Rapid synthesis of bis (2,2′-bipyridine) nitratocopper(II) nitrate using a hydrothermal method and its application to dye-sensitized solar cells

In this study we synthesized bis (2,2′-bipyridine) nitratocopper(II) nitrate in order to examine its the crystal structure, optical property and application to dye-sensitized solar cells (DSSCs). Single X-ray analysis results revealed that the acquired complex exhibited five-coordination with four nitrogen atoms of bipyridine and the oxygen bond of the NO 3 - ion. The reflectance UV–Vis absorptions showed three absorptions that were assigned to ligand-to-ligand at around 230–350 nm, metal-to-ligand charge transfer at around 350–600 nm, and d–d transfer at around ∼650 nm. Cyclic voltammetry in acetonitrile revealed a reversible Cu(I) → Cu(II) oxidation process at a highest occupied molecular orbital (HOMO) and a lowest unoccupied molecular orbital (LUMO) levels of −4.692 and −4.071 eV, respectively. The photoelectric efficiency in DSSCs was approximately 0.032% with the nanometer-sized TiO2 in the condition of an open-circuit voltage (Voc) of 0.346 V, a short-circuit current density (Jsc) of 0.166 mA/cm2 at an incident light intensity of 100 mW/cm2.