Ruthenium phthalocyanines with axial carboxylate ligands: Synthesis and function in solar cells based on nanocrystalline TiO₂

Abstract

The synthesis and characterization of phthalocyaninato-ruthenium ( PcRu ) complexes with potential functional axial ligands are described. The solubility of these PcRu complexes was much improved compared to their parent phthalocyanines without Ru , enabling purification by normal flash column chromatography and also NMR measurements in common solvents (e. g. DMSO - d 6 and CDCl 3). Adsorption of these phthalocyanine dyes onto the surface of a semiconductor through the carboxyl group(s) in the axial ligands prevents to some extent formation of H-aggregates, which is typical for phthalocyanines. It also prevents stacking of the dye molecules on the surface. The photovoltaic behavior of sandwich solar cells based on nanostructured TiO 2 films sensitized by these PcRu complexes was studied under irradiation with visible light. For a solar cell based on bis(4-carboxypyridine)-phthalocyaninato ruthenium(II) (1) sensitized nanoporous-nanocrystalline TiO 2, a monochromatic incident photon-to-current conversion efficiency (IPCE) of 21% was obtained at 640 nm. The overall conversion efficiency (η) was 0.61%, which is one of the best results for a solar cell based on a phthalocyanine dye. For a cell based on (4-carboxypyridine)-(4-(2-ethoxy)ethyloxycarbo-nylpyridine)-2,3,9,10,16,17,23,24-octa(n-pentyloxy)-phthalocyaninato ruthenium(II) (5) sensitized TiO 2, a IPCE of 6.6% at 640 nm and η of 0.58% were obtained.

Preparation and Characterization of Nonclassical Tetraazaporphyrin, Bis(4‐methylpyridine)[1,3,5,7,9,11,13,15‐octaphenyltetra(3,4‐thieno)tetraazaporphyrinato]ruthenium(II)

“…[18,19] We used a slightly modified procedure. A solution of ruthenium(III) trichloride in 2-ethoxyethanol was heated at reflux until the mixture turned dark blue.…”

Synthesis, characterization and properties of 1,11,15,25-tetrahydroxy-4,8,18,22-bis(bridging butanedioic acid)phthalocyanine copper

“…Most of the reported complexes of ruthenium and naphthalocyanine have N-donor axial ligands; e.g., pyridine, pyrazine and quinoline derivatives [12]. Bridging Ndonor ligands such as pyrazine have been used to prepare conducting oligomers [13] and pyridines with carboxylic acid functional groups have been utilized as anchoring ligands in photovoltaic devices [14,15].…”

Two main chain polymeric metal complexes as dye sensitizers for dye‐sensitized solar cells based on the coordination of the ligand containing 8‐hydroxyquinoline and phenylethyl or fluorene units with Eu(III)

“…Despite recent advances in DSSCs materials, for example, Zn(II) metal‐porphyrins compounds,30, 31 Ru‐sensitized DSSCs exist in which the dye is attached to the TiO 2 via axial ligands32–34 or through anchoring groups on the macrocycle periphery,35 research into ligand design for electronic materials has been dominated by the dipyridine and azaindole moiety. Furthermore, practical applications of these compounds in DSSCs would require a new generation of organic ligands that are inexpensive and robust.…”