro Sayama
A density functional theory (DFT) study was performed to elucidate why variations in the 2-phenylpyrimidinato (L) ligand of cyclometalated Ru(H3tcterpy)L(NCS) dye affect the open-circuit photovoltage (V oc) of a dye-sensitized solar cell (DSSC) using an iodine/iodide redox couple, where tcterpy represents 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine. Neutral dye molecules interact with I2 via the N atom of the L ligand and the S atom of the NCS ligand. Among the nine tested dyes, the intermolecular interaction strengths between the dye and I2 correspond to the reduced V oc of DSSC. Additionally, I−
interacts with oxidized dye via the L ligand and via the NCS ligand, and a second I−
bonds to the first I−
. The interaction strengths of I−
with oxidized dyes strongly correlate with the enhanced V oc. The computational results suggest that the L ligand structure influences the regeneration of oxidized dye and recombination. Consequently, the L ligand structure changes V oc.