Synthesis, characterization and introduction of a new ion-coordinating ruthenium sensitizer dye in quasi-solid state TiO2 solar cells

A new ion-coordinating heteroleptic ruthenium(II) dye was synthesized by attaching two crown ether moieties in the 4,4′ positions of one of the bipyridine ligands. This new dye (named as RC730) was characterized by UV-Vis spectroscopy, CHN elemental analysis, NMR and electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). In order to investigate the properties of these ion-coordinating species, dye-sensitized solar cells were assembled with a gel polymer electrolyte based on two different cations: lithium and sodium. The devices were characterized by J–V curves under 100 mW cm−2, incident photon to current conversion efficiency spectra (IPCE) and photovoltage decay transients under open-circuit conditions. The solar cells based on the new heteroleptic dye provided higher photocurrent and photovoltage when lithium was used in the electrolyte instead of sodium cations, reaching overall conversion efficiencies up to 2%. This behavior might be related to the ability of the ion-coordinating RC730 dye to trap Li ions, minimizing the conduction band edge shift. When the polymer electrolyte based on lithium is used, the IPCE spectra show a maximum efficiency of 31% at the maximum absorption peak of the RC730 dye (ca. 530 nm).