Design and development of cyclometalated ruthenium complexes containing thiophenyl-pyridine ligand for dye-sensitized solar cells

• We report the use of thiocyanate-free cyclometalated ruthenium sensitizers.
• The first report of studying the cyclometalated Ru dyes with 2-thienyl pyridines.
• Incorporation of thienyl pyridine ligands leads to enhanced spectral response.

Two new cyclometalated ruthenium sensitizers NC102 (1) and NC103 (2), where the two NCS- ligands of the N3 analog were replaced with the 2-thiophen-2-yl-pyridine and 2-benzo[b]thiophen-2-yl-pyridine ligands, respectively, were designed and synthesized for dye-sensitized solar cell applications. The effects of these two ligands on the photophysical behavior of ruthenium complexes were investigated by their optical, electrochemical, and photovoltaic properties. The sensitizer NC103 (2) with the fluoride substitution in the ligand exhibited the best cell performance with a short-circuit current (Jsc) of 9.45 mA/cm2, an open-circuit voltage (Voc) of 630 mV, and a fill factor (FF) of 0.71, giving an overall power conversion efficiency of (η) 4.22% under simulated AM 1.5 irradiation.

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