Unraveling the Dual Character of Sulfur Atoms on Sensitizers in Dye-Sensitized Solar Cells.
Cyclometalated ruthenium sensitizers have been synthesized that differ with number of thiophene units on the auxiliary ligands. Sensitizers possessing four (SA25, SA246, and SA285) or none (SA282) sulfur atoms in their structures, were tested in solar cell devices employing I3-/I-redox mediator, enabling an estimation of the influence of sulfur-iodine/iodide interactions on dye-sensitized solar cell (DSC) performance. Power conversion efficiencies over 6% under simulated AM 1.5 illumination (1 Sun) were achieved with all the sensitizers. Consistently higher open-circuit voltage (VOC) and fill factor (FF) values were measured using SA282. Scrutinizing the DSCs with these dyes by transient absorption spectroscopy (TAS) and electrochemical impedance spectroscopy (EIS) indicate that sulfur atom induced recombination cancels favorable increased regeneration resulting in decreased power conversion efficiencies (PCEs). The data indicate that, to reduce charge recombination channels, the use of sulfur-containing aromatic rings should be avoided if possible in the dye structure when I3-/I-redox mediator is used.
Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1950 Sion, Switzerland.
Sadig
S
Aghazada
Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1950 Sion, Switzerland.
Peng
P
Gao
Aswani
A
Yella
Thomas
T
Moehl
Joël
J
Teuscher
Jacques-E
JE
Moser
Michael
M
Grätzel
Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne , CH-1950 Sion, Switzerland.|Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz, University , Jeddah, Saudi Arabia.
Mohammad Khaja
MK
Nazeeruddin
charge recombination; dye-sensitized solar cells; iodine electrolyte; ruthenium complexes