Synthesis of a carboxylic acid-based ruthenium sensitizerand its applicability towards Dye-Sensitized Solar Cells

Abstract

This work reports the synthesis of ruthenium based Ru(bpy) (dcbpy)(ClO ) [(bpy)2,2′-bipyridine;dcbpy = 4,4′-dicarboxy-2,2′-bipyridine] (RuC) dye and its application in solid andliquid state Dye-Sensitized Solar Cells (DSSCs). Synthesis resulted with high-pure orangecoloured dye with a high yield percentage of 45%. The dye was characterized via NuclearMagnetic Resonance (NMR) spectroscopy, Mass spectroscopy, Cyclic Voltammetry (CV) andUV–vis spectroscopy. The calculated bandgap (E ) of 2.38 eV from absorbance spectra ofpure RuC in ethanol solution showed best proximity with the data obtained from CVmeasurements. The RuC showed strong absorption in near UV region with the highestmolar extinction coefficient (MEC) of 14,746 M cm at 463 nm. Plateau of over 80% ofExternal Quantum Efficiency (EQE) spectra reveals the efficient carrier generation of RuC innear UV region. Carboxylic acid groups of RuC provide the potential for enhanced electrontransfer from TiO surface, and an increased electron density at the interface leads to highercurrent density. The RuC sensitized solid and liquid state DSSCs exhibited a short circuitcurrent density (J ) over 3.04 mA/cm and 5.82 mA/cm , and power conversion efficiency(PCE) of 1.2% and 1.8% respectively under simulated Air Mass 1.5 irradiation (100 mWcm