High Molar Extinction Coefficient Ion-Coordinating Ruthenium Sensitizer for Efficient and Stable Mesoscopic Dye-Sensitized Solar Cells

摘要

Ru(4,4-dicarboxylic acid-2,2'-bipyridine) (4,4'-bis(2-(4-(l,4,7,10-tetraoxyundecyl)phenyl)ethenyl)-2,2'-bipyTidine) (NCS)_2, a new high molar extinction coefficient ion-coordinating ruthenium sensitizer was synthesized and characterized using ~1H NMR, Fourier transform IR (FTIR), and UV/vis spectroscopies and cyclic voltammetry. Using this sensitizer in combination with a nonvolatile organic-solvent-based electrolyte, we obtain a photovoltaic efficiency of 8.4 % under standard global AM 1.5 sunlight. These devices exhibit excellent stability when subjected to continuous thermal stress at 80 ℃ or light soaking at 60 ℃ for 1000 h. An electrochemical impedance spectroscopy study revealed that device stability is maintained by stabilizing the TiO_2/dye/electrolyte and Pt/electrolyte interface during the aging process. The influence of Li~+ present in the electrolyte on the device photovoltaic parameters was studied, and the FTIR spectral and photovoltage transient study showed that Li~+ coordinates to the triethyleneoxide methylether side chains on the K60 sensitizer molecules.