New dyes of the type Ru(II)(bdmpp)(bpy) [where bdmpp is 2,6-bis(3,5-dimethyl-N-pyrazoyl)pyridine and bpy is 2,2'-bipyridine-4,4'-dicarboxylic acid] are prepared and characterized by infra-red (IR), mass (MS) and electrospray mass spectroscopy (ES-MS) as well as ¹H NMR (1D and 2D) spectroscopies. The compounds present broad and very high intensity MLCT absorption bands in the visible and can be chemically anchored on TiO₂ films via ester-like linkage involving carboxylato groups. These complexes have been tested with success as potential molecular antennas in dye-sensitized solar cells. Both opaque and transparent nanocrystalline TiO₂ thin film electrodes obtained by a doctor blade technique sensitized by these complexes were incorporated in a sandwich type regenerative photoelectrochemical solar cell containing 0.1M LiI +0.01M I₂ in propylene carbonate as well as a platinized conductive glass counter electrode. The cell was characterized by Raman spectroscopy under anodic and cathodic bias. Two new vibration bands were observed in the lower frequency region. The first one at 112 cm^-1 is due to tri-iodide formed on the photoactive electrode, and the second one at 167 cm^-1 is a sign of the dye/iodide interaction and corresponds to a vibration in a chemically stable "DI" intermediate species. Under direct sunlight illumination (solar irradiance of 60 mW/cm²) by using a composite polymer solid state electrolye, the cell ITO/TiO₂/(Ru(II)(bdmpp)(bpy)(NCS))(PF6)/electrolyte/Pt-ITO produced a continuous photocurrent as high as 4.29mA/cm², and gave IPCE values about half of the corresponding values obtained by the standard N3 dye under the same conditions. The photovoltage is about 600 mV and the overall energy conversion cell’s efficiency is as high as 1.72%.

Date Published: 26 February 2003
PDF: 11 pages
Proc. SPIE 4801, Organic Photovoltaics III, (26 February 2003); doi: 10.1117/12.452446

Published in SPIE Proceedings Vol. 4801:
Organic Photovoltaics III
Zakya H. Kafafi, Editor(s)